Episode 364: Animals Who Will Outlive Us All

Thanks to Oz from Las Vegas for suggesting this week’s topic!

Further reading:

Bobi, the supposed ‘world’s oldest dog’ at 31, is little more than a shaggy dog story

Greenland sharks live for hundreds of years

Scientists Identify Genetic Drivers of Extreme Longevity in Pacific Ocean Rockfishes

Scientists Sequence Chromosome-Level Genome of Aldabra Giant Tortoise

Giant deep-sea worms may live to be 1,000 years old or more

A Greenland shark [photo by Eric Couture, found at this site]:

The rougheye rockfish is cheerfully colored and also will outlive us all:

An Aldabra tortoise all dressed up for a night on the town:

Escarpia laminata can easily outlive every human. It doesn’t even know what a human is.

Show transcript:

Welcome to Strange Animals Podcast. I’m your host, Kate Shaw.

This week we have a great suggestion by Oz from Las Vegas. Oz wanted to learn about some animals that will outlive us all, and gave some suggestions of really long-lived animals that we’ll talk about. We had a similar episode several years ago about the longest lived animals,where for some reason we talked a lot about plants, episode 168, but this is a little different.

But first, a quick correction! Last week we talked about the dodo and some of its relations, including the Nicobar pigeon. I said that the Nicobar pigeon lived in the South Pacific, but Pranav caught my mistake. The Nicobar pigeon lives in the Indian Ocean on the Nicobar Islands, which I should have figured out because of the name.

Anyway, back in the olden days when I was on Twitter all the time, I came across a tweet that’s still my absolute favorite. Occasionally I catch myself thinking about it. It’s by someone named Everett Byram who posted it in January 2018. It goes:

“DATE: so tell me something about yourself

“ME: I am older than every dog”

Not only is it funny, it also makes you thoughtful. People live a whole lot longer than dogs. The oldest living dog is a chihuahua named Spike, who is 23 years old right now. A dog who was supposed to be even older, 31 years old, died in October of 2023, but there’s some doubt about that particular dog’s actual age. Pictures of the dog taken in 1999 don’t actually look like the same dog who died in 2023.

The oldest cat who ever lived, or at least whose age is known for sure, died in 2005 at the age of 38 years. The oldest cat known who’s still alive is Flossie, who was born on December 29th, 1995. If your birthday is before that, you’re older than every cat and every dog.

The oldest human whose age we know for sure was Jeanne Calment, who died in 1997 at the age of 122 years. We talked about her in episode 168. The oldest human alive today, as far as we know, is Maria Branyas, who lives in Spain and will turn 117 years old on her next birthday in March 2024.

It’s not uncommon for ordinary people to live well into their 90s and even to age 100, although after you reach the century mark you’re very lucky and people will start asking you what your secret for a long life is. You might as well go ahead and make something up now to tell people, because it seems to mainly be genetics and luck that allow some people to live far beyond the lives of any dog or cat or most other humans. Staying physically active as you age also appears to be an important factor, so keep moving around.

But there are some animals who routinely outlive humans, animals who could post online and say “I am older than every human” and the others of its species would laugh and say, “Oh my gosh, it’s true! I’m older than every human too!” But they don’t have access to the internet because they are, for instance, a Greenland shark.

We talked about the Greenland shark in episode 163. It lives in the North Atlantic and Arctic Oceans where the water is barely warmer than the freezing point. It can grow up to 23 feet long, or 7 meters, with females being larger than males. Despite getting to such enormous sizes, it only grows one or two centimeters a year, and that was a clue for scientists to look into how old these sharks can get.

In 2016, a team of scientists published a study about how they determined the age of Greenland sharks that had been accidentally caught by fishing nets or that had otherwise been discovered already dead. The lenses inside vertebrate eyeballs don’t change throughout an animal’s life. They’re referred to as metabolically inactive tissue, which means they don’t grow or change as the animal grows. That means that if you can determine how old the lens is, you know when the animal was born, or hatched in the case of sharks.

In the past, scientists have been able to determine the age of dead whales using their eye lenses, but the Greenland shark was different. It turns out that the shark can live a whole lot longer than any whale studied, so the scientists had to use a type of carbon-14 dating ordinarily used by archaeologists.

The Greenland shark may be the oldest-living vertebrate known. Its life expectancy is at least 272 years, and probably closer to 500 years. Individual sharks can most likely live much longer than that. It’s not even mature enough to have babies until it’s about 16 feet long, or 5 meters, and scientists estimate it takes some 150 years to reach that length. Females may stay pregnant for at least 8 years, and maybe as long as 18 years. Babies hatch inside their mother and remain within her, growing slowly, until they’re ready to be born.

The Greenland shark is so big, so long-lived, and lives in such a remote part of the ocean that taking so long to reproduce isn’t a problem. Its body tissues contain chemical compounds that help keep it buoyant so it doesn’t have to use very much energy to swim, and which have a side effect of being toxic to most other animals. Nothing much wants to eat the Greenland shark. But it is caught by accident by commercial fishing boats, with an estimated 3,500 sharks killed that way every year. Scientists hope that by learning more about the Greenland shark, they can bring more attention to its plight and make sure it’s protected. There’s still a lot we don’t know about it.

At least one species of whale does live much longer than humans. In 2007, researchers studying a dead bowhead whale found a piece of harpoon embedded in its skin. It turned out to be a type of harpoon that was manufactured between 1879 and 1885. After that, scientists started testing other bowhead whales that were found dead. The oldest specimen studied was determined to be 211 years old when it died, and it’s estimated that the bowhead can probably live well past 250 years if no one harpoons it and it stays healthy. It may be the longest-lived mammal. It has a low metabolic rate compared to other whales, which may contribute to its longevity.

Most small fish don’t live very long even if nothing eats them. Rockfish, for instance, only live for about 10 years even if they’re really lucky. Well, most rockfish. There is one species, the rougheye rockfish, that lives much, much longer. Its lifespan is at least 200 years old.

The rougheye rockfish has a lot of other common names. Its scientific name is Sebastes aleutianus. It can grow over 3 feet long, or 97 cm, and is red or orangey-red. It lives in cold waters of the Pacific, where it usually stays near the sea floor. It eats other fish along with crustaceans.

Naturally, scientists are curious as to why the rougheye rockfish lives so long but its close relations don’t. In 2021 a team of scientists published results of a genetic study of the rougheye rockfish and 87 other species. They discovered a number of genes associated with longevity, along with genes controlling inflammation that may help the fish stay healthy for longer.

The rougheye rockfish only evolved as a separate species of rockfish about ten million years ago. Because the longest-living females lay the most eggs, the genes for longevity are more likely to be passed on to the next generation, which means that as time goes on, lifespans of the fish overall get longer and longer. The rougheye also isn’t the only species of rockfish that lives a long time, it’s just the one that lives longest. At least one other species can live over 150 years and quite a few live past 100 years.

Another animal that can easily outlive humans is the giant tortoise, which we talked about in episode 95. Giant tortoises are famous for their longevity, routinely living beyond age 100 and sometimes more than 200 years old. The oldest known tortoise is an Aldabra giant tortoise that may have been 255 years old when it died in 2006. The Aldabra giant tortoise is from the Aldabra Atoll in the Seychelles, a collection of 115 islands off the coast of East Africa.

Scientists studied the Aldabran tortoise’s genetic profile in 2018 and learned that in addition to genes controlling longevity, it also has genes that control DNA repair and other processes that keep it healthy for a long time.

Oz also suggested the infinite jellyfish, also called the immortal jellyfish. An adult immortal jelly that’s starving or injured can transform itself back into a polyp, its juvenile stage. We talked about it in episode 343 in some detail, which was recent enough that I won’t cover it again in this episode. Scientists are currently studying the jelly to learn more about how it accomplishes this transformation and how long it can really live.

So far all the animals we’ve talked about, except the immortal jellyfish, are vertebrates. It’s when we get to the invertebrates that we find animals with the longest lifespans. The ocean quahog, a type of clam that lives in the North Atlantic Ocean, grows very slowly compared to other clams, and populations that live in cold water can live a long time. Sort of like tree rings, the age of a clam can be determined by counting the growth rings on its shell, and a particular clam dredged up from the coast of Iceland in 2006 was discovered to be 507 years old. Its age was double-checked by carbon-14 dating of the shell, which verified that it was indeed just over 500 years old when it was caught and died. Researchers aren’t sure how long the quahog can live, but it’s a safe bet that there are some alive today that are older than 507 years, possibly a lot older.

The real long-lived animals are very simple ones, especially sponges and corals. Some species of both can live for thousands of years. Various kinds of mollusks and at least one urchin can live for hundreds of years.

It’s probable that there are lots of other animals that routinely outlive humans, we just don’t know that they do. Scientists don’t always have a way to check an animal’s age, or they don’t think to do so while studying an organism. There are also plenty of animals that we just don’t know exist, especially ones that live in the ocean. For example, a species of tube worm named Escarpia laminata wasn’t even discovered until 1985, and it wasn’t until 2017 that scientists realized it lived for hundreds or even thousands of years.

The tube worm doesn’t have a common name, since it lives in the deepest parts of the Gulf of Mexico around what are called cold seeps, so no one ever needed to refer to it until it was discovered by scientists. A cold seep isn’t actually cold, it just isn’t as hot as a hydrothermal vent. In a cold seep, oil and methane are released into the ocean from fissures in the earth’s crust. Life forms live around these areas that live nowhere else in the world.

Many tube worms can grow quite long and can live over 250 years, with the giant tube worm growing almost 10 feet long, or 3 meters. Escarpia laminata is smaller, typically only growing about half that length. In a study published in 2017, a team of scientists estimated that it routinely lives for 250 to 300 years and potentially much, much longer. A tube worm doesn’t actually eat; instead, it forms a symbiotic relationship with bacteria that live in its body. The bacteria have a safe place to live and the tube worm receives energy from the bacteria as they oxidize sulfur released by the cold seeps. The tube worm, in other words, lives a stress-free life with a constant source of energy, and nothing much wants to eat it. The limit to its life may be the limit of the cold seeps where it lives. Cold seeps don’t last forever, although many of them remain active for thousands of years.

Humans are probably the longest-living terrestrial mammal. This may not seem too impressive compared to the animals we’ve talked about in this episode, but our lives are a whole lot more interesting than a tube worm’s.

You can find Strange Animals Podcast at strangeanimalspodcast.blubrry.net. That’s blueberry without any E’s. If you have questions, comments, or suggestions for future episodes, email us at strangeanimalspodcast@gmail.com. We also have a Patreon at patreon.com/strangeanimalspodcast if you’d like to support us for as little as one dollar a month and get monthly bonus episodes.

Thanks for listening!

Episode 362: The Sawfish and the Sawshark

Thanks to Murilo for suggesting this week’s episode about the sawfish and the sawshark!

Further Reading:

Sawfish or sawshark?

Two New Species of Sixgill Sawsharks Discovered

Do not step:

The underside of a largetooth sawfish [photo by J. Patrick Fischer – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=17421638]:

The sawshark has big eyes [photo by OpenCago.info – Wikimedia Commons [1], CC BY-SA 2.5, https://commons.wikimedia.org/w/index.php?curid=25240095]:

A comparison of rostrums. The sawskate is in the middle, the one with barbels is the sawshark, and the really toothy one is the sawfish [picture by Daeng Dino – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=137983599]:

Show transcript:

Welcome to Strange Animals Podcast. I’m your host, Kate Shaw.

