Category Archives: sharks

Episode 463: The Big Fish Episode

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It’s an episode just absolutely full of fish! Thanks to Arthur, Yuzu, Jayson, Kabir, Nora, Siya, Joel, Elizabeth, Mac, Ryder, Alyx, Dean, and Riley for their suggestions this week!

Further reading:

Study uncovers mechanics of machete-like ‘tail-whipping’ in thresher sharks

Business end of a sawfish:

Giant freshwater stingray!

The frilled shark looks like an eel:

The frilled shark’s teeth:

The thresher shark and its whip-like tail [photo by Thomas Alexander – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=50280277]:

The Halmahera epaulette shark, looking a little bit like a long skinny koi fish [photo by Mark Erdmann, California Academy of Sciences, Attribution, https://commons.wikimedia.org/w/index.php?curid=30260864]:

A mudskipper, which is a fish even though it kind of looks like a weird frog [photo by Heinonlein – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=44502355]:

The red-lipped batfish wants a big kiss:

The male blue groper is very blue [photo by Andrew Harvey, some rights reserved (CC BY) – https://www.inaturalist.org/photos/62196538, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=157789928]:

The giant oarfish is very long:

Show transcript:

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

This week we have a big fish episode! I mean, it’s a big episode about a lot of different fish, not necessarily fish that are big—although some of them sure are! Thanks to Arthur, Yuzu, Jayson, Kabir, Nora, Siya, Joel, Elizabeth, Mac, Ryder, Alyx, Dean, and Riley. I told you this is a big fish episode.

Let’s jump right in with a fish suggested by Jayson, the sawfish. There are five species of sawfish alive today. The smallest 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.

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 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 most sharks: 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.

Since the sawfish has plenty of teeth in its mouth, you may be wondering how and why it also has extra teeth on both sides of its saw. It’s because the rostral teeth evolved from dermal denticles.

Dermal denticles look like scales but they’re literally teeth, they’re just not used for eating. Sharks have them too, along with some other fish. In the case of the sawfish, the rostral teeth grow much larger than an ordinary dermal denticle, and stick out sideways.

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. That’s also why it doesn’t want to eat people. Its mouth is too small.

Yuzu wanted to learn about another shark relation, the giant freshwater stingray, which lives in rivers in southeast Asia. It’s dark gray-brown on its back and white underneath, and it has a little pointy nose at the front of its disc. It also has dermal denticles on its back.

The giant freshwater stingray has a rounded, flattened body, and it’s really big. A big female can grow over 7 feet across, or 2.2 meters. Its tail is long and thin with the largest spine of any stingray known, up to 15 inches long, or 38 cm. Its tail is so long that if you measure the giant freshwater stingray by length including its tail, instead of by width of its disc, it can be as much as 16 feet long, or about 5 meters. Some researchers think there might be individuals out there much larger than any ever measured, possibly up to 16 feet wide. The length and thinness of the tail gives the ray its other common name, the giant freshwater whipray, because its tail looks like a whip.

While we’re talking about shark relations, let’s go ahead and talk about a few actual sharks. Kabir wanted to learn about the frilled shark, which looks and acts more like an eel than a shark. A big female can grow up to 6 and a half feet long, or 2 meters. Males are a little shorter on average. The frilled shark has the same anatomy found in ancient sharks from the fossil record, dating back at least 95 million years. It’s found a body type that works for it.

The frilled shark lives on the continental shelf in many parts of the world, and while it technically lives near the sea floor, at night it migrates closer to the ocean surface to find fish, squid and other cephalopods, and other food. There are two species known, with the southern African frilled shark only discovered in 2009.

The frilled shark is dark brown or gray, and its jaws are long and contain clusters of teeth in little rows. Each tooth has three sharp points, and there are 300 teeth, so a frilled shark has 900 points in its mouth. The points are so sharp that scientists examining dead sharks have gotten cut on the teeth, which would be really embarrassing if you’re a shark expert that was bitten by a dead shark. The frilled shark can open its jaws extremely wide to swallow fish and other animals that are up to about half the size of the shark itself. It even eats other sharks.

