Category Archives: fish

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 401: El Gran Maja and Other Giant Eels

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Thanks to Murilo for suggesting El Gran Maja for our first monster month episode of 2024!

Further reading:

The Loch Ness Monster: If It’s Real, Could It Be an Eel?

Further watching:

Borisao Blois’s YouTube channel [I have not watched very many of his videos so can’t speak to how appropriate they all are for younger viewers]

El Gran Maja, YouTube star:

The European eel [photo by GerardM – http://www.digischool.nl/bi/onderwaterbiologie/, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=284678]:

A supposed 21-foot eel, a product of trick photography:

The slender giant moray eel [photo by BEDO (Thailand) – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=40262310]:

Show transcript:

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

It’s monster month, where we talk about weird, mysterious, and sometimes spooky creatures! This year I’ve decided to be less spooky and more weird, so let’s kick off the month with an episode all about gigantic eels. Thanks to Murilo for suggesting our first giant eel, El Gran Maja.

El Gran Maja is an eel that is supposed to live off the coast of northern Puerto Rico, and it’s supposed to grow 675 meters long. That’s 2,215 feet, or almost half a mile. That is an excessive amount of eel.

Obviously, an eel that big couldn’t actually exist. By the time its front end noticed danger, its back end could already be eaten by a whole family of sharks. But maybe it was based on a real eel that grows really long. Let’s take a look at some eels we know exist, and then we’ll return to El Gran Maja and learn some very interesting things about it.

Eels are fish, but not every animal that’s called an eel is actually an eel. Some are just eel-shaped, meaning they’re long and slender. Electric eels aren’t actually eels, for instance, but are more closely related to catfish. Most eels live in the ocean at the beginning and end of their lives, and freshwater in between.

For example, the European eel has a life cycle that’s pretty common among eels. It hatches in the ocean into a larval stage that looks sort of like a transparent leaf. Over the next six months to three years, the larvae swim and float through the ocean currents, closer and closer to Europe, feeding on plankton and other tiny food. Toward the end of this journey, they grow into their next phase, where they resemble eels instead of leaf-shaped tadpoles, but are still mostly transparent. They’re called glass eels at this point. The glass eels make their way into rivers and slowly migrate upstream. Once a glass eel is in a good environment it metamorphoses again into an elver, which is basically a small eel. As it grows it gains more pigment until it’s called a yellow eel. Over the next decade or two it grows and matures, until it reaches its adult length—typically around 3 feet, or about a meter. When it’s fully mature, its belly turns white and its sides silver, which is why it’s called a silver eel at this stage. Silver eels migrate more than 4,000 miles, or 6500 km, back to the Sargasso Sea to spawn, lay eggs, and die.

One place where European eels live is Loch Ness in Scotland, and in the 1970s the idea that sightings of the Loch Ness Monster might actually be sightings of unusually large eels became popular. A 2018 environmental DNA study brought the idea back up, since the study discovered that there are a whole, whole lot of eels in Loch Ness. The estimate is a population of more than 8,000 eels in the loch, which is good since the European eel is actually critically endangered. But most of the eels found in Loch Ness are smaller than average, and the longest European eel ever measured was only about 4 feet long, or 1.2 meters.

An eel can’t stick its head out of the water like Nessie is supposed to do, but it does sometimes swim on its side close to the water’s surface, which could result in sightings of a string of many humps undulating through the water.

But the Loch Ness monster aside, the European eel isn’t very big compared to many species of eel. The European conger eel is the heaviest eel known, although not the longest. It lives off the coast of Europe down to northern Africa, and also in the Mediterranean Sea. An exceptionally large female might be as much as 10 feet long, or 3 meters, but it’s also chonkier than other eels. The largest conger ever measured reportedly weighed 350 lbs, or almost 159 kg, and was caught in a net off the coast of Iceland, although that report isn’t very reliable.

In 2015, a lot of newspaper reports talked about a huge eel caught off the coast of Devon, England. They printed pictures of a massively huge eel hung up in front of the fishermen who caught it. The articles said the eel was as much as 21 feet long, or 6.4 meters, and weighed 160 lbs, or just over 72 kg.

But if you think about it, there’s something fishy (sorry) about the story. If you picture a big man, say a football player who’s fit and strong, he might be about six feet tall, or 1.8 meters, and weigh a bit more than 200 lbs, or maybe 95 kg. But the eel weighed a lot less than that hypothetical man, and eels are strongly muscled even though they’re slender in shape. A 21 foot eel should weigh much more than a football player.

Most likely, reporters looked at the photo and compared it to the fishermen, and came up with the 21 foot length themselves. But it’s a trick photo, even if the trick wasn’t planned, because the eel was hung up very close to the camera while the fishermen were much farther back, which makes the eel look huge in comparison. Not only that, but when you hang a dead eel up by its head, it stretches so that it looks longer than it really was when it was alive. Other pictures of the eel make it look much shorter.

As it turns out, the fishermen who caught the eel didn’t even measure it. They thought it might have been up to 10 feet long, but it might have been closer to 7, or 2 meters. That’s still a big eel, and the weight may be close to a reliable record of heaviest eel, but it’s nowhere near the longest eel ever measured.

That record goes to the slender giant moray eel, which lives in muddy coastal water of the Pacific Ocean. It’s brown and isn’t especially exciting to look at unless you’re an eel enthusiast or an actual eel yourself, but the longest eel ever reliably measured was a slender giant moray. That was in 1927 in Queensland, Australia. The eel measured just shy of 13 feet long, or 3.94 meters.

