The complete cypris larva and its significance in thecostracan phylogeny

The Cirripedia normally hatch as nauplii but the terminal pelagic instar is highly specialized and called cyprid or cypris larva. All Cirripedia are sessile animals and the process in which the larvae settle, attach, and metamorphose has therefore been at the focus of biologists since Darwin’s monumental papers on this specialized crustacean taxon ( Darwin 1852 , 1854 ). It is the task of the cyprid to complete this process to success. It is therefore often mentioned as one of the unique, derived characteristics (autapomorphies) for the Cirripedia, but unfortunately both the concept “Cirripedia” and “cyprid” are often used in ill-defined ways both in textbooks and professional papers.