This week we’re going to learn about an amazing fish suggested by Murilo. It’s the sawfish, and while we’re at it, we’re also going to learn about a different fish called the sawshark.

There are five species of sawfish alive today in two genera, and they’re all big. The smallest species can still grow over 10 feet long, or 3 meters, while the biggest species can grow over 20 feet long, or 6 meters. The largest sawfish ever reliably measured was 24 feet long, or 7.3 meters. Since all species of sawfish are endangered due to overfishing, pollution, and habitat loss, really big individuals are much rarer these days.

The sawfish lives mostly in warm, shallow ocean waters, usually where the bottom is muddy or sandy. It can also tolerate brackish and even freshwater, and will sometimes swim into rivers and live there just fine. The largetooth sawfish is especially happy in freshwater.

Let’s talk specifically about the largetooth sawfish for a moment, since we know the most about it. Like other sawfish, the female gives birth to live young, up to 13 babies at a time, and the babies can be up to three feet long at birth, or 90 cm. When a baby is born, its saw, which we’ll talk about in a minute, is covered with a jelly-like sheath that keeps it from hurting its mother. The sheath dissolves soon after birth.

The mother usually gives birth around the mouth of a river, and instead of swimming into the ocean, the babies swim upstream into the river. They live there for the next several years, and some individuals and even some populations may live their whole lives in the river. It’s sometimes called the river sawfish or the freshwater sawfish for this reason.

One interesting thing about the largetooth sawfish is how agile it is. All sawfish are good swimmers, but the largetooth sawfish is especially good. It can swim backwards, it can jump more than twice its own length out of the water, and it can climb over rocks and other obstacles using its fins, even if the obstacle isn’t completely submerged. It’s possible that other species of sawfish can do the same, but scientists just haven’t observed this behavior yet. We actually don’t know that much about most species of sawfish because of how rare they’ve become.

The sawfish is a type of ray, and rays are most closely related to sharks. Like sharks, rays have an internal skeleton made of cartilage instead of bone, but they also have bony teeth. You can definitely see the similarity between sharks and sawfish in the body shape although the sawfish is flattened underneath, which allows it to lie on the ocean floor. There’s also another detail that helps you tell a sawfish from a shark: the rostrum, or snout. It’s surprisingly long and studded with teeth on both sides, which makes it look like a saw.

The teeth on the sawfish’s saw are actual teeth. They’re called rostral teeth and the rostrum itself is part of the skull, not a beak or a mouth. It’s covered in skin just like the rest of the body. The sawfish’s mouth is located underneath the body quite a bit back from the rostrum’s base, and the mouth contains a lot of ordinary teeth that aren’t very sharp.

So, you may be asking, if the sawfish has plenty of teeth in its mouth, how and why does it also have those extra teeth on both sides of its saw? It’s because the rostral teeth evolved from dermal denticles. We’ve talked about dermal denticles a few times before, but a few months ago we had a Patreon bonus episode that went into more detail. In that episode, I talked about an article about a type of catfish, so let me just quote the whole section of that episode. It’s not long and I think it’s really interesting. Heck, I’ll just drop the audio in directly from that Patreon episode:

Our next article is from October 2017 and is intriguingly titled “When teeth grow on the body.” It sounds horrific, but it’s actually a study of certain catfish that grow bony plates with tiny teeth on their bodies as defense.

Catfish don’t have scales, but some species of denticulate catfish that live in South America grow bony plates that act like armor. Many of these plates are covered in thin little teeth–actual teeth, including enamel and dentin, with pulp inside. They’re called extra-oral teeth, dermal denticles, or odontodes, and the study determined that they appeared about 120 million years ago in ancient catfish that hadn’t yet evolved the bony plates. The teeth regrow when they’re lost, and in some species, males grow larger teeth than females and use them to fight other males. Imagine biting someone without needing to open your mouth.

Anyway, dermal denticles aren’t all that rare in fish. Sharks and rays are both covered with them. They’re also called placoid scales but they’re literally teeth, they’re just not used for eating. In the case of the sawfish, the rostral teeth grow much larger than an ordinary dermal denticle, and stick out sideways like the teeth of a saw. Different species have differently shaped rostral teeth. The teeth grow throughout the sawfish’s life, but unlike the teeth in the mouth, if the sawfish loses a rostral tooth, it doesn’t grow back. If it chips the top off a rostral tooth, though, that part will grow back.

The sawfish uses its rostrum to find the fish, crustaceans, and mollusks it eats. Both the rostrum and the head are packed with electroreceptors that allow the sawfish to sense tiny electrical charges that animals emit as they move. This might mean a school of fish swimming through muddy water, or it might mean a crustacean hiding in the sand. The sawfish sometimes uses its rostrum to dig prey out of the sand, but it also uses it to slash at fish or other animals. Then the sawfish can either grab the injured or dead animal with its mouth or pin it to the sea floor with its rostrum to maneuver it into its mouth. Its mouth is relatively small and it prefers to swallow its food whole, head-first, so it can only eat fish that are smaller than its mouth.

This means the sawfish leaves humans alone, because we’re way too big to fit into its mouth. It doesn’t want anything to do with us. Unfortunately, people keep bothering the sawfish, either by catching it illegally, leaving fishing nets and other trash in the ocean that sawfish and lots of other animals get tangled in, or by destroying its habitat with destructive dredging or trawling. The largetooth sawfish used to live around southern North America, but it relied on mangrove swamps to act as a nursery for baby sawfish. So many of the mangrove swamps have been destroyed so that people can build fancy hotels and shopping centers that the largetooth sawfish hasn’t been seen around North America in over 50 years, although the smalltooth sawfish is still hanging on.

Sawfish do well in captivity but require gigantic tanks, and even when given the best of care, they almost never breed in captivity. They live a long time, though, sometimes for decades.

Luckily for the sawfish, the female can reproduce without a male if she can’t find a mate. Instead of her eggs being fertilized by the male’s sperm, sometimes a female’s eggs will just develop into her genetic clones. Conservationists are working to make sure the sawfish and its habitat are protected so the babies can grow up safe and healthy.

We can’t talk about the sawfish without mentioning the sawshark. It’s a shark, not a ray, but it looks a whole lot like a sawfish–so much so that in places where both animals live, such as around Australia, people have a hard time telling them apart.

The sawshark mostly lives in much deeper water than the sawfish and is much smaller on average, about five feet long, or 1.5 meters. It has a pair of barbels about halfway down its saw that help it find food when there’s not much light to see by. Another major difference is that its gill slits are on the sides of its neck instead of under its body. It eats fish, squid, and crustaceans.

The sawshark’s rostrum also contains electroreceptors, although we don’t know for sure that it uses its saw the same way as the sawfish does. We actually don’t know very much about the sawshark, not even how many species are alive today. A new species was described in 2013 and two new species were described in 2020. There are probably more that are completely unknown to science, and maybe completely unknown to people in general.

Finally, there’s another fish that looks like a sawfish or sawshark, the sawskate, but its entire suborder, Sclerorhynchoidei, is completely extinct. It disappears from the fossil record 66 million years ago. I feel like I need a sound effect to play every time I mention that an animal went extinct 66 million years ago, to remind listeners that that’s the date of the extinction event that killed off the non-avian dinosaurs and many other animals. Maybe something like this. What do you think?

[comet sound]

Anyway, scientists are pretty sure the sawskate wasn’t very closely related to sawfish or sawsharks, but was more closely related to modern skates. Skates look a lot like rays but belong to a different family. Modern skates don’t have much of a rostrum at all, but the sawskate had a long tapering rostrum and some species had rostral teeth. Most species of sawskate were fairly small, but at least one grew an estimated 6 feet long, or about 2 meters.

If you’ve been thinking that a rostrum with teeth on both sides sounds like the kind of sword that old-timey warriors would use, you’re actually right. Traditionally, people in parts of the world where sawfish are common would sometimes use a big dried rostrum as a weapon.

These days, of course, sawfish are protected species. That means you can’t have a sawfish rostrum sword, sorry. Let the sawfish keep its sword.

You can find Strange Animals Podcast at strangeanimalspodcast.blubrry.net. That’s blueberry without any E’s. If you have questions, comments, or suggestions for future episodes, email us at strangeanimalspodcast@gmail.com. We also have a Patreon at patreon.com/strangeanimalspodcast if you’d like to support us for as little as one dollar a month and get monthly bonus episodes.

Thanks for listening!

Episode 353: Warm-Blooded Fish

This week we’re going to learn about some fish that feature warm-bloodedness! Thanks to Eilee for suggesting the moonfish, or opah.

Further reading:

Are all fish cold-blooded?

The Opah Fish Is Warm-Blooded!

Basking Sharks Are Partially Warm-Blooded, New Research Suggests

Megalodon Was Partially Warm-Blooded, New Research Shows

The opah, or moonfish, looks like a pancake with fins but is an active swimmer [picture from first article linked above]:

An opah not having a good day [photo by USA NOAA Fisheries Southwest Fisheries Science Center – https://swfsc.noaa.gov/ImageGallery/Default.aspx?moid=4724, Public Domain]:

Show transcript:

Welcome to Strange Animals Podcast. I’m your host, Kate Shaw.

Months ago now, Eilee suggested we talk about the sunfish. We’re actually not going to talk about the sunfish this week, although it is on the list to cover eventually. Instead, we’re going to talk about something else in Eilee’s email. Eilee asked if there was a moonfish too, and not only is there a moonfish, it’s basically the most unique fish alive today in one particular way. It’s warm-blooded!

The moonfish is also called the opah. It’s golden-orange in color with little white spots, and it’s very round and flattened side-to-side, like a pancake with orange fins. It has big golden eyes and a tiny mouth. It’s also quite large, with the biggest species growing up to 6 and a half feet long, or 2 meters. That’s a really big pancake. It lives in the ocean, sometimes diving deeply, and despite looking like a pancake, it can swim very quickly to catch squid and small fish. It also eats krill. The reason it can swim so quickly is because it has huge muscles that power its fins, and the muscles also generate a lot of heat, enough to keep its entire body at least several degrees warmer than the surrounding water. This is a warm-blooded trait, but fish are supposed to be cold-blooded.

The scientific term for warm-bloodedness is endothermy. Mammals and birds are endothermic, meaning our internal body temperature stays roughly the same no matter what temperature it is outside. Cold-bloodedness, called ectothermy, means an animal’s internal body temperature fluctuates depending on the temperature outside its body. Reptiles, amphibians, fish, and invertebrates are all cold-blooded.

To us as mammals, it feels like warm-bloodedness is a really good idea, but it comes at a high cost. Mammals and birds have to eat a lot more and a lot more often than cold-blooded animals do, because keeping our body temperature steady takes a whole lot of energy. An endothermic animal generates heat mainly by metabolizing food, although muscle movements like shivering and running also generate heat. An endothermic animal can be as active at night as it is during the day, and can be as active in winter as it is in summer.

Some otherwise cold-blooded animals can generate enough heat with muscle movements to warm parts of the body, called regional endothermy, or can generate heat with muscle movements in certain situations, called facultative endothermy. The female of some species of snake, especially some pythons, will wrap her body around her eggs and shiver, which generates enough heat to keep the eggs warm. Bumblebees can also shiver to warm their bodies enough to allow them to fly in cold weather. At least some species of sea turtle, including the green sea turtle and the leatherback, generates enough heat in its muscles while swimming that it’s able to migrate long distances in very cold water. Some scientists think all marine reptiles may be regional endotherms to some degree.

