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Episode 215: The Cutest Invertebrates

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Thanks to Lorenzo and Page for suggestions used in this week’s episode, and a belated thanks to Ethan for last week’s episode! Let’s learn about some of the cutest invertebrates out there!

Further reading:

Photosynthesis-like process found in insects

Mystery of the Venezuelan Poodle Moth

Further viewing:

Dr. Arthur Anker’s photos from his Venezuela trip, including the poodle moth

The pea aphid, red morph and regular green

So many ladybugs:

The sea bunny is a real animal, but it’s not a real bunny:

A larval sea bunny is SO TINY that fingertip looks like it’s the size of a BUILDING:

The bobtail squid not hiding (left) and hiding (right):

The bobtail squid is SO CUTE I MIGHT DIE:

The Venezuelan poodle moth:

Not a Venezuelan poodle moth–it’s a female muslin moth from Eurasia:

Not a Venezuelan poodle moth–it’s a silkworm moth from Asia:

The dot-lined white moth:

Show transcript:

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

This week I promised we’d cover a cute, happy animal to make up for last week’s extinction event episode, but instead of mammals let’s look at some cute invertebrates! One of them is even a mystery animal. Thanks to Page and Lorenzo for suggesting two of the animals we’re going to cover today!

We’ll start with Lorenzo’s suggestion, the pea aphid. Years and years ago I spent a slow day at work making a list of cute foods with a coworker, and peas were at the top of the list. Blueberries were second and I don’t remember the rest of the list. Generally, cuteness depended on how small the food was and how round. Aphids are really small and peas are round, so the pea aphid has to be adorable.

The pea aphid, however, is not round. It’s shaped sort of like a tiny pale-green teardrop with long legs, long antennae, and teeny black dots for eyes. It’s actually kind of big for an aphid, not that that’s saying much since it only grows 4 mm long at most. It’s called the pea aphid because it likes to live on pea plants, although it’s also happy on plants related to peas, such as beans, clover, and alfalfa. Cute as it is, farmers and gardeners do not like the pea aphid because it eats the sap of the plants it lives on, which can weaken the plant and can spread plant diseases.

During most of the year, all pea aphids are females. Each adult produces eggs that don’t need to be fertilized to hatch, but instead of laying her eggs like most insects, they develop inside her and she gives birth to live babies, all of them female. An aphid can have up to 12 babies a day, called nymphs, and the nymphs grow up in about a week or a little longer. Then they too start having babies. Even though lots of other insects and other animals eat aphids, as you can see, they will always be numerous.

As the summer turns to fall and the days become shorter, some of the baby aphids are born with wings. Some are also born male, and sometimes the males also have wings, although they might not have mouths. These males and winged females mate and the females fly off to lay their eggs on clover and alfalfa plants, assuming they aren’t already on clover or alfalfa plants. The eggs don’t hatch until spring, and all the resulting nymphs are female.

Sometimes winged females are born if the plants where the aphids live get too crowded. The winged females can fly away and find new plants.

If you’ve ever had a garden, you’re probably familiar with aphids. They spend most of the time on the undersides of leaves, drinking sap through specialized mouthparts called stylets. You may also have noticed that when you try to smush the aphids, all of them immediately drop to the ground. This protects them not just from being smooshed by a gardener’s thumb, but from being eaten along with the leaves when a deer or other animal browses on the plants where they live.

Sometimes, instead of being leaf green, pea aphids are a pale reddish color. This is called the red morph. Red morph pea aphids are more likely to live on certain plants while the ordinary green pea aphids are more likely to live on others, although many times you can find both varieties on a single plant.

The red coloration of red morph pea aphids is due to larger quantities of a chemical called carotenoid [kerOTenoid] in its body. All pea aphids contain carotenoids, though, and it’s not just used for coloration. Research suggests that the carotenoids absorb sunlight and produce energy that the aphid can use. It’s a limited form of photosynthesis—you know, that thing that only plants do.

Not only that, the pea aphid produces the carotenoids in its body. Every other animal that needs carotenoids absorbs them from plants it eats, with the possible exception of a type of mite. The genetic sequence that allows the pea aphid to make its own carotenoids originally came from fungi. Somehow the aphid captured the genetic material from fungi, probably after eating it, and passed those genes down to its descendants. This is called lateral gene transfer and scientists aren’t sure exactly how it works or how common it is.

Pea aphids also contain beneficial bacteria that produce nutrients it needs that it doesn’t get from the sap it eats. The aphids can’t live without the bacteria, and the bacteria can’t survive outside of the aphids.

