Isotopic tracing of sediment components assimilated by epibiontic juveniles ofHolothuria scabra(Holothuroidea)

Abstract

DespiteHolothuria scabra's wide distribution and status as one of the best candidates for sustaining the development of tropical sea cucumber aquaculture, very few data are available regarding the organic fraction it assimilates in practice. In this paper we report experimental results whereH. scabra's diet was supplemented with various15N-labelled organic fractions of sediment. We used juveniles weighing between 38 and 88 mg at the beginning of the experiment (~2 cm long and 30 days old). Their growth was measured over a four-week period and their15N composition recorded. The results showed thatH. scabrajuveniles assimilated all added organic components from both dissolved and particulate fractions of the sediment. Bacteria seem to be an important food source for juveniles, even more so than microphytobenthos (diatoms).