Life history traits and functional immune parameters in the wild trout of the Kerguelen Islands

Abstract

Common trouts (Salmo trutta L.) over 3 years old, were sampled in hydrosystems of Kerguelen Islands in 2010. Biometric and biogeographical data of caught fish were collected in the field. Ages and migratory status of individuals were determined by scale reading and validated by otolithometry and otolith microchemistry (LA-ICPMS). Prey types ingested by trout were determined by analysis of stomach contents. Molecules organochlorine pesticides (OCPs) and PCBs accumulated in the liver and muscle tissues of fish were analyzed by GC-ECD. The immunomarkers were measured directly in the field by appropriate protocols in flow cytometry. Five groups of trouts associated with distinct ecological niches, were defined by the nature of ingested preys. Groups 1 and 3 fed from only benthic invertebrates, group 2 from terrestrial origin preys (insects or arthropods drained by runoff waters), group 4 from pelagic invertebrates (insect larvae) and the group 5 fed exclusively from marine organisms. High significant variations in oxidative burst of blood and pronephros leukocytes were observed between groups. It was particularly true for trouts whose diet consisted in benthic or terrestrial preys which had the highest levels in leukocyte oxidative burst. In addition, a negative influence of hepatic contamination by DDT, HCB and PCB was observed on oxidative burst of pronephrotic leukocytes. The basal level of apoptosis in pronephrotic leukocytes was strongly correlated with muscle bioaccumulation of OCPs, PCBs and PBDEs. Levels of induced apoptosis were particularly high in the blood or in the pronephros of trouts predating preferentially pelagic organisms. This factor was positively correlated with the levels of hepatic OCP, such as DDT. Chronic contamination of trout was also associated with low blood phagocytic activity in migratory trout feeding exclusively marine organisms. In the natural environment, the ecological niche occupied by the fish influence their chemical contamination and plays a major role in the expression levels of immune cell functionality.