The Chinese mitten crab (Eriocheir sinensis) is an important economic species in China, and its reproductive performance and embryo quality are particularly important for the quality of newly hatched larvae. E. sinensis is a weak thermoregulator among crustaceans. From November to May every year, the broodstock crabs complete mating and spawning and early larval development in the Yangtze River Estuary. During this period, they are more sensitive to environmental changes. Too low or too high water temperature will have a direct or indirect effects on the breeding of E. sinensis. Therefore, temperature is an important environmental factor affecting the breeding of E. sinensis. In order to explore the effects of temperature on the reproductive performance and embryo quality of female E. sinensis, the reproduction and oviposition experiments of parent crabs at different temperatures (6 °C, 9 °C, 12 °C, 15 °C, 18 °C, 21 °C) were carried out. Three parallel groups were set up for each temperature, three samples were taken for each parallel groups. The reproductive performance of females at different temperatures, such as the mating rate, spawning rate, spawning volume and fertility, as well as the quality of the embryos produced, such as the egg diameter, the dry weight of a single egg and the wet weight of embryos, were analyzed through observation and calculation. The crude protein content of embryos was determined by Kjeldahl method; the total fat content was determined by acid hydrolysis method; the composition and content of fatty acids were detected by gas chromatography; the moisture content of embryos was determined by taking 2~3 mg of wet embryos from each temperature group and drying them at 70°C until constant weight; the ash content was determined by burning them at 550°C until constant weight; and the content of triglyceride, phospholipids, and cholesterol was determined by enzyme immunoassay kit. The enzyme-linked immunoassay kit was used to determine triglyceride, phospholipid and cholesterol. The results showed that: (1) With the increase of temperature, the mating rate of parent crabs increased gradually, and the spawning rate, spawning capacity, fecundity and reproductive index all increased first and then decreased. When the temperature was 15 °C, the spawning rate, spawning capacity, fecundity and reproductive index of female crabs were the highest, with the averages of (80±10)%, (15.38±1.81)×104 grains/only, (0.23±0.03)×104 grains/only and (20.01±1.59)%, respectively, and there were significant differences with other temperature groups (P<0.05). (2) At 18 °C, the egg diameter of the embryos was the largest, with an average of (431.17±13.69) μm. At 15 °C, the dry weight of a single embryo was the heaviest, with an average of (31.28±4.61) μg, but there was no significant difference between the 15 °C group and the 18 °C group (P>0.05). (3) With the increase of temperature, the content of ash and phospholipids in embryos increased gradually, while the content of total fat decreased gradually. The content of triglyceride and total cholesterol increased first and then decreased, while the content of crude protein and water did not change significantly. The contents of crude protein, triglyceride and total cholesterol in embryos were the highest at 18 °C, with an average of (20.83±1.72)%, (26.2±0.71) μmol/g and (97.3±1.19) μmol/g, respectively. (4) A total of 21 fatty acids were detected in the embryos of E. sinensis, of which saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) were the highest at 12 °C, but there was no significant difference with other groups (P>0.05). The total contents of C20:5n3 (EPA), C22:6n3 (DHA), C20:4n6 (ARA) and polyunsaturated fatty acids (PUFA) in embryos at 6 °C were the highest, with an average of (4.26±0.85) mg/g, (4.93±0.79) mg/g, (2.96±0.44) mg/g and (22.74±3.22) mg/g, respectively. This study showed that temperature had a certain effect on the quality of embryos produced by Chinese mitten crab, and the reproductive performance of Chinese mitten crab was the best at 15 °C. The study provide basic data for the study of breeding biology of E. sinensis, and also provide scientific support for the conservation of fishery resources of E. sinensis in the Yangtze River estuary. |