Effects of dietary microalgae on growth and survival of larval development of sea urchin (Anthocidaris crassispina)

To investigate the growth and survival of sea urchin (Anthocidaris crassispina) larvae, we fed six microalgal diets Dicrateria zhanjiangensis, Chaetoceros gracilis, Pavlova viridis, Platymonas subcordiformis, Chlorella vulgaris, and mixture of C. gracilis and D. zhanjiangensis (1∶1). The results show that different diets had different effects on the growth and development of the planktonic larvae of sea urchin. D. zhanjiangensis was the optimal microalgal diet. C. gracilis was the second, and then were P. viridis, C. vulgari, and mixture of C. gracilis and D. zhanjiangensis. However, P. subcordiformis was not suitable to be used as the opening bait for sea urchin larvae rearing. In terms of baits, D. zhanjiangensis was the best, since the survival rate of the larvae could reach (23.12 ±1.8)%, significantly higher than those of other unicellular algae (P<0.05). In terms of growth rate, mixture of C. gracilis and D. zhanjiangensis was the best, since the average length of the larvae could reach (885.25±30.49) μm, significantly higher than those of the other five treatments (P<0.05). The growth of the larvae fed with P. viridis was slow at early stage with body length of (337.98±24.56) μm, but it grew faster than the other unicellular algae at later stage with body length of (580±32.95) μm, so P. viridis is the suitable bait for planktonic larvae of A. crassispina at later stage.