Mouthpart morphology of six freshwater species of Cymothoidae (Isopoda) from Amazonian fish compared to that of three marine forms, with the proposal of Artystonenae subfam. nov

Abstract

The mouthpart morphology of six Amazonian freshwater species of Cymothoidae (Isopoda) was compared to that of three marine forms. The freshwater species were: Braga cichlae SCHIÖDTE & MEINERT, 1881; Braga nasuta SCHIÖDTE & MEINERT, 1881; Riggia brasiliensis SZIDAT & SCHUBART, 1960; Vanamea symmetrica (VAN NAME, 1925) THATCHER, 1993; Asotana magnifica THATCHER, 1988; and Artystone minima THATCHER & CARVALHO, 1988. The marine forms used were: Elthusa vulgaris (STIMPSON, 1857); Ceratothoa gaudichaudii (MILNE EDWARDS. 1810); and Nerocila orbignyi (GUERIN-MENEVILLE, 1832). The marine species were found to have biting mandibles with shearing blades and sharp incisors. Mandibles of the freshwater species lacked such structures. The mandibles of Riggia and Artystone were seen to have numerous lateral recurved spines which may aid these genera in penetrating to the body cavities of their hosts. Maxillules of freshwater species had five recurved spines near their tips (3-4 terminal and 1-2 subterminal) whereas in marine forms, it was more usual to find four spines, all terminal. The maxillae of most of the species studied were bilobed and bore 2 spines near the tip of each lobe. Exceptions were: Asotana, in which the maxillae are undivided and provided with a few spinules and Ceratothoa which has trilobed maxillae with numerous small spines. The maxillipeds were found to have two large recurved spines on the terminal article of the palp. Exceptions were: Ceratothoa and Nerocila in which that article was provided with several spines. On the basis of comparative mouthpart morphology, it is suggested that the freshwater species studied should all be included in Artystonenae subfam. nov.