Cardiac performance as a function of temperature in the larvae of the American lobster (Homarus americanus)

Abstract

American lobster larvae are subject to rapidly warming waters in the Gulf of Maine due to climate change, yet gaps remain in our understanding of their physiological response to temperature stress. Cardiac performance and respiration are metabolic metrics for assessing response to thermal stress. We measured heart rate, stroke volume, cardiac output and gill bailer beats in lab-reared stage I-IV larvae, and wild-caught stage IV larvae at 4, 8, 18, 26 and 30°C. Heart rate increased with temperature in all stages but there were no significant differences between stages of laboratory reared larvae, nor between lab reared and wild-caught stage IV larvae. Stroke volume and cardiac output decreased at high and low temperature extremes. Gill bailer beats increased with temperature but decreased at 30°C. Our results suggest that heart rate alone is an insufficient metric for thermal stress in lobster larvae and misses non-linear relationships between cardiac function and temperature. Reduced cardiac output at high and low temperatures is consistent with the hypothesis that thermal tolerances are defined by limitations in the ability to deliver oxygen to the tissues.