Episode 337: Ghost Shrimp and Snapping Shrimp

Thanks to Zachary and Anbo for their suggestions this week! Let’s learn about some shrimp!

Further reading:

This is why the pistol shrimp is immune to its own powerful shock waves

The Symbiotic Relationship Between Gobies and Pistol Shrimp

An eastern ghost shrimp:

A snapping shrimp:

A goby fish and its snapping shrimp buddy:

Show transcript:

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

This week we’re going to have an episode about a few different types of shrimp, with suggestions from Zachary and Ambo.

Let’s start with the ghost shrimp, since Zachary recently got an aquarium and has some ghost shrimp in it.

The name ghost shrimp refers to various species of freshwater shrimp in the genus Palaemon. One of the most popular species to keep as a pet is Palaemonetes paludosus. It’s sometimes called the glass shrimp since it’s mostly transparent, or the eastern ghost shrimp.

The eastern ghost shrimp can grow up to about an inch long, or 2.5 cm. It’s native to the southeastern United States, mostly east of the Appalachian Mountains, where it lives in lakes and eats plankton.

Even though the eastern ghost shrimp is mostly transparent, it can actually change its color to blend in with its background. Only one other species of ghost shrimp is known to do this, a very similar species that is only found in the Mississippi River.

There are dozens of species of ghost shrimp, though, and they live throughout the world. Some species are freshwater, others are marine. Most are at least partially transparent and rarely grow more than two inches long, or maybe 5 cm at most. In some cases people catch them to eat, although more often they’re caught to use as bait or fish food, and of course they’re eaten by a whole lot of wild animals.

We actually don’t know a whole lot about many species of ghost shrimp. Some have only recently been discovered, and some are endangered. For instance, the Florida cave shrimp is only found in a single sinkhole near Gainesville, Florida. It’s the only known species of ghost shrimp that lives in a cave, and it’s closely related to the eastern ghost shrimp.

The Florida cave shrimp grows a little over one inch long, or about 3 cm. It has eyes but doesn’t need them, so they don’t work anymore. It’s mostly transparent with some white spots. It was discovered in 1953 during a scientific exploration of a sinkhole in the Squirrel Chimney Cave and hasn’t been seen since 1973. It may even be extinct by now, but further explorations of the sinkhole have revealed that it connects with a much larger underwater cave system. Hopefully the little shrimp lives within this cave system, but it hasn’t been found anywhere else so far and we know almost nothing about it.

That’s pretty much all there is to know about the ghost shrimp, so congratulations to Zachary for keeping a mysterious little friend in your aquarium.

Next, Anbo wanted to learn about snapping shrimp. (Anbo also wanted to learn about the mantis shrimp, but it turns out that the mantis shrimp isn’t actually a shrimp, or a mantis, and it deserves its own episode one day.) We talked about the snapping shrimp before in episode 273, but there’s definitely more to learn about it. There are a whole lot of species–like, more than a thousand. They’re especially common in coral reefs and live in colonies that communicate with each other by snapping their claws. The sound is so loud that it can sound like a gunshot, which is why it’s sometimes called the pistol shrimp.

The snapping shrimp is about the same size as the ghost shrimp, about 2 inches long at most, or 5 cm. One of its claws is ordinary, but the other claw is much bigger, and it’s the large claw that makes the snapping sound. As we discussed in episode 273, the snapping shrimp will hide in a burrow or rock crevice with its antennae sticking out, and when a small animal like a fish happens by, the shrimp will emerge from its hiding place just far enough to get a good shot at the animal. It opens its big claw and snaps it shut so fast and so forcefully that it shoots tiny bubbles out at speeds of over 60mph, or 100 km/hour. The bubbles only travel a few millimeters in distance, but the shock wave is powerful enough at this short range to stun or outright kill a small animal.

Scientists figured out how the snapping shrimp’s snap worked in 2020, but it wasn’t until 2022 that they discovered why the shrimp doesn’t damage its tiny shrimp brain when it snaps. It turns out that its brain is protected by a translucent helmet called an orbital hood. It needs to be translucent because it covers the shrimp’s eyes as well as the rest of its head. The hood is an extension of the shrimp’s exoskeleton, and it has an opening at the back. Scientists think that when the shock wave of a snap meets the hood, the change in water pressure under the hood is expelled out the opening instead of affecting the brain.

Scientists want to learn how exactly the orbital hood works to redirect pressure waves, in hopes of being able to replicate it. That way we can make really effective armor for people who work with explosives, or for military personnel.

In episode 332 we talked about mutualism, and the snapping shrimp actually has a mutualistic relationship with the goby fish. Gobies are little fish that are usually even smaller than snapping shrimp, or not much bigger. The order Gobiiformes is one of the largest fish families, and we’ve talked about at least one type of goby before. That was back in episode 189 when we learned about the lumpsucker. Not all gobies are buddies with snapping shrimp, but about 130 species are, most of which live in the Pacific Ocean.

