Metabolic and transcriptional responses demonstrating enhanced thermal tolerance in domesticated abalone

Global warming threatens aquatic systems and organisms. Many studies have focused on the vulnerability and stress responses of aquaculture organisms to future thermal conditions. However, it may be of more practical significance to reveal their acclimation potential and mechanisms. In this study, the physiological, metabolic, and transcriptional responses to long-term temperature acclimation of northern and southern populations of Pacific abalone Haliotis discus hannai, a commercially important gastropod sensitive to environmental changes, were compared. This study conducted two common-garden experiments, including a thermostatic experiment in the lab and an aquaculture experiment on the farm. The abalone population cultured in warmer southern waters was tolerant of ongoing high temperatures, whereas the abalone population originally cultured in cooler northern waters exhibited vulnerability to high temperatures but could enhance its thermal tolerance through the process of natural selection in warmer southern waters. This difference was linked to divergence in the metabolic and transcriptional processes of the two populations. The tolerant population exhibited a greater capacity for carbohydrate and amino acid metabolism regulation and energy redistribution to cope with heat stress. This capacity may have been selected for, and accumulated, over many generations because the tolerant population originated from the intolerant population over two decades ago. This work provides insight into the vulnerability and acclimation potential of abalone to heat stress and discloses the molecular and metabolic traits underlying this phenomenon. Future research on the ability of abalone and other commercial shellfish species to acclimate to global warming should take this potential into account.