Impact of helminth infection on sexual morphology, reproduction and survival of the freshwater amphipod, Hyalella patagonica

Effects of helminth infection on sexual morphology and reproduction of the crustacean intermediate host are not well understood. Therefore, in the present study, we investigated the effects of parasitic infections on the amphipod Hyalella patagonica. Specimens were collected from Lake Mascardi, Argentina, between spring 2018 and summer 2019. We focused on three parasites: the acanthocephalans Pseudocorynosoma enrietti and Acanthocephalus tumescens and the nematode Hedruris suttonae. Morphological alterations in sexual traits, pairing success, and survival rates were analyzed. Significant morphological alterations were induced by P. enrietti, including castration and mixed sexual characteristics. Hedruris suttonae was the parasite most frequently found in amphipods in precopula, indicating that this parasite does not affect pairing success. Reduced survival rates were found in amphipods infected with H. suttonae or co-infected with P. enrietti and A. tumescens. These findings underscore the varying pathogenic effects of parasites on amphipod hosts and highlight the importance of considering multiple factors when evaluating host-parasite interactions and their ecological consequences in aquatic ecosystems.