STUDIES OF DIGESTION IN DIDEMNUM MOLLE, A REEF ASCIDIAN LIVING IN ASSOCIATION WITH SYMBIOTIC ALGAE

Abstract

Fine structural studies of the gut of D. molle reveal four basic cell types. They are mucous cells, vacuolated cells, zymogenic cells and endocrine - like cells. These cells are ascribed functions on the basis of comparison with the results of other studies. In the case of the vacuolated cells, cytochemical evidence confirms an absorptive role. A region of morphologically different cells, the intercellular lacunae cells are characterized by large intercellular spaces of unknown function. Evidence of direct harvesting and ingestion of symbiotic algae by the host colony suggests an alternative pathway for uptake of photosynthate and provides further evidence of the intimate association symbiont. between D. molle and its algal symbiont.