Changes in low salinity and hypoxia tolerance in F1hybrids of the ivory shell, Babylonia areolata

Salinity and dissolved oxygen concentration are two of the most important factors affecting the geographic distribution, survival, and physiological processes of estuarine and mariculture organisms. In this study, the effects of low salinity and hypoxia on survival and physiology were evaluated for two populations of Babylonia areolata, a Thailand population (TT) and a Hainan population (HH), and their reciprocal hybrids TH (TT♀ × HH♂), HT (HH♀ × TT♂). HH was more sensitive to low salinity, with a survival rate close to zero after 54 h of low salinity stress, while the survival rates of the other three populations remained above 50%, and the median lethal times (LT50) of the four populations after 72-h low salinity stress were in the order TT > TH > HT > HH. In addition, comparing the heterosis levels calculated from the 72 h-LT50and the 48-h and 72-h survival rates of TH and HT under low salinity stress, the mid-parent heterosis (HMP) values of the three indicators of TH were 24.56%, 79.56%, and 80.97%, respectively, and the HMPvalues of the corresponding indicators of HT were 19.67%, 70.47%, and −42.88%, respectively. Moreover, with the increase in time under hypoxia, TH and HT began to die, and the survival rates of TH and HT were lower than those of their parental populations. The oxygen consumption rates (OCR) of TH and HT under hypoxic conditions were lower than those of TT and HH. The results showed that the crossbreeding between TT and HH improved the low salinity tolerance of their hybrids but decreased their tolerance to hypoxia. This study provides information concerning this ivory shell hybrid system that could aid in the application of heterosis in ivory shell aquaculture.