In other words, the longest eel ever measured is approximately 2,202 feet, or 671 meters, shorter than El Gran Maja. But to learn more about El Gran Maja we have to talk about something called the bloop.

The bloop is a sound recorded in 1997 off the tip of South America by the National Oceanic and Atmospheric Administration, AKA NOAA. The sound itself came from the middle of the South Pacific Ocean, and was so loud that it was recorded by sensors 3,000 miles away, or 5,000 km. But it was also an ultra-low-frequency sound, so that humans and most other animals wouldn’t be able to hear it at all.

This is what the bloop sounds like, sped up 16 times so that people can hear it:

[bloop sound]

It turns out that the bloop was made by a big iceberg breaking into pieces, and similar sounds have been recorded since by NOAA and other researchers. But when the bloop was first made public, its source was still a mystery, and pretty much everyone on the internet lost their minds with excitement thinking it was a deep-sea creature far bigger than a blue whale. People speculated about the size of the bloop monster and estimated it had to be about 705 feet long, or 215 meters, for it to make such a loud call.

A film-maker and artist named Borisao Blois was interested in the bloop monster and wanted to animate it, but decided it needed a rival to fight—and he wanted the rival to be even bigger. He invented El Gran Maja and animated a fight between the two. Because Blois wanted his monster to be exciting to look at during his films, he gave it a huge wide mouth filled with sharp, comb-like teeth, and six all-white eyes. The first video was released in 2001 and has more than 89 million views. Many more videos followed, along with creations made by other artists who were inspired by the original.

The videos Blois has made about El Gran Maja are popular, and some people even think it might be a real monster. Considering that an eel that big would need to eat an astounding amount of food every day to survive, and it’s big enough to swallow entire ships whole, it’s probably a good thing that it’s just a made-up monster.

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 400: Four no wait Five Mysteries!

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To donate to help victims of Hurricane Helena:

Day One Relief – direct donation link

World Central Kitchen – direct donation link

It’s the big 400th episode! Let’s have a good old-fashioned mystery episode! Thanks to Richard from NC for suggesting two of our animal mysteries today.

Further reading:

A 150-Year-Old Weird Ancient Animal Mystery, Solved

The Enigmatic Cinnamon Bird: A Mythical Tale of Spice and Splendor

First ever photograph of rare bird species New Britain Goshawk

Scientists stumbled onto toothy deep-sea “top predator,” and named it after elite sumo wrestlers

Bryde’s whales produce Biotwang calls, which occur seasonally in long-term acoustic recordings from the central and western Pacific

A stylophoran [drawing by Haplochromis – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=10946202]:

A cinnamon flycatcher, looking adorable [photo by By https://www.flickr.com/photos/neilorlandodiazmartinez/ – https://www.flickr.com/photos/neilorlandodiazmartinez/9728856384, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=30338634]:

The rediscovered New Britain goshawk, and the first photo ever taken of it, by Tom Vieras:

The mystery fish photo:

The yokozuna slickhead fish:

The Biotwang maker, Bryde’s whale:

Show transcript:

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

We’ve made it to the big episode 400, and also to the end of September. That means monster month is coming up fast! To celebrate our 400th episode and the start of monster month, let’s have a good old-fashioned mysteries episode.

We’ll start with an ancient animal called a stylophoran, which first appears in the fossil record around 500 million years ago. It disappears from the fossil record around 300 million years ago, so it persisted for a long time before going extinct. But until recently, no one knew what the stylophoran looked like when it was alive, and what it could possibly be related to. It was just too weird.

That’s an issue with ancient fossils, especially ones from the Cambrian period. We talked about the Cambrian explosion in episode 69, which was when tiny marine life forms began to evolve into much larger, more elaborate animals as new ecological niches became available. In the fossil record it looks like it happened practically overnight, which is why it’s called the Cambrian explosion, but it took millions of years. Many of the animals that evolved 500 million years ago look very different from all animals alive today, as organisms evolved body plans and appendages that weren’t passed down to descendants.

As for stylophorans, the first fossils were discovered about 150 years ago. They’re tiny animals, only millimeters long, and over 100 species have been identified so far. The body is flattened and shaped sort of like a rectangle, but two of the rectangle’s corners actually extend up into little points, and growing from those two points are what look like two appendages. From the other side of the rectangle, the long flat side, is another appendage that looks like a tail. The tail has plates on it and blunt spikes that stick up, while the other two appendages look like they might be flexible like starfish arms.

Naturally, the first scientists to examine a stylophoran decided the tail was a tail and the flexible appendages were arm-like structures that helped it move around and find food. But half a billion years ago, there were no animals with tails. Tails developed much later, and are mainly a trait of vertebrates.

That led to some scientists questioning whether the stylophoran was an early precursor of vertebrates, or animals with some form of spinal cord. The spikes growing from the top of the tail actually look a little bit like primitive vertebrae, made of calcite plates. That led to the calcichordate hypothesis that suggested stylophorans gave rise to vertebrates.

Then, in 2014, scientists found some exceptionally well preserved stylophoran fossils in the Sahara Desert in Africa. The fossils dated to 478 million years ago and two of them actually had soft tissue preserved as the mineral pyrite. Pyrite is also called fool’s gold because it looks like gold but isn’t, so these were shiny fossils.

When the soft tissue was observed through electron microscopes in the lab, it became clear that the tails weren’t actually tails. Instead, they were more like a starfish arm, with what may be a mouth at the base. The arm was probably the front of the animal, not the back like a tail, and the stylophoran probably used it to grab food and maybe even to crawl around.

