Biometrical key-characters for species separation during ontogenesis in fairy shrimps (Crustacea, Anostraca)

Species identification at the larval stage in Anostraca is a major problem, particularly in field studies when two or more species are co-occuring. Investigation into the possibility of telling larval species apart was performed by means of a biometrical study on wild larvae and juveniles of six fairy shrimp species of the genera Chirocephalus, Branchipus and Tanymastix. A total of ten characters and their relationships with body length were analysed within each of the six developmental stages considered. Most of the variables differed significantly (P<0.001) among the taxa examined. Discriminant analysis allowed individuals to be differentiated according to species and to provided evidence of the existence of a few diagnostic traits of use as key-characters.