Next, Joel wanted to learn about the thresher shark. It’s a truly big fish that can grow up to 20 feet long, or over 6 meters. It’s a fast, slender shark with a tail fin that can be as long as its body. It eats a lot of other animals, including birds and crustaceans, but it specializes in hunting fish that travel in schools, like tuna, sardines, and mackerel. It uses its incredibly long tail as a whip, slapping a fish to stun it so the shark can eat it. When it whips its tail, its body flexes so that its head points downward in the water with the tail snapping forward over it. A 2024 study determined that the thresher shark’s vertebral column is fortified to allow it to work like a catapult. The thresher shark can also use its long tail to help it leap out of the water completely, although scientists don’t know why it wants to do that.

There are three species of thresher shark known to science, but in 1995 a genetic analysis revealed the possible presence of a fourth species. Scientists think it lives in the eastern Pacific and may look similar to the bigeye thresher, enough that it gets misidentified as that species when it’s seen. The three known species of thresher shark are hard to tell apart at a distance as it is.

And for our last shark, Siya asked about the Halmahera epaulette shark. It’s light brown with darker and lighter spots, and is a slender shark that can grow a little over 2 feet long, or 68 cm. It lives around Indonesia, and it might live in other places too. We don’t know yet, because it was only discovered in 2013 and only two specimens have ever been found.

Epaulette sharks are also called walking sharks, because they use their fins to walk along the sea floor and explore crevices in rocks. Some species can even walk short distances on land to enter tidal pools and other places where they can find food. They live in warm, shallow water, usually near reefs or islands, and they eat whatever small animals they can find. There are nine species known, but there are undoubtedly more than haven’t yet been discovered by science. You might think this is strange for a shark that can walk on land, but walking sharks are nocturnal and not very big, so it’s easy to miss them when they’re out and about.

That brings us to Arthur’s suggestion, the mudskipper. The mudskipper also uses its fins to walk. Its pectoral fins are muscular and allow it to climb out of the water and onto land, climb into low branches, and even jump. Its pectoral fins look like little arms, complete with an elbow. The elbow is actually a joint between the actual fins and the radial bones, which in most fish are hidden within the body but which stick out of the mudskipper’s sides a short distance. 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.

The mudskipper is so good at living on land that it’s 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–yes, it can rotate its mouth, which has led to me trying to rotate my mouth, something humans can’t actually do–so that its mouth is 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. It also has sharp teeth, so when an animal is in its mouth, it’s not getting out again.

Alyx, Dean, and Riley suggested we talk about the red-lipped batfish, a type of anglerfish only found around the Galapagos Islands in the Pacific Ocean. It lives on the ocean floor where the water is fairly shallow, and it grows about 8 inches long, or 20 cm. It’s usually a mottled brown, green, or grey with a white stomach, but its mouth is bright red. It looks like it’s wearing lipstick. It eats fish and other small animals, which it attracts using a lure on its head, a highly modified dorsal fin called an illicium.

The weirdest thing about the red-lipped batfish is actually its fins. It prefers to walk on the bottom of the ocean instead of swim, and it has modified pectoral fins called pseudolegs. The pseudolegs make it look a little bit like a weird frog with lipstick. Researchers think the red lips may be a way to attract potential mates, presumably ones who are hoping for a big smooch. At this rate I’m wondering if there are any fish that don’t walk on their fins.

Next, Mac wanted to learn about a fish called the payara. The problem is, there are two fish with that name, so let’s learn about them both!

The first payara is a pretty, silvery fish with a couple of small dark spots on its body. It’s found in the Amazon basin in South America and can grow at least 1 foot 8 inches long, or 51 cm. It’s sometimes kept in large aquariums, and is sometimes called the vampire tetra or the vampire fish because it has a pair of long fangs that it uses to stab other fish with before eating them. Its fangs stick up from its lower jaw, though, so if it’s a vampire fish, it’s an upside-down vampire.

