RETINOIC ACID ACTS AS A MORPHOGEN IN FRESH-WATER SPONGES

The effect of retinoic acid [RA] on the morphogenesis of freshwater sp onges (Spongilla lacustris, Ephydatia fluviatilis, Ephydatia muelleri) was studied. At a concentration of 2 mu M, RA had no overt effect on pinacocytes and choanocytes but had already altered mesohyl cell movem ent and adhesion after I h treatment. It interfered with morphogenesis of sponges developing both from larvae and gemmules, inhibiting the f ormation of the aquiferous system, and promoting formation of reductio n bodies. The same was observed in treatment of functional sponges wit h RA. We conclude that RA induces modifications in mesohyl cell adhesi on and interaction, analogous to that observed in induction of reducti on bodies formation or gemmulogenesis.