Anguillicoloides crassus, an invasive parasite of the American eel, Anguilla rostrata: Population dynamics in South Carolina estuaries and health impacts on the host
Hein, Jennifer Lucille
de Buron, Isaure
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A survey of American eels, <italic>Anguilla rostrata</italic>, was performed from five localities in South Carolina (SC) to evaluate the status of infection by the invasive parasite nematode <italic>Anguillicoloides crassus</italic>, and compare it with historical data from SC and other areas in North America as well as to determine how infection affects the health of the eels. The biomass of adult worms did not vary significantly with eel body length, salinity, season or locality, although prevalence and intensity of infection by adults did vary by locality. Larval intensity was significantly greater in the winter and also differed among localities. The lack of seasonal effects on the adult worm stage contrasts with studies from higher latitudes (north of 35 degrees latitude along the coast of North America). Significant variation in parasites among localities reflects possible differences in abundance of intermediate and/or paratenic hosts. A large portion of eels (25%) exhibited severe swimbladder damage, indicative of previous <italic>A. crassus</italic> infections. Swimbladder damage was lowest in the summer, possibly indicating mortality caused by the extreme water conditions that occur during SC summers including high temperatures and low dissolved oxygen values. A reduction in spleen, liver, and eviscerated mass associated with infection by adult <italic>A. crassus</italic> indicated that infection may cause anemia and reduction in energy stores and these effects appear to be more severe in smaller eels due to a higher parasite biomass to body mass ratio.