Some fish demonstrate regional endothermy too. So far, 35 species of fish are known to be partially warm-blooded, including some species of tunas, sharks, and billfish. Scientists originally thought that only predatory fish needed the extra boost of speed and endurance that endothermy provides, but then they discovered the basking shark is regionally endothermic, and the basking shark is a filter feeder that doesn’t need to chase after fast-moving fish. Also, almost nothing eats it, so it’s not running from anything either.

The basking shark is also huge, one the largest sharks alive today. It can grow over 40 feet long, or more than 12 meters, and possibly longer, although most individuals are closer to 25 feet long, or around 7 1/2 meters. It mostly lives in cold waters, sometimes diving quite deeply but sometimes feeding at the surface of the ocean. It just goes where it can find lots of tiny food that it filters out of the water with structures called gill rakers. The basking shark just swims forward with its gigantic mouth open, water flows through its gills, and the gill rakers catch any tiny particles of food. The gill rakers funnel the food toward the throat so the shark can swallow it. It mostly swims slowly and isn’t a threat to anything in the ocean except the tiniest of tiny animals. So why does it need parts of its body to be warmer than the water it’s in?

Scientists think it may have something to do with how far the basking shark travels in a year, since endothermy provides more energy for endurance swimming. The basking shark migrates thousands of miles, presumably following the best conditions to find plenty of food, although we don’t know for sure. It could be that it prefers a specific type of environment to breed or have babies. In the summer basking sharks do congregate in groups even though the rest of the year they’re solitary. The female retains fertilized eggs in her body, where the eggs hatch and the babies continue developing until they’re born a few months later. Scientists think the unborn babies eat unfertilized eggs after the food in their yolk sacs runs out.

The basking shark is critically endangered and is protected in many countries, but because it migrates such long distances it doesn’t always stay where it’s safe. Learning more about it helps conservationists know how best to protect it, and that’s how scientists discovered it was regionally endothermic. It generates heat from muscles deep inside its body as it swims, which helps keep its organs warmer than the surrounding water.

Other sharks are known to share this trait, and in June of 2023, a new study about megalodon indicated that it was probably regionally endothermic too. Megalodon went extinct almost 4 million years ago and was so big that it makes even the largest great white shark look like a teeny little baby shark. I may be exaggerating a little bit. The great white’s teeth grow around 2 and a half inches long, or a little over 6 cm. Megalodon’s teeth were 7 inches long, or 18 cm. We don’t know how big Megalodon’s body was, but it could probably grow at least 34 feet long, or 10.5 meters, and possibly grew as much as 67 feet long, or 20 meters. It ate whales. Like the basking shark and some other living sharks, including the great white, the heat generated by its muscles as it swam would have kept its internal organs, eyes, and brain warmer than the water around it.

But the opah takes this a step farther. Instead of keeping parts of its body warm, it’s just full-on endothermic. It’s warm-blooded. It mainly generates heat by moving its muscles, and it retains heat with a layer of special fatty tissue around its gills, organs, and some muscles. It also has a heat exchange system in its blood vessels that’s incredibly efficient. Cold water flowing through the gills chills the blood, but as the chilled blood flows deeper into the body, it’s warmed up by passing closely alongside heated blood flowing out from the heart. As a result, the opah can maintain its body temperature even when spending lots of time in cold water.

We actually don’t know that much about the opah, even though it’s a fish people like to catch and eat. It was described scientifically in 1799, which means it took well over 200 years for scientists to figure out that it was a warm-blooded fish. That means it’s very likely that it’s not the only endothermic fish alive today, it’s just the only one we’ve found so far.

You can find Strange Animals Podcast at strangeanimalspodcast.blubrry.net. That’s blueberry without any E’s. If you have questions, comments, or suggestions for future episodes, email us at strangeanimalspodcast@gmail.com. We also have a Patreon at patreon.com/strangeanimalspodcast if you’d like to support us for as little as one dollar a month and get monthly bonus episodes.

Thanks for listening!

Episode 280: Lesser-Known Sharks

Thanks to Tobey and Janice this week for their suggestions of lesser-known sharks!

Further reading/watching:

CREATURE FEATURE: The Spinner Shark [this site has a great video of spinner sharks spinning up out of the water!]

Acanthorhachis, a new genus of shark from the Carboniferous (Westfalian) of Yorkshire, England

150 Year Old Fossil Mystery Solved [note: it is not actually solved]

The cartoon-eyed spurdog shark:

The spinner shark spinning out of the water:

The spinner shark not spinning (photo by Andy Murch):

A Listracanthus spine:

Show transcript:

Welcome to Strange Animals Podcast. I’m your host, Kate Shaw.

This week we’re going to learn about three sharks you may have never heard of before! The first was suggested by my aunt Janice and the second by listener Tobey. The third is a mystery from the fossil record.

You may have heard about the findings of a study published in November of 2021, with headlines like “Venomous sharks invade the Thames!” My aunt Janice sent me a link to an article like this. Nobody is invading anything, though. The sharks belong where they are. It was their absence for decades that was a problem, and the study discovered that they’re back.

The Thames is a big river in southern England that empties into the North Sea near London. Because it flows through such a huge city, it’s pretty badly polluted despite attempts in the last few decades to clean it up. It was so polluted by the 1950s, in fact, that it was declared biologically dead. But after a lot of effort by conservationists, fish and other animals have moved back into the river and lots of birds now visit it too. It also doesn’t smell as bad as it used to. One of the fish now found again in the Thames is a small shark called the spurdog, or spiny dogfish.

The spurdog lives in many parts of the world, mostly in shallow water just off the coast, although it’s been found in deep water too. A big female can grow almost three feet long, or 85 cm, while males are smaller. It’s a bottom dweller that eats whatever animals it finds on the sea floor, including crabs, sea cucumbers, and shrimp, and it will also eat jellyfish, squid, and fish when it can catch them. It’s even been known to hunt in packs.

It’s gray-brown in color with little white spots, and it has large eyes that kind of look like the eyes of a cartoon shark. It also has a spine in front of each of its two dorsal fins, which can inject venom into potential predators. The venom isn’t deadly to humans but would definitely hurt, so please don’t try to pet a spurdog shark. If the shark feels threatened, it curls its body around into a sort of shark donut shape, which allows it to jab its spines into whatever is trying to grab it.

The spurdog used to be really common, and was an important food for many people. But so many of them were and are caught to be ground into fertilizer or used in pet food that they’re now considered vulnerable worldwide and critically endangered around Europe, where their numbers have dropped by 95% in the last few decades. It’s now a protected species in many areas.

The female spurdog retains her fertilized eggs in her body like a lot of sharks do. The eggs hatch inside her and the babies develop further before she gives birth to them and they swim off on their own. It takes up to two years before a pup is ready to be born, and females don’t reach maturity until they’re around 16 years old, so it’s going to take a long time for the species to bounce back from nearly being wiped out. Fortunately, the spurdog can live almost 70 years and possibly longer, if it’s not killed and ground up to fertilize someone’s lawn. The sharks like to give birth in shallow water around the mouths of rivers, where the water is well oxygenated and there’s lots of small food for their babies to eat, which is why they’ve moved back into the Thames.

Next, Tobey suggested we talk about the spinner shark. It’s much bigger than the spurdog, sometimes growing as much as 10 feet long, or 3 meters. It lives in warm, shallow coastal water throughout much of the world. It has a pointy snout and is brown-gray with black tips on its tail and fins, and in fact it looks so much like the blacktip shark that it can be hard to tell the two species apart unless you get a really good look. It and the blacktip shark also share a unique feeding strategy that gives the spinner shark its name.

The shark eats a lot of fish, especially small fish that live in schools. When the spinner shark comes across a school of fish, it swims beneath it, then upward quickly through the school. As it swims it spins around and around like an American football, but unlike a football it bites and swallows fish as it goes. It can move so fast that it often shoots right out of the water, still spinning, up to 20 feet, or 6 meters, before falling back into the ocean. The blacktip shark sometimes does this too, but the spinner shark is an expert at this maneuver.

There’s a link in the show notes to a page where you can watch a video of spinner sharks spinning out of the water and flopping back down. It’s amazing and hilarious. Tobey mentioned that the spinner shark is an acrobatic shark, and it certainly is! It’s like a ballet dancer or figure skater, but with a lot more teeth. And fewer legs.

Because spinner sharks mainly eat fish, along with cephalopods, they almost never attack humans because they don’t consider humans to be food. Humans consider the spinner shark food, though, and they’re listed as vulnerable due to overhunting and habitat loss.

We’ll finish with a mystery shark. I’ve had Listracanthus on my ideas list for a couple of years, hoping that new information would come to light, but let’s go ahead and talk about it now. It’s too awesome to wait any longer.

We know very little about Listracanthus even though it was around for at least 75 million years, since it’s an early shark or shark relative with a cartilaginous skeleton. Cartilage doesn’t fossilize very well compared to bone, so we don’t have much of an idea of what the shark looked like. What we do have are spines that grew all over the fish and that probably made it look like it was covered with bristles or even weird feathers. The spines are a type of denticle that could be up to 4 inches long, or 10 cm. They weren’t just spines, though. They were spines that had smaller spines growing from their sides, sort of like a feather has a main shaft with smaller shafts growing from the sides.

The spines are fairly common in the fossil record from parts of North America, dating from about 326 million years ago to about 251 million years ago. Listracanthus was closely related to another spiny shark-like fish, Acanthorhachis, whose spines have been found in parts of Europe and who lived around 310 million years ago, but whose spines are less than 3 inches long at most, or 7 cm.

Some researchers think the spines were only present on parts of the shark, maybe just the head or down the back, but others think the sharks were covered with the spines. Many times, lots and lots of the spines are found together and probably belong to a single individual whose body didn’t fossilize, only its spines. Some researchers even think that the flattened denticles from a shark or shark relation called Petrodus, which is found in the same areas at the same times as Listracanthus, might actually be Listracanthus belly denticles.

The spines probably pointed backwards toward the tail, which would reduce drag as the fish swam, and they might have been for display or for protection from predators, or of course both. The main parts of the spine were also hollow and there’s evidence there were capillaries inside, so they might have had a chemosensory or electrosensory function too.

Modern sharks have denticles that make their skin rough, sort of like sandpaper. One modern shark, the sandy dogfish, Scyliorhinus canicula, which is common in shallow water off the coasts of western Europe and northern Africa, and in the Mediterranean, has especially rough denticles on its tail. They aren’t precisely spines, but they’re more than just little rough patches. The sandy dogfish is a small, slender shark that barely grows more than about three feet long, or about a meter, and it eats anything it can catch. Young dogfish especially like small crustaceans, and sometimes they catch an animal that’s too big to swallow whole. In that case, the shark sticks the animal on the denticles near its tail, which anchors it in place so it can tear bite-sized pieces off. Some other sharks do this too, so it’s possible that Listracanthus and its relations may have used its spines for similar behavior.

We don’t know much about these sharks because all we have are their spines. Only one probable specimen has been found, by a paleontologist named Rainer Zangerl. Dr. Zangerl found the remains of an eel-like shark in Indiana that was covered in spines, but unfortunately as the rock dried out after being uncovered, the fossil literally disintegrated into dust.

In August of 2019, a fossil hunter posted on an online forum for fossil enthusiasts to say he’d found a Listracanthus specimen. He posted pictures, although since the fossil hasn’t been prepared it isn’t much to look at. It’s just an undulating bump down a piece of shale that kind of looks like a dead snake. Fortunately, the man in question, who goes by RCFossils, knew instantly what he’d found. He also knew better than to try to clean it up himself. Instead, he’s been working on trying to find a professional interested in taking the project on. In May of 2022 he posted again to say he’d managed to get an X-ray of the fossil, which shows a backbone but no sign of a skull. He’s having trouble finding anyone who has the time and interest in studying the fossil, but hopefully he’ll find someone soon and we’ll all learn more about this mysterious pointy shark.

