Thermal Biology and Metabolic Scope of Two Species of Juvenile Gastropod Mollusks Inhabiting Kelp Forests.

Temperature is one of the main abiotic factors that influence the growth, reproduction, food availability, distribution, and survival of many species of marine ectotherms. Megastraea undosa and Megathura crenulata are gastropod mollusks with economic, commercial, and biomedical importance that are part of the kelp forest community in the temperate waters of the northern Pacific of Mexico. As knowledge about the thermal biology of these two species is scarce, this study aimed to determine the effect of different acclimation temperatures on the thermal biology and metabolic scope of these two species. 120 M. undosa juveniles were collected from the wild and acclimated to four temperatures (13, 16, 19, and 22°C ± 1°C), while 90 M. crenulata juveniles were cultured in an aquaculture facility (Stellar Biotechnologies, Inc) and acclimated to three temperatures (17, 20, and 23°C ± 1°C). Subsequently, experiments were performed to determine the thermal tolerance, thermal window, thermal safety margin, future thermal safety margin, and thermal metabolic scope of these species. The thermal tolerances of both species were relatively similar (M. undosa juveniles: CT_max = 25.3, 21.0, 25.4 and 27.4°C, CT_min = 6.0, 9.2, 16.3 and 17.3°C; M. crenulata juveniles: CT_max = 27.7, 28.1 and 28.8°C, CT_min = 11.2, 12.1 and 14.7°C). Both species had a small thermal window area (M. undosa: 77.2°C²; M. crenulata: 65.25°C²). The values of the thermal safety margin and the future thermal safety margin of both species were lower during the summer than winter. The optimal temperature proxies of M. undosa and M. crenulata juveniles were 16 and 20°C, respectively. This study shows that the two species of marine gastropods could be moderately affected by ocean warming, being forced to modify their current distribution patterns. The data on thermal limits and optimal temperatures can be used to initiate and maximize the cultivation of both species, which would also help mitigate the impact of overfishing on natural populations.