Even though the pea aphid is really common just about everywhere these days, it’s actually an invasive species in most places. It’s native to temperate parts of Eurasia but has spread to the rest of the world on cultivated plants. For small infestations of aphids, some people release certain species of ladybugs into their gardens, because many ladybugs love eating aphids.

Ladybugs, of course, are another cute invertebrate, specifically a family of beetles. They’re also small and round, although not as small as aphids. A typical ladybug grows about 10 mm long at most. Depending on the species, a ladybug can be red, orange, yellow, or brown, usually with black spots but sometimes with black stripes, or it may be mostly black with red or yellow spots. Most eat tiny insects and other animals, but some species eat plant material.

The ladybug’s bright coloring warns birds and other predators that it contains a toxin that makes it taste nasty. This even affects humans. I mean, obviously don’t eat ladybugs, but sometimes if there are ladybugs on grapes used to make wine, and the ladybugs end up crushed along with the grapes in a wine press, the whole batch of wine will end up tasting bad. It’s called ladybird taint so winemakers try to make sure any ladybugs are removed from the grapes before they’re crushed.

In many cultures around the world, ladybugs are supposed to bring good luck. In some places, if you see a ladybug you should make a wish. We’ve talked about ladybugs before, most recently in episode 203, so let’s move on to our next cute invertebrate.

This one lives in the ocean. It’s called the sea bunny or sea rabbit, a type of nudribranch [noodi-bronk] that lives along the coastline of the Indian Ocean, especially in tropical waters. Nudibranchs are a type of mollusk that are sometimes called sea slugs. Many are brightly colored with beautiful patterns. Compared to some, the sea bunny is a little on the plain side. It’s white, yellow, or rarely green, with tiny brown or black speckles. It looks fuzzy because it’s covered in little protuberances that it uses to sense the world around it, as well as longer, thinner fibers called spicules. It also has two larger black-tipped protuberances that look for all the world like little bunny ears, although they’re actually chemoreceptors called rhinophores. It really is amazing how much the sea bunny actually resembles a little white bunny with dark speckles, which would make it cute right there, because bunnies are cute, but it’s also really small. It barely grows an inch long, or 2.5 cm.

Like other nudibranchs, the sea bunny is a hermaphrodite, which means it produces both eggs and sperm, although it can’t fertilize its own eggs. When it finds a potential mate, they both perform a little courtship dance to decide if they like each other. After mating, both lay strings of eggs in a spiral pattern. The eggs hatch into larvae that are free-swimming, although the adults crawl along the ocean floor looking for small animals to eat. Some nudibranch larvae have small coiled shells like snails, which they shed when they metamorphose into an adult, but the sea bunny hatches into a teeny-tiny miniature sea bunny.

Cute as it is, don’t pet a sea bunny! It’s toxic! One of the things that sea bunnies especially like to eat are sponges, and many sponges contain toxins. The sea bunny absorbs these toxins to protect it from predators. Even its eggs are toxic.

Next we’ll talk about another intensely cute marine animal, the bobtail squid. It’s only a few inches long, or up to 8 cm at most, with a rounded mantle and short little arms. Small and round, the hallmarks of cuteness. It’s also sometimes called the dumpling squid, which is extra cute and potentially delicious. Basically, it’s no longer than your thumb and smaller around than a golf ball.

The bobtail squid lives along the coast of the Pacific Ocean and parts of the Atlantic and Indian oceans, and it’s not just one species. It’s an entire order containing around 70 species. The oceans are full of adorable little squids.

The bobtail squid has a symbiotic relationship with a type of bacteria, much like the pea aphid and its beneficial bacteria, but in the bobtail squid’s case, the bacteria don’t provide nutrients, they provide light. The bacteria are bioluminescent and help the squid hide from predators. You may be thinking, “Wait a minute, how does it help the squid hide to be lit up from within like a tiny squid-shaped lamp?” but that just proves that you’re a land animal and not a water animal. If you’re a big fish on the hunt for yummy bobtail squid to eat, you’re probably hiding in deep water where the squid can’t see you in the darkness, looking up for the telltale shadowy outline of a squid against the surface of the water. Day or night, the water’s surface is much brighter than the water underneath it because it’s reflecting sun, moon, or starlight, but if the squid is glowing faintly, instead of showing up as a dark shape against the brighter surface, it blends in. The light only shines downward and the squid adjusts it to be brighter or dimmer to match the amount of light shining on the water.

The bobtail squid is mostly nocturnal and will hide in the sand during the day or if it feels threatened, using its arms to pull sand over its body. All squids have large eyes, but the bobtail squid’s eyes are especially large in comparison to its small body, which makes it even cuter. It eats small animals and especially likes shrimp. It can also change colors to blend in with its surroundings and communicate with other squid.