You can find Strange Animals Podcast at strangeanimalspodcast.blubrry.net. That’s blueberry without any E’s. If you have questions, comments, or suggestions for future episodes, email us at strangeanimalspodcast@gmail.com. If you like the podcast and want to help us out, leave us a rating and review on Apple Podcasts or Podchaser, or just tell a friend. We also have a Patreon at patreon.com/strangeanimalspodcast if you’d like to support us for as little as one dollar a month and get monthly bonus episodes.

Thanks for listening!

Episode 261: Walking Fish

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Thanks to my brother Richard for suggesting one of the fish we talk about this week–fish that can walk! (Sort of.)

Further watching:

Video of a gurnard walking

Further reading:

Walking shark moves with ping-pong paddle fins

Walking sharks discovered in the tropics

The Hawaiian seamoth (the yellowy one is a larval seamoth, the brighter one with the snoot the same fish as a juvenile, both pictures by Frank Baensch from this site):

 

The slender seamoth (an adult, photo from this site):

A flying gurnard with its “wings” extended:

A flying gurnard with its “wings” folded, standing on its walking rays:

An eastern spiny gurnard standing on its walking rays:

A mudskipper’s frog-like face:

Mudskippers on land:

Walking sharks:

Show transcript:

Welcome to Strange Animals Podcast. I’m your host, Kate Shaw.

This week we’re going to look at some weird fish, specifically fish that use their fins to walk. Well, sort of walk. Thanks to my brother Richard for suggesting one of these fish.

Before we get started, let’s learn the terms for a fish’s two main pairs of fins. Different types of fish have different numbers and locations of fins, of course, but in this episode we’re focusing on the pectoral fins and the pelvic fins. Pectoral fins are the main fins in most fish, the ones near the front on each side. If a fish had arms, that’s roughly where its arms would be. The pelvic fins are near the tail on either side, roughly where its legs would be if fish had legs. If you remember that people lift weights with their arms to develop their pectoral muscles in the chest, you can remember where pectoral fins are, and if you remember that Elvis Presley was sometimes called Elvis the Pelvis because he danced by shaking his hips, you can remember where the pelvic fins are.

So, let’s start with the seamoth, which lives in shallow tropical waters of the Indo-Pacific Ocean and the Red Sea, including around Australia. We don’t know enough about it to know if it’s endangered or not, but since it’s considered a medicine in some parts of Asia, it’s caught to sell as an aquarium fish, and its habitat is increasingly impacted by bottom trawling and coastal development, it probably isn’t doing great. It’s never been especially common and doesn’t reproduce very quickly. Researchers think it may even be a social fish that forms a pair bond with its mate, since pairs are often found together.

The seamoth doesn’t even look that much like a fish at first glance. It’s covered with bony plates that act as armor, including bony rings around its tail. It even has to shed its skin as it grows larger.

The seamoth has a long, pointed snout with a tiny mouth underneath, but it can protrude its mouth out of its…mouth–okay that doesn’t make sense. Basically it’s able to extend its mouth into a tube that it uses like a straw to slurp up worms and other small animals from the sea floor.

It can change colors to match its surroundings too. If all this makes you think of seahorses and pipefish, the seamoth is related to both, but it looks very different because of its fins.

The seamoth’s pectoral fins are so large they resemble wings, and its modified pelvic fins are stiff and more fingerlike than fin-like so that it can walk across the sea floor with them. It spends most of its time walking on the sea floor, only swimming when it feels threatened and has to move faster. Sometimes a seamoth will cover itself with sand to hide from a predator. During breeding season, males develop brightly colored patterns on their pectoral fins.

The seamoth is a small fish, with the largest species growing about five inches long, or 13 cm. One species of seamoth, the little dragonfish, sheds its armor in one big piece—not just once or twice a year, but as often as every five days or so when it needs to rid itself of parasites. Its body is flattened but broad, which makes it look kind of like a piece of shell from above.

The flying gurnard is similar in some ways. It lives in warm coastal waters where it spends most of its time on the sea floor, looking for small animals to eat. We’ve talked about it before, in episode 101, but let’s go over it again in case like me you haven’t listened to episode 101 since it came out over three years ago.

The flying gurnard is a bulky fish that grows more than a foot and a half long, or 50 cm. It has a face sort of like a frog’s and can be reddish, brown, or greenish, with spots and patches of other colors. But most importantly, its pectoral fins are extremely large, looking more like fan-like wings than fins. The so-called wings are shimmery, semi-transparent, and lined with bright blue. They sort of look like butterfly wings and can be more than 8 inches long, or 20 cm. The fins actually have two parts, a smaller section in front and the larger wing-like section behind. The front section is stiff and makes the fish able to walk along the sea floor. It’s possible the flying gurnard can also use its wing-like fins to glide above the water for short distances like a flying fish, but at the moment we don’t know for sure.

The flying gurnard hasn’t traditionally been recognized as being related to the seamoth despite their similarities, but DNA studies suggest that they might actually be related after all. The flying gurnard may be related to the true gurnards, too. Both the flying gurnard and the true gurnard have a special muscle that beats against the swim bladder to make a drumming sound, and they look and act alike in many other ways too.

The gurnard is the fish my brother Richard recommended. There are actually a lot of different gurnards and they’re all kind of weird. Gurnards in the family Triglidae are bottom dwellers that grow around 16 inches long, or 40 cm. Some species have armor plates that make their heads so strong that a gurnard will occasionally ram snorkelers with its forehead if they get too close. Like the flying gurnard, the gurnard has pectoral fins that are divided into a front section and a rear section, with the rear section being larger and the front section highly modified, called walking rays, used by the fish to walk across the sea floor.

Walking rays look more like long, thin, stiff fingers than a fish’s fins, although they’re also bendy. The gurnard has three walking rays on each side of the body, and they have special muscles that allow the fish to actually use them as little legs. It’s really disturbing to watch an otherwise pretty ordinary fish crawl forward on what look like invertebrate legs.

The mudskipper is another fish that uses its fins to walk, but not like the fish we just talked about. Instead of having walking rays, its pectoral fins are muscular and allow it to climb out of the water and onto land. In fact, it can climb into low branches and can even jump.

It’s so good at living on land the mudskipper is actually considered semi-aquatic. It lives in mudflats, mangrove swamps, the mouths of rivers where they empty into the ocean, and along the coast, although it prefers water that’s less salty than the ocean but more salty than ordinary freshwater. It only lives in tropical and subtropical areas because it needs high humidity to absorb oxygen through its skin and the lining of its mouth and throat.

The mudskipper is a fish, but it looks an awful lot like a frog in some ways, due to convergent evolution. It has a wide mouth and froglike eyes at the top of its head and will often float just under the water with its eyes above water, looking for insects it can catch. The largest species grows about a foot long, or 30 cm, and while it has some scales, its body is coated with a layer of mucus to help it retain moisture. It spends most of the day on land, hunting for insects and other small animals. Not only can it absorb oxygen through its skin, it keeps water in its gill chambers to keep the gills wet too. It even has a little dimple under its eye that holds water, that helps keep its eyes moist.

The mudskipper also takes a big mouthful of water with it when it climbs on land, but not to breathe. It uses the water to hunt with. When it encounters an insect or other small animal on land, it carefully rotates its mouth–you heard me right, it can rotate its mouth–so that it’s just above the animal. Then it spits out the mouthful of water onto the insect and immediately sucks the water back into its mouth, carrying the insect with it. When it catches an animal underwater, it opens its big mouth quickly, causing suction that sucks the animal right into its mouth that way. It also has sharp teeth, so when an animal is in its mouth, it’s not getting out again.

The mudskipper’s pectoral fins look like little arms, complete with an elbow. The elbow is actually a joint between the radial bones, which in most fish are hidden within the body but which stick out of the mudskipper’s sides a short distance, and the actual fins. This helps it move around on land more easily. Its pelvic fins are also shaped in such a way that they act as little suction cups on land.

Another bottom-dwelling fish that uses its fins to walk on the sea floor is the walking shark. There are several species known but they’re not very big, only around four feet long at most, or 107 cm. It lives in shallow coastal waters, often around reefs, and spends most of the time swimming just above the sea floor or using its pectoral and pelvic fins to walk on the sea floor while it searches for small animals to eat. It doesn’t walk like gurnards do, and it doesn’t skip or climb the way mudskippers do. Instead, it wriggles like a salamander as it uses its fins to push itself along.

At least one species of walking shark can also walk on land. That’s right: land shark. Don’t worry, it’s harmless to humans. (Still: land shark.) Because the walking shark often lives in really shallow water, including in tidal pools that sometimes dry up completely between high tides, it has to be able to reach water by walking on land. The walking shark can also survive in water with low oxygen content for short periods of time. Four newly identified species of walking shark were announced in January 2020, all from around New Guinea and northern Australia.

The really interesting thing is that the walking shark’s pectoral and pelvic fins are different from other shark fins. Not only are they strongly muscled, they can rotate to make it easier for the shark to use them as legs. Researchers think that this type of locomotion may have given rise to land animals in our far, far-distant ancestors. In other words, we’re all land sharks if you think about it.

You can find Strange Animals Podcast at strangeanimalspodcast.blubrry.net. That’s blueberry without any E’s. If you have questions, comments, or suggestions for future episodes, email us at strangeanimalspodcast@gmail.com. If you like the podcast and want to help us out, leave us a rating and review on Apple Podcasts or Podchaser, or just tell a friend. We also have a Patreon at patreon.com/strangeanimalspodcast if you’d like to support us for as little as one dollar a month and get monthly bonus episodes.

Thanks for listening!

Episode 229: Blue Ghosts and Vanishing Sharks

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I got to meet some listeners this week to see the synchronous fireflies, so thanks to Shannon, Diana, Derek, and Autumn for hanging out with me! This week we’ll learn about a different kind of lightning bug as well as a shark mystery!

Derek’s photography, Enchanting Ectotherms

Further reading:

A shark mystery millions of years in the making

I suspect this is a doctored image but it’s gorgeous so here it is anyway, supposedly some blue ghost fireflies:

This is a real photo, no photoshop, taken by Derek Wheaton during our trip. The long line of light in the middle is a blue ghost moving with its light on during a long exposure:

A synchronous firefly on Derek’s hand (photo by Derek Wheaton):

A tiny blue ghost firefly on Derek’s hand (photo by Derek Wheaton):

Show transcript:

Welcome to Strange Animals Podcast. I’m your host, Kate Shaw. It’s been an amazing week for me because I got to take some people to see our local synchronous fireflies! The fireflies put on a brilliant show for us and the weather was perfect, and it was so much fun to meet Shannon and Diana! Then, two nights later, I also took Derek and Autumn out to see the fireflies. In between, I started research on the blue ghost firefly, since I had originally thought it was just another name for the synchronous firefly, but it’s not. So this week we’re going to learn about the blue ghost firefly, along with some interesting breaking news about a shark mystery.

The blue ghost firefly only lives in parts of the eastern and central United States. In most places it’s rare, but like the synchronous fireflies that all flash together, the blue ghost fireflies are actually pretty common in the southern Appalachian Mountains. The reason why people don’t see them more often is that these days, most people don’t spend much time in the woods at night.

