Dietary effects on cardiac lipid composition, mitochondrial respiration, stress proteins and thermal tolerance in the American lobster (Homarus americanus).

Lipids are fundamental components of many biological structures, and their composition is partially diet dependent. Differences in lipid composition can impact the functioning of cellular membranes and proteins, subsequently altering the organism's ability to respond to environmental conditions. The American lobster (Homarus americanus) is an economically important shellfish in New England and is frequently kept in lobster impoundments (pounds) for prolonged periods, typically on a diet of herring, which differs from the natural diet of wild-caught lobsters. In this study, we compared the lipid composition of lobster muscle, heart and hepatopancreas from wild-caught and from pound-kept lobsters that were fed either herring or blue mussels. We performed lipidomic analysis, measured mitochondrial function, determined gene expression of cellular stress markers and evaluated thermal stress tolerance by assessing heart and ventilation rate, as well as hemolymph oxygenation during a fast progressive temperature challenge. We found a significant shift in lipid composition in pound-kept lobster hearts together with reduced mitochondrial function, and increased gene transcription of the cellular stress markers HSP70 and AMPK, indicating a worse nutritional state, compared with wild-fed lobsters. The changes did not lead to a shift in thermal thresholds, indicating a substantial plasticity and tolerance to compensate for adverse diet-induced conditions. This study mechanistically links diet, lipid composition, mitochondrial function and thermal tolerance and highlights the need for a more detailed understanding of cellular processes to understand climate change-induced impacts on marine invertebrates.