Development of three commercial sea cucumbers, Holothuria scabra, H-fuscogilva and Actinopyga mauritiana: larval structure and growth

Development of the tropical sea cucumbers Holothuria scabra, H. fuscogilva and Actinopyga mauritiana was investigated. Holothuria scabra developed through the feeding auricularia, the non-feeding doliolaria and the pentactula larval stages in 14-17 days at 26-28degreesC. Holothuria fuscogilva and A. mauritiana were reared to the auricularia and doliolaria stages respectively. The auricularia stage was reached by 40-70 h and the larvae developed lateral processes and a prominent ciliated band. Transformation to the doliolaria stage took 10-12 h and occurred on Days 9-12 in H. scabra and Days 12-22 in A. mauritiana. During this transition the ciliated band fragmented into ciliary rings, the location of which coincided with the lateral processes in the auriculariae. In H. scabra, metamorphosis to pentactulae (13-15 days) was marked by development of five primary tentacles and a ventroposterior podium. This podium was used to attach to the substratum. Newly settled pentactulae of H. scabra used their tentacles to test, adhere and move across the substratum. Development of a second podium marked the development of juveniles (14-17 days). Hyaline spheres were conspicuous in late auriculariae of H. scabra and may be an indicator of larval competence. They disappeared in the doliolaria stage, which suggests that they may function as nutritive reserves to sustain H. scabra through the non-feeding perimetamorphic period. Absence of these spheres in H. fuscogilva, and their poor growth in A. mauritiana, suggests the feeding protocol used may not be sufficient to support complete development in these species. Determination of food and culture conditions that promote hyaline sphere formation and control bacteria may be essential for successful culture of H. fuscogilva and A. mauritiana.