EFFECTS OF SUSTAINED HIGH-TEMPERATURE STRESS ON GROWTH PERFORMANCE, DIGESTIVE ENZYME ACTIVITIES AND IMMUNE INDEXES OF CRAYFISH, PROCAMBARUS CLARKII

In order to investigate the effects of sustained high-temperature stress on the growth performance and health status of crayfish, Procambarus clarkii, the P. clarkii of (7.19±0.29) g were cultured at the suitable temperature (24℃, the control) and the higher temperatures (29℃, 32℃ and 35℃) for 30 days, respectively. The results showed as follows: (1) With the increase of the stress temperature, the survival rate (SR) of P. clarkii decreased significantly (P<0.05); the growth performance indexes including final body weight (FBW), final body length (FBL), weight gain rate (WGR) and specific growth rate (SGR) increased firstly and then decreased with the rise of temperature. The growth performance indexes reached the peak at 29℃ and was significantly higher than those of other treatments (P<0.05); compared with 24℃, 32℃ of high-temperature stress had no significant effect on the growth performance (P>0.05), but the growth performance decreased significantly under 35℃ of high-temperature stress (P<0.05); (2) The activities of pepsin, amylase and lipase firstly increased and then decreased with the increasing temperature. The activities of three digestive enzymes reached the peak at 29℃ and were significantly higher than those of other treatments (P<0.05), the activities of amylase and lipase at 32℃ were significantly higher than those of the control (P<0.05), and the pepsin activity at 35℃ was significantly lower than that of the control (P<0.05); (3) Under the conditions of high-temperature stress, the activities of acid phosphatase (ACP) and alkaline phosphatase (AKP) in serum significantly decreased while the activities of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) gradually increased significantly with the increasing temperature (P<0.05); The total antioxidant capacity (T-AOC) and total superoxide dismutase (T-SOD) activity in hepatopancreas were the lowest at 29℃ (P<0.05), and the T-SOD activity was significantly lower than those of other treatments (P<0.05), while the malondialdehyde (MDA) contents gradually increased with increasing temperature (P<0.05). The relative expression of heat stress protein gene (HSP70) of hepatopancreas and gill increased significantly at 29℃ (P<0.05) and was the highest at 35℃ (P<0.01). The results revealed that the 29℃ of sustained high-temperature significantly promote the growth performance and the digestion but significantly affects the immune function of P. clarkii adversely, and the sustained high-temperature stress of 32℃ and above has serious detriment to its survival and growth, digestion, immune and antioxidant functions.