Most scientists today agree that stylophorans are related to modern echinoderms like starfish and urchins, but there is one big difference. Echinoderms show radial symmetry, but no stylophoran found so far does. It doesn’t really even show bilateral symmetry, since the two points aren’t really symmetrical to each other. We’re also not sure what the points were for and how such an unusual body plan really worked, so there are still a lot of mysteries left regarding the stylophoran.

Next let’s talk about a mythical bird, called some variation of the word cynomolgus, or just the cinnamon bird. Naturalists from the ancient world wrote about it, including Pliny the Elder and Aristotle, and it appeared in medieval bestiaries. It was said to be from Arabia and to build its nest of cinnamon sticks in the tops of very tall trees or on the sides of cliffs.

Cinnamon comes from the inner bark of cinnamon trees, various species of which are native to southern Asia and Oceania. It’s an evergreen tree that needs a tropical or subtropical climate to thrive, and it smells and tastes really good to humans. You might have seen cinnamon sticks, which are curled-up pieces of dried cinnamon bark, and that’s the same type of cinnamon people used in the olden days. Ground cinnamon is just the powdered bark. Like many other spices, it was highly prized in the olden days and cost a fortune for just a little bit of it. Ancient Egyptians used it as part of the embalming process for mummies, ancient Greeks left it as offerings to the sun god Apollo, ancient Romans burnt it during the funerals of nobility, and it was sought after by kings throughout the world.

One interesting thing is that if you live in the United States, the cinnamon in your kitchen cupboard is probably actually cassia, also called Chinese cinnamon because it’s native to southern China. Cassia is often mentioned alongside cinnamon in old writings, because they’re so similar, but true cinnamon comes from a tree native to Sri Lanka. It’s usually marketed as Ceylon cinnamon and is more expensive, but cassia is actually better for baking. True cinnamon has a more subtle flavor that’s especially good with savory dishes, but it loses a lot of its flavor if you bake with it.

Anyway, back in the olden days, no one outside of subtropical Asia and Oceania knew where cinnamon came from. The traders who bought it from locals to resell definitely weren’t going to tell anyone where it was from. They made up stories that highlighted just how hard cinnamon was to find and harvest, to discourage anyone from trying to find cinnamon on their own and to keep prices really high. As Pliny the Elder pointed out 2,000 years ago, the cinnamon bird was one of those stories.

The cinnamon bird was supposedly the only animal that knew where cinnamon trees grew, and it would peel pieces of the bark off with its beak, then carry them to the Arabian desert or somewhere just as remote, where it would build a nest of the bark. The birds were supposed to be enormous, sometimes so big that their open wings stretched from horizon to horizon. Their nests were equally large, but so hard to reach that no human could hope to climb up and collect the cinnamon. Instead, cinnamon hunters left dead oxen and other big animals near the area where the birds had nests. The birds would swoop down and carry the oxen back to their nests to eat, and the extra weight would cause the nests to fall. In other stories, cinnamon hunters would shoot at the nests with arrows with ropes attached. Once several arrows were lodged into a nest, the hunters would pull the ropes to dislodge the nest and cause it to fall, so they could collect the cinnamon.

Of course none of that is true. Some scholars think the cinnamon bird is probably the same mythical bird as the phoenix, but without any magical abilities. Others agree with Pliny the Elder that it was just a way for traders to raise their prices for cinnamon even more. Either way, the cinnamon bird is probably not a real animal.

There are birds with cinnamon in their name, but that’s just a reference to their coloration. Cinnamon is generally a reddish-brown in color, and in animals that color is often referred to as rufous, chestnut, or cinnamon. For example, the cinnamon flycatcher, which lives in tropical and cloud forests along the Andes Mountains in South America. It’s a tiny round bird, only about 5 inches long including its tail, or 13 cm. It’s dark brown and red-brown in color with black legs and beak, and a bright cinnamon spot on its wings. It eats insects, which you could probably guess from the name.

This is what a cinnamon flycatcher sounds like:

[tiny bird sound]

Next, we need to talk about the New Britain goshawk, which Richard from NC told me about recently. It lives in tropical forests of Papua New Guinea, and is increasingly threatened by habitat loss. In fact, it’s so rare that it was only known from four specimens, and it hadn’t been officially spotted since 1969 and never photographed—until March of 2024.

During a World Wide Fund for Nature expedition, a wildlife photographer named Tom Vierus took lots of pictures of birds. One bird he photographed was a hawk sitting in a tree. He didn’t realize it was a bird that hadn’t been seen by scientists in 55 years, until later when he and his team were going through his photographs.

The goshawk is large, and is gray and white with an orange face and legs. We know very little about the bird, naturally, but now that scientists know it’s alive and well, they can work with the local people to help keep it safe. It’s called the keango or kulingapa in the local languages.

Next, we have a bona fide mystery animal, and a deep-sea mystery animal at that—the best combination!

In 1965, the U.S. Navy teamed up with Westinghouse to build a submersible designed by the famous diver and naturalist Jacques Cousteau. The craft was called Deepstar 4000 and between 1965 and 1972 when it was retired, it conducted hundreds of dives in different parts of the world, allowing scientists to learn a lot about the ocean. It could safely dive to 4000 feet, or 1200 meters, which isn’t nearly as deep as many modern submersibles, but which is still impressive.