Let’s finish with Page’s suggestion, the Venezuelan poodle moth. I was going to start the episode with this one because it’s so fuzzy and cute, but when I started research I realized that there’s a mystery associated with this insect. I like to end episodes with a mystery if I can. I want to keep everyone guessing.

In late 2008 and early 2009, a zoologist named Arthur Anker was in southeastern Venezuela in South America, and photographed a fuzzy white moth he found. He didn’t know what it was so he labeled it as a poodle moth when he posted the picture online. I’ve put a link in the show notes to all the photos he posted from his trip, including the poodle moth, and they’re absolutely gorgeous. He has a lot of moth photos but the poodle moth was the one that went viral in 2012.

There are other cute, fuzzy moths that sometimes get called poodle moths, such as the silkworm moth. Silkworm moths are native to Asia and are one of the few domesticated insects in the world, together with the honeybee. If you’ve ever had a silk shirt, that silk probably came from the domestic silkworm, which has been raised for at least 5,000 years in China and other places.

Silk comes from the cocoons the silkworm moth larva spins. Each cocoon can contain up to a mile of silk fiber, or 1.6 km, in one long, thin thread. The problem is, to harvest the silk properly, you have to kill the silkworm inside, usually by throwing the cocoon into boiling water. If the silkworm is allowed to mature, it releases enzymes to break down the silk so it can get out of the cocoon, and that weakens any fabric made from the silk. You can get silk made from cocoons of silkworms that weren’t killed, though, sometimes collected from wild moths.

Domestic silkworm moths have been bred so that they don’t produce pigments, since that means the silk won’t have any pigments either and can be dyed more easily. Domestic silkworms differ from their wild relatives in other ways too. Their cocoons are bigger, they no longer have any fear of predators, and they can no longer fly because their wings are too small for their bodies. The moth is covered in short white hairs that make it look fuzzy and cute, with black eyes. The larvae eat the leaves of the white mulberry tree or related trees, but adult moths don’t eat at all and don’t even have functional mouths.

So the silkworm moth is definitely a cute invertebrate, but what’s going on with the Venezuelan poodle moth? What’s the big mystery?

Well, no one knows what species it is. Some people have even accused Dr. Anker of making it up completely. Considering how many thousands of moths live in Venezuela, and how many new moth species are discovered every year, it’s likely that the poodle moth is new to science. The trouble is that no one has seen it since. Anker wasn’t on a collecting trip and he didn’t realize the poodle moth might be something new to science, so he just took a picture of it and left it alone.

The best guess by entomologists who’ve examined the picture is that the poodle moth is a member of the genus Artace, possibly a close relation of the dot-lined white moth. The dot-lined white moth is white and fuzzy with tiny black dots on its wings. It mostly lives in the southeastern United States but there have been sightings in Colombia, which is a country in South America just west of Venezuela.

There are other fuzzy white moths in the world that are known to science, including the muslin moth that’s equally small and cute. Female muslin moths are white and fuzzy with some gray or brownish-gray speckles on the wings, while male muslin moths are dark gray and fuzzy with black speckles on the wings. They live mostly in Eurasia.

Hopefully soon a scientist can find and capture a Venezuelan poodle moth and solve the mystery once and for all. Hopefully that scientist will also take lots of pictures so we can verify that it’s just as cute as it looks in its first picture.

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

Thanks for listening!

 

Episode 203: Swarms!

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Thanks to Nicholas and Juergen for their suggestions! Let’s learn about some insects that migrate and swarm!

Further listening:

The Animal Migrations Patreon episode (it’s unlocked so anyone can listen)

Further reading:

Ladybugs Are Everywhere!

Monarch butterflies gathered in winter:

The painted lady butterfly:

The bogong moth:

The globe skimmer dragonfly:

Ladybugs spend the winter in bunches, sometimes in your house:

A stink bug, one of many potentially in your house:

This person is not afraid of locusts even though I would be freaking out:

A field in Australia being eaten by locusts (the brown part):

Show transcript:

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

Let’s learn about some insects this week, but not just any old insects. Let’s learn about insects that swarm. Thanks to Nicholas and Juergen for suggestions that led to this episode!

Nicholas suggested long-distance migrators ages ago, and I did do an episode about migration for a Patreon episode. I’ve unlocked that episode so anyone can listen to it, with a link in the show notes. I’ve also used some of the information in that episode for this one, specifically the part about monarch butterflies.

