Abstract:

To investigate the effects of different salinity conditions on physiological indices and analyze the physiological regulation mechanism of Urechis unicinctus Juvenile in the face of salinity stress, the salinity of aquaculture water were maintained at 15‰, 20‰, 25‰, 30‰ and 35‰ in five experimental groups. Serum, intestinal homogenate and body wall samples were collected at 0h, 6h, 12h, 18h, 24h, 48h and 72h and the activities of SOD, CAT, ACP, intestinal lipase and glycogen content were measured. In conclusion, salinity stress has a significant effect on antioxidant capacity and nonspecific immunity of Urechis unicinctus. A certain degree of salinity stimulation can activate the activities of digestive enzymes and accelerate metabolism; the increase rate of digestive enzyme activity under low-salt stimulation is slower than that under high-salt stimulation; the time of digestive enzymes and muscle glycogen reaching the highest value in the medium-high salinity group was earlier than that in the low-salinity group. However, when the salinity of water exceeds the limit tolerance range of Urechis unicinctus or the stress time is too long, the regulatory load of osmotic pressure will increase, which will inhibit the activities of the immune system and digestive enzymes, and even cause severe damage to the body. In contrast, the changes of each index in salinity 25‰ group are relatively stable, which are suitable for Urechis unicinctus cultivation.

Key words: Urechis unicinctus Juvenile, salinity stress, antioxidant enzymes, lipase, digestive enzyme activity, muscle glycogen, physiological regulation mechanism, nonspecific immunity