This was long before remotely operated vehicles, so the submersible had to have a crew inside, both scientists and pilots. One of the pilots of Deepstar 4000 was a man named Joe Thompson. In 1966 Thompson maneuvered the craft to the ocean floor off the coast of California to deploy water sensors, in an area called the San Diego Trough. They touched down on the ocean floor and Thompson looked out of the tiny porthole, only to see something looking in at him.

Thompson reported seeing a fish with mottled gray-black skin and an eye the size of a dinner plate. He estimated it was 25 feet long, or over 7 ½ meters, which was longer than the Deepstar 4000 itself. Within seconds, the fish swam away into the darkness.

But that’s not the end of the story, because the water sensors the craft had already placed sensed the animal’s movement. There was definitely something really big near the craft. Even more interesting, an oceanographer had placed some underwater cameras in the area, and soon after Thompson’s sighting, the cameras took pictures of a huge gray fish.

While Thompson was positive the fish had scales, which he described as being as big around as coffee cups, the photo shows a more shark-like skin criss-crossed with scars. The oceanographer consulted with an ichthyologist, who identified the fish as a Pacific sleeper shark. We’ve talked about other sleeper sharks in episode 74. We don’t know a lot about these sharks, but they are gray, live in deep water, and can grow over 23 feet long, or 7 meters.

But Thompson was never satisfied with the identification of his mystery fish as a big Pacific sleeper shark. He was adamant that his fish had scales, a much larger eye than sharks have, and a tail that was more reminiscent of a coelacanth’s lobed tail than a shark’s tail.

One suggestion is that Thompson saw a new species of slickhead fish. Slickheads are deep-sea fish that can grow quite large, but we don’t know much about them since they live in such deep waters. The largest known species grows at least 8 feet long, or 2.5 meters, and possibly much longer. That’s the yokozuna slickhead, which was only discovered in 2021 by a scientific team studying cusk eels off the coast of Japan.

Most slickheads are small and eat plankton. This one was purplish in color, had lots of small sharp teeth, and was a strong, fast swimmer. When it was examined later, its stomach contents consisted of other fish, so it’s definitely a predator. Its eyes are also proportionately larger than a shark’s eyes. The slickhead gets its name because it doesn’t have scales on its head, but it does have scales on the rest of its body.

The yokozuna slickhead was discovered in a bay that’s well-known to both scientists and fishers, so the team didn’t believe at first that they could possibly have found a new species of fish there, especially one that was so big. But it definitely turned out to be new to science. More individuals have since been spotted, but they live very deep in the ocean, which explains why no one had seen one before. Interestingly, when the scientists first pulled the slickhead out of the water, they thought it looked a little like a coelacanth.

This episode was going to end there, but Richard from NC sent me another article about a whale mystery I’ve been talking about for years! It’s the so-called biotwang that we covered way back in episode 27.

In 2016 and early 2017, NOAA, the U.S. Coast Guard, and Oregon State University dropped a titanium-encased ceramic hydrophone into Challenger Deep. To their surprise, it was noisy as heck down there in the deepest water on earth. The hydrophone picked up the sounds of earthquakes, a typhoon passing over, ships, and whalesong—including the call of a whale researchers couldn’t identify. This is what it sounds like:

[biotwang whale call]

Well, as of September 2024, we now know what animal produces the biotwang call. It’s a whale, and one already known to science, although we don’t know much about it. It’s Bryde’s whale, a baleen whale that can grow up to 55 feet long, or almost 17 meters. The calls have all been associated with groups of Bryde’s whales, or a mother with a calf, so the scientists think the whales might use the unusual call to communicate location with its podmates. Bryde’s whales make lots of other sounds, and the scientists also think they might be responsible for some other mystery whale calls.

If you remember episode 193, about William Beebe’s mystery fish, he reported spotting a massive dark fish from his bathysphere a few decades before the Deepstar 4000 was built. He didn’t see it well enough to identify it and never saw it again. It just goes to show that there are definitely mystery animals just waiting to be discovered, whether it’s in the deep sea or perched in a treetop.

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 398: Repeating Scientific Names

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Thanks to Alexandra, Pranav, Eilee, Conner, and Joel for their suggestions this week!

Velella velella, or by-the-wind-sailor [photo from this page]:

Porpita porpita, or the blue button [photo from this page]:

Cricetus cricetus, or the European hamster, next to a golden hamster:

Nasua nasua, or the South American coati [photo from this page]:

Mola mola, or the ocean sunfish:

Quelea quelea, or the red-billed quelea [photo from this page]:

Show transcript:

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

This week we’re going to learn a little bit about scientific names, and along the way we’re going to learn about several animals. Thanks to Alexandra, Eilee, Conner, Joel, and Pranav for their suggestions!

Alexandra inspired this episode by suggesting two animals, the by-the-wind-sailor and the blue button. Both are marine invertebrates that look superficially like jellyfish, but they’re actually colonial organisms. That means that although they look like a single animal, they’re actually made up of lots of tiny animals that live together and function as one organism.

The blue button is closely related to the by-the-wind-sailor and both are related to siphonophores. Both the blue button and the by-the-wind-sailor spend most of the time near or on the ocean’s surface and have a gas-filled chamber that helps keep them afloat, with stinging tentacles that hang down into the water, but both are made up of a colony of tiny animals called hydroids. Different hydroids have different functions, and all work together to find tiny food that will benefit the entire colony.

