Effects of light intensity on artificial breeding of Sinonovacula constricta

Abstract

In the present study, we aimed to explore the optimal light intensity for the breeding of Sinonovacula constricta, and the effect of light intensity on the growth of S. constricta at different developmental stages was studied. Four developmental stages (spawning, fertilized eggs, planktonic larvae, and juveniles) and different light intensities were set up in our current experiments. The results showed that various light intensities had significantly different effects on spawning amount and initial spawning time, while it had little influence on the hatchability of fertilized eggs (P > 0.05). The spawning amount of the razor clam peaked at a light intensity of 44–250 lx (P < 0.05). In the planktonic larvae experiment, the highest survival rate appeared at 487 ± 31 lx (58.61 ± 4.0%).For juvenile S. constricta, two substratum thicknesses (1 and 5 mm) and four light intensities, including L1 (14 ± 11 lx), L2 (380 ± 145 lx), L3 (3792 ± 2105 lx), and L4 (12,244 ± 5290 lx), were set up in a 10-day experiment. When the substratum thickness of 1 mm was applied, the body length and survival rate of S. constricta juveniles (0.26 ± 0.02 mm) in the L2 group were found to be the largest, which were significantly different compared with the other groups. When the substratum thickness was changed to 5 mm, the body length and survival rate among those groups showed no significant difference. However, when the shellfish samples were changed to a larger size of razor clam (1.45 ± 0.16 mm), a more obvious effect of light intensity on the growth was observed in a 1-mm substratum group compared with the 5-mm group. These results indicated that light intensity exerted a significant effect on the growth of S. constricta at different stages, and each stage exhibited a distinct sensitivity to light intensity. Further study from the aspects of photoreceptors and relevant genes is currently in progress in our laboratory.