Category Archives: crustaceans

Episode 290: Lobsters!



Thanks to Pranav for this week’s suggestion, lobsters!

Happy birthday to Jake!!

Visit Dr. Oné R. Pagán’s site for links to his podcast and his free book Arrow: The Lucky Planarian! You can also order his other books from your favorite book store. Here’s the direct link to his interview with me!

Further reading:

Don’t Listen to the Buzz: Lobsters Aren’t Actually Immortal

An ordinary lobster:

A blue lobster!

The scampi looks more like a prawn/shrimp than a lobster, but it’s a lobster:

 

The rosy lobsterette is naturally red because it lives in the deep sea:

The deep-sea lobster Dinochelus ausubeli was only discovered in 2007 and described in 2010:

Show transcript:

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

As invertebrate August continues, this week we’re going to talk about lobsters. Thanks to Pranav for the suggestion!

But first, we have a birthday shout-out! A great big happy birthday this week to Jake! I hope your birthday is epic fun!

I’d also like to let you know that Dr. Oné R Pagán interviewed me recently about my book, Beyond Bigfoot & Nessie: Lesser-Known Mystery Animals from Around the World, and you can hear that interview on his podcast, the Baldscientist Podcast. Baldscientist is all one word. I’ll put a link in the show notes. While you’re at it, you should definitely buy his books, including his latest one, Drunk Flies and Stoned Dolphins: A Trip Through the World of Animal Intoxication, which just came out this year and is a lot of fun, as well as being full of interesting science! He also has a free children’s story called Arrow, the Lucky Planarian that you can download and read. It’s completely charming and you’ll learn a lot about planarians, which are also called flatworms, which are invertebrates, so this is all coming together!

This week’s episode isn’t about planarians, though, but about lobsters. I don’t think we’ve ever discussed lobsters on the podcast before, oddly enough, but it’s been on my ideas list for a long time. When Pranav emailed me recently to suggest we do a lobster episode, I realized it was time! Time for lobsters!

The lobster is a crustacean, and while there are plenty of different lobsters in the world, we’re going to focus on the clawed lobsters this time. There are lots of them, all grouped in the family Nephropidae.

The lobster has eight legs that it walks on, and two more legs with pincers. That’s why it’s in the order Decapoda. Deca means ten and poda means feet. Ten feet. Some of which can pinch you if you’re not careful.

The lobster uses its claws to defend itself from potential predators, and uses them to grab and kill small animals. It eats pretty much anything it can find, from fish and squid to sea stars and mollusks, to dead animals and some plant material. But its claws are too big and clumsy to use to eat with, which is why it has much smaller pincers on its next pairs of legs. These pincers are equipped with chemoreceptors that allow the lobster to taste its food before it actually eats it, which is a neat trick.

The lobster uses these small claws to pull its food into smaller pieces and convey it to the mouthparts, which are under its head. Some mouthparts have sensory hairs that can taste food, some have sharp spines that act as teeth to tear food into smaller pieces, and others are small and just flutter to help keep pieces of food from floating away. The stomach is only about an inch away from the mouth, or about 2.5 cm, no matter the size of the lobster. The stomach itself, and the short esophagus leading to the stomach, are lined with chitin spines that act like teeth to grind food up while enzymes break it down to fully digest it. This seems like a really complicated way to eat, but it’s actually not all that different from the way we eat, it’s just that instead of mouthparts and stomach teeth, we do all our grinding up of food in the mouth with just one set of teeth.

The lobster’s body is protected by an exoskeleton made of chitin, but the trouble with exoskeletons is that they don’t grow. The lobster has to shed its exoskeleton every so often and grow a new one that fits better, and until the new exoskeleton has hardened, the lobster is vulnerable and will usually hide. This can take several weeks. When a lobster is young and growing rapidly, it may molt its exoskeleton every few months or even more often, while an adult lobster typically only molts once every year or two.

Molting takes energy, though, and the bigger a lobster is, the more energy it takes to molt. It’s not like taking off a shirt. The lobster has to wriggle carefully out of its exoskeleton through a split between its tail and abdomen, making sure not to hurt its soft body in the process, and it even molts its stomach teeth, more properly called a gastric mill.

It’s a long, difficult process, during which time the lobster is mostly helpless. Some studies indicate that something like 10% of all lobsters actually die during the molting process. A lobster usually eats its shed exoskeleton in order to extract calcium from it, which helps its new exoskeleton harden faster.

Unlike many animals, lobsters keep growing throughout their lives. Since they can live a long time, that means sometimes people catch really big lobsters. The biggest ever reliably measured was an American lobster caught in 1977 off the coast of Nova Scotia, Canada in North America. It weighed 44 lbs, 6 oz, or 20.14 kg and was 3.5 feet long, or 106 cm. A more ordinary weight of a good-sized lobster is about 2 lbs, or 910 grams.

The lobster can definitely live at least 50 years, and some researchers suggest it can live much longer than that. But it’s really hard to tell the age of a lobster. You can’t go by size since individual lobsters grow at different rates depending on how much food they can find and other factors. A study published in September 2021 reports that a DNA test of genetic modifications that lobsters and other animals accumulate during their lives can determine a lobster’s age with a good degree of accuracy. This is important since it will help conservationists learn more about lobster populations, many of which are under increasing pressure from commercial fishing.

There’s a lot of talk online about how the lobster is actually immortal, and that if nothing kills it, it will just live forever. This rumor got started when scientists reported that lobsters express an enzyme called telomerase that repairs damage to DNA sequences at the ends of chromosomes. Most adult animals lose the ability to express telomerase, but the lobster doesn’t.

But lobsters aren’t immortal. A really old lobster stops shedding its exoskeleton, which slowly becomes more and more battered. The exoskeleton is part of the lobster’s body and can contract bacterial infections when it’s injured. Sometimes the infections are bad enough that it fuses the exoskeleton to the body permanently, so if the lobster does eventually get to the point where it can molt, it gets stuck trying to and dies. Sometimes the exoskeleton just rots away, which leads to the lobster’s death.

Still, the telomerase probably helps the lobster live for such a long time. Now that scientists have a way to determine a lobster’s actual age without harming it, hopefully soon we’ll learn more about how old they really get. We might be surprised, who knows?

Most species of lobster are brown, black, or greenish, which helps them hide on the sea floor. When a lobster is cooked by boiling, chemicals in its exoskeleton react with the hot water and turn it bright red. But sometimes—like, once every 10 million lobsters—a live lobster is found that is red. Researchers aren’t sure what causes this coloration.

Sometimes lobsters can be blue too. It’s still rare but not as rare as red coloration, estimated at about one every two million lobsters. While some species of lobster are naturally dark blue or even dark purple, a blue lobster is a really pretty shade of bright blue. It’s caused by a genetic mutation that results in it producing more of a protein that reacts with the pigments in its body, turning it blue. Since blue lobsters are so striking and attractive, lobster fishers usually either throw blue lobsters back or donate them to local aquariums. People sometimes assume blue lobsters are poisonous even though they’re not, so mostly no one wants to eat them anyway.

Lobsters are closely related to crabs and shrimp, and some clawed lobsters look a lot like their close relatives. This includes the scampi, which is the pinkish and silvery-white coloration of a prawn or shrimp, and only grows about 10 inches long at most, or 25 cm. It lives in parts of the northeastern Atlantic and parts of the Mediterranean Sea, where it digs a burrow in the muddy sea floor and spends most of its time hiding. It eats worms, small fish, jellyfish, and anything else it can catch. There are other species of scampi that live in other parts of the world’s oceans too.

Another lobster that looks even more like a shrimp is the rosy lobsterette, which only grows about 5 inches long, or 13 cm, and which is naturally red. This isn’t a rare coloration but an adaptation to its habitat. Unlike most lobsters, which live in shallow coastal waters, the rosy lobsterette lives in much deeper water where there’s very little light. As we’ve talked about before, the wavelength of light that is red can’t penetrate very far into water, so a red animal in the deep sea is basically invisible. A lot of deep-sea animals can’t even perceive the color red. The rosy lobsterette lives in the Gulf of Mexico, around the Caribbean, and in the western Atlantic Ocean.

