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.