A New Genus of Ridgewayiidae (Copepoda: Calanoida) from a Karstic Cave of the Western Caribbean

The calanoid copepod family Ridgewayiidae, containing demersal and cave-dwelling forms, has representatives worldwide, but most have been known from the Northwestern Tropical Atlantic. Eight valid genera were hitherto known, most of them were described recently (Ridgewayia Thompson and Scott, Exumella Fosshagen, Brattstromia Fosshagen and Iliffe, Placocalanus Ohtsuka, Fosshagen and Soh, Exumellina Fosshagen and Iliffe, Normancavia Fosshagen and Iliffe, Robpalmeria Fosshagen and Iliffe, Stargatia Fosshagen and Iliffe). Biological collections in cave environments in an island off the Caribbean coastline of Honduras, Central America, showed the presence of ridgewayiid copepods. These specimens were found to belong to an undescribed genus of the family. The new genus Hondurella is distinguished from the other eight known ridgewayiid genera by a combination of characters that include a simple rostrum with no filaments, maxilliped with modified setae, first leg with a modified exopod and a reduced endopodal armature, and most importantly, a female fifth leg with a slightly modified exopod and a 1-segmented endopod, plus a reduced right exopod of the male fifth leg, and the presence of spines on the middle segments of the male right antennule. As all other ridgewayiids, the new genus retains several plesiomorphic characters, thus confirming the primitive profile of this family. The distribution of Ridgewayiidae in the Caribbean region remains largely unknown, but it is suggested that distributional patterns and a relatively high degree of endemism are related to the geological origin and dynamics of the area. Aside the modified maxillipedal setae, mouthparts in the new genus,are normally developed; this, together with our observations of the gut contents, suggest that this ridgewayiid is more a particle-feeder than a carnivorous form.