There are actually quite a few species of lobster that live in the deep sea, with more being discovered every so often. In 2010 a new species of deep-sea lobster was described, Dinochelus ausubeli, which lives near the Philippines in South Asia. It was discovered during the ten-year Census of Marine Life, which sponsored 540 expeditions by thousands of scientists all over the world. It only grows a few inches long, or about 5 cm, and is mostly transparent with some pinkish coloring. It has one really long, thin, spiny claw with a bulbous base, while the other claw is much smaller.

There are a whole lot of other clawed lobster species, some of them known from only a few specimens. The Cape lobster, for instance, lives off the coast of South Africa in rocky areas, and even though it’s been known to science since the late 18th century, we don’t know much about it. It’s small, only growing about 4 inches long, or 10 cm, and ranges in coloration from greenish to yellowish to brown, even sometimes red, and it looks like a miniature version of the European or American lobsters although it’s not very closely related. In 1992 someone found one, which was such a rare occurrence that it was reported in the news. It was only the 14th specimen ever found at the time, although the publicity it received got other people out looking for the little lobster and more have been found since.

In other words, there are undoubtedly lots more species of lobster than we know about, just waiting to be discovered.

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

Thanks for listening!


Episode 288: Mystery Invertebrates



Thanks to Joel for suggesting this week’s topic!

Happy birthday to Fern this week!

Further reading:

Small, rare crayfish thought extinct is rediscovered in cave in Huntsville city limits

Hundreds of three-eyed ‘dinosaur shrimp’ emerge after Arizona monsoon

An invertebrate mystery track in South Africa

The case of the mysterious holes in the sea floor

Contemplating the Con Rit

The Shelton Cave crayfish, rediscovered:

The three-eyed “tadpole shrimp” or “dinosaur shrimp,” triops [photo from article linked above]:

A leech track in South Africa [photo from article linked above]:

A track, or at least a series of holes, discovered in the deep seafloor [photos from article linked above]:

Show transcript:

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

Thanks to Joel who suggested we do an episode about mystery invertebrates! It took me a while, but I think you’re really going to like this episode. Some of the mysteries are solved and some are not, but they’re all fun.

Before we get to the mystery animals, though, we have a birthday shout-out! A great big happy birthday to Fern! I hope you have your favorite type of birthday cake or other treat and get to enjoy it with your loved ones.

Our first mystery starts in a cave near Huntsville, Alabama in the southern United States, which is in North America. Shelta Cave is a relatively small cave system, only about 2,500 feet long, or 760 meters. That’s about half a mile. It’s a nature preserve now but in the early 1900s it was used as an underground dance hall with a bar and everything.

Biologist John Cooper studied the cave’s aquatic ecosystem in the 1960s when he was doing his dissertation work. His wife Martha helped him since they were both active cavers. At the time, the cave ecosystem was incredibly diverse, including three species of crayfish. One was called the Shelta Cave crayfish, which was only a few inches long, or about 5 cm, mostly translucent or white since it didn’t have any pigment in its body, and with long, thin pincers.

It was rarer than the cave’s other two crayfish species, and unlike them it had only ever been found in Shelta Cave. From 1963 to 1975, only 115 individuals had been confirmed in repeated studies of the cave’s ecosystem.

Then, in the 1970s, several things happened that caused a serious decline in the diversity of life in the cave.

The first was development of the land around the cave into subdivisions, which meant that more pesticides were used on lawns and flower beds, which made its way into the groundwater that entered the cave. It also meant more people discovering the cave and going in to explore, which was disturbing a population of gray bats who also lived in the cave. To help the bats and keep people out, the park service put a gate over the entrance, but the initial gate’s design wasn’t a very good one. It kept people out but it also made it harder for the bats to go in and out, and eventually the bats gave up and moved out of the cave completely. This really impacted the cave’s ecosystem, since bats bring a lot of nutrients into a cave with their droppings and the occasional bat who dies and falls to the cave floor.

The gate has since been replaced with a much more bat-friendly one, but studies afterwards showed that a lot of the animals found in the cave had become rare. The Shelta Cave crayfish had disappeared completely. One was spotted in 1988 but after that, nothing, and the biologists studying the cave worried that it had gone extinct.

Then, in 2019, a team of scientists and students surveying life in the cave spotted a little white crayfish with long, thin pincers in the water. The team leader dived down and scooped it up with his net to examine more closely. The crayfish turned out to be a female Shelta Cave crayfish with eggs, which made everyone excited, and after taking a tiny tissue sample for DNA testing, and lots of photographs, they released her back into the water. The following year they found a second Shelta Cave crayfish.

The Shelta Cave crayfish is so little known that we don’t even know what it eats or how it survives in the same environment with two larger crayfish species. Biologist Dr. Matthew Niemiller is continuing Dr. Cooper’s initial studies of the cave and will hopefully be able to learn more about the crayfish and its environment.

Next let’s travel from a cool, damp, flooded cave in Alabama to northern Arizona. Arizona is in the western United States and this particular part of the state has desert-like conditions most of the year. Almost a thousand years ago, people built what is now called Wupatki Pueblo, a 100-room building with a ballcourt out front and a big community room. It was basically a really nice apartment building. Wupatki means “tall house” in the Hopi language, and while the pueblo people who built it are long gone, Wupatki is still an important place for the Hopi and other Native American tribes in the area. It’s also a national monument that has been studied and restored by archaeologists and is open to the public.

In late July 2021, torrential rain fell over the area, so much rain that it pooled into a shallow temporary lake around Wupatki, including flooding the ballcourt. The ballcourt is 105 feet across, or 32 meters, and surrounded by a low wall. One day while the ballcourt was still flooded, a tourist came up to the lead ranger, Lauren Carter. The visitor said there were tadpoles in the ballcourt.

There are toads in the area that live in burrows and only come out during the wet season when there’s rain, and Carter thought the tadpoles might be from the toads. She went to investigate, saw what looked like tadpoles swimming around, and scooped one up in her hands to take a closer look. But the tadpoles were definitely not larval toads. In fact, they kind of looked like teensy horseshoe crabs, with a rounded shield over the front of the body and a segmented abdomen and tail sticking out from behind, with two long, thin spines at the very end that are called caudal extensions. It had two pairs of antennae and lots of small legs underneath, some adapted for swimming. The largest of the creatures were about two inches long, or 5 cm.

What on earth were they, and where did they come from? This area is basically a desert. Carter stared at the weird little things and remembered hearing about something similar when she worked at the Petrified Forest National Park, also in Arizona. She looked the animal up and discovered what it was.

It’s called Triops and is in the order Notostraca. Notostracans are small crustaceans shaped sort of like tadpoles, which is why it’s sometimes called the tadpole shrimp, but it’s not a shrimp. It has two eyes on the top of its head visible through its flattened, smooth carapace. Species in the genus Triops also have a so-called third eye between the two ordinary eyes, although it’s a very simple eye that probably only detects light and dark. Many crustaceans have these third eyes in their larval forms but very few retain them into adulthood.

Notostracans have been around for about 365 million years, and haven’t changed much in the last 250 million years. It’s an omnivore that mostly lives on the bottom of freshwater pools and shallow lakes, often temporary ones like the flooded ballcourt, although some species live in brackish water and saline pools, or permanent waterways like peat bogs.

Triops eggs are able to tolerate high temperatures and dry conditions, with the eggs remaining viable for years or even decades in the sediment of dried-up ponds. When enough water collects, the eggs hatch and within 24 hours are miniature versions of the adult Triops. They grow up quickly, lay lots of eggs, and die within a few months or when the water dries up again.

Triops eggs are even sold as aquarium pets, since they’re so unusual looking and are easy to care for. They basically eat anything. They especially like mosquito larvae, so if you see some in your local pond or other waterway, give them a tiny high-five.

