TENDÊNCIAS EVOLUTIVAS DO PARASITO ISÓPODO Livoneca redmanni Leach, 1818 (CRUSTACEA, ISOPODA, CYMOTHOIDAE) EM DUAS ESPÉCIES DE PEIXES MARINHOS DO RIO GRANDE DO NORTE, BRASIL.

The present study investigated the reproductive cicle of the ectoparasitic isopods in two marine fish species, Choloroscombrus chrysurus and Scomberomorus brasiliensis . Emphasis was given to ecological parasitic indices, the size and fecundity of isopods in fish-hosts of different body sizes. The isopod Livoneca redmanni Leach, 1818 was found parasitizing the gill chambers of the hosts and showed different values of prevalence, intensity and mean abundance for the two hosts. S. brasiliensis (mean Lt 31.42 + SD 9.71 cm) had a larger body size than C. chrysurus (12.42 + 2.51 cm), providing relatively more space for the parasites in the gill chamber. Big sized L. redmanni were registered (Lt media 16.3 + SD 5.5 mm) on S. brasiliensis whereas smaller sized L. redmanni were observed in C. chrysurus (10.8 + 4.5 mm). The fecundity of female isopods were positively related to their body size. During the rainy season many isopod females were found to be in the reproductive stage. The body size of the hosts determines the space of the gill chamber. However, it does not influence the space occupied by the isopod, since the parasites always occupied approximately 35 to 36% of the gill chamber independent of the body size of hosts. The isopod parasite L. redmanni showed different evolutionary trends for both hosts, wherein C. chrysurus had a smaller body size than S. brasiliensis . Keywords: Isopod ectoparasite, Choloroscombrus chrysurus, Scomberomorus brasiliensis, ecological parasitic indices.