The occurrence of Diplostomum spathaceum metacercariae in the freshwater drum, Aplodinotus grunniens

Abstract

Strigeoid metacercariae from the lenses of freshwater drum, Aplodinotus grunniens, were morphometrically analyzed and compared with those of the North American subspecies of Diplostomum spathaceum: Diplostomum spathaceum indistinctum and Diplostomum spathaceum huronense. The metacercariae resembled D. s. indistinctum in mean body length, mean body width, oral sucker size, and holdfast size. Prevalence of infection in drum was 99% and intensity ranged from 0 to 260 worms per fish (mean ± SD = 35 ± 32). A significant difference (P < 0.05) in mean intensity between male and female fish was observed, with females harboring a greater worm burden (i.e., 43 in females versus 24 in males). Differences in infection intensity between left and right lenses from all fish were not significant (P > 0.05); however, the degree of asymmetry between left and right lenses of individual fish was highly significant (P < 0.005) according to heterogeneity χ2 analysis. In this case, neither left nor right lenses were consistently favored.