In 1996, some workers near Indianapolis, Indiana were servicing a tank full of chemical byproducts from making plastic auto parts when they noticed movement in the toxic goo. They investigated and saw several squid-like creatures swimming around. They were red-brown and about 8 inches long, or 20 cm, including their arms or tentacles, but were only about an inch wide, or 2.5 cm.

The workers managed to capture one and put it in a jar, which they stuck in the break room refrigerator. By the time someone in management arranged to have it examined by a scientist, the jar had been thrown out. If you’ve ever tried to keep food in a break room fridge, you’ll know that there’s always someone who will throw out everything in the fridge that isn’t theirs, no matter whether it’s labeled or brand new or not. I have had my day’s lunch thrown out that had only been in the fridge a few hours. Anyway, when the tank was cleaned out the following year, no one found any creatures in it at all.

This sounds really interesting, but there’s precious little information to go on. The story appeared in a few newspapers but we have no names of the people who reportedly saw the creatures, no follow-up information. It has all the hallmarks of a hoax or urban legend. The creatures’ size also seems quite large for extremophiles in a small, closed environment. What would they find to eat to get so big?

Next let’s talk about some mysterious tracks made by invertebrates, as far as we know. We’ll start with a track on land that was a mystery at first, but was solved. A man in the Kruger National Park in South Africa named Rudi Hulshof came across a weird track in the sandy dirt that he didn’t recognize. It was maybe 10 mm wide and kind of looked like a series of connected rectangles, as though a tiny person was moving a tiny cardboard box by rolling it over and over, but there weren’t any footprints, just the body track.

Curious, Hulshof followed the track to find what had made it, and finally discovered the culprit. It was a leech! Most leeches live in water, whether it’s the ocean, a pond or swamp, a river, or just flooded ground. Most species are parasitic worms that attach to other animals with suckers, then pierce the animal’s skin and suck its blood. The leech stays on the animal until it’s full, then drops off. Some leeches are terrestrial, but it appears that this one was a freshwater leech that had attached to an animal passing through the water, then dropped off onto land. It had crawled as far as it could trying to find a better environment, but when Hulshof found it it was dead, so it had not had a good day.

The leech moves on land by stretching the front of its body forward, then dragging its tail end up in a bunch kind of like a worm (it is a kind of worm), so that’s why its track was so unusual-looking. It’s a good thing Hulshof found the leech before something ate it, or else he’d probably still be wondering what had made that track.

We have photographs of other tracks that are still mysterious. You may have heard about one that’s been in the news lately. This one was found by a deep-sea rover in July 2022, more than a mile and a half deep, or 2500 meters, in the north Atlantic Ocean.

The track may or may not actually be a track, although it looks like one at first glance. It consists of a line of little holes in the seafloor, one after the other, although they’re not all the same distance apart. The rover saw them on two separate dives in different locations, so it wasn’t just one track, but although the scientists operating the rover remotely tried to look into the holes, they couldn’t get a good enough view. It does look like there’s sediment piled up next to the holes, so researchers think something might actually be digging the holes, either digging down from the surface to find food hidden in the sediment, or digging up from inside the sediment to find food in the water. The rover did manage to get a sample of sediment from next to one of the holes and a water sample from just above it, and eventually those samples will be tested for possible environmental DNA that might help solve the mystery.

This wasn’t the first time these holes have been seen in the area, though. An expedition in 2004 saw them and hypothesized that the holes are made by an invertebrate with a feeding appendage of some kind that it uses to dig for food. Not only that, we have similar-looking fossil holes in rocks formed from deep marine sediments millions of years ago.

Other deep-sea tracks have a known cause, and humans are responsible. In the 1970s and 1980s, ships with deep-sea dredging equipment traveled through parts of the Pacific Ocean, testing the ocean floor to see whether the minerals in and beneath the sediment were valuable for mining. A few years ago scientists revisited the same areas to see how the ecosystems impacted by test mining had responded.

The answer is, not well. Even after 40 years or so since the deep-sea mining equipment sampled the sea floor, the marks remain. The deep sea is a fragile ecosystem to start with, and any disturbance takes a long, long time to recover—possibly thousands of years. So while the holes discovered in 2022 were almost certainly made by an animal or animals, they might be quite old.

Let’s finish with a mystery animal we’ve talked about before, but a really long time ago—way back in episode 6. It’s definitely time to revisit it.

In 1883 when he was 18 years old, a Vietnamese man named Tran Van Con had seen the body of an enormous creature washed up on shore at Hongay in Vietnam. Van Con said it was probably 60 feet long, or 18 meters, but less than three wide wide, or 90 cm. It had dark brown plates on its back with long spines sticking out from them to either side, and the segment at its tail end had two more spines pointing straight back. It didn’t have a head, which had presumably already rotted off, or something bit it off before the animal washed ashore. It had been dead for a long time considering the smell. In fact, it smelled so terrible that locals finally towed it out to sea to get rid of it. It sank and that was the last anyone ever saw of it. The locals referred to it as a con rit, which means “millipede,” since the armor plates made it look like the segmented body of an immense millipede.

Lots of people have made suggestions as to what the con rit could be, but nothing really fits. It was the length of a whale, but it doesn’t sound like any kind of whale known. The armored plates supposedly rang like metal when hit with a stick. Even if this was an exaggeration, it probably meant the armor plates were really hard, not just the skin of a dead whale that had hardened in the sun. It also implies that the plates had empty space under them, allowing them to echo when hit. Zoologist Dr. Karl Shuker suggests that the plates might have been the exoskeleton of a crustacean of some kind, which makes a lot more sense than a whale, but the sheer size of the carcass is far larger than any crustacean, or even any arthropod, ever known.

There’s also some doubt that the story is accurate. It might even be a hoax. We only know about the con rit at all because the director of Indochina’s Oceanographic and Fisheries service, Dr. A. Krempf, talked to Tran Van Con about it in 1921. That was 38 years after Van Con said he saw the creature, so he might have misremembered details. Not only that, Krempf translated the story from Vietnamese, and there’s no way of knowing how accurate his translation was.

The con rit is also a monster from Vietnamese folktales, a sort of sea serpent that had lots of feet. It was supposed to attack fishing boats to eat the sailors, until a king caught it and chopped it up into pieces. A local mountain was supposedly formed from its head, and the other pieces of its body turned into the unusual stones found on a nearby island.

There’s always the possibility that Tran Van Con actually told Krempf this folktale, but that Krempf misunderstood and thought he was telling him something he actually witnessed. Then again, there are eight reports from ships in the area between 1893 and 1915 of creatures that might have been a con rit. One account from 1899 was a sighting of a creature estimated as being 135 feet long, or 41 meters, which was rowing itself along at the surface by means of multiple fins along its sides.

Whatever the con rit was, there haven’t been any sightings since 1915. That doesn’t mean there isn’t a population of incredibly long invertebrates living in the deep ocean in southeast Asia. If it does exist, maybe one day a deep-sea rover will spot one. Maybe it dug those little holes, who knows?

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

Thanks for listening!


Episode 287: Sand Crabs, Sea Slugs, and a Mystery Octopus



Sign up for our mailing list! Even though I hardly ever send an email to it!

It’s INVERTEBRATE AUGUST! Thanks to Elizabeth, Richard, and Llewelly for their suggestions this week!

Further reading:

Meet Phylliroe: the sea slug that looks and swims like a fish

Hey, so these sea slugs decapitate themselves and grow new bodies

Found, Then Lost, Then Found Again: Scientists Have Rediscovered the Sand Octopus

A sand crab in the air:

Sand crabs in the water, feeding:

Phylliroe is a sea slug that looks like a fish (pictures from article linked to above):

How I used to draw snails when I was a kid, adding an extra foot because I didn’t understand that the “foot” of a snail/slug is the flat part of the body that touches the ground:

The mysterious sand octopus in mid-swim:

Show transcript:

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

It’s the first week of invertebrate August and we’re heading to the ocean for our first episode! Let’s jump right in with an episode about sand crabs, a couple of sea slugs, and an octopus mystery that was recently solved. Thanks to Elizabeth, my brother Richard, and Llewelly for their suggestions!

