The importance of the compound community on the parasite infracommunity structure in a small benthic fish.

The extent to which the structure of parasite infracommunities and component communities is determined by the composition of the compound community was assessed by determining the importance of unspecific larval parasites relative to the other guilds (ectoparasites and adult endoparasites). This was analyzed under the hypothesis that the infracommunities harbored by any fish species in coastal waters of the northern Argentine sea will be dominated by unspecific larval stages, which also will be the determinants of the infracommunity structure. These predictions were tested in the Atlantic sea robin, Prionotus nudigula. A total of 1,570 metazoans belonging to 11 species were found in the overall sample (total prevalence = 98%). Larval endoparasites, especially Corynosoma australe and Grillotia sp., were the best represented species, with a deep influence on the infracommunity structure, accounting for the highest proportion of individuals, dominating about 60% of the infracommunities, greatly determining all infracommunity descriptors, and producing marked changes in the similarity among infracommunities. Given the abundance and broad distribution of unspecific larval parasites in the compound community, infracommunities can be considered as subsets of the species available regionally. They are obtained by passive sampling of infective stages as fish feed, and lead to predictable assemblages, with a non-random composition and structure modeled mainly by ecological filters.