The Afro-Asian Mesocyclops aspericornis (Daday) (Copepoda, Cyclopidae) in Mexico:: Comments on morphology and distribution

The known distribution of Mesocyclops aspericornis in the Americas included the central and northern areas of South America and the insular Caribbean. It had not been collected before in continental North America. The analysis of samples collected in a pond in the state of Sinaloa, on the Pacific coast of Mexico, yielded female individuals of this species. The Mexican individuals tended to be smaller than the African females (1.14-1.20 mm vs 1.3-1.5 mm), but the morphology of the Mexican specimens is identical in most characters to that described or depicted in previous works. This is the first morphological study of this species aided with SEM; it includes detailed data on several microstructures, some of which undescribed previously. It also is the first report of its effective occurrence in Mexico. All previous records of this species in the Americas are related to the Atlantic coasts. This record, in the Mexican Pacific area, suggests that this supposedly introduced Afro-Asian species had an alternative route of dispersion from the Pacific coast. This is also the second documented record of an introduced freshwater copepod in Mexico.