In fact, let’s start with the monarch butterfly. The monarch is a good-sized butterfly, with orange and black wings with white spots along the edges and a wingspan of up to four inches, or 10 cm. It lives in many parts of the world, but only the North American subspecies of monarch migrates.

Every autumn, monarch butterflies living in North America, where they breed, head south to winter in the mountains of central Mexico, a trip that can be as long as 3,000 miles, or 4,800 km. They spend the winter in oyamel fir trees, millions of butterflies in the branches. When spring arrives, the butterflies head north again, but they don’t get all the way back to their original range. If they’re lucky, they reach Texas, where they mate and lay eggs on milkweed plants before dying. The caterpillars hatch, eat up the milkweed, spin cocoons, and emerge transformed into new butterflies that continue the flight north, deeper into North America. But those butterflies don’t make it all the way to their parents’ home range either. They too stop to mate, lay eggs, and die. It can take four or five generations for monarch butterflies to reach Canada and other distant parts of North America, and by that time it’s autumn again. The butterflies fly back to Mexico.

Butterflies heading north live out their entire life cycle in only five or six weeks, but the butterflies that return to Mexico live up to eight months. Researchers think the northward migration follows the blooming of milkweed plants. Milkweed contains toxins that make the monarchs poisonous to a lot of animals, but some birds and a lot of insects will eat the caterpillars. Some populations of North American monarchs overwinter in California, Arizona, or Florida instead of Mexico.

The North American monarch is declining in numbers, probably mostly due to the decline of milkweed. The best way to help the butterfly is to plant milkweed in any area you don’t want to mow very often.

While the monarch migration is astounding, it’s not the only butterfly that migrates. A small, pretty butterfly called the painted lady lives throughout much of the world, even the Arctic, but not South America for some reason. Some populations stay put year-round, but some migrate long distances. One population winters in tropical Africa and travels as far as the Arctic Circle during summer, a distance of 4,500 miles, or 7,200 km, which takes six generations. The butterflies who travel back to Africa fly at high altitude, unlike monarch butterflies that fly quite low to the ground most of the time. Unlike the monarch, painted ladies like many kinds of flowers, not just one plant, and they don’t always migrate every year.

In Australia, some populations of the bogong moth migrate some 600 miles, or 965 km. It’s a dark brown moth with a wingspan of up to two inches across, or 5 cm, and naturally enough, it migrates at night. Unlike the butterflies we’ve talked about, the migration doesn’t take successive generations. In spring the moths fly from the lowlands into the mountains, where they spend the summer mostly hiding in caves and other dark places. The bogong moth actually breeds and lays eggs in winter, because it doesn’t like hot weather.

Birds and some other animals depend on the moth migration for food, when they can eat a lot of big fat moths and get lots of protein. Some Aboriginal tribes of southeastern Australia also used to follow the migration into the mountains, where they would gather lots of moths from caves and roast them. Apparently they taste like nuts.

But the insect that migrates farthest is a species of dragonfly. The globe skimmer, also called the wandering glider or winged wanderer, lives in much of the world, but not in Europe. Researchers think it can’t cross the Sahara to reach Europe, but it can cross the Himalayas. It’s the highest-flying dragonfly known as a result. Even though it’s a small dragonfly, less than two inches long, or 4.5 cm, it has big wings, with a wingspan of almost three and a half inches, or 8 and a half cm. Its abdomen is usually yellow, although males are sometimes more reddish. It’s a strong, fast flier and that’s a good thing, because an individual dragonfly may fly as far as 3,700 miles, or 6,000 km, during migration.

Different populations migrate to different areas, naturally, but scientists have compared the genetic profiles of globe skimmers from different parts of the world and discovered that they’re all extremely similar. This can only happen if the dragonflies from different continents are breeding with each other, which suggests that they’re traveling even farther than we already know. The globe skimmer crosses the Indian Ocean between Asia and Africa, and it shows up on incredibly remote islands, so obviously it’s able to cross vast distances without too much trouble.

The reason the globe skimmer migrates is that it needs fresh water to lay its eggs in. Many parts of the world have well-defined rainy seasons and dry seasons, and the globe skimmer wants to stay where it’s rainy. As it travels, it meets up with other dragonflies, mates, and lays eggs as it goes. The eggs develop quickly and the larvae mature within a few weeks, and immediately join the migration.

The reason the globe skimmer is able to migrate is because of its big wings and flying style. Its wings are broad as well as long, which allows it to ride the wind like a surfer riding a wave. It can glide long distances without needing to move its wings, which saves a lot of energy.

But most insects don’t exactly migrate, or at least they only travel relatively short distances to find a place to winter. The ladybug, for instance.