Like other fireflies, the blue ghost lives in forests with deep leaf litter where there’s a lot of moisture in the ground. The female lays her eggs in the leaf litter and when the eggs hatch, the larval fireflies eat tiny insects and other invertebrates like snails.

The blue ghost firefly is different from other firefly species in several ways. First, it doesn’t flash. The male stays lighted up for around a minute at a time while he flies low over the ground watching for a female to light up too. Its glow also appears bluish-white to human eyes, at least in the distance and when it’s really dark out. Up close, it looks yellow-green like other firefly lights. Researchers think it only looks blue because of the way human eyes perceive color in low light.

In the daytime, blue ghost fireflies don’t look like much. They’re small, around 7 mm long, and males are all brown. The females don’t have wings, and in fact they never metamorphose into the adult form and still look like larvae as adults. The female crawls to the end of a twig or blade of grass and glows to attract a mate.

When I was doing my research to learn about blue ghost fireflies, I kept seeing articles comparing its size to a grain of rice. I looked up the average size of a grain of rice, and that’s where I got 7 mm. I didn’t think too much about it.

When Shannon, Diana, and I were watching the synchronous fireflies, we noticed some fireflies that didn’t flash, just stayed glowing while they drifted along low over the forest floor. After I started researching blue ghost fireflies, I realized that was what had seen! So I was especially excited to go back out with Derek and Autumn and confirm it.

Derek works for a nonprofit that breeds endangered fish for conservation projects, which is awesome, but he’s also a photographer, so he brought his camera to try and get pictures and video of the fireflies. His photographs are amazing so if you want to see them I’ve linked to his Facebook page, EnchantingEctotherms, in the show notes. He does a lot of snorkeling so a lot of the animals he photographs are fish or other water animals like turtles and snakes, and he gives information about them in his posts.

Anyway, he wanted to get close-up pictures of a synchronous firefly and a blue ghost firefly, so we all spent some time trying to catch one of each—gently, of course, and without leaving the trail. We didn’t want to hurt ourselves in the dark or disturb the fireflies’ habitat. Derek caught a synchronous firefly first, and it looks like an ordinary firefly that I’m used to, the common eastern firefly, which grows to about 14 mm long. That’s half an inch long. Then, eventually, he also caught a blue ghost. It was so small that at first we thought he might have caught some other beetle by accident, until we looked more closely and saw the telltale head shape of a lightning bug. I took a photo myself and put it in the show notes so you can see just how small it is.

From my own observation, the blue ghosts are much dimmer than other fireflies, which makes sense since they’re so much smaller. The light does look faintly blue-white in the distance, but when it’s closer to you it looks like an ordinary firefly’s light. They do indeed fly very low to the ground while lit up, but they’re also cautious. We had trouble catching one because when we got too close, the firefly would fly down to the ground and put his light out.

Naturally, after photographing our lightning bugs we let them go again. I’m happy to report that the synchronous fireflies have expanded their range a lot since I first stumbled across them about ten years ago, and the blue ghosts seem reasonably common too. They live in a protected area of our local watershed so they’ll be safe and sound forever, hopefully.

This is good, because blue ghosts in particular are vulnerable to habitat loss. Since the female can’t fly, she can’t travel far to lay her eggs. During mating season, some state and national parks in the southern Appalachians close some trails to protect the blue ghost and other fireflies, especially from light pollution from flashlights.

The synchronous fireflies and blue ghosts are only active for a few weeks in June, which is their mating season. We’ll probably be just about at the end of this year’s display by the time you hear this, but if you’re going to be in East Tennessee and want to go out and see them with me next summer, just let me know. As we talked about in episode 180, they only live a few minutes’ walk away from a small parking lot but no one but me seems to know about them.

Next, let’s learn about a shark mystery that’s 19 million years old but that scientists only learned about recently. This month, June of 2021, a team of researchers published results of a shark study in the journal Science. The team had decided to graph the number and diversity of shark species known from the fossil record so they’d have a baseline to compare modern shark diversity to. But they discovered something really surprising.

Nineteen million years ago, there were over ten times as many sharks in the oceans as there are today. They were an important part of the ocean’s ecosystems, especially in the open ocean. And then…they disappear from the fossil record. Over 90% of the world’s sharks died, with shark diversity decreasing by more than 70%. Not only that, sharks never fully recovered from whatever happened.

So what did happen? We don’t know yet. There was a small extinction event called the Middle Miocene extinction peak five million years after the sharks vanished, which researchers think was due to global cooling leading to climate change. The cooling period was caused by a lot of factors, but a big cause was changes in ocean currents and air currents as the continents moved into new positions. Before that, though, the world was comfortably warm for millions of years and the shark population was overall quite stable. Researchers have found no reason why sharks suddenly started dying in such huge numbers, especially in the open ocean instead of in coastal waters.

The leader of the study, Elizabeth Sibert, says that there might have been a climate event of some kind that was disastrous to sharks but that was over relatively quickly, leaving very little evidence behind except for the fossil remains of way more sharks than usual and a lack of sharks afterwards.

Other scientific teams have already started studying the open ocean ecosystem from 19 million years ago and earlier for clues as to what happened, whether other animals were affected, and why sharks never regained their supremacy in the world’s oceans afterwards. That’s how science works: someone makes a discovery and that inspires lots of new studies, which lead to more discoveries. When we do learn more about the great shark die-off of the Miocene, I will keep you posted.

You can find Strange Animals Podcast at strangeanimalspodcast.blubrry.net. That’s blueberry without any E’s. If you have questions, comments, or suggestions for future episodes, email us at strangeanimalspodcast@gmail.com. If you like the podcast and want to help us out, leave us a rating and review on Apple Podcasts or Podchaser, or just tell a friend. We also have a Patreon at patreon.com/strangeanimalspodcast if you’d like to support us that way, and don’t forget to join our mailing list. There’s a link in the show notes.

Thanks for listening!

 

Episode 227: The Great Dying

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It’s another extinction event episode! This one’s about the end-Permian AKA the Permian-Triassic AKA the GREAT DYING.

Further Reading:

Ancient mini-sharks lived longer than thought

Lystrosaurus’s fossilized skeleton:

Lystrosaurus may have looked something like this but I hope not:

This artist’s rendition of lystrosaurus looks a little less horrific but it might not be any more accurate:

Show transcript:

Welcome to Strange Animals Podcast. I’m your host, Kate Shaw.

It’s time for our next extinction event episode, and this week it’s the big one. Not the extinction event that killed the dinosaurs, but one you may not have heard of, one that almost destroyed all life on earth. I mean, obviously it didn’t and things are fine now, but it was touch and go there for a while. It’s the Permian-Triassic extinction event, or end-Permian, which took place just over 250 million years ago. It was so bad that scientists who aren’t given to hyperbole refer to it as the Great Dying.

Don’t worry, we won’t talk about extinction the whole time. We’ll also learn about some interesting animals that survived the extinction event and did just fine afterwards.

We have a better idea of what happened at the end of the Permian than we have about the earlier extinction events we talked about in episodes 205 and 214. Right about 252 million years ago, something caused a massive volcanic eruptive event in what is now Siberia. Some researchers speculate that the cause of the volcanic eruptions may have been a huge asteroid impact on the other side of the Earth, which was so powerful that it caused magma to move away from the impact like water sloshing in a jostled glass. The magma rose up toward the earth’s crust and eventually through it onto the surface.

The result was probably the largest volcanic event in the last half-billion years and it continued for an estimated two million years. Most of the eruptions were probably pretty low-key, just runny lava pouring out of vents in the ground, but there was just so much of it. Lava covered almost a million square miles of land, or 2.6 million square km. Ash and toxic gases from some eruptions also ended up high in the atmosphere, but one big problem was that the lava poured through sediments full of organic material in the process of turning into coal. Lava, of course, is molten rock and it’s incredibly hot. It’s certainly hot enough to burn a bunch of young coal beds, which added more ash and toxic gases to the air—so much ash that shallow water throughout the entire world became choked with ash.

The carbon dioxide released by all that burning coal caused severe ocean acidification and ocean anoxia—a lack of oxygen in the water. But it gets worse! A lot of lava erupted into the ocean right at the continental shelf, where the shallow coastal water becomes much deeper. This is exactly the place where you find methane deposits in the sediments on the ocean floor. When those deposits were suddenly disturbed by lava flowing into them, all the methane in the formerly tranquil depths was released and bubbled to the surface. Methane is a powerful greenhouse gas, meaning that if a whole lot of it ends up in the atmosphere in a short amount of time, it can cause rapid global warming—much faster than that caused by carbon dioxide. This global warming would have happened after a period of global cooling due to reduced sunlight reaching the earth through ash clouds, which lasted long enough and was severe enough that sea levels dropped as glaciers formed. Then everything heated way, way up. The ice caps melted, which may have led to a stagnation of ocean currents. This in turn would have contributed to the water’s anoxicity and toxicity. The average temperature of the ocean would have increased by almost 15 degrees Fahrenheit, or 8 degrees Celsius. Atmospheric warming may have been as much as 68 degrees Fahrenheit in places, or 20 degrees Celsius. That’s not the average temperature of the world, that’s the temperature increase.

So, basically, everything was terrible and it happened very quickly in geologic terms. A 2018 study found that everything looked pretty much fine for the 30,000 years leading up to the great dying. Some researchers even think the initial extinction event might have taken place over just a few centuries.

Marine animals were affected the most, especially marine invertebrates. Trilobites and placoderms went extinct, eurypterids went extinct, and corals went extinct until about 14 million years later when modern corals developed. Some researchers estimate that 95% of all marine species went extinct.

Things were better on land, but not that much better. At the end of the Permian, life was good on land and it was especially good for insects because of the high percentage of oxygen in the air and the variety of plant life in huge swamps around the supercontinent Pangaea. The largest insects that ever lived were buzzing around in the Permian. This included an order of insects called Meganisoptera, or griffinflies. Griffinflies looked like dragonflies and may be related to them. Some species had a wingspan 28 inches across, or 71 cm. The arthropod Anthopleura, sometimes called the giant millipede, lived in the Permian too. Some species grew six feet long, or 2.5 meters, and were about 18 inches wide, or 45 cm. It looked like a millipede but had even more legs. It probably looked scary, but it only ate plants as far as we know.

Instead of actively breathing the way most vertebrates do, most invertebrates use a passive system to absorb oxygen from the air. This is great when there’s a lot of oxygen. When the level of oxygen drops, though, the largest species can’t absorb enough oxygen to function and die out rapidly. That’s one reason why you don’t have to worry about spiders the size of bears. So all the large invertebrates and a lot of the smaller ones went extinct as oxygen was replaced with carbon dioxide, methane, and other toxic gases in the atmosphere.

The acid rain caused by toxic gases and the reduced sunlight caused by ash in the atmosphere also killed off plants. Forests died, so that the fossil record during and after the extinction event contains massive amounts of fungal spores from fungi that decompose trees. Some researchers think all of the world’s trees died. Forests disappeared for some four million years. Since trees absorb carbon dioxide from the atmosphere and release oxygen, the lack of trees made oxygen levels drop even more.

Animals that depended on forests to survive also went extinct, including about two-thirds of all amphibians, reptiles, and therapsids. Therapsids were proto-mammals and it’s a good thing they didn’t all die out because they eventually gave rise to mammals.

Everything I’ve described sounds so incredibly bad, you may be wondering how anything survived. One stroke of luck was probably the size of Pangaea. That was the supercontinent made up of most of the world’s landmasses all smushed together. Before the extinction event, the middle of Pangaea was probably pretty dry with swampier climates around the edges. After the extinction event, the interior of the supercontinent was the safest place to be.

