On the taxonomic status of Monstrilla leucopis Sars (Crustacea: Copepoda: Monstrilloida) from Norway, with comments on the male of M. longiremis Giesbrecht

Abstract

Specimens of monstrilloid copepods collected and described in the early 20 th century by G.O. Sars from the coasts of Norway and deposited in the Sars Collection (University of Oslo) were re-examined. Monstrilla leucopis Sars, 1921 was described based on female and male specimens, but the species was later synonymized with M. conjunctiva Giesbrecht, 1902 by several authors. Females of this species were analyzed and compared with closely related congeners, particularly with M. conjunctiva. This analysis includes the description of previously unknown morphological details following upgraded descriptive standards in this group. Evidence was found to support the notion that the female type specimens from Kvalø, Norway represent a distinct species; thus, M. leucopis is redescribed and reinstated as a valid taxon. Previous tropical records of female M. conjunctiva are questionable, but differences with M. leucopis can be found in body and antennule proportions, the structure of the genital spines and fifth legs, and most probably, their geographical ranges. Furthermore, M. leucopis has a modified thick-walled seta on the endopods of legs 2–4, so far a unique character among monstrilloids. The single male specimen labeled as M. leucopis in the Sars Collection was also examined and it is not the male of this species as depicted by G.O. Sars (1921). It is in fact a male of M. longiremis Giesbrecht, 1893, a species for which a short supplementary description and taxonomic comments are also provided herein. The male of M. leucopis also shares some important characters with that of M. conjunctiva, but also with another male specimen that was questionably assigned to the latter species; this male probably represents an undescribed species.