Monogenoidea Communities Differ Between Male Morphotypes of Bluegill Sunfish (Lepomis macrochirus)

Bluegill sunfish (Lepomis macrochirus) are a North American sport fish that exhibit two different male morphotypes. Alpha-males are large, colorful, territorial, and have significant parental investment, while β-males are small, drab, and have two reproductive phenotypes, neither of which involves parental investment. Due to the two different reproductive strategies, the level of interaction between congenerics varies, which may impact parasites that are spread via close contact, such as Monogenoidea that infect the gills. Monogeneans are ectoparasites on the gills and skin of fish hosts that may cause significant pathology in high numbers and be an indicator of host behavior and interaction between hosts.

In this study, 328 L. macrochirus (106 α-males, 92 β-males, and 130 females) were necropsied from 8 lakes and ponds in northwestern Virginia to identify and enumerate monogenean parasites from the gills.

Alpha-males had a significantly greater parasite abundance and species richness compared to β-males. This may be due to the increased size and surface area of gills in α-males, increased interaction with females during mating, and stationary behavior when guarding nests, which enhanced the chances of α-males contracting the parasites. This also led to significant differences in the monogenean communities infecting the two morphotypes, which were also significantly influenced by the size of the hosts.

It is important in future studies regarding parasitism that behavioral morphotypes within a sex, such as α-male and β-male L. macrochirus in this study, be treated separately as behavioral and morphometric differences between them can potentially lead to differences in parasitism.