Comparative pleopod morphology of eleven species of parasitic isopods from Brazilian fish

The pleopod morphology of eleven species of parasitic isopods from Brazilian fish was compared. Ten species of Cymothoidae were studied, as follows: Asotana magnifica THATCHER, 1988; Artystone minima THATCHER & CARVALHO, 1988; Braga cichlae SCHIODTE & MEINERT, 1881;Braga nasuta SCHIODTE & MEINERT, 1881; Braga patagonica SCHIODTE & MEINERT, 1884; Braga spp. 1 & 2; Riggia brasiliensis SZIDAT & SCHUBART, 1960; Telotha henselii (VON MARTENS, 1869); and Nerocila orbignyi (GUERIN-MENEVILLE, 1832). All of these species are from freshwater in the Brazilian Amazon except for N. orbignyi which is marine. The pleopods of Excorallana berbicensis BOONE, 1918, a freshwater representative of the family Excorallanidae, were also studied. The pleopods of the cymothoid species are individually characterized. Pleopod morphology is shown to be useful in defining species and genera. The evolution of the ''appendix masculinum'' from a reproductive structure to an accessory gill is also indicated.