As for the other payara, it’s related to the first kind and is also found in South America, but it’s even larger. It can grow a little over 3 feet long, or 3.3 meters. Its teeth are also large and sharp, including two big fangs sticking up from its lower jaw. In a big individual, its fangs may be 4 inches long, or 10 cm. This is not a fish you want to get bitten by! You are probably not in any danger of being bitten by this payara, though, unless you happen to spend a lot of your time swimming along the bottom of rivers in the Amazon.

Quite a while ago, Ryder suggested we learn about the pipe cichlid. I tried to find more about it and I think it’s actually a fish called the pike cichlid. Pike cichlids are popular freshwater aquarium fish that are native to tropical and subtropical parts of eastern South America, and there are about 45 species known so far. They’re typically quite small, with most species only growing a few inches long, or around 8 cm, although some species are more than twice that length. The pike part of their name comes from their shape, like a teeny-tiny pike, a predatory fish that can grow up to 5 feet long, or 1.5 meters. Pike and pike cichlids aren’t related, but pike cichlids are predatory. It’s just that instead of eating other fish, ducks, frogs, and even reptiles and mammals that end up in the water, the pike cichlid mostly eats insects.

Elizabeth wanted to learn about the blue groper, a fish found around Australia and nowhere else in the world. It lives around reefs and rocky areas near the coast, where it can find plenty of starfish, urchins, crustaceans, and other small animals to eat. It can grow almost six feet long, or 1.75 meters, and its teeth are peg-shaped to help it pick mollusks and other animals off of rocks before crushing them.

It’s called the blue groper because males are a beautiful blue color, while females are brown or reddish-brown and young fish are green. All young blue gropers are female, and as they grow up some change to become males while most remain females. The fish grow very slowly and can live to be at least 70 years old, so the fish don’t even reach maturity until they’re 15 or 20 years old. When a fish is around 30 or 35 years old, it will change gender again, this time becoming a male. But if the male of a group dies, the group’s dominant female will change into a male and turn blue. This is common in the family of fish that the blue groper belongs to, Labridae, also called wrasses.

Let’s finish with a suggestion from Nora, the oarfish. The giant oarfish and Russell’s oarfish can both grow at least 26 feet long, or 8 meters, and possibly much longer. Most of its length is tail, which often shows damage from being bitten. Since its organs are all close to the front of its body, and it doesn’t need its tail for swimming, if a predator takes a bite out of its tail, the fish is going to be fine. The oarfish can even detach pieces of its tail if it needs to, the same way some lizards can, to distract a potential predator. Like those lizards, the tail doesn’t grow back.

The oarfish is silvery in color with a red crest on its head and a mane-like fin down its back, although it’s actually an elongated dorsal fin. It has extremely long pelvic fins too.

The giant oarfish has a short, blunt snout and no teeth because it filters krill and other tiny animals from the water. It doesn’t have scales. Instead, its skin is soft with a delicate layer called ganoine that gives it a shimmery, almost metallic appearance. The long filaments of the crest on its head and its pelvic fins are also delicate. But although it’s long and slender like an eel, it actually swims vertically with its head pointing up and its tail down. We’re not sure why, although one theory is that this minimizes its profile to predators looking up from below. It can swim quickly straight up and down to avoid predators that mostly just swim forward.

We know so little about the oarfish, and what we know is so strange, that it’s the next best thing to a sea serpent. The first living giant oarfish was only filmed in 2001. Most oarfish are only seen when they’re dead or dying. It seems to live throughout the world’s oceans, except for the Arctic and Antarctic, and is a deep-sea fish but may migrate closer to the surface at night to find more food.

A Japanese legend says the oarfish predicts earthquakes. If an oarfish is seen near the surface or washes up on a beach, an earthquake is supposed to be imminent. That seems to be a coincidence, though.

