Infection Patterns of Posthodiplostomum cf. centrarchi and Uvulifer cf. ambloplitis in Centrarchid Hosts from Lake Holiday, Virginia, U.S.A.

Differences in parasite infection patterns between hosts can be influenced by numerous factors placed into 2 categories: encounter filters (precontact) and compatibility filters (postcontact). The influence of these factors in shaping the patterns of parasite infection was investigated in Lake Holiday, a 100-ha lake in northern Virginia, U.S.A. In total, 1,586 fish in the family Centrarchidae, encompassing 4 species—Lepomis macrochirus, Lepomis cyanellus, Lepomis auritus, and Micropterus salmoides—were collected and necropsied over a 7-yr period. The length, weight, age, stomach contents, and counts of 2 diplostomid parasites—Posthodiplostomum cf. centrarchi and Uvulifer cf. ambloplitis—were recorded. The prevalence and intensity of P. cf. centrarchi differed between host species, which was likely influenced by both encounter and compatibility filters. However, U. cf. ambloplitis infection showed significant correlations with the prevalence, but not the intensity, of infection. This indicates that encounter filters may play a larger role in shaping the infection patterns of U. cf. ambloplitis than compatibility filters. Furthermore, the infection pattern differences between host species exhibited by P. cf. centrarchi indicate that the parasite species complex are likely specialists, whereas U. cf. ambloplitis represents a true generalist parasite because there are no apparent differences in compatibility between hosts. In addition, P. cf. centrarchi infections follow distinct patterns in the tissues that they infect, thereby allowing single organ counts, particularly the liver, to be proxies for total parasite infection, whereas the correlations in U. cf. ambloplitis are less predictable and do not allow for single tissue infections to be reliable indicators for total parasite load.