Juergen emailed me a few months ago about meeting one ladybug outside, then going inside to find a bajillion ladybugs. This happens a lot in autumn and it’s amazing how such a pretty little insect can suddenly seem horrifying when there are hundreds or even thousands of them in your home. It happens because many species of ladybug gather together to spend the winter in a sheltered area. Usually the sheltered area is a forest floor or a rock with lots of crannies for them to hide in. But sometimes it’s your house.

The outside of a light-colored house reflects heat from the sun, which is good for your house but which also attracts ladybugs. When a ladybug finds a nice place to spend the winter, it releases pheromones that attract other ladybugs, and before you know it, your house is ladybug central. Even if you bring in an exterminator to get rid of the bugs, the pheromones remain and will continue to attract ladybugs for years. All you can do is make sure ladybugs can’t get into your house by sealing up every little crack and gap. If the ladybugs do remain, a lot of them will probably die because most houses are too dry for them in winter. The ones that do survive will leave in spring, and at least they don’t eat anything while they’re hibernating. Ladybugs eat aphids and other plant pests during warmer months, so they’re helpful to gardeners and farmers. There are special traps you can get that attract ladybugs and hold them inside until you take them out and release them.

Another insect, commonly called the stinkbug for the nasty odor it releases if it feels threatened, also called the shield bug for its shape, also sometimes comes into houses to spend the winter, sometimes in huge numbers. The most common species in North America these days is the brown marmorated stinkbug, which is a mottled brown with small black and white markings to help it blend in with tree bark. It can grow up to three-quarters of an inch long, or two cm, and is big and heavy and a very clumsy flyer.

The brown marmorated stinkbug is an invasive species from Asia that arrived in North America in the 1990s and has spread throughout the continent, especially the eastern United States. It eats plants and can destroy fruit crops and other crops like beans and tomatoes. So unlike the ladybug, it’s not a beneficial insect to humans. But despite its bad smell, it’s not dangerous to humans or pets. The stinkbug will often appear in your house in fall but also in spring, when it emerges from its little hiding spot in your house and tries to find its way outside.

Finally, let’s look at an infamous swarming insect, the locust. Locusts are responsible for untold thousands of humans dying of starvation when clouds of them sweep through a location, eat up every scrap of food they can find, and move on when all the food is gone. But what are locusts, and why do they do this?

The locust is a type of grasshopper. Specifically, it’s one of several species of short-horned grasshoppers. Ordinarily the grasshoppers are no different from other grasshoppers. But occasionally there’s a drought where a population of the grasshoppers live, and after the drought is over and the plants that died back start to grow really fast, the grasshoppers change.

First, the grasshoppers start to breed much more than usual. When those eggs hatch, the nymphs, which is what baby grasshoppers are called, stay together in groups instead of dispersing and start moving together. They don’t have wings until they grow up so they just hop together and meet up with more and more nymphs. Once they metamorphose into adult grasshoppers, they’re called locusts although they’re still the same grasshoppers as before, just with different behaviors. Some species also look a little different during swarming seasons, often larger than usual and sometimes with different coloration or markings.

Many of these species of grasshopper are large, up to four and a half inches long, or 11 cm, with large wings that make them strong fliers. The swarms can fly up to 93 miles a day, or 150 km, and land when they find a lot of food, which may be crops planted by humans. After the swarm has eaten everything it can find, it moves on to find more. It also leaves behind lots of eggs that soon hatch into new grasshopper nymphs that eat anything that’s started growing again.

If you’re wondering how even a whole bunch of grasshoppers can cause people to starve to death, you don’t have an idea yet of the size of the swarms. Locust swarms can contain tens of billions of grasshoppers. That’s billion with a B. An individual swarm can easily cover more than 100 square miles, or 260 square km, and when they land, they will literally eat every growing plant down to the ground, every single leaf, every single blade of grass, everything. Not only is there nothing left of crops when a locust swarm has come through, there’s no grass or leaves for animals to eat.

The largest locust swarm that we know of was seen in 1875 in the western United States. The swarm covered an estimated 198,000 square miles, or 510,000 square km. That’s larger than the entire state of California. There may have been over 12 trillion individual grasshoppers in that swarm.

This was the Rocky Mountain locust, which was adapted to the prairies of North America. As white settlers pushed west and planted crops where there had formerly only been prairie grass and other prairie plants, the farmers were repeatedly visited by locusts that ate not just their crops, but everything else they could find. The locusts ate leather, wool, wood, and there are even reports of locusts eating the clothes people were actually wearing. There were so many locusts that they couldn’t be avoided. They would get into houses and eat up food in the pantries, along with blankets and clothing. People tried everything they could think of to destroy the locusts, from setting entire fields on fire to building horse-drawn bulldozers that smashed the locusts flat. But nothing helped. There were too many of them.