The oarfish looks like a sea serpent, and some people think it might have given rise to some sea serpent sightings. This may or may not be the case, but it’s certainly a mysterious fish.

You can find Strange Animals Podcast at strangeanimalspodcast.blubrry.net. That’s blueberry without any E’s. If you have questions, comments, corrections, or suggestions, email us at strangeanimalspodcast@gmail.com.

Thanks for listening!

Episode 407: Cookie Cutter Shark

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Thanks to Alyx for this week’s suggestion, the cookie cutter shark!

Further reading:

If You Give a Shark a Cookie

The business end of the cookie cutter shark:

Show transcript:

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

This week we’re going to learn about a little shark suggested by Alyx, but first let’s learn about something else that might be related to the shark.

In the 1970s, the U.S. Navy started having trouble with the navigation of their submarines. The Ohio-class submarine had what was called a sonar dome that was filled with oil, and the oil helped transmit sound. But repeatedly the subs would lose navigation abilities, and investigations turned up strange chunks removed from the electric cables, the oil lines, the sound probes, and the sonar dome itself—anywhere made of rubber that was soft enough for what looked like a hole saw to damage.

The Navy thought they were dealing with a state-of-the-art weapon. The United States and the former Soviet Union were bitter enemies, so the Navy thought the USSR had invented a technologically sophisticated underwater stealth drone of some kind that could damage the subs and leave no trace—nothing but circular chunks removed from the sonar dome and its components.

Thirty submarines were damaged before the Navy figured out the cause. It wasn’t a super-secret weapon at all. It was just a little fish called the cookie-cutter shark.

The cookie cutter shark doesn’t look very scary. It only grows 22 inches long at most, or 56 cm, and is brown in color. It has lots of very sharp evenly spaced teeth on its lower jaw, but compared to a great white shark, it’s nothing to worry about. But somehow it was able to disable 30 of the world’s most advanced submarines at the time.

That’s because of how the cookie cutter shark eats, which is also how it gets its name. It picks a target fish or some other animal, such as a whale or a seal, or possibly the sonar dome of an Ohio-class submarine, and sneaks up to it. It’s just a little fish and its coloration helps it blend in with its surroundings, so most animals barely notice it. It has lips that act like a suction cup, so quick as a wink it sticks itself to the animal, bites down, and spins around. In moments it’s cut a circular chunk out of the animal’s side like a horrible cookie, which it swallows, and by the time the animal even realizes it’s hurt, the cookie cutter shark is long gone.

The shark used to be called the cigar shark because of its shape. It wasn’t until 1971 that experts realized how the cookie cutter shark eats. Until then the circular wounds on fish and whales and other animals were thought to be from lamprey bites or from some kind of parasite.

The cookie cutter shark does have teeth in its upper jaw but they’re much smaller than the lower teeth. When it sheds its lower teeth to replace them, instead of shedding just one tooth, it sheds them all at once. Like most sharks, it swallows its old teeth so it can reuse the calcium to grow new teeth.

The shark also has photophores on the underside of its body that glow greenish, which is a common way that some fish escape predators from below. A big fish looking up toward the surface of the water high above it sees a lot of light shining down from the sun, so a fish with a glowing underside just blends in. But in the case of the cookie cutter shark, it has a strip of skin on its underside without photophores, and from below that strip shows up. It’s a sort of collar that’s actually darker brown than the rest of the fish. It looks, in fact, like a tiny fish silhouetted against the surface. The would-be predator fish approaches, expecting an easy meal. Instead, the cookie cutter shark darts around and takes a big bite out of the fish, then takes off. It’s a remarkably fast swimmer, but most of the time it hangs almost motionless in the water waiting for another animal to approach. Its eyes are large and it has good vision.

Sometimes the cookie cutter shark will travel in schools, which attracts even more predators who think they’re looking at a bunch of little bitty fish. Then all the sharks get a bite.

