Effects of temperature on energy metabolism andantioxidant enzyme activities of Scapharca broughtonii

The energy metabolism and antioxidant enzyme activities of Scapharca broughtonii at different temperature levels (20, 23, 26 and 29 °C) were studied in the laboratory. The results showed that the ingestion rate and the faecal egestion rate of S. broughtonii decreased with the increase of temperature. One-way ANOVA showed that temperature significantly affected the ingestion rate of S. broughtonii, but had no significant effect on the faecal egestion rate. The oxygen consumption rate and the ammonia excretion rate of S. broughtonii first increased and then decreased with the increase of temperature. Through the energy balance equation, we found that the temperature affected the energy allocation of S. broughtonii. Under the condition of 20 °C, the energy of respiration was accounting for 13.71%, 1.89% in excretion, 22.94% in defecation, and 61.47% in growth. However, when the temperature was above 20 °C, the ingested energy could be significantly decreased. Even negative growth occurred. The analysis of variance showed that the temperature had significant differences on the feeding capacity and growth capacity of S. broughtonii. The activities of antioxidant enzymes in the mantle membrane, gill and hepatopancreas of S. broughtonii were sampled and tested at 0, 4, 8, 12, 24, 48 and 72 h after the treatments of temperature. In the range of 20–29 °C, the activity of T-AOC first increased and then decreased, and it was significantly lower at 29 °C than those at any other temperature groups. The results suggested that the short-term high-temperature stimulation promoted the activities of SOD and CAT, but decreased them beyond 24 h. The activities of SOD and CAT in gill and hepatopancreas were significantly affected by temperature, however, they were not significantly affected by temperature in mantle membrane. GST activity increased significantly with the increase of temperature within 4–12 h, but decreased significantly beyond 24 h, especially when the temperature rose to 29 °C. Our studies have speculated that high temperature may lead to the reduction of antioxidant capacity in the organism, which has a serious impact on the energy metabolism and immune capacity of S. broughtonii. This may be an important reason for high death rate of S. broughtonii in summer. All the results suggest that the temperature for the actual production of S. broughtonii should be maintained below 23 °C. It will generate a large amount of energy consumption of S. broughtonii if the temperature exceeds 26 °C.