Snapping shrimp live in burrows, and the 20 species or so of snapping shrimp that partner with gobies will dig an extra-large burrow. That’s because it’s making room for its goby friend, or even more than one goby friend. The burrow can extend as much as two feet deep, or about 61 cm, with different chambers. While the shrimp is digging the burrow, the goby watches for danger. If a predator approaches, the fish warns the shrimp by moving its fins in a specific way, which signals that the shrimp should hide. If part of the burrow collapses and buries the fish, it just waits until the shrimp digs it out of the sand.

The shrimp and the goby live together in the burrow. They leave the burrow together so they can watch out for each other. The snapping shrimp doesn’t see very well so while it’s outside of the burrow, it will keep track of the goby with its long antennae. The goby watches out for danger and warns the shrimp if it needs to hide.

Both eat small animals, but the shrimp also likes eating some types of algae that grow on rocks. The shrimp will even bring pieces of algae to its burrow to snack on later, and at least one researcher has witnessed the goby help transport algae to the burrow.

During mating season, the goby brings its mate into the burrow, where the female lays eggs in the male’s chamber. Only the male takes care of the eggs, and he spends almost all of his time guarding them and swimming around them to keep them oxygenated. When he has to leave, he blocks the entrance with sand. The eggs hatch after a little over a week and the larvae swim out of the burrow immediately. The female shrimp carries her eggs around until they hatch, which they do in the burrow, and they too leave the burrow right away and float off on their own.

Both the goby eggs and the shrimp eggs hatch at night or sometimes early in the morning, which is important because those are times when both the goby and the shrimp are not active. In other words, that’s a time when the larva can safely leave the burrow without being eaten by its parent’s roommate. Having a buddy is great, but when it comes to your kids, it’s always safety first, even among fish and snapping shrimp.

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 273: Noisy Invertebrates

Thanks to Isaac, Joel, Ethan, and Richard E. for their suggestions this week!

Don’t forget to check out our crowdfunding campaign for some cute enamel pins!

Further reading:

Snapping Shrimp Drown Out Sonar with Bubble-Popping Trick

One example of a pistol shrimp–there are many, many species (photo from this site):

A walnut sphinx moth sitting on someone’s hand (photo by John Lindsey, found on this page):

A caterpillar (photo by Ashley Bosarge, found on this page):

The Asian longhorned beetle (from this site):

The white-spotted sawyer pine beetle is another type of longhorned beetle:

Show transcript:

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

It’s been too long since we’ve had an invertebrates episode, so this week let’s learn about some invertebrates that make noise. Thanks to Isaac, Joel, Ethan, and Richard E. for their suggestions!

We don’t have a birthday shout-out this week, but we do have a reminder that the next five episodes, the ones releasing in May, are our Kickstarter episodes! Those are from the Kickstarter level where the backer got to choose the topic and work with me to craft the episode. I’ve been amazed at how fantastic those episodes turned out, and I think you’ll like them.

Speaking of crowdfunding campaigns, a quick reminder that the Tiny Pin Friends Indiegogo is still going on. It’s sort of stuck halfway to our goal, probably because I got busy with the book release and haven’t been telling people about the pins, so if you want to take a look at the pin designs, there’s a link in the show notes. Thanks!

Now, on to the invertebrates! Both Isaac and Joel suggested the same topic at different times, pistol shrimp. This is a group of shrimps also called snapping shrimps. Most species live in warm, shallow coastal habitats like coral reefs, but some live in colder water and at least one lives in freshwater caves.

The pistol shrimp only grows a few inches long at most, or about 5 cm. It gets its name from its big claw, which functions in a similar way to the workings of a pistol (sort of). But instead of shooting bullets, the claw shoots bubbles—but so incredibly fast, they might as well be bullets.

A pistol shrimp has two claws, but one is small and used for picking stuff up and grabbing food. The other claw is the pistol claw that’s much bigger and stronger. Which claw is which depends on the individual, and if a shrimp’s pistol claw gets damaged or bitten off, its other claw will develop into a pistol claw. The damaged or lost claw eventually regenerates into a little claw for manipulating food.

The pistol shrimp is mostly an ambush hunter. It will hide in a burrow or rock crevice with its antennae sticking out, and when a small animal like a fish happens by, the shrimp will emerge from its hiding place just far enough to get a good shot at the animal. It opens its big claw and snaps it shut so fast and so forcefully that it shoots tiny bubbles out at speeds of over 60mph, or 100 km/hour. Obviously the bubbles don’t travel very far at that speed, really only a few millimeters, but it’s powerful enough at this short range to stun or outright kill a small animal. The shrimp then grabs its stunned or dead prey and drags it back into its hiding spot to eat.

