Pseudocyclops costanzoi, a new species (Copepoda, Calanoida, Pseudocyclopidae) from Mediterranean Sea, Faro Lake, Sicily.

A single copepod specimen belonging to Pseudocyclops but with characteristics never observed within the known species of the genus, was collected in wash water from specimens of Pinna nobilis Linnaeus, 1758 (Mollusca, Bivalvia). The most important characteristic useful to distinguish P. costanzoi n. sp. from all other species of the genus, is the tooth on the 5th pedigerous somite, but also unique within the genus is the setation of the endopod of leg 5, with one seta on the first and two setae on the second endopodal segment. The discovery of P. costanzoi n. sp. increases the number of Mediterranean species of Pseudocyclops to four. Of these, P. xiphophorus Wells, 1967 and P. costanzoi n. sp., are known to occur, until now, as far as the Mediterranean Sea is concerned, only in Faro Lake, Sicily.