The blue button gets its name because its float is round and flat like a button, and often blue or teal in color. It’s quite small, only a little over an inch across, or about 3 cm, and its tentacles are not much longer. The by-the-wind-sailor is a little larger than the blue button, with a blue sail-shaped float that’s only a few inches across, or maybe 7 cm, with stinging tentacles of about the same size. The stings of both organisms aren’t very strong and aren’t dangerous to humans, but they do hurt, so it’s a good idea not to touch one. Since both can be very common in warm ocean waters and they sometimes get blown ashore by the wind in large numbers, it can be hard to avoid them if you’re visiting the beach at the wrong time. They can still sting you if they’re dead, too.

The by-the-wind sailor has the scientific name of Velella velella while the blue button’s scientific name is Porpita porpita. The term for a scientific name that contains the same words is a repeating scientific name, also called a tautonym or tautonymous name, and that’s the subject of this episode.

A scientific name is something we mention a lot but if you’re not sure what it means, it can sound confusing. Every organism with a scientific name has been described by a scientist, meaning it’s been studied and placed somewhere in the great interconnected web of life. The system of giving organisms scientific names is called binomial nomenclature. The first word of the name indicates which genus the organism belongs to, while the second word indicates what species it is. These are called generic and specific names. Some organisms also have a third word in their scientific name which indicates its subspecies.

The reason scientists use a complicated naming system is to make it easier for other scientists to know exactly what organism is being discussed. For example, let’s say a scientist has been studying hamsters in the wild to learn more about them, and publishes a paper about her observations. If she just calls the animal a hamster, someone reading it might assume she was talking about the hamster found in their part of the world, when the paper is actually about a totally different, although closely related, hamster that lives somewhere else. And that brings us to Pranav’s suggestion, the European hamster, whose scientific name is Cricetus cricetus [cry-SEE-tus].

The hamster most of us are familiar with is actually the golden hamster, also called the Syrian hamster, more properly called Mesocricetus auratus. That’s the most common species kept as a pet. We can learn from the different scientific names that the European hamster is in a different genus from the golden hamster, which usually means it’s pretty different in some significant ways.

The European hamster lives throughout parts of Eurasia, especially eastern Europe through central Asia, and used to be extremely common. It’s also called the black-bellied hamster because the fur on its underside is black, while the fur on its upper side is tan or brown with white markings. These days it’s critically endangered due to habitat loss and being killed by farmers who think it hurts their crops. It does eat seeds, vegetables, and some roots, but it also eats grass and many other plants that are considered weeds, as well as insects, including insects that farmers also don’t want in their gardens.

In many respects, the European hamster is a lot like the golden hamster. It carries food home to its burrow in its cheek pouches and stores food in a larder. It hibernates in cold weather but wakes up around once a week to have a snack from its larder, which honestly sounds like the best way to spend the winter. But the European hamster is larger than the golden hamster. Like, a lot larger. The golden hamster is maybe 5 inches long, or 13 cm, which is small enough that you can easily hold it in your hand. The European hamster grows up to 14 inches long, or 35 cm. That’s the size of a small domestic cat, but with a short little hamster tail and short little hamster legs.

Even though an organism’s scientific name only designates genus and species, and subspecies when applicable, it allows scientists to look up a more detailed family tree. Every genus is classified in a family and every family is classified in an order, and every order in a class, and every class in a phylum, and every phylum in a kingdom, and every kingdom in a domain. Almost all of the organisms we talk about in this podcast belong to the kingdom Animalia. The more of these categories an organism shares with another organism, the more closely related they are.

Conner suggested we learn more about the coati, which we talked about in episode 302. The South American coati’s scientific name is Nasua nasua [NAH-sue-uh]. It grows almost four feet long, or 113 cm, which makes it sound enormous, but half of its length is its long ringed tail. It lives in much of South America, especially the northern part of the continent.

The coati is related to the raccoon of North America, and the two animals’ scientific names can help us determine how closely they’re related. The common raccoon’s scientific name is Procyon [PROSE-eon] lotor, so we already know it belongs to a different genus than the coati. But both the genus Procyon and the genus Nasua are classified in the family Procyonidae. So we know they’re closely related, because they belong to the same family, but not as closely related as they’d be if they belonged to the same genus, so we can expect to see some fairly significant differences between the two animals.

The South American coati is diurnal, unlike the nocturnal raccoon. While female raccoons often live in small groups of a few animals that share the same territory, female coatis live in groups of up to 30 animals who forage for food together and are very social. The coati also doesn’t have a set territory. The male coati is completely solitary, while the male raccoon will also live in small groups of three or four animals. Both are omnivorous but the coati eats more fruit and insects than the raccoon does, and the coati doesn’t dunk its food in water the way the raccoon famously does.

The system of binomial nomenclature that we use today was developed by the Swedish botanist Carolus Linnaeus in 1735. We talked about some of his mistakes in episode 123. Linnaeus built on a system developed by a zoologist almost a century before him, but streamlined it and made it easier to use. In the 300 years since Linnaeus came up with his system, many other scientists have made changes to reflect increased knowledge about the natural world and how best to denote it.

I keep saying “organism” instead of “animal,” and that’s because all living organisms may be given a scientific name as they are described. This includes everything from humans to maple trees, from earthworms to harpy eagles, from bumblebees to mushrooms. Linnaeus originally included minerals in his classification system, but minerals don’t evolve the way living organisms do. One group that wasn’t given scientific names until 2021 are viruses. There’s still a lot of controversy as to whether viruses are technically alive or not, but giving them scientific names helps organize what we know about them.

