Effects of different temperatures on ovarian development, lipid metabolism and nutritional quality of Eriocheir sinensis during fattening

Ovarian development in the Chinese mitten crab ( Eriocheir sinensis ) enters a rapid development period after the reproductive molt. During this process, low-temperature stimulation seems to be a key initiating factor. To verify this, the current study simulated a nine-week long-term low-temperature experiment during the fattening stage in an indoor thermostatic water circulation system, including a high-temperature control group (30 °C), a medium-temperature group (25 °C) and low-temperature group (20 °C). Based on multi-omics sequencing and histological analysis, we found that chronic low-temperature exposure promotes ovarian development by up-regulating the mRNA expression of crucial genes ( e75 / 74 , vg / vgr , 17β-estradiol , erα ) and promoting the secretion of GIH, MF, and E2 hormones. This can be evidenced by the densely distributed yolk granules, significantly increased oocyte diameter, and GSI index. Interestingly, the significantly increased lipid droplet area and crude lipid level indicate that chronic cold stimulation can promote fat accumulation in the ovary. Significantly, the peroxisome proliferator-activated receptor (PPAR) signaling pathway and phospholipids, including phosphatidylcholine (PC) and phosphatidylethanolamine (PE), play important roles in this process. In addition, continuous cold exposure can significantly increase the levels of monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs) of hepatopancreas and ovarian tissue, and inhibit the synthesis of saturated fatty acids (SFAs) to promote the deposition of nutrients and flavor substances. In conclusion, our current data reveal a series of physiological responses to continuous cold exposure during fattening, providing valuable data support for the fattening strategy and quality improvement of Chinese mitten crabs.