We’ll start with Elizabeth’s suggestion. The sand crab is also called the sand bug, the mole crab, or similar names that refer to its habit of burrowing into the sand. It’s common throughout much of the world’s oceans, especially in warm areas, and can be extremely numerous. It’s also sometimes called the sand flea, but it’s not the kind of tiny jumping crustacean that bites, also called the sand flea. This little crustacean is harmless to humans. It doesn’t even have pincers.

The sand crab isn’t a true crab although it is closely related to them. It’s gray-brown and has a tough carapace to protect it when it’s washed around by waves and to help protect it from predators. Females are larger than males and can grow up to an inch and a half long in the largest species, or about 35 mm, and an inch wide, or 25 mm. So it’s longer than it is wide, unlike most crabs, and its carapace is domed sort of like a tiny tortoise shell. Overall, it’s shaped sort of like a streamlined barrel. I saw one site that called it the sand cicada and it is actually about the same size and shape as a cicada, which it isn’t related to at all except that they’re both invertebrates. Some species have little spines on the carapace while others are smooth.

The sand crab lives in the ocean, specifically in the intertidal zone right at the area where waves wash up on the beach. This is called the swash, by the way, which is a great word. The sand crab burrows into the sand tail-first, using its strong rear legs, and during the time that there’s water over the sand, it unfurls its feathery antennae to filter tiny food particles from the water. When the wave goes out, it retracts its antennae and works on staying buried in the sand as the next wave rolls in.

In some species, males are very similar to females, but smaller. In other species, they’re tiny, barely 3 mm long at most, and even as adults they resemble larvae. The male finds a female and grabs hold of her leg, and there he stays. I tried to find out more about this, but it doesn’t look like the humble sand crab gets a lot of attention. If you’re interested in becoming a scientist who studies invertebrates and you want to spend a lot of time on the beach, the sand crab would make a good study buddy.

Lots of fish and birds eat sand crabs, and people do too. In many places they’re considered a delicacy and grilled as a snack. This isn’t surprising since they’re related to other crustaceans people like to eat, like crabs and lobsters.

Next, let’s learn about two strange sea slugs. We’ve talked about sea slugs a few times before, including in episodes 215 and 129, but there are a lot of species, with more being discovered pretty often.

Llewelly sent me a link ages ago about a sea slug that’s related to the sea bunny, which we talked about in the cutest invertebrates episode, 215. It’s called Phylliroe and doesn’t look like a little bunny or a slug. It looks like a fish.

Phylliroe grows a few inches long at most, or 5 cm, and the article Llewelly sent, which I’ve linked to in the show notes, points out that it’s about the size of a goldfish. Its rear end is shaped roughly like a fish tail, which it uses just like a fish tail to propel itself through the water. It’s probable that Phylliroe’s shape doesn’t have anything to do with disguising it, but instead is just the result of convergent evolution. A body streamlined to move through the water with minimal resistance is always going to be fish-shaped, because that’s why fish are shaped the way they are. The fish-like tail is also an efficient way to move through the water relatively quickly.

Phylliroe mostly eats tiny jellyfish, which it grabs with its small foot. It doesn’t need a big flat foot to glide on, since it doesn’t live on the sea floor like some of its relations, so over many, many generations its foot has become smaller and smaller until it’s just a little tiny foot near its mouth. It’s still sticky, though, which means jellies stick to it, which means it’s easier for Phylliroe to eat the jellies.

Phylliroe is mostly see-through, although you can see its digestive system. It also has two so-called horns, called rhinophores, that it probably uses to sense the chemical signature of its prey in the water. If you remember the sea bunny, its rhinophores look like bunny ears. Phylliroe’s look more like thick antennae or barbels. Phylliroe also exhibits bioluminescence, which is not a typical trait for a sea slug.

My brother Richard alerted me to another sea slug a while back, this one referred to as the Deadpool slug. The reason why it’s called the Deadpool slug is lost on me because I haven’t seen that movie or read the comic book, but the sea slug can separate its head from its body when it wants to, and it just grows a new body. The old body eventually dies instead of growing a new head.

The Deadpool slug is one of a type of sea slug that we talked about back in episode 129, about the blurry line between plants and animals. It eats algae and incorporates the algae’s chloroplasts into its body to use. Chloroplasts are what allows a plant to photosynthesize energy from sunlight, and the sea slug absolutely uses them for the same thing. Researchers think the Deadpool slug uses the energy from photosynthesis to regrow its body even though it has no digestive system after it separates its head from its body.

The big question is why the Deadpool slug wants to grow a new body in the first place. It doesn’t seem to be a defensive strategy if the sea slug is attacked. Instead, researchers think it often happens when the body contains too many parasites, specifically a type of tiny parasitic copepod, which is a crustacean. It might also happen after a predator bites a big chunk off the slug. Instead of hauling around a damaged body, the sea slug just jettisons the old body and regrows it.

Let’s finish with a recently solved octopus mystery that goes back almost 200 years. In 1838, the United States launched a scientific expedition throughout the Pacific Ocean and parts of the Atlantic that lasted four years. While it was mostly for exploration and mapping of places seldom or never visited by outsiders, the expedition also brought along a team of scientists and artists to document and study all the animals and plants they found. One of the things they found was an octopus.

The scientists didn’t fish the octopus up themselves. They actually bought several of them at a fish market in Brazil. It was red with little white spots all over it and not very big, although a dead octopus tends to shrink, especially when it’s out of water. The specimens were preserved in a jar of alcohol and brought back to the United States, where in 1852 they were studied by an expert on mollusks, Augustus Addison Gould. Octopuses are in the phylum Mollusca and Gould had examined lots and lots of octopuses. He decided this one was a new species and named it Callistoctopus furvus.

At some point the specimens were either lost or destroyed. Decades passed, then a century, then almost two centuries. Modern scientists thought Gould was probably wrong and that the little red octopus was one known from the Mediterranean Sea, Calistoctopus macropus. It’s red with little white spots, and has a mantle length only about 8 inches long, or 20 cm, although it has long arms and has been measured as almost five feet long, or 1.5 meters, if you include the arms. It lives in shallow water, where it spends a lot of time hunting for small animals that live in coral or in sea grass. It’s sometimes called the grass octopus.

Then a graduate student in Brazil named Manuella Dultra was studying octopuses, and part of her research involved talking to local fishers. They told her about an octopus that lived in shallow water and often buried itself in sand to hide, which is why they called it the sand octopus. They also said it was generally only seen when the wind blew from the east, and was more likely to be out and about during the new moon. Naturally Dultra wanted to find one. She asked the fishers to keep an eye out, and in 2013 she was given a freshly caught specimen.

The biologists at Dultra’s university identified the octopus as C. macropus, the grass octopus. Dultra wasn’t so sure. She noticed a lot of differences that seemed significant, and decided to do more research. She and her team gathered genetic material from specimens the local fishers caught, and sure enough, it was different from the grass octopus.

At the same time, researchers in Mexico had also found a sand octopus that they thought might be C. furvus. When Dultra compared her specimens’ DNA profile with the DNA profile from the Mexican octopus, it matched.

The discovery is still very new and isn’t accepted by all scientists yet, not until more studies are completed. The sand octopus appears to be rare, and once it’s definitely identified as its own species or subspecies and we learn more about it, we can do more to protect it.

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

Thanks for listening!


Episode 251: Modern Mimics and HIREC



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This week let’s look at some animals that have evolved rapidly to adapt to human-caused environmental pressures. Thanks to Otto and Pranav for their suggestions!

