A female Sacculina carcini larva – crab hacker barnacle -set…

A female Sacculina carcini larva – crab hacker barnacle -settles on a suitable crab host and inhibits the development of the crab’s gonads, which eventually atrophy. The parasite causes a male crab to develop certain feminine characteristics including the broadening of its abdomen. In females crabs, the abdomen becomes narrower and the pleopods degenerate. Both male and female crabs become sterile. The eggs of the parasite develop and both male and female crabs carry these eggs around, secured under their abdomen, in the way that female crabs normally care for their own brood.  What is described here is an example of: