Heritability of acquired thermotolerance and its genetic correlation with basic thermotolerance in Fujian oyster (Crassostrea angulata)

The question of how to increase the heat tolerance of oysters has been a subject of great interest, given that they are a sessile ectotherm. It has been demonstrated that selective breeding can enhance heat tolerance of oysters. The heat tolerance of oysters encompasses both their ability to withstand single heat stress and their capacity to enhance their resistance to lethal heat stress following exposure to non-lethal heat stress, referred to as basic and acquired thermotolerance, respectively. However, previous studies have concentrated on the basic thermotolerance traits in oysters, while the acquired thermotolerance that are crucial for oyster's response to repetitive heat stress have been overlooked. In this study, the heritability of acquired thermotolerance trait and its correlation with basic thermotolerance trait in C. angulata were assessed using 19 full-sib families and 35 full-sib families constructed in 2021 and 2023, respectively. The survival rates of the different families exhibited considerable discrepancies in both the acquired (41.18 % - 100 %) and basal thermotolerance (0 % - 90 %) experiments, suggesting that both traits are subject to genetic influence and has a basis for selection. Moreover, the heritability of acquired thermotolerance in C. angulata was estimated to range between 0.12 and 0.25, with the genetic and phenotypic correlations to basic thermotolerance of 0.192 - 0.194 and 0.105 - 0.108, respectively. These results indicated that the acquired thermotolerance in C. angulata exhibits a low to medium heritability, suggesting its potential for improvement through selection. Furthermore, the acquired and basic thermotolerance traits are suitable for independent selection. Overall, these results demonstrate that acquired thermotolerance is heritable and independent of the basic thermotolerance trait. This work reports the first estimations of the genetic parameters associated with the acquired heat tolerance trait in oysters. The findings advance our comprehension of the genetic basis of this trait and provided valuable information toward its utilisation in thermotolerance selection.