One of the most common land animals after the extinction event was a herbivore called Lystrosaurus. Lystrosaurus was a therapsid, and it was nothing exciting to look at unless you were also a lystrosaurus. Some species were the size of a cat while some were much larger, up to 8 feet long, or 2.5 m. It had a short snout, a short tail, and a semi-sprawling gait. A lizard walks with its legs stuck out to the sides, while a dog or cat or pig walks with its legs underneath its body. Lystrosaurus was somewhere between the two.

It probably lived in burrows that it dug with its strong front legs. While it had a pair of tusks that grew down from the upper jaw, those were its only teeth. Instead it probably had a turtle-like beak that helped it bite off pieces of vegetation.

Lystrosaurus lived in the central part of Pangaea, in what is now Asia, Antarctica, South Africa, and eastern Europe back when all those areas were all scrunched up close together. It survived the extinction event and expanded its range, and for millions of years it was almost the only big land animal in the world. It had almost no predators because they’d all gone extinct, and it had very few competitors for food because they’d all gone extinct. Lystrosaurus made up 90% of all land vertebrates for millions of years.

How did it survive when so many other animals died out? There are several theories, but the most important factor was probably its lack of specialization. It could survive on any kind of plant instead of needing to feed on specific species of plant. There’s also evidence that it could enter a torpor similar to hibernation where its metabolism slowed way down. This would have been a literal lifesaver during the time when the air and water were toxic and very little plant life survived. Lystrosaurus could hunker down in its burrow for long stretches of time, then come out and find enough food and water to keep it going for another stretch of torpor.

Just imagine the world back then, after the initial extinction event but before the world had recovered—say, a million years after the volcanic activity stopped. Picture a series of gentle rolling hills dotted with grazing animals. It’s peaceful and very open because there are no trees. Grass hasn’t evolved yet so the ground is covered in fern-like plants from the genus Dicroidium, which lives in dry conditions. As you look closer with your mind’s eye, you realize that every single one of those grazing animals—thousands of them visible in every direction—are the same kind of animal that looks sort of like a fuzzy pig with a stumpy lizard tail, clawed feet, and a turtle’s beak. Lystrosaurus, living the good life.

In the ocean, the situation was similar. The shallows were toxic waste dumps of ash where the water had so little oxygen that nothing could survive. But the deeper ocean was still livable for some animals.

For a long time, scientists thought a group of early sharks called cladodontomorphs had gone extinct during the great dying. Their distinctive teeth had been common in the fossil record, but after the extinction event they disappeared. Cladodontomorphs only grew about a foot long at most, or 30 cm, and may have had a weird-shaped dorsal fin that pointed forward. They lived in shallow coastal waters. You know, the worst possible place to be 252 million years ago.

Then palaeontologists found some of those teeth in rocks that were in much deeper water 135 million years ago. It turns out the little sharks had survived the extinction event by moving into the open ocean where conditions were better. And they didn’t just survive, they lasted for another 120 million years.

So let’s break it down. It was probably four million years before trees developed again from different plants. It was some 14 million years before coral reefs could rebuild as modern corals developed after their cousins went extinct. It took 30 million years for terrestrial vertebrates to recover from the great dying and 50 million years for all the ocean’s ecosystems to fully recover. That’s a colossally long time. But it did recover.

So what animals arose once the recovery was well underway? Icthyosaurs. Archosaurs, which eventually evolved into pterosaurs, crocodilians, dinosaurs, and birds. And therapsids that eventually gave rise to modern mammals.

I don’t usually tease the following week’s show, but next week we’re going to learn about some weird and interesting animals that developed in the early to mid Triassic, after the extinction event was over and life started evolving in new directions. As I’ve said in the previous extinction event episodes: no matter how bad things get, there’s always going to be some little animal stumping along out of the carnage to get on with the business of surviving and thriving.

You can find Strange Animals Podcast at strangeanimalspodcast.blubrry.net. That’s blueberry without any E’s. If you have questions, comments, or suggestions for future episodes, email us at strangeanimalspodcast@gmail.com. If you like the podcast and want to help us out, leave us a rating and review on Apple Podcasts or Podchaser, or just tell a friend. We also have a Patreon at patreon.com/strangeanimalspodcast if you’d like to support us that way.

Thanks for listening!

Episode 216: Gentle Giant Sharks

Let’s learn about some of the biggest sharks in the sea–but not sharks that want to eat you!

Further reading:

‘Winged’ eagle shark soared through oceans 93 million years ago

Manta-like planktivorous sharks in Late Cretaceous oceans

Before giant plankton-eating sharks, there were giant plankton-eating sharks

An artist’s impression of the eagle shark (Aquilolamna milarcae):

Manta rays:

A manta ray with its mouth closed and cephalic fins rolled up:

Pseudomegachasma’s tooth sitting on someone’s thumbnail (left, photo by E.V. Popov) and a Megachasma (megamouth) tooth on someone’s fingers (right):

The megamouth shark. I wonder where its name came from?

The basking shark, also with a mega mouth:

The whale shark:

Leedsichthys problematicus (not a shark):

Show transcript:

Welcome to Strange Animals Podcast. I’m your host, Kate Shaw.

This week we’re going to look at some huge, weird sharks, but they’re not what you may expect when you hear the word shark. Welcome to the strange world of giant filter feeders!

This episode is inspired by an article in the brand new issue of Science, which you may have heard about online. A new species of shark is described in that issue, called the eagle shark because of the shape of its pectoral fins. They’re long and slender like wings.

The fossil was discovered in 2012 in northeastern Mexico, but not by paleontologists. It came to light in a limestone quarry, where apparently a quarry worker found it. What happened to it at that point isn’t clear, but it was put up for sale. The problem is that Mexico naturally wants fossils found in Mexico to stay in Mexico, and the authors of the study are not Mexican. One of the authors has a history of shady dealings with fossil smugglers too. On the other hand, the fossil has made its way back to Mexico at last and will soon be on display at a new museum in Nuevo León.

Fossils from this quarry are often extremely well preserved, and the eagle shark is no exception. Sharks don’t fossilize well since a shark’s skeleton is made of cartilage except for its teeth, but not only is the eagle shark’s skeleton well preserved, we even have an impression of its soft tissue.

The eagle shark was just slightly shorter than 5 ½ feet long, or 1.65 meters. Its tail looks like an ordinary shark tail but that’s the only ordinary thing about it. The head is short and wide, without the long snout that most sharks have, it doesn’t appear to have dorsal or pelvic fins, and its pectoral fins, as I mentioned a minute ago, are really long. How long? From the tip of one pectoral fin to the other measures 6.2 feet, or 1.9 meters. That’s longer than the whole body.

Researchers think the eagle shark was a filter feeder. Its mouth would have been wide to engulf more water, which it then filtered through gill rakers or some other structure that separated tiny animals from the water. It expelled the water through its gills and swallowed the food.

The eagle shark would have been a relatively slow swimmer. It glided through the water, possibly flapping its long fins slowly in a method called suspension feeding, sometimes called underwater flight. If this makes you think of manta rays, you are exactly correct. The eagle shark occupied the same ecological niche that manta rays do today, and the similarities in body form are due to convergent evolution. Rays and sharks are closely related, but the eagle shark and the manta ray evolved suspension feeding separately. In fact, the eagle shark lived 93 million years ago, 30 million years before the first manta remains appear in the fossil record.

The eagle shark lived in the Western Interior Seaway, a shallow sea that stretched from what is now the Gulf of Mexico straight up through the middle of North America. Because it’s the only specimen found so far, we don’t know when it went extinct, but researchers suspect it died out 65 million years ago at the same time as the non-avian dinosaurs. We also don’t have any preserved teeth, which makes it hard to determine what sharks it was most closely related to. Hopefully more specimens will turn up soon.

Now that we’ve mentioned the manta ray, let’s talk about it briefly even though it’s not a shark. It is big, though, and it’s a filter feeder. If you’ve never seen one before, they’re hard to describe. If it had gone extinct before humans started looking at fossils scientifically, we’d be as astounded by it as we are about the eagle shark—maybe even moreso because it’s so much bigger. Its body is sort of diamond-shaped, with a blunt head and short tail, but elongated fins that are broad at the base but end in drawn-out points.

Manta rays are measured in width, sometimes called a wingspan since their long fins resemble wings that allow it to fly underwater. There are two species of manta ray, and even the smaller one has a wingspan of 18 feet, or 5.5 meters. The larger species can grow 23 feet across, or 7 meters. Some other rays are filter feeders too, all of them closely related to the manta.

The manta ray lives in warm oceans, where it eats zooplankton. Its mouth is wide and when it’s feeding it moves forward with its mouth open, letting water flow into the mouth and through the gills. Gill rakers collect tiny food, which the manta ray swallows. It has a pair of fins on either side of the mouth that are sometimes called horns, but which are properly called cephalic fins. Cephalic just means “on the head.” These fins help direct water into the mouth. When a manta ray isn’t feeding, it closes its mouth just like any other shark, folding its shallow jaw shut. For years I thought it closed its mouth by folding the cephalic fins over it, but that’s not the case, although it does roll the fins up into little points. The manta ray is mostly black with a white belly, but some individuals have white markings on the back and black speckles and splotches underneath. We talked about some mysteries associated with its coloring in episode 96.

The eagle shark isn’t the only filter feeding shark. The earliest known is Pseudomegachasma, the false megamouth, which lived around 100 million years ago. It was only described in 2015 after some tiny shark teeth were found in Russia. The teeth looked like those of the modern megamouth shark, although they’re probably not related. The teeth are only a few millimeters long but that’s the same size as teeth from the megamouth shark, and the megamouth grows 18 feet long, or 5.5 m.

Despite its size, the megamouth shark wasn’t discovered until 1976, and it was only found by complete chance. On November 15 of that year, a U.S. Navy research ship off the coast of Hawaii pulled up its sea anchors. Sea anchors aren’t like the anchors you may be thinking of, the big metal ones that drop to the ocean’s bottom to keep a ship stationary. A sea anchor is more like an underwater parachute for ships. It’s attached to the ship with a long rope on one end, and opens up just like a parachute underwater. The tip of the parachute has another rope attached with a float on top. When the navy ship brought up its sea anchors, an unlucky shark was tangled up in one of them. The shark was over 14 ½ feet long, or 4 ½ m, and didn’t look like any shark anyone had ever seen.

The shark was hauled on board and the navy consulted marine biologists around the country. No one knew what the shark was. It wasn’t just new to science, it was radically different from all other sharks known. Since then, only about 100 megamouth sharks have ever been sighted, so very little is known about it even now.

The megamouth is dark brown in color with a white belly, a wide head and body, and a large, wide mouth. The inside of its lower lip is a pale silvery color that reflects light, although researchers aren’t sure if it acts as a lure for the tiny plankton it eats, or if it’s a way for megamouths to identify each other. It’s sluggish and spends most of its time in deep water, although it comes closer to the surface at night.

The basking shark is even bigger than the megamouth. It can grow up to 36 feet long, or 11 meters. It’s so big it’s sometimes mistaken for the great white shark, but it has a humongous wide mouth and unusually long gill slits, and, of course, its teeth are teensy. It’s usually dark brown or black, white underneath, and while it spends a lot of its time feeding at the surface of the ocean, in cold weather it spends most of its time in deep water. In summer, basking sharks gather in small groups to breed, and sometimes will engage in slow, ponderous courtship dances that involve swimming in circles nose to tail.

