THERMAL ACCLIMATION AND MEAL ITEM SHAPE POSTPRANDIAL AEROBIC PERFORMANCE IN THE AMERICAN LOBSTER (HOMARUS AMERICANUS)

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Abstract Rapid warming in the Gulf of Maine and shifts in bait usage in Maine’s lobster industry are altering the thermal and nutritional landscapes for American lobsters (Homarus americanus), with unknown sublethal impacts on lobster physiology. Specific dynamic action (SDA) is the postprandial rise in metabolism that comprises the energy needed to digest and assimilate a meal. SDA may influence lobsters’ survival by occupying a portion of their aerobic scope, thus limiting their capacity to deal with environmental stressors. Here, we used intermittent-flow respirometry to investigate the combined impacts of acclimation temperature (15℃ or 18℃) and the consumption of a bait item (frozen menhaden [Brevoortia tyrannus], fresh mussel [Mytilus edulis], or salted pig hide [Sus domesticus]) on aerobic metabolism and SDA in adult male lobsters. While standard metabolic rate and peak SDA were not significantly impacted by temperature, SDA duration was, indicating thermal plasticity and resilience to present and near-future oceanic conditions. Postprandial residual aerobic scope was not significantly impacted by bait item, suggesting tolerance of short-term nutritional variation. Lobsters fed pig hide demonstrated the greatest peak SDA, likely due to its higher caloric content and an artificially reduced need for mechanical digestion of menhaden and mussel hard parts. Our findings demonstrate that while metabolic function appears robust to moderate warming and altered nutrition in isolation, temperature-diet interactions can constrain maximum aerobic capacity with potential implications for post-capture survival and bait regulation.

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