That leads us to the uncomfortable question: has the cookie cutter shark ever bitten a piece out of a human? The answer is yes, but no one has ever died from a cookie cutter shark attack. The shark usually stays in deep water during the day and rises closer to the surface at night, so it’s not likely to encounter humans except at night. Occasionally a swimmer has been bitten, and shipwreck survivors have reported being bitten at night while waiting for rescue, which is just insult to injury. In 2023 a swimmer was bitten by two cookie cutter sharks, but he saw them and was able to just grab them both and throw them away before he was seriously hurt. That’s not something you can do with a great white.

As for the submarines, the Navy started putting fiberglass shields over the sonar dome and other softer parts of the sub, and that solved the problem. It only cost $2 billion each to repair the subs.

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 370: Animals Discovered in 2023

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Let’s look at some of the most interesting animals discovered last year!

Further reading:

Newly-discovered ‘margarita snails’ from the Florida Keys are bright lemon-yellow

Tiny spirits roam the corals of Japan—two new pygmy squids discovered

Strange New Species of Aquifer-Dwelling Catfish Discovered in India

Bizarre New Species of Catfish Discovered in South America

Unicorn-like blind fish discovered in dark waters deep in Chinese cave

New Species of Hornshark Discovered off Australia

Cryptic New Bird Species Identified in Panama

New Species of Forest Hedgehog Discovered in China

New species of voiceless frog discovered in Tanzania

The weird new spiny katydid:

Show transcript:

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

It’s time for our annual discoveries episode, where we learn about some animals discovered in the previous year! There are always lots more animals discovered than we have time to talk about, so I just choose the ones that interest me the most.

That includes the cheerfullest of springtime-looking marine snails discovered in the Florida Keys. The Florida Keys are a group of tropical islands along a coral reef off the coast of Florida, which is in North America. A related snail was also discovered off the coast of Belize in Central America that looks so similar that at first the scientists thought they were the same species with slightly different coloration. A genetic study of the snails revealed that they were separate species. The one found in the Keys is a lemony yellow color while the one from Belize is more of a lime green.

The snails have been placed into a new genus but belong to a group called worm snails. When a young worm snail finds a good spot to live, it sticks its shell to a rock or other surface and stays there for the rest of its life. Its shell isn’t shaped like an ordinary snail shell but instead grows long and sort of curved or curly. The snail spreads a thin layer of slime around it using two little tentacles, and the slime traps tiny pieces of food that float by.

The new snails are small and while the snail’s body is brightly colored, its shell is drab and helps it blend in with the background. Scientists think that the colorful body may be a warning to potential predators, since its mucus contains toxins. It mainly lives on pieces of dead coral.

Another invertebrate discovery last year came from Japan, where two new species of pygmy squid were found living in seagrass beds and coral reefs. Both are tiny, only 12 mm long, and are named after little forest spirits from folklore. Despite its small size, it can eat shrimp bigger than it is by grabbing it with its little bitty adorable arms. Both species have been seen before but never studied until now. The scientists teamed up with underwater photographers to find the squid and learn more about them in their natural habitats.

As for invertebrates that live on land, an insect called the blue-legged predatory katydid was discovered in the rainforests of Brazil. It’s a type of bush-cricket that’s dark brown in color except for the last section of its legs, which are greenish-blue. Those parts of its legs are also really spiny. That is literally all I know about it except for its scientific name, Listroscelis cyanotibiatus, but it’s awesome.

Let’s leave the world of invertebrates behind and look at some fish next. This was the year of the catfish, with new species discovered in both India and South America. Catfish can be really weird in general and both these new species are pretty strange.

The first is tiny, only 35 mm long at most, or a little over an inch, and it has four pairs of barbels growing from its face. It looks red because its blood shows through its skin, because its skin doesn’t have any pigment. The fish also doesn’t have any eyes. If this makes you think it’s a cave-dwelling fish, you’re exactly right, but instead of an ordinary cave it actually lives in an aquifer.

