One of the coolest things in the world is the mighty claw. Just ask the aliens from Toy Story. But there are some lobsters that make their way in the world without them. The members of the infraorder Achelata (literally meaning “without claws”) are the only major group of decapod crustaceans to entirely lack chelae on any of their pereopods (walking legs). They make up for this with an enlargement of the second antennae in two very distinct ways. These two ways dilineate the two families of extant achelate lobsters: the Scyllaridae and the Palinuridae.
The Scyllaridae, or slipper lobsters, have large flattened antennae. They lack the ability to perform the retrograde escape response characteristic of shrimp and lobsters, commonly referred to as the “tail flip.” Instead, their predator avoidance depends on their ability to bury themselves in the substrate. At night, however, they come out and feed on a variety of invertebrates. Scyllarids are among my favorite animals, their unsusual shape and beady eyes are adorable.
The Palinuridae have long, spiny second antennae- hence their common name, spiny lobsters. These include many commercially harvested species. They have a completely novel way of producing sound- by rubbing their plectrum, an extension at the base of each antenna, against a file-shaped region of their carapace. Furthermore, some palinurids seasonally migrate between different depths, and what is especially astounding is they do it in single file!