Wikipedia
Entoniscidae
The '''Entoniscidae ''' are a family of marine isopod crustaceans in the suborder Cymothoida. Members of this family are parasites of brachyuran and anomuran crabs, living in their hosts' haemocoel. A small chitinised hole develops through the host's exoskeleton through which the isopod can communicate with the environment. The female isopod bears little resemblance to any free-living isopod, but the morphology of the larvae show their taxonomic affiliations.