But the biggest filter feeder shark alive today, and possibly alive ever, is the whale shark. It gets its name because it is literally as large as some whales. It can grow up to 62 feet long, or 18.8 meters, and potentially longer.

The whale shark is remarkably pretty. It’s dark gray with a white belly, and its body is covered with little white or pale gray spots that look like stars on a night sky. Its mouth is extremely large and wide, and its small eyes are low on the head and point downward. Not only can it retract its eyeballs into their sockets, the eyeballs actually have little armored denticles to protect them from damage. The body also has denticles, plus the whale shark’s skin is six inches thick, or 15 cm.

The whale shark lives in warm water and migrates long distances. It mostly feeds near the surface although it sometimes dives deeply to find plankton. It filters water differently from the megamouth and basking sharks, which use gill rakers. The whale shark has sieve-like filter pads instead. The whale shark doesn’t need to move to feed, either. It can gulp water into its mouth by opening and closing its jaws, unlike the other living filter feeders we’ve talked about so far.

We talked about the whale shark a lot in episode 87, if you want to know more about it.

All these sharks are completely harmless to humans, but unfortunately humans are dangerous to the sharks. Even though they’re all protected, they’re vulnerable to getting tangled in nets, killed by ships running over them, and killed by poachers.

One interesting thing about these three massive filter feeding sharks is their teeth. They all have tiny teeth, but the mystery is why they have teeth at all. Their teeth aren’t just tiny, they have a LOT of teeth, more than ordinary sharks do. It’s the same for the filter feeding rays. They have hundreds of teensy teeth that the animals don’t use for anything, as far as researchers can tell. One theory is that the babies may use their teeth before they’re born. All of the living filter feeders we’ve talked about, including manta rays, give birth to live pups instead of laying eggs. The eggs are retained in the mother’s body while they grow, and she can have numerous babies growing at different stages of development at the same time. The babies have to eat something while they’re developing, once the yolk in the egg is depleted, and unlike mammals, fish don’t nourish their babies through umbilical cords. Some researchers think the growing sharks eat the mother’s unfertilized eggs, and to do that they need teeth to grab hold of slippery eggs. That still doesn’t explain why adults retain the teeth and even replace them throughout their lives just like other sharks. Since all of the filter feeders have teeth although they’re not related, the teeth must confer some benefit.

So, why are these filter feeders so enormous? Many baleen whales are enormous too, and baleen whales are also filter feeders. Naturally, filter feeders need large mouths so they can take in more water and filter more food out of it. As a species evolves a larger mouth, it also evolves a larger body, and this has some useful side effects. A large animal retains heat even if it’s not actually warm-blooded. A giant fish can live comfortably in cold water as a result. Filter feeding also requires much less effort than chasing other animals, so a giant filter feeder has plenty of energy for a relatively low intake of food. And, of course, the larger an animal is, the fewer predators it has because there aren’t all that many giant predators. At a certain point, an adult giant animal literally has no predators. Nothing attacks an adult blue whale, not even the biggest shark living today. Even a really big great white shark isn’t going to bite a blue whale. The blue whale would just bump the shark out of the way and probably go, “HEY, STOP IT, THAT TICKLES.” The exception, of course, is humans, who used to kill blue whales, but you know what I mean.

Let’s finish with a filter feeder that isn’t a shark. It’s not even closely related to sharks. It’s a ray-finned fish that lived around 165 million years ago, Leedsichthys problematicus. Despite not being related to sharks and being a member of what are called bony fish, its skeleton is partially made of cartilage, so fossilized specimens are incomplete, which is why it was named problematicus. Because the fragmented fossils are a problem. I’m genuinely not making this up to crack a dad joke, that’s exactly why it got its name. One specimen is made up of 1,133 pieces, disarticulated. That means the pieces are all jumbled up. Worst puzzle ever. Remains of Leedsichthys have been found in Europe and South America.

As a result, we’re not completely sure how big Leedsichthys was. The most widely accepted length is 50 feet long, or 16 meters. If that’s anywhere near correct, it would make it the largest ray-finned fish that ever lived, as far as we know. It might have been much larger than that, though, possibly as long as 65 feet, or 20 meters.

Leedsichthys had a big head with a mouth that could open extremely wide, which shouldn’t surprise you. Its gills had gill rakers that it used to filter plankton from the water. And we’re coming back around to where we started, because like the eagle shark, Leedsichthys had long, narrow pectoral fins. Some palaeontologists think it had a pair of smaller pelvic fins right behind the pectoral fins instead of near the tail, but other palaeontologists think it had no pelvic fins at all. Because we don’t have a complete specimen, there’s still a lot we don’t know about Leedsichthys.

The first Leedsichthys specimen was found in 1886 in a loam pit in England, by a man whose last name was Leeds, if you’re wondering where that part of the name came from. A geologist examined the remains and concluded that they were part of (wait for it) a type of stegosaur called Omosaurus. Two years later the famous early palaeontologist Othniel Marsh examined the fossils, probably rolled his eyes, and identified them as parts of a really big fish skull.

In 1899, more fossils turned up in the same loam pits and were bought by the University of Cambridge. IA palaeontologist examined them and determined that they were (wait for it) the tail spikes of Omosaurus. Leeds pointed out that nope, they were dorsal fin rays of a giant fish, which by that time had been named Leedsichthys problematicus.

In 1982, some amateur palaeontologists excavated some fossils in Germany, but they were also initially identified as a type of stegosaur—not Omosaurus this time, though. Lexovisaurus. I guess this particular giant fish really has been a giant problem.

You can find Strange Animals Podcast at strangeanimalspodcast.blubrry.net. That’s blueberry without any E’s. If you have questions, comments, or suggestions for future episodes, email us at strangeanimalspodcast@gmail.com. If you like the podcast and want to help us out, leave us a rating and review on Apple Podcasts or just tell a friend. We also have a Patreon at patreon.com/strangeanimalspodcast if you’d like to support us that way.

Thanks for listening!

Episode 168: The Longest Lived

This week let’s take a look at some animals (and other living organisms) that live the longest!

This isn’t Methuselah itself (scientists aren’t saying which tree it is, to keep it safe), but it’s a bristlecone pine:

The Jaya Sri Maha Bodhi, a sacred fig tree in Sri Lanka, planted in 288 BCE by a king:

Some trees of the quaking aspen colony called Pando:

Glass sponges (this one’s called the Venus Flower Basket):

Further reading:

Glass sponge as a living climate archive

Show transcript:

Welcome to Strange Animals Podcast. I’m your host, Kate Shaw.

This week we’re going to look at the world’s longest lived animals and other organisms. We’re straying into plant territory a little bit here, but I think you’ll agree that this is some fascinating information.

The oldest human whose age we can verify was a French woman who lived to be 122 years old, plus 164 days. Her name was Jeanne Calment and she came from a long-lived family. Her brother lived to the age of 97. Jeanne was born in 1875 and didn’t die until 1997. But the sad thing is, she outlived her entire family. She had a daughter who died of a lung disease called pleurisy at only 36 years old—in fact, on her 36th birthday—and her only grandson died in a car wreck in his late 30s. Jeanne remained healthy physically and mentally until nearly the end of her life, although she had always had poor eyesight.

It’s not all that rare for humans to live past the age of 100, but it is rare for anyone to live to age 110 or beyond. But other animals have average lifespans that are much, much longer than that of humans.

In episode 163 we talked about the Greenland shark, which can live for hundreds of years. The oldest Greenland shark examined was possibly as old as 512 years old, and the sharks may live much longer than that. It’s actually the longest-lived vertebrate known.

No one’s sure which terrestrial vertebrate lives the longest, but it’s probably a tortoise. Giant tortoises are famous for their longevity, routinely living beyond age 100 and sometimes more than 200 years old. The difficulty of verifying a tortoise’s age is that to humans, tortoises all look pretty much alike and we don’t always know exactly when a particular tortoise was hatched. Plus, of course, we know even less about tortoises in the wild than we do ones kept in captivity. But probably the oldest known is an Aldabra giant tortoise that may have been 255 years old when it died in 2006. We talked about giant tortoises in episode 95.

But for the really long-lived creatures, we have to look at the plant world. The oldest individual tree whose age we know for certain is a Great Basin bristlecone pine called Methuselah. Methuselah lives in the Inyo National Forest in the White Mountains in California, which of course is on the west coast of North America. In 1957 a core sample was taken from it and other bristlecone pines that grow in what’s called the ancient bristlecone pine forest. Many trees show growth rings in the trunk that make a pattern that’s easy to count, so the tree’s age is easy to determine as long as you have someone who is patient enough to count all the rings. Well, Methuselah was 4,789 years old in 1957. It probably germinated in 2833 BCE. Other trees in the forest were nearly as old, with at least one possibly older, but the sample from that older tree is lost and no one’s sure where the tree the sample came from is.

Another bristlecone pine, called the Prometheus Tree, germinated even earlier than Methuselah, probably in 2880 BCE, but it’s now dead. A grad student cut it down in 1964, possibly by accident—stories vary and no one actually knows why he cut the tree down. The bristlecone pine is now a protected species.

There are other trees estimated to be as old as Methuselah. This includes a yew in North Wales that may be 5,000 years old and is probably at least 4,000 years old, and a cypress in Iran that’s at least 2,000 years old and possibly 5,000 years old. Sequoyahs from western North America, baobabs from Africa, and kauri trees from New Zealand are all documented to live over a thousand years and possibly many thousands of years.

In at least one case, a sacred fig tree in Sri Lanka, we know exactly when the tree was planted. A Buddhist nun brought a branch of the original sacred fig tree, the one that the Buddha was sitting under when he achieved enlightenment, to Sri Lanka and presented it to King Devanampiya Tissa. He planted the branch in the royal park in 288 BCE, where it grew into a tree which remains in the park to this day, more than 2,000 years later. It’s cared for by Buddhists monks and people come from all over Sri Lanka to visit the tree. If this sounds a little too good to be true, the easiest way to grow a sacred fig is to use a cutting from another tree. The cutting will root and grow into a new tree.

Not all trees are individuals. You may not know this and I didn’t either until recently. Some trees grow as colonies. The most well known tree colony is called Pando, made up of quaking aspens that live in Utah in North America. While the individual trees are only around 130 years old on average, Pando itself has been alive for an estimated 80,000 years. Each tree is a male clone and all the trees are connected by a root system that covers 106 acres, or 43 hectares. Because its root system is so huge and deep, Pando is able to survive forest fires that kill all other trees. Pando’s trees die, but afterwards the roots just send up shoots that grow into new trees. Researchers estimate that it’s been 10,000 years since Pando’s trees actually flowered. Unfortunately, Pando is currently threatened by humans stopping the forest fires that otherwise would kill off rival trees, and threatened by grazing livestock that kill off young trees before they can become established.

Pando isn’t the only quaking aspen colony known, though. There are a number of smaller colonies in western North America. Researchers think it’s an adaptation to frequent forest fires and a semi-arid climate that makes it harder for seedlings to grow. Quaking aspens that live in northeastern North America, where the climate is much wetter, grow from seeds instead of forming colonies.

Other species of tree form colonies too, including a spruce tree in Sweden whose root system dates to nearly 10,000 years ago and a pine colony in Tasmania that is about the same age but with individual trees that are themselves 3,000 years old. Not all long-lived plant colonies are trees, though. A colony of sea grass in the Mediterranean may be as much as 200,000 years old although it may be only 12,000 years old, researchers aren’t sure.