Eilee suggested the ocean sunfish, which has the scientific name Mola mola. Because its scientific name is easy to say, and because there’s also a freshwater sunfish that isn’t related to the ocean sunfish, a lot of people just call it the mola-mola, or just the mola. We talked about it way back in episode 96, so we’re definitely due to revisit it.

The ocean sunfish doesn’t look like a regular fish. It looks like the head of a fish that had something humongous bite off its tail end. It has one tall dorsal fin and one long anal fin, and a little short rounded tail fin that’s not much more than a fringe along its back end. This isn’t even a real tail but part of the dorsal and anal fins. The sunfish uses the tail fin as a rudder and progresses through the water by waving its dorsal and anal fins the same way manta rays swim with their pectoral fins. Pectoral fins are the ones on the sides, while the dorsal fin is the fin on a fish’s back and an anal fin is a fin right in front of a fish’s tail. Usually dorsal and anal fins are only used for stability in the water, not propulsion. The ocean sunfish does have pectoral fins, but they’re tiny.

The ocean sunfish lives mostly in warm oceans around the world, and it eats jellies, small fish, squid, crustaceans, plankton, and even some plants. It has a small round mouth that it can’t close and four teeth that are fused to form a sort of beak. It also has teeth in its throat, called pharyngeal teeth. Its skin is thick and rough like sandpaper with a covering of mucus, and its bones are mostly cartilaginous. It likes to sun itself at the water’s surface, and it will float on its side like a massive fish pancake and let sea birds stand on it and pick parasites from its skin. This also helps it absorb heat from sunlight after it’s been hunting in deeper water.

The female ocean sunfish can lay up to 300 million eggs at a time. That is the most eggs known to be laid by any vertebrate. When the eggs hatch, the larval sunfish are only 2 ½ mm long. Once they develop into their juvenile form, they have little spines all around their thin end, which kind of make them look like tiny stars. If that seems weird, consider that the ocean sunfish is actually related to the pufferfish, although not very closely. The largest adult ocean sunfish ever reliably measured was 14 feet tall, or 4.3 meters, including the long fins, which is a whole lot bigger than 2 ½ mm.

Sometimes after an organism is initially described and named, later scientists learn more about it and determine that it doesn’t actually belong in the genus or family where it was initially placed. If it gets moved to a different genus, its scientific name also needs to change. Some organisms get moved a lot and their scientific names change a lot. But typically, the species name doesn’t change. That’s the case for a little bird from Africa.

Joel suggested a bird called the red-billed quelea [QUEE-lee-ya], whose scientific name is Quelea quelea. When Linnaeus described it in 1758, he thought it was a type of bunting, so he named it Emberiza quelea. Another scientist moved it into a new genus, Quelea, in 1850.

I’d never heard of the red-billed quelea, which is native to sub-Sarahan Africa, but it may actually be the world’s most numerous non-domesticated bird, with an estimated 1.5 billion birds alive at any given moment.

The red-billed quelea mainly eats grass seeds, and unlike the European hamster, it is actually a problem to farmers. The bird doesn’t know the difference between yummy grass seeds and yummy wheat, barley, milt, oats, sunflowers, and other food that humans eat. In fact, some researchers suggest that the bird has become incredibly numerous because it has all this great food to eat that was planted by people.

A flock of red-billed quelea birds can number in the millions. The flock flies until they find grassland or fields with food they like. The first birds land, the birds behind them land a little bit farther along, and so on until all the birds have landed and are eating. But by the time the last birds of the flock land, the first ones have eaten everything they can find, so they fly up and over the rest of the birds until they find fresh grass to land in again. This is happening constantly with the entire flock of millions of birds, so that from a distance the flock’s movement looks like a cloud of smoke rolling across a field.

The red-billed quelea also eats insects, mostly during nesting season. Insects and other small invertebrates like spiders are especially nutritious for nestlings.

The quelea is about the size of a sparrow, which it resembles in many ways, although it’s actually a member of the weaver bird family, Ploceidae. It grows less than five inches long, or about 12 cm, including its tail, and it’s mostly brown and gray. Its beak and legs are orangey-red, and during breeding season the male has a rusty-red head with a black mask on his face.

One subspecies of red-billed quelea is native to western and central Africa. Since it’s a subspecies, it has three words in its scientific name: Quelea quelea quelea.

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 397: Some Colorful Fishies

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Thanks to Cosmo, William, and Silas for their fishy suggestions this week!

You have until Sept. 13, 2024 to back the enamel pin Kickstarter!

Further reading:

The Handfish Conservation Project

Researchers Look in Tank and See Promising Cluster of Near-Extinct Babies

The unique visual systems of deep sea fish

A red handfish:

Another red handfish. This one is named Hector:

The black dragon fish:

The white-edged freshwater whipray [photo by Doni Susanto]:

Show transcript:

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

This week we return to the vertebrate world, specifically some strange and colorful fishies. Thanks to William, Cosmo, and Silas for their suggestions!

We’ll start with Silas’s suggestion, the red handfish. We talked about it before back in episode 189, but it’s definitely time to revisit it. When we last discussed it, scientists estimated there were fewer than 100 red handfish left in the wild, meaning it was in imminent danger of extinction. Let’s find out how it’s doing now, four years later.

The handfish gets its name because its pectoral fins look like big flat hands. It spends most of its time on the sea floor, and it uses its hands to walk instead of swimming. It can swim, although it’s not a very strong swimmer, and anyway if you had great big hands you might choose to walk on them too. It doesn’t have a swim bladder, which helps most fish stay buoyant.

