Mancae - AbsoluteAstronomy.com

The manca are post-larval

Crustacean larvae

Crustaceans may pass through a number of larval and immature stages between hatching from their eggs and reaching their adult form. Each of the stages is separated by a moult, in which the hard exoskeleton is shed to allow the animal to grow...

juveniles

Juvenile (organism)

A juvenile is an individual organism that has not yet reached its adult form, sexual maturity or size. Juveniles sometimes look very different from the adult form, particularly in terms of their colour...

in some crustacean

Crustacean

Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...

s. The manca stage is the defining characteristic of a clade called Mancoida which comprises all the member of the Peracarida

Peracarida

The superorder Peracarida is a large group of malacostracan crustaceans, having members in marine, freshwater, and terrestrial habitats. They are chiefly defined by the presence of a brood pouch, or marsupium, formed from thin flattened plates borne on the basalmost segments of the legs Other...

except the Amphipoda

Amphipoda

Amphipoda is an order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. The name amphipoda means "different-footed", and refers to the different forms of appendages, unlike isopods, where all the legs are alike. Of the 7,000 species, 5,500 are classified...

. Mancae closely resemble the adult form, but for the absence of the last pair of pereiopods. In some isopods

Isopoda

Isopods are an order of peracarid crustaceans, including familiar animals such as woodlice and pill bugs. The name Isopoda derives from the Greek roots and...

, specifically the family Cymothoidae

Cymothoidae

Cymothoidae is a family of isopods. Several species are parasites, usually of fish. These include the bizarre "tongue-biter", Cymothoa exigua.-Genera:Around forty genera are recognised *Aegathoa Dana, 1853...

, the manca stage is a parasite of fish, and is also known as the praniza.