Monthly Archives: August 2025

Episode 447: So Many Legs!

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Thanks to Mila for suggesting one of our topics today!

Further reading:

The mystery of the ‘missing’ giant millipede

Never-before-seen head of prehistoric, car-size ‘millipede’ solves evolutionary mystery

A centipede compared to a millipede:

Show transcript:

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

Let’s finish invertebrate August this year with two arthropods. One is a suggestion from Mila and the other is a scientific mystery that was solved by a recent discovery, at least partially.

Mila suggested we learn about centipedes, and the last time we talked about those animals was in episode 100. That’s because centipedes are supposed to have 100 legs.

But do centipedes actually have 100 legs? They don’t. Different species of centipede have different numbers of legs, from only 30 to something like 300. Like other arthropods, the centipede has to molt its exoskeleton to grow larger. When it does, some species grow more segments and legs. Others hatch with all the segments and legs they’ll ever have.

A centipede’s body is flattened and made up of segments, a different number of segments depending on the centipede’s species, but at least 15. Each segment has a pair of legs except for the last two, which have no legs. The first segment’s legs project forward and end in sharp claws with venom glands. These legs are called forcipules, and they actually look like pincers. No other animal has forcipules, only centipedes. The centipede uses its forcipules to capture and hold prey, and to defend itself from potential predators. A centipede pinch can be painful but not dangerous unless you’re also allergic to bees, in which case you might have an allergic reaction to a big centipede’s venom. Small centipedes can’t pinch hard enough to break a human’s skin.

A centipede’s last pair of legs points backwards and sometimes look like tail stingers, but they’re just modified legs that act as sensory antennae. Each pair of a centipede’s legs is a little longer than the pair in front of it, which helps keep the legs from bumping into each other when the centipede walks.

The centipede lives throughout the world, even in the Arctic and in deserts, but it needs a moist environment so it won’t dry out. It likes rotten wood, leaf litter, soil, especially soil under stones, and basements. Some centipedes have no eyes at all, many have eyes that can only sense light and dark, and some have relatively sophisticated compound eyes. Most centipedes are nocturnal.

The largest centipedes alive today belong to the genus Scolopendra. This genus includes the Amazonian giant centipede, which can grow over a foot long, or 30 cm. It’s reddish or black with yellow bands on the legs, and lives in parts of South America and the Caribbean. It eats insects, spiders–including tarantulas, frogs and other amphibians, small snakes and lizards, birds, and small mammals like mice. It’s even been known to catch bats in midair by hanging down from cave ceilings and grabbing the bat as it flies by.

Some people think that the Amazonian giant centipede is the longest in the world, but this isn’t actually the case. Its close relation, the Galapagos centipede, can grow 17 inches long, or 43 cm, and is black with red legs.

But if you think that’s big, wait until you hear about the other animal we’re discussing today. It’s called Arthropleura and it lived in what is now Europe and North America between about 344 and 292 million years ago.

Before we talk about it, though, we need to learn a little about the millipede. Millipedes are related to centipedes and share a lot of physical characteristics, like a segmented body and a lot of legs. The word millipede means one thousand feet, but millipedes can have anywhere from 36 to 1,306 legs. That is a lot of legs. It’s probably too many legs. The millipede with 1,306 legs is Eumillipes persephone, found in western Australia and only described in 2021. It lives deep underground in forested areas, where it probably eats fungus that grows on tree roots. It’s long and thin with short legs and no eyes. It’s only about 1 mm in diameter, but can grow nearly 4 inches long, or almost 10 cm.

Millipedes mostly eat decaying plant material and are generally chunkier-looking than centipedes. They have two pairs of legs per segment instead of just one, with the legs attached on the underside of the segment instead of on the sides. A millipede usually has short, strong antennae that it uses to poke around in soil and decaying leaves. It can’t pinch, sting, or bite, although some species can secrete a toxic liquid that also smells terrible. Mostly if it feels threatened, a millipede will curl up and hope the potential predator will leave it alone.

The biggest millipede alive today is probably the giant African millipede, which can grow over 13 inches long, or almost 34 cm, but because millipedes are common throughout the world and are often hard for scientists to find, there may very well be much larger millipedes out there that we just don’t know about.

As an example, in 1897 scientists discovered a new species of giant millipede in Madagascar and named it Spirostreptus sculptus. One specimen found was almost 11 inches long, or over 27 cm. But after that, no scientist saw the millipede again—until 2023, when a scientific expedition looking for lost species rediscovered it, along with 20 other species of animal. It turns out that the millipede isn’t even uncommon in the area, so the local people probably knew all about it.

But Arthropleura was way bigger than any millipede or centipede alive today. It could grow at least 8 ½ feet long, or 2.6 meters, and possibly longer. It probably weighed over 100 lbs, or 45 kg. We have plenty of fossilized specimens, but not one of them has an intact head. Then scientists discovered two beautifully preserved juvenile specimens in France, and CT scans in 2024 revealed that both specimens had nearly complete heads.

The big question about Arthropleura was whether it was more closely related to millipedes or centipedes, or if it was something very different. Without a head to study, no one could answer that question with any confidence, although a lot of scientists had definite opinions one way or another. Studies of the head scans determined that Arthropleura was indeed more closely related to modern millipedes—but naturally, since it lived so long ago, it also had a lot of traits more common in centipedes today. It also had something not found in either animal, eyes on little stalks.

There are still lots of mysteries surrounding Arthropleura. For instance, what did it eat? Because of its size, scientists initially thought it might be a predator. Now that we know it was more closely related to the millipede than the centipede, scientists think it might have eaten like a millipede too. That would mean it mostly ate decaying vegetation, but we don’t know for sure. We also don’t know if it could swim or not. We have a lot of Arthropleura tracks that seem to be made along the water’s edge, so some scientists hypothesize that it could swim or at least spent part of its time in the water. Other scientists point out that Arthropleura didn’t have gills or any other way to absorb oxygen while in the water, so it was more likely to be fully terrestrial. The first set of scientists sometimes comes back and argues that we don’t actually know how Arthropleura breathed or even why it was able to grow so large, and maybe it really did have gills. A third group of scientists then has to come in and say, hey, everyone calm down, maybe the next specimen we find will show evidence of both lungs and gills, and it spent part of its time on land and part in shallow water, so there’s no need to argue. And then they all go for pizza and remember that they really love arthropods, and isn’t Arthropleura the coolest arthropod of all?

At least, I think that’s how it works among scientists. And Arthropleura is really cool.

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 446: Termites

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Thanks to Yonatan and Eilee for this week’s suggestion!

Further reading:

Replanted rainforests may benefit from termite transplants

A vast 4,000-year-old spatial pattern of termite mounds

A family of termites has been traversing the world’s oceans for millions of years

Worker termites [photo from this site]:

Show transcript:

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

This week we have a topic I’ve been wanting to cover for a while, suggested by both Yonatan and Eilee. It’s the termite episode!

We talk a lot about animals that eat termites, and in many cases termite-eating animals also eat ants. I’ve always assumed that termites and ants are closely related, but they’re not. Termites are actually closely related to cockroaches, which are both in the order Blattodea, but it’s been 150 million years since they shared a common ancestor. They share another trait too, in that no one wants either insect infesting their house.

Like most cockroach species, though, most termite species don’t want anything to do with humans. They live in the wild, not in your house, and they’re incredibly common throughout most of the world. That’s why so many animals eat termites almost exclusively. There are just so many termites to eat!

There are around 3,000 species of termite and about a third of them live in Africa, with another 400 or so in South America, 400 or so in Asia, and 400 or so in Australia. The rest live in other parts of the world, but they need warm weather to survive so they’re not very common in cold areas like northern Europe.

A termite colony consists of a queen, soldiers, and workers, which sounds very similar to ants, but there are some major differences. Worker termites take care of the nest and babies, find and process food so the other termites can eat it, and store the processed food. They also take care of the queen. Unlike ants and bees, worker termites aren’t only female and aren’t always sterile. Soldiers are bigger and stronger than workers, with much bigger heads and jaws so they can fight off potential predators. In some species, the soldiers have such big jaws that they can’t actually eat without help. Worker termites feed them. Finally, the queen is the largest individual in the colony, usually considerably larger than workers, but unlike queen bees and ants, she has a mate who stays with her throughout her life, called a king. Some termite queens can live to be as much as 50 years old, and she and the king spend almost their entire lives underground in a nesting chamber.

The larger the colony, the more likely it is that the colony has more than one queen. The main queen is usually the one that started the colony along with her king, and when it was new they did all the work—taking care of the eggs and babies, foraging for food, and building the nest itself. As the first workers grew up, they took on more of those tasks, including expanding the nest.

Workers are small and their bodies have little to no pigment, so that they appear white. Some people call them white ants, but of course they’re not ants. Workers have to stay in a humid environment like the nest or their bodies dry out. Workers and soldiers don’t have eyes, although they can probably sense light and dark, and instead they navigate using their antennae, which can sense humidity and vibrations, and chemoreceptors that sense pheromones released by other termites.