All species of handfish are small, only growing to about 6 inches long at most, or 15 cm. This is surprising considering the handfish is closely related to anglerfish, and some anglerfish can grow over 3 feet long, or about a meter.

As for the red handfish specifically, it generally only grows about 4 inches long at most, or 10 cm, and it once lived in shallow water around much of Australia. These days, it’s only found on two reefs southeast of Tasmania. Some populations are bright red while some are pink with red spots. It has a wide downturned mouth that makes it look like a grumpy red toad with big hands.

So how is the red handfish doing? Four years ago it was almost extinct in wild, with fewer than 100 individuals alive. These days the Handfish Conservation Project estimates that the wild population is probably about the same, although because the red handfish is so small and hides so well among sea grass, algae, and rocks that make up its home, it’s hard to get a good count of how many are really alive. It’s also under even more pressure than before as an overpopulation of urchins is overgrazing the plants where it lives, which may sound familiar to you if you listened to episode 395 a few weeks ago. But there is one fantastic change that gives conservationists hope that the red handfish won’t go extinct after all.

The red handfish is so endangered, and its remaining habitat is so small, that a few years ago scientists decided they needed to start a captive breeding program. But even though the fish did just fine in captivity, they didn’t breed at first. Then, in November 2023, one of the fish laid 21 eggs and all 21 hatched safely. Hopefully it won’t be long until the babies are old enough to release into the wild.

The red handfish is one of very few fish that hatch into tiny baby fish instead of into a larval form. Newly hatched babies are only about 5 mm long. Most fish colonize new habitats after they float around aimlessly as larvae, until they grow enough to metamorphose into adults. Since the red handfish doesn’t have this larval stage, and babies just walk around on the sea floor finding tiny worms and other food, it’s hard for the fish to expand its range. Hopefully, as the captive breeding program continues and more young fish are released into the wild, scientists can start releasing red handfish into areas where they used to live.

Next, William asked about the dragon fish. We’ve talked about a few dragonfish before, in episodes 193 and 231, but there are lots of species in many genera in the family Stomiidae. Many have barbels with photophores at the end that lure prey, and most have long needle-like teeth and jaws that can open incredibly wide. They also have stretchy stomachs so they can hold whatever they manage to catch. As you may have guessed from these traits, the dragon fish lives in the deep sea where there’s little or no light from the surface.

You may wonder why deep-sea fish even have eyes if there’s no light. Fish that live in cave systems eventually evolve to be eyeless, since they don’t need their eyes to see and growing eyes is just a waste of their energy. It’s because even though there’s no sunlight in the deep sea, there is light from lots of different organisms. Many, many deep-sea animals produce bioluminescent light to attract mates or trick smaller animals into coming closer.

Any sunlight that does find its way to the depths of the ocean is blue, because blue has the shortest wavelength and can travel farther. Red wavelengths are longest so that red is the first color lost when you start descending into the water. One article that I’ve linked to in the show notes mentions that if a diver gets a cut, the blood looks brown or even black if the water is deep enough. That’s creepy.

As a result, deep-sea fish are most sensitive to the color blue. Most of them can’t perceive red at all because there just isn’t any red in their environment. And that’s where the dragon fish comes in, because some species of dragon fish can not only see red, they produce red light that illuminates everything around them. A fish or other animal swimming along has no idea that it’s lit up like it’s under a red spotlight because it can’t even see that color.

At least one species, the black dragon fish, perceives red light very differently from the way other animals do. As far as we know it’s unique among all animals. Its eyes contain a photosensitizer derived from chlorophyll, which allows it to see shorter lightwaves. Chlorophyll is found in plants and some bacteria, and it’s actually a specialized pigment that absorbs energy from light. It’s the reason why plants are green. But the black dragonfish uses the chlorophyll it digests to perceive red light.

But remember how dragon fish have giant sharp fangs and will eat pretty much anything they can swallow? Where does the black dragon fish get the chlorophyll it needs? There aren’t any plants in the deep sea anyway.

The answer seems to be that the black dragon fish eats a whole lot of copepods, tiny crustaceans that live throughout the world. The particular species of copepods that the black dragon fish prefers contain a type of chlorophyll.

Finally, Cosmo wanted to learn about the freshwater stingray. We talked about it in episode 296, but mostly we concentrated on the South American fish in that episode. There are freshwater stingrays that live in other parts of the world, such as Asia. This includes the white-edge freshwater whipray, which is extremely rare and only found in four rivers in Southeast Asia.

The white-edge freshwater whipray grows up to two feet across, or 60 cm, with a thin tail about two and a half times longer than the body itself so that technically it can grow around 6 and a half feet long, or 2 meters. Most of that length is tail, though. It’s mostly brown so it can hide in the sandy mud at the bottom of the river, with black dermal denticles down the middle of its back. The tail is mostly white, though, and has two long stinging spines that can be over 3 inches long, or 8 cm.

While the white-edged whipray lives in rivers, it can also tolerate brackish water where the ocean and the river waters mix. It eats small animals it finds on the bottom of the river, including crustaceans and mollusks. It’s endangered due to habitat loss, overfishing, and pollution.

The white-edged whipray is so rare these days that it’s unlikely that anyone would accidentally step on one in the water. But if they did, the ray would whip its long tail up and jab the spines into the person’s leg or foot. The spines can do a lot of damage on their own, but the venom they inject makes the wound incredibly painful and can even potentially kill the person.

If you plan to do some wading in a South Asian river anytime soon, make sure to shuffle your feet as you walk to scare away any potential whiprays before you step right on 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. 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 374: PUFFERFISH!

