Effects of LED light quality on the growth, survival and metamorphosis of Haliotis discus hannai Ino larvae

Light is a key environmental factor influencing the growth, development and survival of aquatic organisms. We examined the effects of different light qualities (red, orange, white, blue, green or no light) and developmental stage at initial lighting [fertilized egg (FE), trochophore larva (TL), or eye-spot larva (EL)] on the growth, development, and survival of larvae of the Pacific abalone Haliotis discus hannai Ino. Larva-hatching success was significantly higher under blue, green, or no light compared with red, orange or white light (P < 0.05). Larval abnormalities were significantly increased under red, orange or white light compared with all other light qualities (P < 0.05). The incidence of metamorphosis in larvae illuminated from the TL stage was significantly higher under blue compared with other light qualities. Irrespective of the stage at initial illumination, the incidence of metamorphosis was lower in larvae cultured under red, orange or no light compared with other light qualities, but the differences were not significant (P > 0.05). Juvenile survival was significantly higher under blue or green compared with other light qualities (P < 0.05), with no significant effect of stage at initial illumination (P > 0.05). Larval size at completion of the shell was unaffected by stage at initial illumination, but was greater under blue or green light, while size at metamorphosis was greatest following illumination with blue or green light since the TL or EL stage (P < 0.05). Metamorphosis time was shortest with blue or green light and in cultures illuminated from the FE or TL stage (P < 0.05). Larval development from the FE to formation of the fourth tubule on the cephalic tentacles was fastest in larvae exposed since the FE or TL stage to blue or green light, compared with other light qualities (P < 0.05). However, there was no difference in terms of the rate of development from the FE to the TL stage between cultures lit or unlit since the FE egg stage (P > 0.05). These results suggest that a blue or green light source applied from the TL stage can increase the hatching and yield of H. discus hannai Ino, with important implications for the development of the aquaculture industry.