Termites have another caste that’s not as common, usually referred to as reproductives. These are future kings and queens, and they’re larger and stronger than workers. They also have eyes and wings. When outside conditions are right, usually when the weather is warm and humid, the reproductive termites leave the nest and fly away. Males and females pair off and search for a new nesting site to start their own colony.

Termites mainly eat dead plant material, including plant material that most other animals can’t digest. A termite’s gut contains microbes that are found nowhere else in the world, which allow the termite to digest cellulose found in plants, especially wood. Baby termites aren’t born with these microbes, but they gain them from worker termites when the babies are fed or groomed.

In some areas termites will eat the wood used to build houses, which is why people don’t like them, but termites are actually important to the ecosystems where they live, recycling nutrients and helping break down fallen trees so other plants can grow. They also host nitrogen-fixing bacteria, which are important to plant life.

A recent study in Australia determined that termites are really important for rainforest health. In some parts of Australia, conservation groups have started planting rainforest trees to restore deforested areas. Decomposers like termites are slower to populate these areas, with one site that was studied 12 years after planting showing limited termite activity. That means it takes longer for fallen branches, logs, and stumps to decay, which means it takes longer for the nutrients in those items and others to be available for other plants to use.

The problem seems to be that the new forests don’t have very many dead trees yet, so the termites don’t have a lot to eat. The team is considering bringing in fallen logs from more established forests so the termites have food and can establish colonies more easily.

Some species of termite in Africa, Australia, and South America build mounds, and those mounds can be huge. A mound is built above ground out of soil and termite dung, held together with termite saliva. It’s full of tunnels and shafts that allow the termites to move around inside and which bring air into the main part of the nest, which is mostly below ground. Different species build differently-shaped mounds, including some that are completely round.

Some termite mounds can be twice the height of a tall person, and extremely big around. The biggest measured had a diameter of almost 100 feet around, or 30 meters. But in at least one place on earth, in northeastern Brazil, there’s a network of interconnected termite mounds that is as big as Great Britain.

The complex consists of about 200 million mounds, each of them about 8 feet tall, or 2.5 meters, and about 30 feet across, or 9 meters. They’re just huge piles of soil excavated from underground, and tests have determined that the mounds range in age from 690 years old to at least 3,820 years old and are connected by tunnels–but the nests under the mounds are still in use!

Not all termite species build mounds or even live underground. A group called drywood termites live in wood and usually have much smaller colonies than other termites. They probably split off from other termites about 100 million years ago, and a 2022 genetic study determined that they probably originated in South America. But drywood termites have spread to many other parts of the world, and scientists think it’s because their homes float. They estimate that over the last 50 million years, drywood termites have actually floated across entire oceans at least 40 times. When their floating log homes washed ashore, the termites colonized the new land and adapted to local conditions.

A lot of people worry that termites will damage their homes, but in many parts of the world, people eat termites. The termites are fried or roasted until they’re nicely crunchy, and they’re supposed to have a nut-like flavor. They’re also high in protein and important fats. So the next time you worry about your house, you can shout at any potential termites that if they’re around, you might just eat them as a snack.

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 445: Salinella

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It’s a tiny mystery animal!

Further reading:

Salinella – what the crap was it?

Some of Frenzel’s drawings of Salinella:

Show transcript:

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

Johannes Frenzel was a German zoologist in the 19th century. He worked in Argentina for several years, studying microscopic and near-microscopic animals, and seemed to be a perfectly good scientist who did good work but didn’t make a real splash. But these days he’s remembered for a mystery animal that is still causing controversy in the scientific community.

Frenzel described a strange worm-like animal he named Salinella salve in 1892, and Salinella hasn’t been seen since. According to Frenzel’s description of it, Salinella is very different from every other animal known. It’s so different, in fact, that some scientists think Frenzel just made the whole thing up.

In 1890 or 1891, a colleague gave Frenzel a soil sample reportedly from the salt pans in Argentina. We don’t know exactly where it came from, just that it’s somewhere in the Río Cuarto region. Frenzel put the sample in an aquarium and added water, although apparently some iodine got mixed in too, either on purpose or maybe by accident. Then he forgot all about the sample for a few weeks. It wasn’t covered and Frenzel reported that some dead flies had fallen into the aquarium.

When Frenzel finally got around to examining the sample, he discovered something he had never seen before. No one else had either, before or since. He said it was a worm-like animal about 2 millimeters long, and there wasn’t just one of them. There were quite a few in the sample, some in the soil and some attached to the glass.

When he studied the tiny worms, he discovered they had a very basic, very unusual body plan. It was basically just a tube open at both ends, with a single layer of cells around the interior sac. Each cell was covered with cilia on both the exterior side of the animal and the interior side. Cilia are hair-like structures, and salinella used them to move around, a method of propulsion called ciliary gliding. It didn’t have any organs or even tissues—basically nothing you’d expect even in a very simple animal. It reproduced by splitting down the middle, called transverse fission.

Assuming Frenzel was describing a real animal, and was describing it accurately, this body plan is unlike any other animal known. It’s most similar to what scientists think the body plan was of the precursors to sea sponges. It’s also similar in some ways to a group of parasitic animals called Mesozoa, which are wormlike, very simple, only a few millimeters long at most, and which have an outer layer of ciliated cells. Mesozoans aren’t well understood and most scientists these days think the group is made up of animals that aren’t closely related to each other. Salinella has sometimes been considered a mesozoan, but it’s still not that close of a match.

Frenzel took detailed notes and made careful drawings of Salinella, and compared it to known animals like protozoans. His description of the animal is solid, and he described many other animals in his career that are well-known to scientists today. The main reason some scientists now think Frenzel made Salinella up is because it’s so weird and no one has been able to find it since. Frenzel died in 1897 without ever having the chance to look for more specimens.

In 1963 an American biologist placed Salinella in its own phylum, which he named Monoblastozoa. In the early 2010s, a team of German scientists visited various saline lakes in Argentina and Chile in hopes of finding Salinella specimens, but without luck. The area where the original soil sample came from has mostly been converted to farmland, so if Salinella was restricted to that one spot, it might well be extinct now.

So what happened to the type specimens that Frenzel collected? We don’t know. They vanished sometime between 1891 when Frenzel moved back to Germany from Argentina, and now. It might even be that he couldn’t preserve the specimens, since he reported that every time he tried to preserve one, it disintegrated.

While I was researching this episode, I wondered if Salinella actually came from the flies that reportedly fell into the aquarium. Many parasites evolve to become very simple, like Myxozoa that we talked about in episode 422. But Frenzel observed Salinella apparently eating organic matter in the soil, which isn’t something a fly parasite would or could do.

At this point, unless we can find a living Salinella specimen, there’s no way to know if the animal was real or a figment of Frenzel’s imagination. Some scientists even suggest that Frenzel was mistaken in his description and the real animal might actually be very different from what he described. Considering how detailed and careful Frenzel’s notes and drawings are, and how many other species he described without causing any controversy at all, I think Salinella was a real animal, just a weird one. Let’s hope that one day it’s discovered again so we can learn more about it.

You can find Strange Animals Podcast at strangeanimalspodcast.blubrry.net. That’s blueberry without any E’s. If you have questions, comments, or suggestions for future episodes, email us at strangeanimalspodcast@gmail.com. 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 444: Diskagma and Horodyskia

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It’s Invertebrate August! These creatures are the most invertebrate-y of all!

Further reading:

Dubious Diskagma

Horodyskia is among the oldest multicellular macroorganisms, finds study

A painting of diskagma, taken from the top link above:

Little brown jug flowers (not related to diskagma in any way!):

Show transcript:

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

This episode started out as the March 2025 Patreon episode, but there was more I wanted to add to it that I didn’t have time to cover in that one. Here’s the expanded version to kick off Invertebrate August, which also happens to be episode 444 and releasing on August 4th! It’s about two mystery fossils.

The first is named Diskagma, which means disc-shaped fragment, and it was only described in 2013. That’s partly because it’s so small, barely two millimeters long at most, and partly because of where it’s found. That would be fossilized in extremely old rocks.

When I saw the illustration accompanying the blog post where I learned about Diskagma, I thought it was a cluster of cup-like flowers, sort of like the flowers of the plant called little brown jug. I was ready to send the link to Meredith Hemphill of the Herbarium of the Bizarre podcast, which by the way you should be listening to. But then I saw how old Diskagma is.

It’s been dated to 2.2 billion years old. That’s older than any plant, probably by as much as a billion years.

Even more astounding, it lived on land.

As a reminder, the Cambrian explosion took place about half a billion years ago, when tiny marine animals diversified rapidly to fill new ecological niches. That happened in the water, though, mainly in shallow, warm oceans. If you go back to around 850 million years ago, that may have been roughly the time that land plants evolved from green algae that lived in fresh water. Plant-like algae, or possibly algae-like plants, might be as old as 1 billion years old. But before then, scientists don’t find evidence of anything except microbes living on land, and they were probably restricted to lakes and other bodies of fresh water. That’s because there wasn’t much soil, just broken-up rock that contained very few nutrients and couldn’t retain much water.

