Effects of different water temperatures on the ovarian development and biochemical composition of Portunus trituberculatus after mating (Decapoda, Portunidae)

Abstract This study investigated the effects of different water temperatures (20, 23, 26 and 29°C) on the ovarian development and biochemical composition of Portunus trituberculatus (a swimming crab) after mating. The results showed that the higher the water temperature was, the faster the ovarian development, especially the GSI in the 29°C group was significantly higher than that in the 20°C and 23°C groups ( ). The hepatosomatic index (HSI) decreased with increasing water temperature, but there was no significant difference between the groups at different water temperatures ( ). The muscle yield (MY) was basically maintained at approximately 34%. The condition factor (CF) of the crab reached 0.62 in the 29°C group, which was significantly higher than that in the 20°C and 23°C groups ( ). Histological observation revealed that the number of lipid droplets and the degree of homogenization of yolk granules in ovarian oocytes gradually increased with the increase of the water temperature. From the perspective of conventional biochemical composition, the moisture and crude protein contents in muscle and the crude fat content in hepatopancreas did not change much among the groups, but the crude protein content in the ovary of the 29°C group was as high as 24.65%, which was significantly higher than that in the other three groups ( ). In terms of fatty acid composition, there was little difference in the fatty acid content in the ovaries of the different water temperature groups. The contents of C22 : 2n6 and C18 : 3n3 in polyunsaturated fatty acids were significantly higher in the 29°C group than in the other three groups ( ). In the hepatopancreas, the contents of C22 : 5n3 (DPA) and C22 : 6n3 (DHA) in the 20°C group were the lowest, 0.07% and 0.15%, respectively, which were significantly lower values than in the 29°C group ( ). The change of amino acid content is mainly reflected in ovarian tissues, showing a gradual upward trend as a whole. Furthermore, the essential amino acid score (EAAS) and average score of the two tissues in the 20°C and 23°C groups were relatively close, and both reached the highest score in the 29°C group. Overall, with increasing water temperature, the rate of ovarian development significantly accelerated, and the nutritional quality of the tissues improved in these swimming crabs.