The manca (plural: mancae) is the post-larval juvenile in some crustaceans. The term is derived from Latin mancus, meaning "defective, imperfect." [1] The manca stage is the defining characteristic of a clade called Mancoida which comprises all the members of the Peracarida except the Mysidacea and the Amphipoda. [2] Mancae closely resemble the adult form, but for the absence of the last pair of pereiopods. [2] In some isopods, specifically the family Gnathiidae, the manca stage is a parasite of fish, and is also known as the praniza. [3]