Diskagma was shaped like a tiny elongated cup, or an urn or vase, with what looks like a stem on one end and what looks like an opening at the other end. The opening contained structures that look like little filaments, but the filaments didn’t fill the whole cup. Most of the cup was diskagma’s body, so to speak, although we don’t know what it contained. We also don’t know what the filaments were for. We do know that the stem actually did connect diskagma to other cups, so that they lived in little groups. We don’t know if it was a single animal with multiple cuplike structures or if it was a colony, or really anything.

That’s the problem. We don’t know anything about diskagma except that it existed, and that it lived on land 2.2 billion years ago. Tiny as it was, though, it wasn’t microscopic, and it definitely appears more complex than would be expected that long ago, especially from something living on dry land.

One suggestion is that the main part of its body contained a symbiotic bacteria that could convert chemicals to nutrients. As in many modern animals, especially extremophiles, the bacteria would have had a safe place to live and the diskagma would have had nutrients that allowed it to live without needing to eat.

Diskagma lived at an interesting time in the earth’s history, called the great oxygenation event, also called the great oxidation event. We talked about it in episode 341 in conjunction with cyanobacteria, because cyanobacteria basically started the great oxygenation event. Cyanobacteria are still around, by the way, and are doing just fine. They’re usually called blue-green algae even though they’re not actually algae.

Cyanobacteria photosynthesize, and they’ve been doing so for far longer than plants–possibly as much as 2.7 billion years, although scientists think cyanobacteria originally evolved around 3.5 billion years ago. The earth is about 4.5 billion years old, if you were wondering.

Like most plants also do, cyanobacteria produce oxygen as part of the photosynthetic process, and when they started doing so around 2.7 billion years ago, they changed the entire world. Before then, earth’s atmosphere hardly contained any oxygen. If you had a time machine and went back to more than two billion years ago, and you forgot to bring an oxygen tank, you’d instantly suffocate trying to breathe the air. But back then, even though animals and plants didn’t yet exist, the world contained a whole lot of microbial life, and none of it wanted anything to do with oxygen. Oxygen was toxic to the lifeforms that lived then, but cyanobacteria just kept producing it.

Cyanobacteria are tiny, but there were a lot of them. Over the course of about 700 million years, the oxygen added up until other lifeforms started to go extinct, poisoned by all that oxygen in the oceans and air. By two billion years ago, pretty much every lifeform that couldn’t evolve to use or at least tolerate oxygen had gone extinct.

Since Diskagma lived during the time of the great oxygenation event, some scientists suggest that it contained microbes that photosynthesized sunlight into nutrients diskagma could use. And, as in cyanobacteria, the side effect of photosynthesis is oxygen, so diskagma might have been contributing to the oxygen in the air that allows us to breathe these days. On the other hand, it might not have had anything to do with photosynthesis and the great oxygenation event might have driven diskagma to extinction. We have no way to know right now.

What we do know is that 700 million years after diskagma lived, something similar appears in the fossil record. It’s called Horodyskia and its fossils have been found in rocks dating between 1.5 billion years ago to 550 million years ago. Unlike diskagma, which has only been found in rocks from South Africa, horodyskia fossils have been found in Australia, China, and North America. That doesn’t mean diskagma wasn’t widespread, just that we haven’t found it anywhere else. There aren’t all that many rocks that are over two billion years old.

Horodyskia lived in the water, specifically at the bottom of the ocean, probably in shallow water. It’s been described as looking like a row of beads on a thread. The thread seemed to be buried in the sand, and growing up from it in intervals were little pear-shaped bulbs, each no larger than a millimeter long, that stuck up through the sand into the water. There may have been little root-like structures called holdfasts that grew from the bottom of the thread to help keep it in place.

We don’t know a lot about horodyskia either. It wasn’t a plant, since it also lived long before plants evolved. A 2023 study determined that it was a multicellular creature and that it was most likely a protist. Protists are related to animals, plants, and fungi, but aren’t any of those things, and they’re an incredibly diverse group. Most are single-celled and microscopic, but not always. They include algae, amoebas, slime molds, and lots more. Horodyskia’s bulbs might have been encased in a jelly-like substance, as is common in a lot of protists. Some horodyskia specimens found in younger rocks, the ones about 550 million years old, are much smaller than the earlier specimens, with each bulb barely a fraction of a millimeter in size.

We might not know much about these strange life forms, but knowing they existed tells us that even two billion years ago, life was a lot more varied than we used to think. And that’s the most exciting thing of all.

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!