An aquifer is a source of water underground. It’s actually a layer of rock that’s broken up or otherwise permeable so that water can get through it, but with a non-permeable layer underneath. The water is trapped in the layer, sometimes far underground. If you’ve ever seen a spring, where water bubbles up from the ground, that water comes from an aquifer that has found its way to the surface. If you’ve ever drunk water pumped or dipped up from a well, the well-water also comes from an aquifer. The water gets into the aquifer in the first place when rain soaks into the ground, but it takes a long time to fill up.

There are really deep aquifers that are completely sealed off from the surface, created thousands or even millions of years ago. As far as we know, nothing lives in those, although we could be wrong. Aquifers that are closer to the surface with some surface openings develop unique ecosystems, including animals that are found nowhere else on earth. That’s the case with the tiny red catfish found in the state of Kerala in India.

Scientists asked people in the area to watch out for any unusual animals when they had a new well dug or cleaned, and before long people from four towns reported finding the little red fish. Three other related species had previously been found in the state.

On the other side of the world, in South America, a much different type of catfish was discovered in Bolivia and Brazil. This one is an armored catfish, and the male actually grows short dermal teeth on the sides of his head that he uses to fight other males. Dermal teeth are teeth that grow on the skin instead of in the mouth, and it’s surprisingly common in fish, especially armored catfish.

The new catfish has been named Sturisoma reisi and it grows about 8 inches long, or 20 cm. It’s actually been known to scientists for a long time, but until recently no one realized it wasn’t one of five other catfish in the genus Sturisoma. They all look kind of similar. It’s a slender, active catfish with a long tail and a pointy rostrum that lives in swift-moving rivers. It was actually described in 2022, not 2023, but I only just realized I have the wrong year so let’s just move along quickly to another fish.

This one isn’t a catfish but it looks like one at first glance since it has barbels around its mouth. These are the whisker-like feelers that give the catfish its name. The newly discovered fish needs feelers because it doesn’t have working eyes, and it also doesn’t have scales or pigment in its skin. It was found in a cave in China, and in fact it’s only been found in a single pool of water in a single cave. The pool is only about 6 feet across, or 1.8 meters, and about two and a half feet deep, or 80 cm, but it’s home to a perfectly healthy population of fish. The fish grow about 5 inches long on average, or 13 cm.

The fish is a new member of the genus Sinocyclocheilus, and of the 76 known species in the genus, most live in caves. The new fish has been named S. longicornus because of a structure on its head that kind of looks like a unicorn horn, if the unicorn was a pink cave fish and its horn was shaped sort of like the tip of a ballpoint pen, also called a biro.

Some other species in this genus also have a so-called horn, although the new fish’s is larger than most. It juts forward and extends above what we can describe as the fish’s forehead. Scientists have absolutely no idea what it’s for. Since the fish can’t see, it can’t be to attract a mate. It’s also not likely to be a navigational aide since the fish has its barbels and a well-developed lateral line system to find its way around. Besides, it lives in a pool of water not much bigger than the desk I’m sitting at. It doesn’t exactly travel very far throughout its life.

Scientists have a lot of other questions about the fish, including how it survives in such a tiny pool of water.

Speaking of fish with horns, a new species of hornshark was discovered last year off the northern coast of Australia. Hornsharks live in shallow warm waters throughout much of the Pacific and Indian oceans, where they spend most of the time at the bottom looking for small invertebrates like crustaceans to crunch up, although sea urchins are their favorites. They’re also called bullhead sharks because they all have short snouts and broad heads with prominent brows. The name hornshark comes from the fins, some of which have spines.

One species of hornshark is the zebra hornshark, which lives in the Indo-Pacific, from southern Japan down to northern Australia. As you may guess from the name, it has stripes, which makes it popular in aquariums and zoos. It only grows to about 4 feet long, or 1.25 meters. Until last year, scientists thought that all the zebra hornsharks around Australia belonged to the same species. Then they noticed that one population that lives off of northwestern Australia has a different stripe pattern and only grows about two feet long, or 60 cm. After a genetic study, it turns out that it’s a totally different species.