Further reading:

Long-term changes of plumage between urban and rural populations of white-crowned sparrows (Zonotrichia leucophrys)

A light-colored peppered moth (left) and darker-colored peppered moths (right):

Soot is hard to clean off buildings and other items (image from this page):

A white-crowned sparrow in the California countryside:

A (deceased museum specimen being photographed) white-crowned sparrow from the city of San Francisco, CA (taken from the study linked above):

A decorator crab that has attached bits of plastic and other trash to its body (image from this page):

The hermit crab sometimes uses trash instead of shells to hide in:

Show transcript:

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

This week we have two listener suggestions. Otto suggested we learn about camouflage that mimics modern things, and Pranav suggested animals that show rapid evolution due to humans.

We’ve talked about animals that use camouflage in lots of episodes, especially episode 191, Masters of Disguise. If you want to learn more about camouflage itself, that’s a good one to listen to. In addition, rapid evolution due to humans is a hot area of research right now. It even has its own scientific term, human-induced rapid evolutionary change, often shortened to the acronym HIREC.

Let’s start this episode with the story of a humble moth, because it’s a classic example of both HIREC and modern camouflage.

The peppered moth lives throughout much of the northern hemisphere. Its wingspan is a little over 2 inches across, or about 6 centimeters, and its caterpillar looks just like a little twig. Not only that, the caterpillar can change its coloring to match the twigs of the tree it’s on. But it’s not the caterpillars we’re talking about today.

The peppered moth gets its name from the coloring of its wings, which are white with black speckles, like pepper spilled on a plate. The pattern of speckles is unique to each individual, with some moths having more pepper speckles than others. Some moths have so many speckles that they look gray. But in the 19th century, geneticists studying moths in England noticed that the peppered moth seemed to be changing color as a species. Specifically, some of the peppered moths were completely black.

Black peppered moths had never been documented before 1811. They were still rare in the mid-19th century, but by 1900 almost all of the peppered moths in cities in England were black. Scientists noticed this and tried to figure out what was going on.

Pollution is what was going on. The industrial revolution was in full swing, but all those factories and trains and even ordinary houses were burning coal. Burning coal results in soot that’s carried on smoke and settles on everything. If you have a coal fire in your house, your walls and furniture are going to end up dark with soot. My aunt and uncle renovated a house from the late 19th century and had a lot of trouble cleaning soot from the walls and woodwork, even the old curtains that had been in the house. Similarly, when I lived briefly near Pittsburgh, Pennsylvania, there were still a lot of brick and stone buildings that were black from soot, but one beautiful old church had recently been cleaned and it turned out that the stone it was built from was pale gray, not black.

It wasn’t coal soot getting on the moths, though. It was coal soot on the trees where the moths spent most of their time. Most tree trunks are gray, but with all that coal soot in the air, the trees were coated with it and were much darker gray or even black. A light-colored moth that settled on a black tree branch showed up to predators, but a black moth on the same branch was camouflaged. The black moths survived more often to lay eggs while the white or gray moths didn’t, passing on the genetic likelihood that their babies would grow up to be dark-colored instead of light-colored.

It wasn’t just peppered moths that this happened to, either. More than 100 species of moth were documented to be dark gray or black during this time when they were ordinarily much lighter in color. Scientists call this industrial melanism.

Soot is made up of tiny particles that work their way into the crevices of wood and stone and everything else they come in contact with. You can’t just wipe or rinse it off. It’s acidic too and will kill plants, especially lichens that grow on trees, and it even eats away at stone and brick. It’s dangerous to breathe because the tiny particles lodge in your lungs and eventually stop you from being able to absorb oxygen as efficiently. If you’ve heard of the infamous London smog from the olden days, a big contributor to the smog was coal smoke. In 1952 a five-day smog event in London killed an estimated 12,000 people. That led directly to the Clean Air Act of 1956, and these days London doesn’t have that kind of deadly smog anymore.

Once factories and homes switched to electricity, natural gas, or other alternatives to burning coal, and trains switched to diesel fuel, trees stopped being coated with soot. Older trees that had survived were still dark, but young ones grew up with normal colored trunks and branches. Gradually, the black moths became less and less numerous compared to light-colored moths.

Cities in general result in rapid evolution of animals, including how they camouflage themselves. A study published in May of 2021 found that some birds living in cities are developing different colored feathers. Specifically, white-crowned sparrows living in San Francisco, California have much duller, darker feathers on their backs than white-crowned sparrows living outside of the city. Other studies have found that birds in cities sing much louder and at a higher pitch than birds in the countryside, since they have to compete with traffic and other noise.

A Swiss study on the effects of light on ermine moths indicated that while moths who developed from caterpillars collected from the countryside showed a normal attraction to light, moths from caterpillars collected in the city ignored the light. Since moths often die when they collide with electric lights, the city moths who survived to lay eggs were the ones who didn’t fly into a hot lightbulb.

Another study compared the genomes of white-footed mice that live in various parks in New York City with white-footed mice that live in state parks well outside of the city. The mice in city parks showed a lot less genetic diversity, naturally, since those mice are isolated populations. Mice can’t take cabs to visit mice in other parks, much less leave the city for a vacation. But the city mice showed another surprising difference. Their digestive systems have adapted to a much different diet than their country cousins. Some researchers suggest that the city mice may eat more junk food, which people throw away and the mice find, while other researchers think it’s just a difference in the kinds of insects and plants available in city parks for the mice to eat. Either way, it’s a distinct genetic difference that shows how the city mice are evolving to adapt to their urban environments.

Another example is a type of reptile called the crested anole. It’s related to the iguana and is native to the Americas. There are lots of species and subspecies of anole, many of which live on islands and show distinct adaptations to various habitats. The crested anole lives in Puerto Rico and on some nearby islands and grows up to 3 inches long, or 7.5 cm, not counting its long tail. The male is more brightly colored than the female, usually green or brown with darker spots. It’s not related to the chameleon but it is able to change color. It eats small animals, including insects, worms, even other anoles. Anoles are really interesting animals that deserve their own episode one day, so let’s just talk about how the crested anole that lives in cities has adapted to urban life.

One thing the crested anole is known for is its ability to climb right up tree trunks and even perch head-down in a tree. Its toe pads have microscopic scales and hairs that help them adhere to smooth surfaces, something like a gecko’s toes. But there’s a big difference in a tree trunk, no matter how smooth it is, and a pane of glass. Anoles in cities can climb up and down windows and painted walls. Researchers examined the toe pads of city crested anoles and compared them to the toe pads of crested anoles who lived in the countryside. They found that the city anoles had larger toes with more scales, and they even had longer legs. The research team also raced anoles along various surfaces and filmed them in slow motion to study how they were able to maneuver, which sounds like a great day at work.

The crested anoles have only lived in cities for a few decades, so their differences from country anoles evolved very quickly. But not all species of anole can adapt as well and as rapidly as the crested anoles have. Other city anole species don’t show differences from their country cousins.

Human-induced rapid evolutionary change isn’t restricted to cities. Trophy hunters who target the biggest animals with the biggest horns or antlers and leave smaller individuals alone have resulted in only smaller males with smaller horns or antlers surviving to breed. Many populations of bighorn sheep now actually only have small horns. Similarly, elephants have been killed for their tusks for long enough that many elephants are being born without tusks, because tuskless elephants are the ones that survive to breed. Entire populations of some fish species are smaller overall after many generations of being caught with nets, because only the individuals who are small enough to escape the nets survive to breed.

I tried hard to find more examples of animals that camouflage themselves to blend in to human-made items like roads. I’m sure this is happening throughout much of the world, but I couldn’t find any scientific studies about it. If any of you are thinking of going into biology, that might be an interesting field of study. But I did find one other example.

Self-decoration is a type of camouflage I don’t think we’ve talked about before. It’s where an animal decorates its body with items that help it blend in with its surroundings. Some caterpillars will stick little bits of lichen or other plant pieces to their bodies to help them hide, and some invertebrates of various kinds actually pile their own poop on their back as a disguise.

