The role of diet on the structure and composition of parasite communities in two sympatric paralichthyid flounders from Argentina

ALARCOS, ANA J.; TIMI, JUAN T.

Melbourne

Congreso; XII International Congress for Parasitology.; 2010

Australian Society for Parasitology, World Federation of Parasitologists.

The sea bottom constitutes an exchange zone of parasite infective stages among hosts inhabiting different bathymetric layers; therefore benthic fishes display high levels of parasite diversity, whereas a dilution occurs in the pelagic realm. Fish at higher trophic levels should be also exposed to more infective stages and a broader range of taxa. However, it has been suggested that the highest species richness should be found at intermediate trophic levels where fish act as intermediate, paratenic or definitive hosts by possessing a mixed diet of invertebrates and fish. Fish parasite communities in the northern Argentinean Sea are dominated by trophically-transmitted and little specific larval parasites, but little is known about parasites of benthic fishes. We describe for the first time the parasite communities of two sympatric paralichthyids, Xystreuris rasile (Xr) and Paralichthys isosceles (Pi) and analyze their relationships with the habitat and feeding habits. Xr preys exclusively on benthic invertebrates; whereas Pi also includes a high proportion of fishes. Samples (Xr, n=58) and (Pi, n=51) were caught in the same area and date, and were of comparable size. Infracommunity species richness was similar between hosts, but Xr showed a significantly lower total abundance and higher diversity. Contrarily to expected, component community richness of Xi (S=17) was one of the highest observed in the region, whereas that of Pi (S=10) was one of the lowest. All species harboured by Pi were also found in Xr, and almost all are transmitted by crustaceans. Fish eaten by Pi are small, mainly juvenile, and probably do not harbour infective stages. Therefore, whereas ichthyophagy has not a direct influence on parasite assemblages, this diet shift reduces the range of crustaceans preys, and consequently of potential hosts for different parasites.Prevalence and abundance also varied between hosts, showing that both flatfish also prefer different crustaceans.