| In this study, the effects of light intensities on the growth rate (GR) and digestive enzyme activity of purple sea urchin (Anthocidaris crassispina) larvae were studied by simulating and analyzing the natural light cycle through the flume experiment method, aiming to provide necessary biological parameters for the large-scale breeding of juvenile sea urchins. The sea urchin larvae were exposed to different light intensities (0 lx, 500 lx, 1000 lx, 2000 lx, and 3000 lx) for 18 days (12 h light:12 h dark, 08:00~20:00) and samples were taken on days 8, 11, and 16). The GR was examined to identify the size (larval length, body-rod length, and post-oral arm length). The activities of digestive enzymes (amylase, lipase, and protease) were examined to elucidate their response to light intensities. At the end of the experiment, the GR under different light intensities decreased as follows: 500 lx > 0 lx > 1000 lx > 2000 lx > 3000 lx. The larval length, body-rod length, and post-oral arm length of sea urchin larvae in the 500 lx treatment were the highest among all light intensity treatments (P<0.05), and the activities of lipase and amylase were the strongest. The maximum activity of protease was observed in the 2000 lx treatment (P<0.05). By day 11, all sea urchin larvae died in the 3000 lx treatment. The results showed that the sea urchin larvae could maintain the best GR, digestive enzyme activity, and survival rate under 500 lx light intensity, which was the best light intensity for the growth and development of the sea urchin larvae. |
