Community ecology of the metazoan parasites of grey mullets, Mugil platanus (Osteichthyes: Mugilidae) from the littoral of the state of Rio de Janeiro, Brazil.

One hundred and fifty specimens of grey mullets, Mugil platanus Günther, collected from the littoral of the State of Rio de Janeiro, Brazil, between June 1984 to August 1988, were necropsied to study their infracommunities of metazoan parasites. Twenty-five species of metazoan parasites were collected. One hundred and forty-nine (99.3%) fishes were parasitized by one or more metazoan species. According to their importance values, 13 species were considered dominant, 7 species codominant and 2 species subordinate (digeneans were the majority of the total number of parasite specimens collected, with 63.7%). The presence of larval stages of digeneans and cestodes suggest that M. platanus is at an intermediate level in the marine trophic web. The Simpson index for all parasite species was low (0.059) indicating lack of dominance by a particular species in the parasite community. The parasites of M. platanus showed a typical overdispersed pattern of distribution. The capture localities of the hosts were consolidated into 3 groups and its parasite communities showed high qualitative and quantitative similarity, with high values for the Sorenson similarity coefficient and Percent similarity coefficient. Six species had a positive correlation between the host's total body length and parasite intensity, while three species had a negative correlation. Four species had a positive correlation between the host's total body length and parasite prevalence and one species had negative correlation. Five parasite species had differences in prevalence and intensity in relation to sex of host, but these differences were confounded with the total length of male and female fishes. The mean diversity in the infracommunities of M. platanus was H' = 0.936 +/- 0.477, without correlation with the host's total length and without significant difference between male and female fishes. In the ectoparasites, the infracommunities showed overall positive association, 6 pairs of copepod species had a significant positive association. One pair of species showed a negative covariation between parasite intensities. Infracommunities of endoparasites also showed overall positive association, and four species pairs of digeneans had a significant positive association. Only one had a negative association. The specialist components with low prevalence values predominated in the parasite community, which, based on these factors, was considered closer to the isolationist type.