Atlantic salmon (Salmo salar) and Coho salmon (Oncorhynchus kisutch) display differential metabolic changes in response to infestation by the ectoparasite Caligus rogercresseyi

Caligus rogercresseyi sea lice negatively impact Chilean salmonid farming, but no complete characterization for the metabolic effects of Caligus infestation currently exists. Therefore, the aim of this study was to analyze the effects of C. rogercresseyi infestation on the metabolic responses of Salmo salar and Oncorhynchus kisutch. Energy metabolism responses to C. rogercresseyi were examined over a time-course infestation of both salmonid species. Plasma metabolite levels and enzymatic activities related to intermediate metabolisms of carbohydrate, amino acid, and lipid were evaluated in the liver and muscle. Plasma glucose levels changed in both salmonid species, increasing at 1–3 days post-infestation. In turn, triglyceride levels increased at days 3 and 7 in O. kisutch and S. salar, respectively, while protein and total α-amino acids increased in O. kisutch but decreased in S. salar during infestation. Amino acid intermediate catabolic metabolism in the liver and muscle of O. kisutch increased during infestation, indicating a higher use of the gluconeogenic pathway than S. salar. Lipid intermediate anabolic metabolism increased in O. kisutch liver, remained unchanged in S. salar liver, and increased 1 day post-infestation in the muscle of both salmonids. Liver and muscle carbohydrate intermediate anabolic metabolism in O. kisutch increased during infestation, suggesting that this species preferentially uses the glycogenolytic-glucolytic pathway, in contrast with S. salar. In conclusion, amino acid and carbohydrate catabolism enzymes in O. kisutch activated soon after initial sea lice infestation, which would allow this species to dispose of energy substrates earlier than S. salar. This physiological data contributes towards the ability of O. kisutch to more adeptly cope with the increased energy demand imposed by C. rogercresseyi infestation.