But as the years passed and more and more prairie was converted to fields or pastures for cattle, and more cities and towns grew up in the west, the Rocky Mountain locust started to decline in numbers. In 2014 it was declared extinct, but by then no one had seen a Rocky Mountain locust since 1902. It’s possible they’re still around in small numbers, but a combination of habitat loss and active eradication of the insect probably drove it to extinction. Another species of North American grasshopper, the high plains locust, is rare these days and almost never swarms, with the last big swarm reported in the 1930s.

But there are plenty of other locusts throughout the world, reported throughout recorded history, including the ancient Egyptians, ancient Greeks, and ancient Chinese. Plagues of locusts feature in the Quran and the Bible. The most well known species are the desert locust, which lives in Africa and parts of the Middle East and Asia, and the migratory locust, which lives in Africa, Asia, Australia, New Zealand, and Europe, although it’s quite rare in Europe these days.

Not all locust swarms are enormous, of course, but even a small swarm can destroy local farms and pastures. In the days before easy communication and travel, this could mean people starved in one village even if the next village over was fine. Researchers estimate that a locust swarm that’s only one square kilometer in size, which is less than half a square mile, or about 250 acres, can eat as much as 35,000 people in a single day. WHOA, I did not realize when I wrote that that it would make it sound like the locusts were eating people. Locusts don’t eat people, they don’t hurt you, but the locusts eat as much food as 35,000 people do. That’s what I meant.

The thought of locust swarms is scary, but fortunately it doesn’t happen every year or even every decade. But it does still happen. In 1988, locusts swarming in Africa crossed the Atlantic Ocean and arrived in South America. This year, 2020, started out with desert locusts swarming in parts of north and east Africa in January, spreading into parts of Asia by May. In November, some localized swarms of locusts were spotted in parts of Australia after heavy rains, especially in west and northwest Victoria.

These days, though, people have the advantage of early warning. Locust swarms can be tracked by satellite and drones, people whose crops are eaten up can have food shipped in to help keep anyone from starving, and there are pesticides that can kill a lot of locusts in a short amount of time. But a new experimental biological control has been working really well. The dried spores of a fungus that kills grasshoppers are sprayed on the ground where locusts are laying eggs, since grasshoppers lay their eggs in soil or sand. The fungus kills the grasshoppers and stays on the ground to kill the ones that hatch or arrive later. Best of all, unlike chemical pesticides, the fungus doesn’t kill other insects.

And don’t forget, of course, that the locust is edible. Cultures throughout much of the world traditionally ate locusts and they’re still considered delicacies in many places. They’re also more nutritious than meat from mammals like cattle. Besides, if locusts arrive and eat all your food, it’s just smart to eat the locusts that ate your food. You gotta get that food back somehow.

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

Thanks for listening!

Episode 141: Zombie Animals

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We’re inching closer to Halloween and it’s getting spookier out there! This week let’s learn about some animals that get zombified for various reasons. This is an icky episode, so you might not want to snack while you’re listening. Thanks to Sylvan for the suggestion about the loxo and mud crabs!

Further reading:

Zombie Crabs!

Ladybird made into ‘zombie’ bodyguard by parasitic wasp

A mud crab held by a dangerous wizard:

A paralyzed ladybug sitting on a parasitic wasp cocoon:

A cat and a rodent:

Show transcript:

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

It’s another week closer to Halloween, so watch out for ghosts and goblins and zombie animals! Zombie animals?! Yes, that’s this week’s topic! Thanks to Sylvan for suggesting the loxo parasite, which we’ll talk about first. Brace yourself, everyone, because it’s about to get icky!

Before we learn about loxo, let’s learn about the mud crab, for reasons that will shortly become clear. Mud crab is the term for a whole lot of small crabs that live in shallow water, mostly in the Atlantic or eastern Pacific Oceans but sometimes in lakes and other fresh water near the ocean, depending on the species. Most are less than an inch long, or under about 30 mm. The largest is called the black-fingered mud crab, which grows to as much as an inch and a half long, or 4 cm. Most mud crabs are scavengers, eating anything they come across, but the black-fingered mud crab will hunt hermit crabs, grabbing their little legs and yanking them right out of their shells. It also uses its strong claws to crack the shells of oysters.

Loxothylacus panopaei is actually a type of barnacle. You know, the little arthropods that fasten themselves to ships and whales and things. But loxo, as it’s called, doesn’t look a bit like those barnacles except in its larval stages. After it hatches, it passes through two larval stages; during the first stage, it molts four times in only two days as it grows rapidly.

