STRUCTURE AND DIVERSITY OF ENDOPARASITIC INFRACOMMUNITIES AND THE TROPHIC LEVEL OF PSEUDOPLATYSTOMA-CORRUSCANS AND SCHIZODON-BORELLI (OSTEICHTHYES) OF THE HIGH PARANA RIVER

One hundred and ten specimens of Pseudoplatystoma corruscans (Pimelodi dae) and 582 specimens of Schizodon borelli (Anostomidae) collected in the high Parana River were analyzed. On necropsy 74% of P. corruscans were found to be parasitized; proteocephalidean cestodes presented th e greatest number. With regard to S. borelli, the percentage of parasi tism reached 19.42% and the nematode Cucullanus pinnai was the most ab undant. The absence of correlation between the endoparasitic diversity and the standard length of the two host species indicates that each o ne presents homogeneity in alimentary behaviour during all its life ti me, permiting the uniform recruitment of the same species of endoparas ite during all its ontogenetic development. Independence of diversity values in relation to sex of P. corruscans and S. borelli evidences th at the ecological relationships are similar between males and females in these species. Both host's infrapopulations presented a typical ove rdispersed pattern of distribution with isolationist characteristics.