Helminth parasite assemblages in two cyprinids with different life history strategies

Abstract

Parasitic organisms can affect ecosystems by driving population dynamics of the hosts and influencing community interactions. The life history of the host can determine the relationship with its parasites. Reproductive effort and age of the host are two life history aspects often used to explain parasitic infection. In this study, we examined helminth parasite assemblages in two cyprinids with contrasting reproductive strategies, Cyprinella venusta (crevice spawners) and Notropis volucellus (broadcast spawners), in the Paluxy River (Texas) from May 2014 through October 2015. Host reproduction was measured using the gonadosomatic index, and standard length was used as an estimate of age. Parasite infection was measured using total number of helminths, parasite richness, Shannon’s diversity, and Simpson’s diversity. Our results revealed significant differences in parasite number and diversity between the two species, but not between males and females within species. Additionally, our results showed that standard length was a better predictor of parasitic infection than the gonadosomatic index. The relationship between host size and parasitic infection was expected; however, the lack of a relationship between gonadosomatic indices and parasitic infection was surprising. In conclusion, standard length was a better predictor of parasitic infection than the gonadosomatic index, and as such multiple species and life history traits should be considered when investigating host–parasite relationships.