Then, during the cyprid larval stage, the microscopic loxo searches for a place to live. The male remains free-swimming but the female cyprid larva is looking for a mud crab. She enters the crab’s body through its gills and waits for it to molt its exoskeleton, during which time she metamorphoses into what’s called a kentrogon, basically a larva with a pointy end. As soon as the crab molts its exoskeleton, the female loxo uses her pointy end, called a stylet, to stab a hole in the crab’s unprotected body. Then she injects parasitic material that actually seems to be the important part of herself, which enters the crab’s blood—called hemolymph in arthropods like crabs. Like most invertebrates, crabs don’t have blood vessels. The hemolymph circulates throughout the inside of the body, coming into direct contact with tissues and organs. This means that once the loxo has infiltrated the hemolymph, she has access to all parts of the crab’s body.

At this stage, the loxo matures into something that isn’t anything like a barnacle, but is an awful lot like something from a horror movie. She grows throughout the crab, forming rootlets that merge with the crab’s body and changes them. Basically, the female loxo becomes part of her crab host. Eventually she controls its nervous system and molds it to her own needs. She even molds the body to her own needs, since if she’s parasitized a male crab she has to widen its body cavity so it can hold her eggs.

The crab stops being able to reproduce and doesn’t want to. It only wants to care for the eggs that the female loxo produces. She extrudes an egg sac so that it hangs beneath the crab’s abdomen, where a male loxo can fertilize it when he swims by. The crab then treats the egg sac as if it contains its own eggs, protecting them and making sure they get plenty of oxygenated water. This is true even for male crabs, which ordinarily don’t take part in protecting their own eggs. The loxo eggs hatch in about a week, and as soon as they do, the female loxo inhabiting the crab starts the process over again. While a mud crab in the wild can live for a few years, once it’s taken over by the loxo parasite it only lives around 45 days.

Most mud crab populations are reasonably resistant to the parasite, but where the loxo has been introduced to areas where it didn’t live before, it can decimate the local mud crab population. This happened in Chesapeake Bay in the 1960s in North America. The local oysters had been so over-fished that they were nearly completely gone, also nearly destroying the local oyster industry. They imported oysters from the Gulf of Mexico to replenish local stocks, but no one realized they were bringing the loxo with those oysters. These days, up to 90% of the Chesapeake Bay mud crabs are infected with the loxo parasite, while only up to 5% of the Gulf of Mexico mud crabs are infected. Researchers at the Chesapeake Bay Parasite Project are working to figure out more about how the loxo infiltrates its host and changes it genetically, and are monitoring infection rates in the wild.

If you think that’s gross, it’s not going to get any better the rest of this episode.

Next let’s learn about another zombie animal, this one a spider. A number of spiders are parasitized by a tiny wasp called Zatypota percontatoria. It lives throughout much of the northern hemisphere and prefers forested areas with plenty of web-building spiders in the family Theridiidae, also known as cobweb spiders.

Cobweb spiders are really common with around 3,000 species that live throughout the world, including the black widow, which by the way is not nearly as dangerous as people think. Some cobweb spiders are kleptoparasites, which means they steal food and other resources from another animal, in this case larger spiders. A kleptoparasite cobweb spider actually lives in the web of a larger spider, and when a small bug gets caught in the web, it steals it. Sometimes the cobweb spider will kill and eat the spider that built the web in the first place too.

But most cobweb spiders are ordinary spiders, and most are quite small, usually only a few millimeters long. Many are marked with pretty patterns in brown, white, black, and other colors. Different species build different kinds of webs, but they all eat small insects.

As for the wasp, it’s about the same size as the spider it’s trying to parasitize, and sometimes smaller. It has long wings, long antennae, and a long abdomen that in the female ends in a sharp ovipositor. The female finds a spider, usually a young spider that’s less able to defend itself, and stabs it in the abdomen with her ovipositor. Then she lays a single egg inside the spider and flies away.

The egg doesn’t bother the spider, although once the egg hatches into a larva it starts to feed on the spider’s hemolymph. Remember, that’s the equivalent of blood in the invertebrate world. At the same time, it’s releasing hormones into the spider that change its habits. Basically the wasp larva controls the spider so that it acts to the benefit of the larva, not itself.

All this takes about a month. When the larva is ready to pupate and metamorphose into an adult wasp, it secretes a final hormone that influences the spider’s behavior. This one causes the spider to spin a strong, cocoon-like web. When the web is finished, the larva bursts out of the spider’s body, killing it, and eats the spider. Then it enters the cocoon and develops into an adult wasp.

