Effects of Acanthocephalans on Pigmentation of Freshwater Isopods

Abstract

The isopods Asellus intermzedius, Lirceus garmani, and L. lineatus were studied to document further the occurrence of altered in these hosts infected with species of Acanthocephalus. Specimens of A. intermedius from central Illinois, L. garmani from northwestern Arkansas, and L. lineatus from northwestern Ohio revealed differences in normal integumental related to species, sex, reproductive state, and size. Integument of males and females of the three species was found to be more lightly pigmented when specimens harbored male, female, or multiple infections with acanthocephalans. Comparisons of light transmission through wholemounts of respiratory opercula of A. interinedius dem- onstrated that there was no significant difference in among infection types. Regression analyses indicated (1) that the normnnal relationship between isopod length and had been disrupted by acanthocephalan infections; (2) that a developmental relationship existed between isopod (length) and acanthocephalan (volume); (3) that there was not a direct relationship between acanthocephalan size and altered as might be expected for a gradual depigmentation process; and (4) that eye size was unaffected by parasitism. On the basis of these findings, the terminol- ogy, pigmentation dystrophy, is proposed as more appropriate than the previously used terms, non- pigmentation, 'depigmentation, and color dichromatism.