Developmental temperature has a greater influence on larval performance than parental thermal history in the rocky intertidal mussel, Mytilus californianus

Abstract As marine species are increasingly met with extreme warming events—such as marine and aerial heatwaves—identifying acclimatory mechanisms that have the potential to alleviate thermal stress is critical to predicting species response to ongoing and future warming. Acclimation induced by parental and developmental thermal history may be an important pathway to increasing thermal tolerance, specifically for early life stages which are often considered sensitive to thermal stress. In this field-to-laboratory experiment, we examined how thermal history, both trans- and intragenerational, influenced early life history stages of the rocky intertidal mussel Mytilus californianus. Here, adult M. californianus acclimatized to differing temperature regimes in situ (i.e., individuals from high or low tidal heights collected following the summer and winter season) were spawned in the laboratory and offspring were then reared in cool (16 °C) and warm (20 °C) temperature conditions. At the veliger stage, physiological performance of offspring was assessed via measurements of body size, respiration rate, and thermal tolerance. Results revealed that developmental temperature had a prevailing influence on veliger performance, where larvae reared at warmer temperatures were larger, had higher respiration rates, and decreased thermal tolerance. While there was some evidence to suggest adult acclimatization may have also influenced offspring performance, this influence was not strong. Field studies such as this are important to bringing us closer to determining how acclimation processes function in natural populations.