The mesopelagic copepod Gaussia princeps (Scott) (Calanoida: Metridinidae) from the Western Caribbean with notes on integumental pore patterns

The mesopelagic calanoid copepod Gaussia princeps (Scott, 1894) was originally described from the eastern Atlantic. It has been recorded in tropical and subtropical latitudes of the world, but has been reported only occasionally from the northwestern tropical Atlantic (NWTA). Comparative morphological studies, particularly of males, have not included specimens from the NWTA. Based on a collection of zooplankton from the Caribbean Sea, an adult male of G. princeps is illustrated in detail and its morphology compared with other sources in order to explore intraand interoceanic differences within the species. The proportions and structure of the Caribbean specimens agree with the description of specimens from the eastern Atlantic and the Indian Ocean, except in details of the ornamentation of some appendages. Additional intraand interspecific differences were found in the number of integumental pores on the male antennules, swimming legs 1–4, and fifth legs. Integumental pores are consistently fewer in the Caribbean male than in the IndoPacific and eastern Atlantic counterparts, but G. princeps remains as the species of the genus with the largest number of pores on the swimming legs, a potential species-defining character within the genus. The Caribbean record, at 25–50 m deep, is the shallowest occurrence known for this mesopelagic form in the NWTA and represents the first finding of the genus and species in the western Caribbean and in Mexican waters.