Modulation of immune parameters by chemical environmental pressures in wild populations of European bullhead, Cottus sp. from Vesle Basin (Champagne, France)

In freshwater ecosystems, a large number of chemical substances are able to disturb homeostasis and adaptative responses of fish organisms by modulating different physiological functions including immune system. In order to characterize the early biological effects of environmental contaminants on fish health status, some immune-related cellular and biochemical responses were proposed as immunotoxicological biomarkers. The aim of the present study was to evaluate immune status of European bullhead, Cottus sp., natural populations, living in different field contexts characterized by various chemical environmental pressures. In Champagne region (France), five sites of the Vesle watershed in the North East of France were selected with urban (Muizon), intensive agricultural (Bouy and Prunay) or viticultural (Serzy and Prunay) influences. For each location, adult fish were caught by electrofishing in spring, summer and autumn and splenic leucocyte parameters (leucocyte sub populations, cell mortality and phagocytosis) were carried out by flow cytometry. Fish biometric characteristics, such as length and weight, have no impact on immune parameters. Seasonal variations in immune responses depended on the tested immune function without discrepancy between studied sites. For example, the lymphocyte percentages were higher in summer whereas leucocyte mortalities were strongly increased in spring and phagocytosis percentages in autumn. Nevertheless, independently of seasonal variations, environmental characteristics of each site seem to disturb selected immune markers. The highest immune modulations were observed in sites situated in areas with intensive agriculture or viticulture, Bouy, Prunay and Serzy respectively. These first results may indicate possible immunotoxicological impacts of agri-viticultural practices on bullhead natural populations living in Vesle watershed. It is sure that further observations, on many years, have to be done to verify observed immunomodulations. Moreover, data are needed to better characterize the effects of biotic and abiotic confounding factors on these biomarker base levels and to define their natural variability ranges for assessment of wild fish health