Differential Strigeid Infection Patterns in Male Morphotypes of Bluegill Sunfish (Lepomis macrochirus)

Behavioral variation among conspecific organisms can have substantial ecological impacts, particularly affecting parasite infection. Bluegill sunfish (Lepomis macrochirus) exhibit multiple male reproductive morphotypes that differ in their size, feeding dynamics, and reproductive behavior. This study investigated how these morphological and ecological differences contribute to the patterns of infection by strigeid trematodes.

A total of 1961 L. macrochirus was collected from 14 lakes and ponds in northwestern Virginia, USA, and were necropsied to identify and enumerate three common strigeid parasites, white grub (Posthodiplostoum spp.), black grub (Uvulifer ambloplitis), and yellow grub (Clinostomum marginatum) infecting the fish and determine if there were different infection patterns among sexes and morphotypes.

Strigeid infections in L. macrochirus α-males were in greater abundance compared to females and β-males. Additionally, α-males had greater strigeid infection in the kidneys and fins, while females and β-males accumulated more parasites in the liver and body tissues.

Increased nesting responsibilities and potential interaction with snail intermediate hosts by α-males may lead to the differences in infection patterns. The distinction of morphotypes revealed significant differences in abundance and distribution of parasite infections between the sexes of L. macrochirus, trends that were masked when male morphotypes are combined.