Abstract
A new species of Parapleurocrypta Chopra, 1923, a parasitic isopod genus of the family Bopyridae found parasitizing two species of the snapping-shrimp genus Synalpheus Spence Bate, 1888, is described from Brazil. This is the first record of Parapleurocrypta in the Atlantic Ocean, and the first species of bopyrid parasite recorded from the Fernando de Noronha archipelago in northeastern Brazil. Females of Parapleurocrypta duofratres sp. nov. can be distinguished from the other two species of the genus, P. alphei Chopra, 1923 and P. digitata Bourdon, 1976, by the structure of the barbula, the reduced pleopods, the number of dorsolateral bosses, the absence of the frontal lamina (present in P. digitata), and pleomeres with lateral plates (vs. lateral plates absent in P. digitata). Males can be distinguished from those of P. alphei by the number of antennal articles. Variation in the specimens is discussed and ecological and reproductive data are provided. To accommodate the new features of P. duofratres sp. nov., the diagnosis of the genus is expanded. A review of the branchial bopyrids of Synalpheus is included, as well as a discussion of parasitism by members of Parapleurocrypta.