Ultrastructural localization of lysosomal digestion in the fresh water sponge Ephydatia fluviatilis

The digestive capabilities of endocytizing cells of Ephydatia fluviatilis have been determined by the ultrastructural localization of acid phosphatase. Two distinct markers of endocytic activity were supplied to sponges grown in vitro: Latex beads and Escherichia coli. With both markers, an enzymatic activity was found in lysosomes and in phagolysosomes, as well in archaeocytes and choanocytes, as in exo- and endopinacocytes of the dermal membrane, pointing out that each cell type is capable of feeding itself. The digestive capabilities of each cell type were confirmed by the alteration of the bacteria in phagolysosomes. This localization of lysosomal activity, coupled with the endocytosis of particles clearly revises the previously accepted idea that archaeocytes are the sole digesting cells, this function being also supported by the choanocytes and the pinacocytes. The digestive capacity of the exo- and endopinacocytes confirms the importance of the dermal membrane, bypassing the choanocytes not only in their capture role, but also in their digestive role. © 1984 Academic Press, Inc.SCOPUS: ar.j