The effect of Anonchocephalus chilensis Riggenbach (Eucestoda: Bothriocephalidea) on infracommunity patterns in Genypterus maculatus Tschudi (Osteichthyes: Ophidiidae).

The use of parasite body size (i.e. body mass) is a promising proxy to improve the study of patterns in parasite infracommunities, which are usually analysed using only numerical descriptors. This study deals with the importance and effect of the presence of a large endoparasite species, the cestode Anonchocephalus chilensis in a marine fish species, Genypterus maculatus, on the structure of the parasite infracommunities. Numerical and volumetric measures of aggregated properties of parasite infracommunities were compared and their correlation examined. The highly dominant presence of A. chilensis by volume causes a dramatic change in the patterns observed, including a smaller total volume of the remaining species when this volumetrically dominant species is present. However, C-scores and V-ratios, both indices based on null models of species occurrence, do not support the idea of communities structured by interspecific competition. Analyses reveal that numerical and volumetric community descriptors are complementary ways to search for patterns and to reveal processes within these systems.