A new species of Mesocyclops (Copepoda, Cyclopoida, Cyclopidae) from Southeastern Mexico

The taxonomical status of several neotropical species of Mesocyclops is still uncertain. Furthermore, several new species with a restricted distributional range have been described recently in this region. From littoral zooplankton samples collected in the lowlands of the State of Tabasco, Southeastern Mexico, male and female specimens of a previously unknown species of Mesocyclops were found. This new species is described herein based on both sexes and following the upgraded standards set for the taxonomic study of this genus, including SEM analysis. The new species differs from its congeners by a combination of several characters: the unique shape of the antennular hyaline membrane, the ornamentation of both maxillule and maxilla, the ornamentation of the fourth swimming leg, the shape and structure of the genital receptacle, and the ornamentation of the furcal rami. It is most closely related to other neotropical species such as M. meridianus Kiefer, 1926 and M. pseudomeridianus Defaye & Dussart, 1989. This is the eleventh species of Mesocyclops known from Mexico, and also the third new species described upon Mexican material. Due to the affinity of the Tabasco fauna with the Caribbean and the South American copepod faunas, the new species is expected to have a relatively wide geographical distribution in the neotropical region.