Testing non-lethal techniques for endoparasite detection and sex determination in pumpkinseed sunfish (Lepomis gibbosus).

Abstract

Developing non-lethal techniques to estimate parasite infection is critical for studying disease ecology in wild animals. We tested the effectiveness of coelomic ultrasonographic examination and plasma enzyme markers to detect liver infection with bass tapeworms Proteocephalus ambloplitis (Leidy 1887) as well as the effectiveness of ultrasound in predicting fish sex based on gonad imaging ante mortem in two populations of pumpkinseed sunfish Lepomis gibbosus (L. 1758). We also conducted cytopathological and histopathological analyses on a small subset of fish to investigate the potential for these techniques to detect signs of infection and liver disease. We found that fish sex was correctly identified by ultrasound in 87% of fish screened. There was no statistically significant relationship between parasite density and plasma enzyme concentration in infected fish. However, there were clinical differences between individuals from uninfected and infected populations in the enzymes creatine kinase and alanine transaminase. Histopathology and cytopathology assays confirmed the presence of macrophages and clear signs of inflammation within the liver of infected fish. Our results demonstrate that ultrasound, while useful for sex determination, was not effective in detecting infection in small species like sunfish. However, techniques such as blood analysis and potentially cytopathology are promising tools for parasitic detection in L. gibbosus and warrant further investigation, especially for use in other larger species.