New light on the cell location of avarol within the sponge Dysidea avara (Dendroceratida)

Abstract.

Many sponges produce and store secondary metabolites with interesting pharmacological bioactivities. Identification of the cell type(s) responsible for the production and/or storage of these compounds may be a crucial step for the future culture and production of these substances if the biosynthesis is not envisageable and the producer organism is rare or too slow-growing for feasible exploitation. Localisation of these cells within the sponge may also contribute to ascertaining the ecological role of these compounds. The cell type containing the main bioactive metabolite (avarol) and its derivative avarone in the sponge Dysidea avara has been identified by cell isolation in a density gradient and by chromatographic techniques. Preliminary cytological characterisation of the cell types in each particular sponge species under study is required, otherwise the identification of the cells in suspensions is inaccurate. In contrast with the findings reported for other sponge species, the active metabolites of D. avara are not contained within spherulous cells but within choanocytes that line the chambers of the aquiferous system. The possible ecological role of avarol is discussed in the light of its internal position and the biological functions of the cells storing the bioactive compounds.