The family Caprellidae currently includes 360 species in 90 genera. These numbers will change as new species are collected and genera are revised. Their common name of skeleton shrimp hints at their structure. These beasties don't look much like "typical" amphipods and instead are thin and elongate, rather like a praying mantis. They are typically found on living substrates such as eelgrass, bryozoa or hydroids. Caprellids hold onto these using grasping pereopods (modified limbs). The front two pairs are modified into predatory tools called gnathopods.
As with many crustacea, the female can only be impregnated while her skeleton is still soft. Which is why I have difficulty believing this quote from Wikipedia "After mating, the female in some species have been known to kill the males by injecting venom from a claw within their gnathopod." If the claw is soft and the male has his normal exoskeleton I fail to see how envenomation could occur - and unless the female eats the male, there would seem to be little reason to kill Dad. As with the isopods, females lay their eggs in a marsupium. Newly hatched youngsters climb onto their mother and, in some species, feed on whatever growths there are on her exoskeleton. Males are typically significantly larger than females.
Thanks to my friend Rafael Murillo, who first found them, I have seen scorpionfish in the Sea of Cortez covered with dozens of ghost shrimp. This doesn't seem to have been reported previously. There is a photo showing this below.
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Ryan Photographic - Caprellidae - Skeleton shrimp or ghost shrimp
