The Paracyclops fimbriatus-complex (Copepoda, Cyclopoida): a revision

Abstract

The type .species of Paracyclops , P. fimbriatus (Fischer, 1853), is redescribed based on material froni rhe vieilli ty of St Pctersburg in Russia, one of the type localities.The taxonomie status of P. fimbriatus, P. chiltoni ( Thomson, 1882) and P. imminuta Kiefer, 1929 are stabiliscd and a neotype is designated for P. fimbriatus.It is revealed thar faillira lo separate P imminuta front the other two species of the complex was the main factor responsible for the taxonomie confusion concerning ail rhree.Characters tr.lditionally used by taxonomists, such as proportional measurements of the caudal rami and the terminal spines of the third endopodal segment of leg 4 are found to vary considerably within populations as well as between populations.Since there is extensive overlap in variability expressed beeween thse three variable species, it is therefore concluded that most early records are unrelablc.Previously overlooked characters which can help to differentiate benveen them are introduced, including the ornamentation of the frontal surface of the coxobasis of antenna, of the posterior surface of leg 1, and of the caudal rami.