A New Pelagic Shrimp of the Genus Sergia (Decapoda, Sergestidae) from the Atlantic Ocean

The oceanic sergestid shrimp Sergia robusta (Smith, 1882), originally described on material collected off the East coast of U.S., was subsequently reported from the whole Atlantic Ocean, including the Mediterranean Sea. Specimens collected off West Africa south of the Canary Current are characterized by a smaller size and have the clasping organ of the male antennula different from specimens collected in the Northern hemisphere and in the Mediterranean Sea. Other minor differences are also observed in the armature of petasma lobes. The constancy of the shape of the clasping organ with absence of intermediate forms suggests the existence of two species: S. robusta, restricted to the North Atlantic gyre (Gulf Stream, Canary Current, North Equatorial Current) and the whole Mediterranean Sea, and S. manningorum, new species herein described, recorded from northern Namibia to Gulf of Guinea and Senegal. The two species seem to occur sympatrically in the Cape Verde Frontal Zone.