The process is way more complicated than it sounds. When the claw opens, water rushes into a tiny chamber in the claw. When it snaps closed, a tiny point on the claw pushes into the chamber, which leaves no room for the water. The water is therefore forced out of the chamber at such incredibly high pressure that it leaves vapor-filled cavities in the water, the bubbles, which collapse with a loud snapping sound. The pressure wave from the collapsing bubble is what actually kills or stuns an animal. Physics! I don’t understand it! Check the show notes for an article that goes into more detail about this process, which I’ve hopefully described correctly.

The bubble’s collapse makes such a loud noise that the pistol shrimp is one of the loudest animals in the ocean, but the sound lasts for less than a millisecond. It takes 100 to 400 milliseconds for you to blink your eye, to give you a comparison. The collapsing bubble also produces light and intense heat, but it’s such a tiny bubble with such a limited range that the heat and light don’t make any difference. The light isn’t very bright and lasts such a tiny amount of time that the human eye can’t even perceive it.

The pistol shrimp doesn’t only use its big claw to hunt for food and defend itself from potential predators. It also communicates with other pistol shrimp with the sound, and pistol shrimp can live in colonies of hundreds of individuals. With them all snapping together, no matter how short each snap is, the collective sound can be incredibly loud—so loud it interferes with sonar in submarines.

This is what it sounds like, although it also kind of sounds like popcorn popping, if you ask me:

[snapping shrimp sounds]

Next, Ethan suggested the walnut sphinx moth, because his son found one, they looked it up, and they were both amazed at how awesome it is. It lives in the eastern part of North America and is a big, robust moth with a wingspan up to 3 inches across, or 7.5 cm. Its wings and body are mostly brown and gray, often with darker and lighter markings but sometimes all one color. The edges of its wings have an uneven scallop shape and when it perches, it spreads both pairs of wings out in a sort of X shape. Its wing shape and coloring make it look a lot like an old dead leaf.

Like many moths, the walnut sphinx moth doesn’t eat at all as an adult. After it metamorphoses into an adult, it only lives long enough to mate and lay eggs. It spends most of its life as a caterpillar, where it eats the leaves of various kinds of trees, especially nut trees, including walnut, hazelnut, and hickory. The caterpillar is a pretty green with tiny white dots all over and yellow or white streaks along its sides, although some individuals are red, orange, or pink instead of green. It has a red or green horn on its tail end.

The most amazing thing about this moth is how the caterpillar keeps from being eaten. Lots of animals like to eat caterpillars, especially birds, but when a bird tries to grab this caterpillar, it thrashes around and actually makes a sound! You don’t typically think of caterpillars as noisy. It’s actually not very loud, but it does make a little whistle that mimics a bird’s alarm call, and can make a little buzzing sound too. The caterpillar makes the sound through its breathing tubes, called spiracles.

Researchers have played the caterpillar’s whistle sound at bird feeders and the birds react as though they’re hearing a bird making an alarm call.

This is what the whistle sounds like [whistle] and this is what the buzzing sounds like [buzz].

Richard E. recently tweeted some amazing pictures of beetles and suggested we cover more beetles, and I totally agree! We’ll finish with a beetle that makes this weird creaky sound:

[beetle sound]

The Asian longhorned beetle is sometimes called the starry sky beetle because it’s black with white dots. It’s native to eastern China and Korea, but it’s an invasive species in North America, parts of Europe, and other parts of Asia. It can grow about an inch and a half long, or 4 cm, but its antennae are up to twice as long as its whole body.

The female chews little holes in the bark of a tree and lays a single egg in each hole. When the larva hatches, it burrows deeper into the tree, eating sap and wood, until it’s ready to pupate. When it emerges as an adult, it chews its way out of the tree for the first time in its life, and flies away to find a mate. It especially likes poplar, maple, and willow trees. If enough beetle larvae are eating their way through a tree, the tree becomes weakened and can lose branches or even die.

There are lots of other species of longhorned beetle, though, and a lot of them make creaky scraping sounds. The male has ridges on his head that he scrapes along his thorax to attract a mate.

The white-spotted sawyer, also called the pine beetle, is native to North America and is black with a single white spot at the base of the wings, and sometimes with more white spots on the wings. It looks a lot like the Asian longhorned beetle but has black antennae whereas the Asian beetle has black and white antennae.

Like the many other longhorned beetle species, the female chews little holes in a tree to lay eggs in, but in this case she prefers pine and spruce trees, especially ones that are dead or dying or have sustained fire damage. The male white-spotted sawyer finds a good tree and defends it from other males, and if a female likes the tree she’ll mate with the male. But while the male keeps other males away, other females sometimes sneak in and lay eggs in the holes the female has already chewed in the tree. These nest holes take a long time to make and if a female can sneak some of her eggs into holes another female has already made, it saves her a lot of effort.

In addition to the male making a creaking noise to attract a mate, longhorned beetle larvae just generally make a lot of noises as they chew their way through a tree. If you’re ever walking through the woods and hear this sound, now you know what it is:

[creaky beetle sound]

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!