TEMPERATURE ON HERMAPHRODITISM AND SEX REVERSAL IN FRESHWATER PEAL MUSSEL, HYRIOPSIS SCHLEGELII

In order to investigate the effects of temperature on gonadal development of Hyriopsis schlegelii, we screened and observed hermaphrodite phenomena in gonadal glands of H. schlegelii for two consecutive years, and induced reproductive follicular differentiation of H. schlegelii by five temperatures. In this study, qRT-PCR was used to detect the gonads of H. schlegelii in different periods, and in situ hybridization was used to locate the key gene Dmrt1. The results showed that the pool of natural conditions, 6 months H. schlegelii appeared the phenomenon of hermaphrodite and 28 months of hermaphrodite H. schlegelii had different gender differentiation about 30 months (77.8% differentiated into males, 16.7% remained hermaphroditism, and 5.5% differentiated into females). At 32℃, 12.5% of male clam were hermaphroditic at 14 months of age. When stimulated at 27℃, sex reversal of 14-month-old males and 27-month-old males was 37.5% and 12.5%, respectively. When stimulated at 23℃ and 19℃, sex reversal of 14 months old female H. schlegelii were 14.29% and 25%, respectively. The mRNA level of Dmrt1 was significantly higher in embryo of 6 and 27 months than that in other stages. The mRNA level of Dmrt1 of male H. schlegelii of 27 months at 32℃ was significantly higher than that at other temperatures, and its expression of female H. schlegelii of 14 and 27 months at 19℃ was significantly higher than that at other temperatures. The temporal and spatial expression trend of Fem1b and Fem1c was basically the same as that of Tra2a, which inhibited each other with Sox9 at 5 and 32 months of age. The expression of Fem1b, Tra2a and Sox9 in 14-month-old males at 19, 23 and 27℃ was significantly higher than those at other temperatures and the expression of Sox9 in 27-month-old males at 23℃ was also significantly higher than that at other temperatures. The expression of Foxl2 in 27-month-old female H. schlegelii at 27℃ was significantly higher than that at other temperatures. The expression of Tra2a, Fem1b, Fem1c, Sox9 and Dmrt1 were significantly different in the hermaphroditic mussels at different months of age, and the expression of Foxl2 in female hermaphroditic mussels was significantly higher than that in male mussels at the same period. The results of in situ hybridization showed that Dmrt1 mRNA positive signal was mainly located in spermatogonia, primary spermatocytes and mature oocytes. In conclusion, temperature affects the differentiation of reproductive follicles of H. schlegelii. High temperature above 27℃ can easily induce male to female reversal or hermaphrodite phenomenon, and low temperature below 23℃ can easily induce female to male reversal. Temperature probably regulates reproductive follicular differentiation by regulating the expression of Dmrt1 and other sex-related genes.