A lot of animal discoveries are like this, where everyone thinks an animal is one species, but after close study and genetic testing they find out it’s two or more species that just look very similar. That’s one of the great things about DNA testing being so effective and quick these days, but it’s not always as cut and dried as it sounds. There’s no easy way to determine for sure if animals are different species, subspecies, or just the same species with population variants. Scientists can’t just rely on genetics, but they also can’t always rely on observations of the animal’s physical traits or its behavior in the wild. They have to look at all the data available, and then they still argue about the best interpretation of the data.

The notion of a separate species or subspecies is an artificial one that gives us a way to better understand a natural process. If a population of animals is separated from another population, eventually both will develop separately until they’re two related but very different animals. There’s no way to point at a specific generation and say, “well, NOW they’re different from the last generation” because the process is so slow and the changes are usually so small. It’s like looking at a rainbow and trying to determine exactly the point where red turns into orange and orange turns into yellow.

Take the slaty-backed nightingale-thrush as an example. It’s a dark gray songbird with a short tail and bright orange legs and beak, and it lives in the mountains of Central and northern South America. It spends most of its time in thickets where it’s hard to see but easy to hear, since it has a lovely song. This is an example of what it sounds like, although its song varies depending on where it lives.

[bird song]

It turns out that there’s a lot of variation in the bird’s song because the slaty-backed nightingale-thrush probably isn’t all one species. In late 2023 a team of researchers published a ten-year study of the bird, looking at everything from song variations to genetics. They determined that not only was it not a single species, it was most likely seven different species and four subspecies. Because the bird lives in the mountains and doesn’t fly very far during its lifetime, populations that are separated by steep mountains and valleys have developed into separate species.

Naturally, not everyone agrees with these findings, but it’s always good when a little-studied animal gets some attention. Until last year, no one knew much about this shy little bird, and the controversy of whether it’s one species or lots of closely related species will hopefully lead us to learn even more about it. One population of the bird discovered in Panama had never been documented before, too.

This episode is getting pretty long for someone who just got over a cold, so let’s cover one newly discovered mammal and a newly discovered frog. A new species of forest hedgehog was discovered in China last year and it’s adorable! It’s related to the hedgehogs found in Europe and other areas, but is most closely related to four known species of forest hedgehog that live mostly in central Asia. The new species was discovered in eastern China, over 1,000 km away from the nearest population of other forest hedgehogs. Another species was only discovered in 2007 from southwestern China.

Unlike most hedgehogs, the new species is sexually dimorphic, meaning that males and females don’t look identical. Males are mostly gray while females are more reddish-brown in color.

Let’s finish with another adorable animal, a little frog from Tanzania, a country in east Africa. It’s a type of spiny-throated reed frog, which are all rare and increasingly threatened. They’re also very small, not much bigger than an inch long, or about 30 mm. The male has tiny little spines on his throat that researchers think might be a way that females recognize the males of their own species during mating season instead of by a distinctive croaking sound. That’s because spiny-throated reed frogs can’t make sounds, leading to their other common name of the voiceless frog.

In 2019, researchers were in the Ukaguru Mountains in Tanzania looking for a completely different frog, the beautiful tree toad, which may be extinct. While they didn’t find any of the toads, they did find a little greenish-brown frog with copper-colored eyes that turned out to be completely new to science. It was found in a nature reserve and appears to be common locally, which is good, but the nature reserve is also very small, which is not so good. Hopefully now that we know the little frog exists, it will lead to further protections of the area that will help all the other animals and plants where it lives, including the beautiful tree toad.

This is what the voiceless frog sounds like:

[silence]

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 364: Animals Who Will Outlive Us All

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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

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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

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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 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.

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