New extension range of the diaptomid copepod Prionodiaptomus colombiensis Thiébaud (Copepoda, Calanoida) with complementary description of this species

From plankton and littoral samples obtained in several freshwater environments in the Mexican state of Tabasco, the diaptomid calanoid copepod Prionodiaptomus colombiensis Thiébaud, 1912 is recorded herein. The Tabasco specimens were illustrated by camera lucida drawings and with the help of Scanning Electron Microscopy. When compared with descriptions and illustrations of other workers, they show slight morphological variations in several structures such as the male and female fifth legs, and the urosome. These differences were considered to be within the range of species variation. The distributional range of this South American species had its northern limit in Guatemala. Prionodiaptomus colombiensis has been regarded as indicating the extent of the influence of the South American diaptomid copepod fauna into Central America. Hence, this record allows a biogeographically relevant northwards extension of its known range, showing an unexpected influence of the South American diaptomid fauna in Mexico.