A group of crabs called decorator crabs will stick plants, sponges, and other items to their backs, and different species have preferences as to what items they use. Some species prefer stinging or toxic decorations, such as certain sea anemones which they basically pick up and plant on their backs. Researchers think the sea anemones actually benefit from being used as camouflage, because crabs are messy eaters and the anemones can catch and eat pieces of food that float away from the crab’s mouthparts. A decorator crab’s carapace is often rough in texture with tiny hooks to help things stick to it like Velcro.

Some decorator crabs don’t seek out particular decorations but just make use of whatever small items they find in their local environment. In the past few decades, scientists, divers, and other people who find crabs interesting have noticed more and more decorator crabs using little pieces of trash as decoration. This includes fragments of plastic and pieces of fishing nets.

This is similar to what’s happening with hermit crabs, which we talked about in episode 182. In many places hermit crabs are using trash like bottle caps instead of shells since there’s so much trash on beaches these days. This is your reminder to pick up any trash you find on the beach, but be careful not to cut yourself and also make sure you’re picking up actual trash and not a camouflaged crab.

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

Thanks for listening!


Episode 192: Ghostly Animals



Let’s start off October with a spooky episode about some ghost animals–real ones, and some ghost stories featuring animals!

Don’t forget to enter our book giveaway! Details here.

Further reading:

Lolo the Ghost Snake

Barn Related Ghost Stories

What big teef you have, ghost bat:

Nom nom little ghost bat got some mealworms (also, clearly this rehabilitation worker has THE BEST JOB EVER):

Ghost snake!

This is where the ghost snake lives. This photo and the one above were both taken by Sara Ruane (find a link to the article and photos in the “further reading” section):

The ghost crab is hard to see against the sand but it can see you:

Show transcript:

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

It’s finally October, which means it’s monster month on the podcast! Let’s jump right in with an episode about three animals with the word ghost in their name, and some spooky ghost stories that feature animals. (Don’t worry, they won’t be too spooky. I don’t want to scare myself.)

First up is my personal favorite, the ghost bat. That’s, like, twice the Halloween fun in one animal! Not only that, it’s a member of a family of bats called false vampires, and is sometimes called the Australian false vampire bat. I am just, I can’t, this bat is too perfect and I have died.

The ghost bat lives in parts of northern Australia and is actually pretty big for a microbat. Its wingspan is almost 20 inches wide, or 50 cm. Its color is pale gray, sometimes almost white, while babies are darker gray. It has large, long ears and a nose leaf that helps it echolocate, and it’s nocturnal like most microbats. While it doesn’t have a tail, it does have sharp teeth and a strong jaw to help it eat even the bones of small animals.

Most microbats eat insects, but the ghost bat prefers vertebrates like frogs, mice, snakes, lizards, birds, even other species of bat. It hunts by dropping down on its prey, most of which live on the ground. It folds its wings around its prey and bites it in the neck to kill it, which makes it even better as a Halloween bat. I love this bat. It eats almost all of the body of its prey, including fur, bones, teeth, and even small feathers in the case of birds. Sometimes it eats its prey immediately, but sometimes it carries it to a small cave to eat, separate from its roosting area, referred to as a midden since the floor is littered with the remains of past meals. If you’re not familiar with the word midden, it just means a trash heap. Researchers love finding a ghost bat’s midden because they can find out exactly what animals the bat has eaten lately.

Female ghost bats roost in groups during the late spring to have their babies, usually in caves or abandoned mines. A female gives birth to a single baby, and she carries it around until it’s big enough to learn how to fly on its own, in about seven weeks. Once it can fly, it accompanies its mother on hunting trips until it’s fully weaned several months later. A mother bat has two pairs of teats, one pair near her armpits that produces milk for her baby to drink, and one pair near her legs that doesn’t produce milk. The teats near her legs act as little handholds for her baby to help it keep a good grip on her, especially when it’s very young.

The ghost bat is vulnerable to many of the usual concerns, including habitat loss and introduced predators, but it also has an unusual issue with an introduced plant and a type of fencing. The ghost bat doesn’t fly very high most of the time, since it’s usually hunting for small animals that live on the ground or birds roosting in bushes. As a result, its wings frequently get snagged on the spines of a thorny plant called lantana, and on barbed wire fencing. The spines or barbs tear the wings’ delicate patagia, often so badly that the bat can’t fly and starves to death. Since there are only an estimated 8,000 of the bats left in the wild, this is especially bad.

The ghost bat has good hearing, naturally, but it also has good eyesight. It uses a combination of hearing, vision, and echolocation to navigate and find prey. It also makes some sounds within the hearing range of humans. This is what a ghost bat sounds like:

[ghost bat chattering]

That bat sounds adorable and not spooky at all. So let’s bump up the spooky factor with our first ghost story.

This one comes from one of my favorite books, The Telltale Lilac Bush by Ruth Ann Musick, which we talked about in episode 91, about spooky owls. It’s a collection of ghost stories collected by folklorists in West Virginia. This story is called “A Loyal Dog.”

“Many years ago a small boy saw a little dog floating down the river on a log. He swam out, rescued the dog, and took it home with him. After this, the boy and the dog were together at all times. The dog lived for almost twenty years, and when it died, the young man was very sad to see his good friend go.

“Sometime later the young man was walking through a field, when all at once he was pulled down by something behind him. This gave him quite a start, but when he looked around, he saw, just in front of him, a great crack in the ground. Had he not been stopped, he would probably have fallen into it and been killed.

“What saved him, he did not know. There was nothing around that could have knocked him down or that he could have stumbled over. When he examined his clothing, however, there were the marks of a dog’s teeth on his coat, and clinging to the coat some dog hair—the same color as his old dog’s.”

Next let’s talk about the ghost snake, which lives in Madagascar. Not only is it called the ghost snake, it’s a member of a group of nocturnal or crepuscular snakes called cat-eyed snakes. The cat-eyed snakes are relatively small, slender, and have large eyes with slit pupils like cats have.

The ghost snake gets its name because it’s pale gray in color, almost white, with a darker gray pattern, and because it’s elusive and hard to find. Researchers only discovered it in 2014. A team of researchers were hiking through a national park in the pouring rain hoping to find species of snake that had never had their DNA tested. The goal was to collect genetic samples to study later. After 17 miles, or 25 km, of hiking through rugged terrain in the rain, they spotted a pale snake on the path. Fortunately they were able to catch it, and genetic analysis later showed that it was indeed a new species.

We know very little about the ghost snake since it’s so hard to find. It lives in rocky areas, which is probably why it’s pale gray, since the rocks are too. The rocks are uneven pointy limestone formations known locally as tsingy, which translates to “rock you can’t walk on barefoot.” The snake doesn’t have fangs, but it does have toxins in its saliva and a pair of enlarged teeth in the rear of the mouth. We don’t know what it eats yet, but the other cat-eyed snakes in Madagascar are general predators who eat pretty much any small animal they can catch, including frogs and toads, lizards, and rodents. Other cat-eyed snakes also sometimes act like constrictors to help kill prey.

A mysterious pale snake is definitely spooky, but I have a story that’s even spookier. It’s from a 1913 book called Animal Ghosts by Elliott O’Donnell and the story is called “The Phantom Pigs of the Chiltern Hills.”

“A good many years ago there was a story current of an extraordinary haunting by a herd of pigs. The chief authority on the subject was a farmer, who was an eye-witness of the phenomena. I will call him Mr. B.

“Mr. B., as a boy, lived in a small house called the Moat Grange, which was situated in a very lonely spot near four cross-roads, connecting four towns.

“The house, deriving its name from the fact that a moat surrounded it, stood near the meeting point of the four roads, which was the site of a gibbet, the bodies of the criminals being buried in the moat.

“Well, the B——s had not been living long on the farm, before they were awakened one night by hearing the most dreadful noises, partly human and partly animal, seemingly proceeding from a neighbouring spinney, and on going to a long front window overlooking the cross-roads, they saw a number of spotted creatures like pigs, screaming, fighting and tearing up the soil on the site of the criminals’ cemetery.

