Effects of Different Substrates and Photoperiods on Burrowing and Feeding Behavior of Clam Cyclina sinensis
Two-year-old clam(Cyclina sinensis)were placed in a 30 cm×30 cm×30 cm artificially controlled water temperature,light and sound culture tank at a density of 8 individuals per tank at room temperature of(25±3)℃.The LED light source on the box simulated photoperiod of light(12 h)and dark(12 h),and the bottom of the tank was covered with 10 cm thick whole mud(0%sand group),sand-to-mud ratio of 1∶3(25%sand group),sand-mud ratio of 1∶1(50%sand group),sand-mud ratio of 3∶1(75%sand group)and whole sand(100%sand group).Green alga Chlorella was fed once a day in the morning and evening,and burrowing and feeding behavior of the clam were recorded by a camera to investigate effects of different substrates and photoperiods on burrowing and feeding behavior of the clam.The results showed that the burrowing behavior of the clam was primarily divided into five steps:extending the siphon tube,extending the foot,erecting the shell,drilling the mud and completing the burrowing.Moreover,the shorter time of burrowing was observed under dark conditions.The observation found that the clam had significantly lower feeding activity during the light period than that under dark conditions,with feeding activity mainly from 19:00 to 22:00.There were the peak activities of α-amylase and pyruvate kinase in the natural light group(12 h dark∶12 h light),and the maximal activities of pepsin,hexokinase,and lactate dehydrogenase under 24 h dark conditions.The findings indicate that the clam C.sinensis prefers to carry out activities including burrowing,feeding,digestion and metabolism under dark conditions.