What's the difference between mantis shrimps and pistol shrimps?
* At the very basic level, the two are very different critters, with pistol shrimps belonging to a completely different group of organisms which include lobsters and crabs, while mantis shrimps make up the only living order in a superorder called the hoplocarida. You can tell both apart very quickly by the ff:
* Pistol shrimps have two relatively large claws (one significantly larger than the other) that it holds extended in front of it, while mantis shrimps hold their enlarged forelimbs very close to their bodies.
* The carapace of a pistols is relatively "long" (ie. covers the head and thoracic segments), whereas in mantises the carapace is extremely short, which makes them look more "wormlike" because of the exposed abdomen and some thoracic segments. This makes the mantises very flexible, and they like rolling around a lot inside their burrows or cavities.
* Pistols seem to have a very normal looking shrimplike "rostrum" (I don't own a pistol, so I'm basing this on pics), which is a sharplike extension jutting outwards from their head, while mantis shrimps do not clearly show this structure.
* The eyes of pistols are recessed, whereas mantises have extraordinarily stalked and eminently moveable eyes.
* Mantis shrimps have a pair of "winglike" antennal scales along the sides of their head, which you can very clearly see if you look at them face to face.
* Pistol shrimps make those clicking noises by using one of their specially modified claws. Based from different sources, these are either used in mating, hunting (by stunning small prey), and in fighting with other pistol shrimps. Mantises cannot make clicking noises per se.... instead, any clicking noises from a mantis shrimp are due to using its forelimbs to hit something else, either inanimate objects or (more likely) hardshelled prey such as snails or hermit crabs.
* Whether or not pistols are deadly to other inhabitants of the aquarium seems to be an open debate. Some have said they do eat others, while I've read in some reference books that they feed on already dead stuff. I suppose it's really a combination of both, with the shrimp feeding on much smaller prey when the opportunity arises. The mantis is deadly to others (especially when it's pretty hungry), although one mantis that I have has (so far) left other inhabitants alone when kept amply fed. I've seen pics of gobies and pistols cooperating, while I'm sure the mantis would rather eat the fish than live with it.