BROADCASTS.com

Thanks to Anbo and Siya for suggesting the mantis shrimp this week!
\n
\nThe Kickstarter for some animal-themed enamel pins is still going on!
\n
\nFurther reading:
\n
\nRolling with the punches: How mantis shrimp defend against high-speed strikes
\n
\nThe magnificent peacock mantis shrimp [picture by C\xe9dric P\xe9neau, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=117431670]:
\n
\n
\n
\nShow transcript:
\nWelcome to Strange Animals Podcast. I\u2019m your host, Kate Shaw.
\nAs invertebrate August continues, this week we have a topic suggested by Anbo and Siya. They both wanted to learn about the mantis shrimp!
\nThe mantis shrimp, which is properly called a stomatopod, is a crustacean that looks sort of like a lobster without the bulky front end, or a really big crayfish. Despite its name, it\u2019s not a shrimp although it is related to shrimps, but it\u2019s more closely related to lobsters and crabs. It can grow as much as 18 inches long, or 46 cm, but most are about half that size. Most are brown but there are hundreds of different species and some are various brighter colors like pink, blue, orange, red, or bright green, or a rainbow of colors and patterns.
\nThere are two things almost everyone knows about the mantis shrimp. One, it can punch so hard with its claws that it breaks aquarium glass, and two, it has 12 to 16 types of photoreceptor cells compared to 3 that humans have, and therefore it must be able to see colors humans can\u2019t possibly imagine.
\nOne of those things is right, but one is wrong, or at least partially wrong. We\u2019ll discuss both in a minute, but first let\u2019s learn the basics about these fascinating animals.
\nThe mantis shrimp lives in shallow water and spends most of its time in a burrow that it digs either in the sea floor or in crevices in rocks or coral, which it enlarges if necessary. Some species will dig elaborate tunnel systems while others just wedge themselves into any old crack that will hide them. It molts its exoskeleton periodically as it grows, like other crustaceans, and after that it either has to expand its burrow or move to a larger one. Most species live in tropical or subtropical areas, but some prefer more temperate waters.
\nIt has eight pairs of legs, which includes three pairs of walking legs, four pairs with claws that help it grasp items, and its front pair, which are hinged and look a little like the front legs of a praying mantis. That\u2019s where the \u201cmantis\u201d in mantis shrimp comes from, although of course it has lots of other names worldwide. In some places it\u2019s called the thumb splitter.
\nThe mantis shrimp has two eyes on stalks that move independently. Its brain extends into the eye stalks, and the section of the brain in the eye stalks, called the reniform body, is what processes vision. This allows it to process a lot of visual information very quickly. Reniform bodies have also been identified in the brains of some other crustaceans, including shrimp, crayfish, and some crabs. Scientists also think that the eyes themselves do a lot of visual processing before that information gets to the reniform body or the brain at all. In other words, part of the reason the mantis shrimp\u2019s eyes are so complicated and so unusual compared to other animals\u2019 eyes is because each eye is sort of a tiny additional brain that mainly processes color.
\nThe typical human eye can only sense three wavelengths of light, which correspond to red, green, and blue. The mantis shrimp has twelve different photoreceptors instead of three, meaning it can sense twelve wavelengths of light, and some species have even more photoreceptors. But while our brains are really good at synthesizing the three wavelengths of light we can see,