Aglaodiaptomus atomicus, a new species (Crustacea: Copepoda: Calanoida: Diaptomidae) from freshwater wetland ponds in South Carolina, USA, and a redescription of A-saskatchewanensis (Wilson 1958)

A new calanoid copepod, Aglaodiaptomus atomicus, is described from freshwater wetland ponds in Aiken County, South Carolina, U.S.A. It is common in Aiken and Barnwell Counties. It has been collected from shallow, acidic wetland ponds, most of which dry periodically. Aglaodiaptomus atomicus resembles A. saskatchewanensis, which is redescribed from Saskatchewan, Canada, and Louisiana, U. S. A. The male of A. atomicus differs from all of its congeners by possessing a distinctively large distolateral process on the right leg 5, exopod 1. The female differs from its closest congener, A. saskatchewanensis, in possessing nearly symmetrical thoracic wings. In A. saskatchewanensis, the wings are distinctly asymmetrical.