Because spiders are good at defending themselves, only about 1% of spiders end up parasitized. I’m sure the spiders think that’s 1% too many. There are other parasitic wasp species in other places, but they all act about the same as Zatypota.

Another wasp, Dinocampus coccinellae, parasitizes ladybugs. Like Zatypota, the female wasp lays one egg in the ladybug’s body. When it hatches, the larva eats the ladybug’s insides while the ladybug continues to go about its ordinary activities. But after several weeks, the larva is ready to pupate. It paralyzes the ladybug, bursts out of its body, and spins a cocoon that the ladybug sits on.

But the ladybug isn’t dead. It protects the cocoon from other insects by twitching and making grasping motions with its legs.

After about a week, the adult wasp emerges from its cocoon and flies away. The ladybug usually dies, but not always. About a quarter of infected ladybugs recover and are fine. Researchers aren’t sure how the wasp larva causes the paralysis. It may release a virus that infects the ladybug or it may have something to do with venom released by the larva.

This wouldn’t be a proper zombie episode if I didn’t talk about that disgusting parasitic fungus that affects certain carpenter ants in the rainforests in Brazil and Thailand. It completely squicks me out so I’m going to explain it very, very quickly.

Fungal spores float through the air and land on an ant, where they stick. They release enzymes that eventually break down the ant’s exoskeleton, allowing the fungus to spread inside the ant’s body. Finally it’s able to control the ant and makes it crawl up the stem of a plant and bite into a leaf vein. The ant is unable to move at this point and eventually dies. The fungus sprouts from inside the ant and grows into stalks, especially from the ant’s head. About a week later it releases spores that go on to infect other ants. Ugh. So glad I’m not an ant.

Ants can sense when one of the colony has contracted the fungus, and will carry the infected ant far away from the colony so it’s less likely to infect others. The ants also groom each other to remove any spores that may have attached. The fungus can completely destroy ant colonies, but it has a parasite of its own, another fungus that stops the first fungus from releasing spores. A related parasitic fungus also infects certain caterpillars.

Look, I’m totally over talking about fungus, so let’s move on.

So is there any chance that a parasite will turn you into a zombie? There’s not, but a behavior-changing parasite does sometimes infect humans. It’s called Toxoplasma gondii, and while its effects on human behavior has been studied extensively, the effects are so minor as to be nearly nonexistent in most cases.

Toxoplasmosis is a disease caused by a single-celled parasite, and it’s one that not only infects humans, it’s really common. I probably have it but I’m not going to think too hard about that. For most people, it never bothers them and never causes any symptoms, or only mild short-term symptoms like a lowgrade cold that takes a few weeks to clear up. But it can be more serious in people with a suppressed or weak immune system, and can cause problems for the baby if its mother gets infected while she’s pregnant.

There are estimates that up to half the people in the world are infected with toxoplasmosis but never know. The reason it’s so common is that the parasite targets cats, and can be spread in cat feces. And, you know, if you scoop out the cat’s litter box you might be exposed. That’s why pregnant women shouldn’t clean up after a cat. Infection can also result from eating undercooked meat from an infected animal, eating unwashed fruit or vegetables, drinking unpasteurized milk, and drinking untreated water.

Any mammal or bird can contract the parasite, but it can only reproduce in a cat’s digestive system. It doesn’t hurt the cat, it just wants to get inside the cat so it can reproduce. And the best way to get inside a cat is to be part of a rodent that a cat eats.

When a rat or other rodent is infected with Toxoplasma gondii, its behavior changes. Suddenly, it starts to like cats. You can probably see where this is going. Not only does it stop avoiding cats, it actually seeks them out. The cat, naturally, can’t believe its luck, kills and eats the rodent, and may become infected.

If you have a pet cat, the best way to reduce the risk of contracting toxoplasmosis is to scoop the litter box daily, then wash your hands. It takes about a day for the parasite to become active after being shed in cat poop, so if you scoop the litter box right away the risk is lower. Researchers are working on vaccines, and they’ve actually already developed a vaccine that’s now used in sheep. If you keep your cat inside, where it’s safer anyway, it’s much less likely to be exposed to the parasite in the first place.

So, take ordinary precautions but don’t worry too much about toxoplasmosis. Unless, of course, you are a rodent.

You can find Strange Animals Podcast online at strangeanimalspodcast.blubrry.net. That’s blueberry without any E’s. If you have questions, comments, or suggestions for future episodes, email us at strangeanimalspodcast@gmail.com. We also have a Patreon if you’d like to support us that way.

Thanks for listening!