“The sight was so unexpected and alarming that the B——s were appalled, and Mr. B. was about to strike a light on the tinder-box, when the most diabolical white face was pressed against the outside of the window-pane and stared in at them.

“The children shrieked with terror, and Mrs. B., falling on her knees, began to pray, whereupon the face at the window vanished, and the herd of pigs, ceasing their disturbance, tore frantically down one of the high roads, and disappeared from view.

“Similar phenomena were seen and heard so frequently afterwards, that the B——s eventually had to leave the farm, and subsequent enquiries led to their learning that the place had long borne the reputation of being haunted, the ghosts being supposed to be the earth-bound spirits of the executed criminals.”

Our last ghostly animal is the ghost crab. There are many species of ghost crab that live all over the world, especially on tropical and subtropical beaches, including the one I’m familiar with, the Atlantic ghost crab. It’s typically a fairly small crab. The Atlantic ghost crab only grows around 2 inches across, or 5 cm, not counting its legs, while some species may be twice that size.

Its body is squarish and thick, which gives it a boxy appearance, and it has long, club-shaped eyestalks that can swivel so it can see all around it. One of its claws is always larger than the other. It digs a burrow in the sand or mud to stay in during the day, but at night it comes out and scavenges along the beach to find food. It will eat small animals if it can catch them, including insects and smaller crabs, but it also eats dead animals, rotting plants, and anything else it can find. It’s a fast runner and can zoom around on the beach at up to 10 mph, or 16 km/h.

The ghost crab gets its name from its coloration, just like the other ghost animals in this episode. Most species are white, pale gray, or pale yellow, basically the color of the sand where it lives. But it’s able to change colors to match its surroundings. This change usually takes several weeks because it has to adjust the concentration of pigments in its cells. This is useful since beaches can change color over time too.

The ghost crab is semi-terrestrial. It can’t live underwater without drowning, but it also has to keep its gills wet with seawater or it dies. This is sort of the worst of both worlds if you ask me, but it works for the crab. Generally, damp sand is wet enough to keep its gills wet, and its legs also have tiny hairlike structures that help wick moisture from the sand up to its gills.

A female ghost crab will usually join a male she likes in his burrow to mate. She carries her eggs around under her body, keeping them wet by going into the water frequently. When they’re ready to hatch, she releases them into the surf, where the larvae live until they metamorphose into little bitty young crabs that then live on land.

Surprisingly, the ghost crab makes several different sounds. It can rub the ridges on its claws together, drum on the ground with its claws, and make a weird bubbling sound. Until recently scientists weren’t sure how it made this last sound, but new research reveals that it’s made by a comblike structure in the crab’s digestive system called a gastric mill that helps grind up food. It rubs the comb of the gastric mill against another structure called a medial tooth to produce the sound. The crab uses the noises it makes to intimidate potential predators, including raccoons, and making a sound with its digestive system leaves its claws free to pinch if it needs to.

This is what the ghost crab sounds like:

[ghost crab sound]

We’ll finish up with a final spooky ghost story, or actually several short ones. I found an old but fun thread on a horse forum where people were talking about their haunting experiences in and around barns. I’ve chosen a few to read here, but if you want to go read the whole thread, I’ll link to it in the show notes.

The first comes from someone who calls themself Saidapal:

“My old mare (28 years old) and my young gelding (6 years old) were best of friends since the day he arrived at my farm when he was one. Sadly I had to have the mare put down last year. Every day for the first 2 weeks after she passed the gelding would come out of his stall and go straight to hers just like he had been doing for years to wait for her to join him. Broke my heart and still does when I think about it.

“When she had been gone for about 2-3 months I started seeing shadows out of the corner of my eyes and hearing her joints pop so I knew it was her LOL, and always the gelding would be somewhere in the vicinity. After a day or two I dreamed about her, and in the dream she was young and beautiful again. The very next morning the gelding came out of his stall and went straight to hers just like he used to. It was the last time he ever did that and I haven’t seen her since.

“I swear she had come to say goodbye to both of us.”

The next story is by Darken:

“I’ve had a number of things happen in my barn. I’ve had my collar lifted up and tugged from behind. I’ve had what felt like the nose of a big dog go into the palm of my hand, so much so that I turned around expecting to see my neighbor’s German Shepard there. And the best one was when I was walking out to the barn one night in the dark and saw the ghost of a horse run left to right between me and the barn door. Since I was looking down as I was walking, I just missed seeing its head, but I clearly saw its neck, flying mane, back, croup and flagging tail. I could see nothing below its knees, and it ran about 2 feet off the ground. The edges of it were solid white, but towards the center it was so transparent, I could see the stripes of the barn door thru it.”

And our last story is by Watermark Farm:

“Years ago I boarded at a barn where all the horses spooked badly at a certain corner near the entrance to the arena. It was a real problem and several people had been dumped badly in this corner. A boarder had a pet psychic out to work with her horse. The psychic knew nothing about this spooky spot but said ‘He hates that corner, the one with the dead pig. The dead pig thinks it’s funny to run out and scare the horses.’”

Happy Halloween!

You can find Strange Animals Podcast online at strangeanimalspodcast.blubrry.net. That’s blueberry without any E’s. If you have questions, comments, or suggestions for future episodes, email us at strangeanimalspodcast@gmail.com. If you like the podcast and want to help us out, leave us a rating and review on Apple Podcasts or just tell a friend. Don’t forget to contact me if you want to enter the book giveaway which is going on through October 31, 2020! Details are on the website.

Thanks for listening!


Episode 182: The Coconut Crab and Friends



Join us this week for some interesting crabs! Thanks to Charles for suggesting the aethra crab!

Aethra crabs look like little rocks, although some people (who must be REALLY hungry) think they look like potato chips:

A hermit crab using a light bulb bottom as an inadequate shell:

The tiniest hermit crab:

Gimme shell pls:

THE BIGGEST HERMIT CRAB, the coconut crab. It really is this big:

Show transcript:

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

We have a bunch of crustaceans this week! I’m sorry I’ve taken so long to get to Charles’s suggestion of aethra crabs, so we’ll start with those.

There are four species of aethra crabs alive today, and they live in warm, shallow coastal waters. They like areas with lots of rocks on the sea floor, because the crabs look like small flattened rocks. They can tuck their legs under their carapace so that they don’t show at all, and often algae and other marine animals like barnacles will attach to the carapace, increasing the crab’s resemblance to a little rock. What eats rocks? Nothing eats rocks! So the aethra crab is safe as long as it stays put with its legs hidden. It lives throughout much of the world’s tropical oceans, especially around islands and reefs in South Asia, but also around Australia, Mexico, and Hawaii.

We don’t know a whole lot about aethra crabs, not even how many species there really are. There are probably undiscovered species that no one has studied yet, but we do know they used to be even more widespread than they are today. Twelve million years ago, for instance, a species of aethra crab lived in what is now Ukraine, with fossil remains only described in 2018.

Most aethra crabs only grow a few inches across, or maybe 6 cm, but the walking rock crab of Mexico can grow to 6.3 inches across, or 16 cm across. It’s light brown with lighter and darker speckles that give it a mottled appearance like a small rock.

Because they’re so flattened with rounded edges, and because some species are pale in color, aethra crabs are sometimes called potato chip crabs. I don’t like that name because it makes them sound tasty and not like little rocks. I think we have established that they really look like little rocks.

That’s just about all I can find out about the aethra crab, so if you’re thinking of going into biology and aren’t sure what subject to study, may I suggest you focus your attention on the aethra crab and bring knowledge about them to the world.

So let’s move on to a different type of crab, the hermit crab. A big part of being a crab is evolving ways to not be eaten. I mean, that’s what every animal wants but crabs have some novel ways of accomplishing it. Some crabs look like tiny rocks, some crabs hide in shells discarded by other animals.

There are hundreds of hermit crab species, which are generally grouped as marine hermit crabs and land hermit crabs. There’s also a single freshwater hermit crab that lives on a single island, Espiritu Santo, in the south Pacific, and in fact only in a single pool on that island. It was only described in 1990 and is small, less than an inch long, or about two and a half cm. It uses the discarded shells of a snail that also lives in its pool.

