EVIDENCE OF MATROTROPHY IN THE VIVIPAROUS HOLOTHUROID ECHINODERM SYNAPTULA-HYDRIFORMIS

Synaptula hydriformis is a holothuroid echinoderm that retains its you ng in the adult perivisceral coelom. It is also a simultaneous hermaph rodite and is probably self-fertilizing. Eggs are released from the ge rminal epithelium into the lumen of the ovotestis tubule, and from the re into the perivisceral coelom. S. hydriformis is viviparous: eggs ar e never released to the outside of the adult organism, but develop int ernally until juveniles are released. It is also matrotrophic: the you ng rely on the parent to supply nutrition in excess of that supplied b y yolk in the egg. The increase in both dry and organic weight from eg g to 8-mm juvenile is in excess of 100X. The additional nutrition is s upplied as coelomocytes and molecules present in adult coelomic fluid. Brooded juveniles consume naturally occurring particulates and experi mentally introduced 50-nm and 1-mu m microspheres from the adult periv isceral coelom. C-14-palmitic acid was also ingested by brooded juveni les and was incorporated into juvenile tissue, indicating that consume d nutrients are metabolized.