Laboratory-Reared Lobster Larvae Yield Inaccurate Estimates of Thermal Tolerance.

Physiological response to temperature stress defines the distribution of many marine invertebrates, and their thermal limits provide a foundation for understanding marine invertebrate response to climate change. In bottom dwelling species with free swimming planktonic larvae, such as the American lobster (Homarus americanus), thermal tolerance of early life stages influences vertical distribution in the water, settlement patterns on the bottom, and ultimately the species' range. We used measures of scope for activity, size, survivorship, and molecular techniques to demonstrate that wild-caught lobster larvae were more tolerant of temperature stress than laboratory-reared larvae (reared at 18°C and fed brine shrimp). Thermal tolerance in wild larvae exceeded both upper and lower critical temperatures of laboratory-reared larvae by approximately 5°C. The difference appeared to be driven by diet and acclimation temperature, yet altering these parameters still did not produce larvae with a range of thermal tolerance equal to wild larvae. We report that nearly all studies examining physiological response to temperature in marine invertebrate larvae have used laboratory-reared larvae and no studies have compared their thermal tolerance to wild larvae. The lack of similar comparisons in other species reveals a significant gap in our understanding of organismal response to temperature stress spanning multiple phyla. Our research is a novel effort to close this gap and better represent how this species responds to global climate change driven extremes.