Helminth communities of native and introduced fishes in Lake Patzcuaro, Michoacan, Mexico

In Lake Patzcuaro in the Mesa Central of Mexico, a total of 19 species of h elminths was found in 598 fishes and comprised five digeneans, two monogene ans, four cestodes, one acanthocephalan and seven nematodes, of which ten s pecies were represented by larval or immature states. The richest and most diverse helminth communities were found in the native carnivorous goodeid A lloophorus robustus. In general, the helminth communities in the different fish species were not particularly species rich and the parasite assemblage s were numerically dominated by larvae of the bird trematode, Posthodiplost omum minimum. Patterns of helminth community richness and diversity were si milar to those previously observed in north-temperate freshwater fishes. Mo st enteric helminths occurred with low abundance and only a small proportio n of the gut helminth communities was numerically dominated by any one spec ies. Helminths dominating their enteric communities showed some level of ho st specificity. Helminth communities in carnivorous fish species were gener ally richer than those in herbivores and detritivores, with the exception o f the predominantly herbivorous Goodea atripinnis. The helminth fauna of in troduced fishes, Cyprinus carpio, Micropterus salmoides and Oreochromis nil oticus, consisted of either few or no host-specific adult helminth(s) trans located from their original geographical areas and by larval stages of helm inths of piscivorous birds. Based on the geological history of the area and the biogeography of the endemic fish fauna, it is hypothesized that host-s witching and relationships with the nearctic fauna have been fundamental in determining the helminth fauna of the endemic fish hosts. (C) 2000 The Fis heries Society of the British Isles.