That’s the big thing about a hermit crab: it uses the shells of other animals as a temporary home. Like all crabs, the hermit crab is an invertebrate with an exoskeleton. But unlike most crabs, its abdomen isn’t armored. Instead it’s soft and vulnerable, but that’s okay because most of the time it’s protected by a shell that the crab wears. In most species the abdomen is actually curved in a spiral shape to better fit into most shells.

When a hermit crab finds an empty shell, it may quickly slip out of its current shell and into the new shell to see if it’s a good fit. Ideally the shell is big enough for the crab to hide in completely, but not so big that it’s awkward for the crab to carry around. If it likes the new shell it will abandon the old shell, but if it doesn’t like the new shell it will just go back to its old one. But the important thing is that it has a shell, so it spends as little time without a shell as possible. In fact, if it can’t find a shell of the right size, a hermit crab will make do with anything it can find, such as a plastic bottle, an old tin can, or other trash. But it’s safest inside a real shell. Sometimes two hermit crabs of about the same size will fight over a shell. You wouldn’t think that the ability of a hermit crab to find a good shell would be something humans can affect, but in some areas, so many shells are collected to sell as souvenirs that hermit crabs really don’t have very many left to choose from and have to use trash or pieces of driftwood instead.

Other than the freshwater hermit crab, marine hermit crabs all live in the ocean. Some species live in shallow water, others in deep water, and often around reefs. There are even a few species that are specialized to live in permanent structures on the sea floor, such as sponges or the abandoned burrows of various worms. Land hermit crabs spend most of their time on land, although they have to keep their gills wet.

People sometimes keep hermit crabs as pets, either in an aquarium for marine species, or a special terrarium for land species. Some species can live for decades if given proper care. Because a pet hermit crab is safe, it doesn’t really matter what kind of shell it wears as long as it’s comfortable, so people will sometimes give their pets imitation shells that are clear so they can see the crab’s interesting-shaped abdomen. You can also get fake shells that are shaped like skulls or tiny houses. There’s a picture that goes around sometimes online of a hermit crab using a real human skull as a shell, but that’s actually fake. Not only is the skull not real, the hermit crab isn’t real. It’s a sculpture.

The biggest species of hermit crab is the coconut crab, also sometimes called the robber crab since when it finds something that might be food, it will carry it away to investigate it. It’s not just the biggest hermit crab, it’s the biggest arthropod that lives on land. An arthropod is any invertebrate with an exoskeleton and segmented body. That includes all insects and crustaceans and arachnids, and so on.

The coconut crab has a legspan over three feet across, or about a meter. It can weigh up to nine pounds, or 4 kg. Researchers think it’s literally as big as an arthropod can grow these days and continue to live on land. It’s a bulky, strong crab that ranges in color from reddish-orange or brown to blue-gray, sometimes with white markings.

The coconut crab uses shells as protection when it’s young, but as it grows larger, it outgrows most shells available. Instead, it develops a tough exoskeleton on its abdomen. It also develops lungs, so an adult coconut crab can actually drown if it gets trapped underwater for long enough—generally about an hour. It still has gills, but they’re tiny and not very efficient.

Its lungs aren’t like those of most other arthropods. In fact it only has one lung, called a branchiostegal lung, that has traits of true lungs but also traits of gills. It doesn’t breathe like vertebrates do; instead, its lung absorbs oxygen from the air passively. To do this properly, though, the lung tissue needs to be moist. A coconut crab uses its hindmost pair of legs to dip water up and wipe it over the lung tissue, which is inside a cavity in the cephalothorax. This is the main part of the body as opposed to the abdomen. This last pair of legs is tiny compared to the other eight legs, and female coconut crabs also use these legs to tend their eggs. Usually the last pair of legs aren’t even visible, since the crab usually keeps them tucked in the lung cavity. The other legs are much larger, and the first pair of legs ends in claws like other crabs.

The coconut crab lives on lots of islands in the Indian and Pacific Oceans and used to live in Australia and on many more islands. But it’s a big crab and that means it provides a lot of food, so humans have hunted it to extinction in many areas. It’s increasingly rare in many places as a result of hunting and habitat loss. But the coconut crab isn’t helpless. If a coconut crab snaps its pincers on, for instance, a person’s thumb, it will hold on tenaciously, probably while the person flails around in panic and pain. Not only that, but sometimes a population of coconut crabs will feed on plants that contain toxins, such as the sea mango, and will retain the toxins in its body. If a person eats a toxic crab, they may get sick from the poison.

It’s called the coconut crab because it eats coconuts, but it actually doesn’t prefer coconuts. It especially likes bananas. It also eats seeds, nuts, and other plant material, but it’s an omnivore and will eat carrion, other crabs, baby turtles, and even birds. Its antennae have evolved to detect chemicals in the air instead of in the water, which means it has a good sense of smell and can track the smell of rotting fruit or meat from a long distance away.

Even the biggest crabs can climb well and will climb trees, sometimes to get away from potential predators, but sometimes to catch birds. The quickest way to get out of a tree after climbing it is just by falling, and the coconut crab often does this on purpose. Its exoskeleton is so tough that it can fall some 15 feet, or 4.5 meters, without injury. And yes, sometimes a coconut crab will use their claws to break into a coconut to eat it, but it takes a long time—sometimes days. The coconut crab is mostly nocturnal, but it will come out during the day if it’s hungry, especially if it’s raining or foggy out.

A female coconut crab glues her fertilized eggs under her abdomen and carries them around for a few months as they develop. When they’re ready to hatch, she releases them into the ocean. After they hatch, the larvae drift around for several weeks, eating tiny specks of food. As a baby coconut crab grows and develops through its juvenile stages, which generally takes several weeks, it finally settles to the sea floor and finds a shell to hide in, just like other hermit crabs do. If it can’t make it to shore on its own, it will climb onto a floating log or bunch of floating seaweed or a floating coconut, which eventually carries it to shore. It needs to be on shore because only the larvae can swim, and once it reaches its adult stage it has to breathe air.

Like other arthropods, the coconut crab has to molt its exoskeleton periodically as it grows, since the exoskeleton can’t grow. After it molts, it takes up to three weeks for the new exoskeleton to harden. During this time the crab hides in a burrow it digs, because even a gigantic coconut crab is soft and vulnerable without its exoskeleton. It lines its burrow with coconut fibers, which absorb water and helps keep the crab’s lung tissue moist while it rests. The crab will also stop up the entrance to its burrow with one of its claws, to help keep it safe and reduce the loss of moisture from the burrow. The coconut crab continues to grow throughout its life, which can be extremely long—more than sixty years. A big coconut crab’s only predator is people, and frankly I would not want to tangle with one.

Let’s finish the episode with a mystery crab. Wallowa Lake in Oregon, in the United States, is about three and a half miles long, or 5.6 km, and three-quarters of a mile across, or 1.2 km, and is 300 feet at its deepest point, or 91 meters. After gold was found in the area in the late 19th century, the Wallowa band of the Nez Perce was forced out of their ancestral home by the U.S. government, despite the treaties in place to stop that kind of thing happening. Funny how often that happens. Anyway, the gold rushers who moved in spread stories about giant crabs that lived in the lake, which would crawl out at night to grab cattle and pull them into the water to eat.

But the lake was created from melting glaciers near the end of the Pleistocene ice ages, around 11,000 years ago. It’s never been connected to the ocean and is in fact 4,300 feet above sea level, or 1,300 m. It’s also in a part of the world that experiences bitterly cold winters. All freshwater crabs are tropical or subtropical and can’t survive in cold water. Plus, of course, even the biggest coconut crab isn’t big enough to drag a cow into the water.

So the Wallowa Lake crabs are probably just tall tales. But, you know, maybe be careful if you go swimming in the lake at night, just in case.

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

Thanks for listening!