I could go on and on about long-lived plants, but let’s get back to the animals. If the Greenland shark is the longest lived vertebrate known, what’s the longest lived invertebrate? Here’s your reminder that a vertebrate is an animal with some form of spine, while an invertebrate has no spine.

Many invertebrates that live in the ocean have long lifespans. Corals of various kinds can live for thousands of years, for instance. The ocean quahog, a type of clam that lives in the North Atlantic Ocean, grows very slowly compared to other clams. It isn’t fully mature until it’s nearly six years old, and populations that live in cold water can live a long time. Sort of like tree rings, the age of a clam can be determined by counting the growth rings on its shell, and a particular clam dredged up from the coast of Iceland in 2006 was discovered to be 507 years old. Its age was double-checked by carbon-14 dating of the shell, which verified that it was indeed just over 500 years old when it was caught and died. Researchers aren’t sure how long the quahog can live, but it’s a safe bet that there are some alive today that are older than 507 years, possibly a lot older.

But the invertebrate that probably lives the longest is the glass sponge. It’s found throughout the world’s oceans, but is especially common in cold waters of the Northern Pacific and Antarctic. It usually grows up to about a foot tall, or 30 cm, although some species grow larger, and is roughly shaped like a vase. Most species are white or pale in color. In some places the sponges fuse together to form reefs, with the largest found so far 65 feet tall, or 20 meters, and nearly four and a half miles long, or 7 km.

The glass sponge is a simple creature with a lattice-like skeleton made of silica covered with porous tissue. It anchors itself to a rock or the ocean floor, frequently in deep water, and as water flows through the openings in its body, it filters microscopic food out. So it basically lives a very slow, very plant-like existence.

One glass sponge, Monorhaphis chuni, anchors itself to the sea floor with a long basal spicule that looks like a stem. This stem can be over nine feet long, or 3 m. It needs to be long because it lives in deep water where there’s a lot of soft sediment at the bottom. In 1986 the skeleton of a dead Monorhaphis was collected from the East China Sea so it could be studied. Since a glass sponge adds layers of skeleton to its basal spicule every year as it grows, you guessed it, the layers can be counted just like tree rings—although it requires an electron microscope to count since the layers are very small. The sponge was determined to be about 11,000 years old when it died. Researchers are able to determine local ocean temperature changes from year to year by studying the rings, just as tree rings give us information about local climate.

Let’s finish with something called an endolith. An endolith isn’t a particular animal or even a group of related animals. An endolith is an organism that lives inside a rock or other rock-like substance, such as coral. Some are fungi, some lichens, some amoebas, some bacteria, and various other organisms, many of them single-celled and all of them very small if not microscopic. Some live in tiny cracks in a rock, some live in porous rocks that have space between grains of mineral, some bore into the rock. Many are considered extremophiles, living in rocks inside Antarctic permafrost, at the tops of the highest mountains, in the abyssal depths of the oceans, and at least two miles, or 3 km, below the earth’s surface.

Various endoliths live on different minerals, including potassium, sulfur, and iron. Some endoliths even eat other endoliths. We don’t know a whole lot about them, but studies of endoliths found in soil deep beneath the ocean’s floor suggest that they grow extremely slowly. Like, from one generation to the next could be as long as 10,000 years, with the oldest endoliths potentially being millions of years old—even as old as the sediment itself, which dates to 100 million years old.

That is way older than Jeanne Calment and all those trees.

You can find Strange Animals Podcast online at strangeanimalspodcast.blubrry.net. That’s blueberry without any E’s. If you have questions, comments, or suggestions for future episodes, email us at strangeanimalspodcast@gmail.com. If you like the podcast and want to help us out, leave a rating and review on Apple Podcasts or wherever you listen to podcasts. We also have a Patreon at patreon.com/strangeanimalspodcast if you’d like to support us that way.

Thanks for listening!

Episode 163: Three Weird Fish

Thanks to Nathan for his suggestions! This week we’re going to learn about three strange and interesting fish!

A northern snakehead:

A giant snakehead:

A Greenland shark, fish of mystery:

The upside-down catfish is indeed upside down a lot of the time (this is actually a picture of Synodontis nigriventris, closely related to the upside-down catfish we talk about in the episode):

An ancient Egyptian upside-down catfish pendant that ladies wore in their hair:

Show transcript:

Welcome to Strange Animals Podcast. I’m your host, Kate Shaw.

We haven’t done a fish episode in a while, so this week let’s learn about three weird fish. Thanks to Nathan for suggesting the first two fish, the snakehead and the Greenland shark.

The snakehead is a freshwater fish that gets its name because while it’s an ordinary-looking fish for the most part, it has a flattened head that looks a little bit like a snake’s. Different species of snakehead look different in other ways, of course, so let’s examine a couple of typical species.

The northern snakehead is native to Asia, but it’s been introduced into other parts of the world by accident or as a food fish. It’s one of the largest species, with reports of some specimens growing up to five feet long, or 1.5 meters. It’s usually no more than three feet long, though, or 1 meter. It’s brown with darker blotches and has sharp teeth that it uses to catch fish, frogs, and other small animals.

Like other snakeheads, the northern snakehead can breathe air and survive out of water for several days as long as it stays damp. Young snakeheads can even wriggle considerable distances on land to find water. It likes stagnant or slow-moving water.

Because it’s a fierce predator that can find its way to new waterways, introduced snakeheads are invasive species that can cause havoc to populations of native fish. The northern snakehead has been introduced into many waterways in the United States in the last twenty years, as a result of people releasing unwanted aquarium fish and accidental release of snakeheads in fish-farming operations. Since snakeheads reach mature age quickly and females can lay thousands of eggs at a time, snakeheads are illegal to own in many places now and release snakeheads into the wild is even more against the law.

The giant snakehead also grows up to five feet long, or 1.5 m, and is from parts of southeast Asia. Young giant snakeheads are red, but when they grow up they’re black and white with a thick black stripe down each side. It’s also been introduced into a lot of places as a food fish and a game fish, but since it’s a tropical species it can’t survive colder weather and isn’t as invasive as a result, at least not outside of tropical and subtropical areas.

The giant snakehead can be aggressive, though, especially when it’s guarding its nest. Both parents act as guards of the eggs and the newly hatched babies, which follow their mother around wherever she goes. That’s actually really cute.

Next let’s talk about the Greenland shark. We covered it briefly in episode 74, about colossal squid and the things that eat them, but mostly we talked about its close relative the sleeper shark. The Greenland shark is similar in some ways but it’s much bigger than the sleeper shark. It lives in the North Atlantic and Arctic Oceans where the water is barely warmer than the freezing point and it grows up to 24 feet long, or 7.3 meters, with females being larger than males.

But despite how enormous it is, it’s not a shark you need to worry about. First of all, what are you doing swimming in water that cold? Second, the Greenland shark is a slow swimmer, no more than about 1 ½ miles per hour, or 2.6 km/h. You can walk faster than that without even trying. You can probably dog-paddle faster than that.

And yet, the Greenland shark manages to eat seals and fish and other animals that move quickly. Since no one’s actually observed a Greenland shark hunting, no one knows how they catch prey. Some researchers speculate that it sneaks up on sleeping seals and grabs them. It also eats a lot of carrion, including dead moose and reindeer and polar bears that fall into the water and drown. One shark was found with an entire reindeer in its stomach.

The Greenland shark spends winter in shallow water where it’s warmer, but in summer it spends more time in deep water. At least one submersible observed a Greenland shark 7,200 feet below the surface of the ocean, or 2,200 meters. Occasionally a Greenland shark travels more widely, usually in deep water where the water is cold. In 2013 one was caught by researchers in the Gulf of Mexico, which is way far away from the Arctic. It was swimming at over 5,700 feet deep, or 1,750 meters.

The Greenland shark is adapted to the cold and pressure of the deep sea in many ways. Its blood contains three types of hemoglobin, which help it absorb as much oxygen as possible from water that’s poorly oxygenated to start with. Its muscles and other tissues contain high levels of urea and other compounds that increase its buoyancy, so that it doesn’t need to work as hard to stay in one place. But the presence of urea in its muscles means that the Greenland shark not only tastes horrible, it’s toxic. In Iceland Greenland sharks are considered a delicacy, but only after the toxins have been removed from the meat by long treatment. This includes burying it in the ground for weeks, partially fermenting it, and drying it for several months afterwards. Most people don’t bother and any commercial fishing boats that catch Greenland sharks just toss them back overboard.

The Greenland shark has a very slow metabolism and grows extremely slowly too. That’s okay, though, because it lives a very long time. A VERY long time. The biggest Greenland sharks may be as much as 600 years old. Researchers examine the crystals in dead Greenland shark eyeballs to determine when they were hatched.

And speaking of Greenland shark eyeballs…some of you know where this is going. I hope you’re not eating grapes or anything right now. There’s a type of copepod, a crustacean, that acts as a parasite of the Greenland shark and the Pacific sleeper shark, its close relative. The copepod grows to about an inch long, or 28 mm, and attaches itself to the shark’s cornea, which is part of the eyeball. This impairs the shark’s vision but it doesn’t seem to care and it doesn’t seem to have any trouble finding food.

Okay let’s stop talking about that. Our third and final weird fish for this episode is a type of catfish that’s sometimes kept in aquariums. It’s called the upside-down catfish.

There are actually a number of closely-related catfish known as upside-down catfish, but the one we’ll talk about today is Synodontis batensoda. It lives in parts of Africa in marshy areas and slow-moving water. It grows to a little over a foot and a half long, or 50 cm, and eats plankton, algae, mollusks, insects and larvae, and crustaceans.

But the upside-down catfish gets its name from its habit of swimming upside down. Because it’s kept as an aquarium fish so often, many people assume that the upside-down swimming is something it developed because it’s kept in an enclosed aquarium habitat. But that’s actually not the case.

The catfish used to be well-known in Egypt, and there’s even an Egyptian tomb carving depicting a catfish swimming upside down, dating to the Middle Kingdom around 4,000 years ago. The upside-down catfish was often depicted in jewelry, too, including hair ornaments so beautifully made that the species of catfish can be determined. Young women in Egypt traditionally wore fish ornaments to decorate their braids. There’s a story about one young woman who was helping row a king across a lake when her fish pendant fell into the water. She stopped rowing, naturally, which messed up the other rowers. The king wanted to know why the boat had stopped, and when the woman explained, he offered to give her a new fish pendant. But no, she said, she wanted that one, the one that was now at the bottom of the lake. But the king had a magician who said no problem, and caused the water to fold back like a blanket, exposing the lake’s bottom so the pendant could be retrieved. I didn’t make that story up, either. It’s from the Westcar Papyrus that dates to around the 17th century BCE.

So why does the upside-down catfish swim upside down? Like other catfish, its mouth is angled downward so it can find food in the mud at the bottom of the water. So when it wants to grab an insect on the water’s surface, or eat algae off the bottom of a submerged leaf, it can only do so by turning upside down.

So that’s it for this week’s episode. I don’t know what else to say because I’m just sitting here trying to imagine how I’d manage if someone told me I had to swim upside down. But then, I can barely swim right side up. Good job, upside-down catfish!

You can find Strange Animals Podcast online at strangeanimalspodcast.blubrry.net. That’s blueberry without any E’s. If you have questions, comments, or suggestions for future episodes, email us at strangeanimalspodcast@gmail.com. We also have a Patreon at patreon.com/strangeanimalspodcast if you’d like to support us and get twice-monthly bonus episodes for as little as one dollar a month.

Thanks for listening!