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Thanks to River for suggesting this week’s topic, the pufferfish!

Further reading:

Grass puffer fish communicate with each other using a non-toxic version of their deadly toxin

Mystery pufferfish create elaborate circular nests at mesophotic depths in Australia

Pufferfish, puffed:

A starry puffer, un-puffed [picture by Diego Delso, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=116912671]:

A grass puffer, un-puffed:

The mystery structure that turns out to be made by pufferfish:

Show transcript:

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

This week we’re going to learn about a weird fish suggested by River, the pufferfish!

Lots of fish have the name pufferfish, and sometimes they’re also called balloonfish, swellfish, bubblefish, or globefish. You might be able to guess from the names what they can do, but just in case you don’t know, the pufferfish can puff up to make itself big and round. The question you might have at this point is why, and how do they do this?

There are lots of pufferfish in various genera, all of them in the family Tetradontidae. Tetradontidae means “four teeth,” because obviously when you find an incredibly poisonous fish that can blow itself up like a balloon, sometimes with spikes that emerge from the skin, of course you’re going to name it after its teeth.

Most pufferfish live in the ocean, although some live in places where freshwater mixes with ocean water, and some species even live in rivers. It prefers warm, shallow water and eats invertebrates and plant material. Larger pufferfish can use their four big front teeth to crush the shells of mollusks, like clams and mussels.

Most pufferfish are quite small and often brightly colored with spots, stripes, and other markings. You’d think the biggest pufferfish has to be the one called the giant freshwater pufferfish, but while it is big, it’s not the biggest. The giant freshwater pufferfish can grow up to 26 inches long, or 67 cm, which is over two feet long. But the starry puffer is almost twice that length, up to 47 inches long, or 120 cm. That’s almost four feet long!

The starry puffer lives in tropical and subtropical parts of the Pacific Ocean, especially in the Indian Ocean and the Red Sea. It has a big head, two pairs of nostrils, and is a mottled gray and white in color with little black spots all over. It mostly eats crustaceans and mollusks, but will also eat algae, sponges, coral, urchins, and other invertebrates.

The pufferfish is a slow swimmer, but it has two really good defenses. If it feels threatened—for instance if a big fish tries to catch it, or it’s caught in a fishing net and hauled to the surface, or if a diver tries to make friends, the pufferfish will swell up until it looks like a balloon with fins. It does so by gulping air or water into its elastic stomach until it’s completely full.

If you’re wondering how this can help the fish, not only does this make the pufferfish look much larger, it also makes it harder to swallow. Not only that, the pufferfish has spines that may be hidden in the skin most of the time, but when the skin tightens as the fish expands into balloon shape, the spines poke out. Suddenly a potential predator isn’t just trying to swallow a fish way bigger than its mouth is, it’s pointy.

The pufferfish’s second defense is that its body contains a deadly poison. You may have heard about fugu, which is considered a delicacy even though it’s so poisonous that in Japan and some other countries, chefs have to be specially trained and licensed to prepare the fish to eat. It contains tetrodotoxin, or TTX, a neurotoxin that stops your nerves from sending the tiny electrical signals that allow muscles to move. If you’re poisoned with TTX, you start to feel dizzy and sick, then you start having difficulty speaking and moving, then you have trouble breathing, and then, ultimately, you’re paralyzed and can’t breathe, at which point you die. Since the toxin doesn’t affect your brain, you remain completely aware of what’s happening to you but there’s nothing you can do about it. There’s no antidote. Fortunately, you have the option of not eating fugu.

Not all pufferfish are poisonous, although most are, and in many species the amount of toxins in the fish’s body can vary according to the time of year and the individual fish. People who have eaten their local pufferfish many times with no problem can suddenly get sick or die from eating the same type of fish. That’s the bad type of surprise.

At least some pufferfish use their toxins for a surprising purpose. In late 2022, a study was published about the grass puffer, also called the grey-spotted puffer. It’s a small fish that grows not quite 10 inches long, or 25 cm, and is gray with tiny white spots. It’s extremely toxic but its body also contains a non-toxic version of TTX, called TDT. Scientists studying the fish determined that other grass puffers can smell TDT in the water so they can find each other. Not only that, other animals found in the same environment where the grass puffer lives also contain both TTX and TDT, and the pufferfish eats those animals. Naturally, it can find its prey by smell.

Let’s finish with a pufferfish mystery that’s been solved. In 1995, divers in southern Japan noticed a series of mysterious underwater structures in the sand. They were about six feet across, or close to two meters, round in shape, and looked sort of like someone had packed sand into a giant one of those fancy decorative cake pans that make designs around the cake, and turned it out upside down underwater. No one could figure out what they were, how they’d been made, or why they were there. People started calling them underwater crop circles.

It wasn’t until 2011 that the mystery was solved, when a diver saw one of the circles being formed by a little pufferfish. The fish turned out to be new to science and was described in 2014, and is popularly known as the white-spotted pufferfish. The male builds the structure by waving his fins to move sand into geometric shapes and concentric rings, a process that takes over a week. Since water keeps moving the sand, he has to keep working on the structure to keep it looking good, and he wants it to look good because that’s how he attracts a mate. The specific patterns he creates direct water currents to the center of the structure, where it deposits fine, soft sand. If a female likes the structure, she will lay her eggs in the soft sand in the middle so that the male can fertilize them.

In 2018, similar nests were discovered off the coast of western Australia, but so far no one knows whether the nests are built by a known species of pufferfish or a species new to science.

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!