CORRELATION OF LYSOSOMAL ACTIVITY AND INGESTION BY THE MANTLE EPITHELIUM

¹ Department of Histology, The University of Texas Dental Branch, Houston, Texas 77025
² The Bermuda Biological Station for Research

1. Ingestion of particulate matter by the outer mantle fold of the calico clam, Macrocallista maculata, was studied. Following the introduction of carmine into the pallial space, dye particles were subsequently localized in the epithelia of the entire outer surface.

2. In an attempt to identify the cell structure in which the dye particles were localized, histochemical tests to identify acid phosphatase, lipids and mucopoly-saccharides were employed. All of the above methods gave a positive reaction at the site corresponding to the locus in which the carmine was observed.

3. Additional experiments were carried out in which colloidal gold was injected into the pallial fluid. Subsequent examination of epithelial cells showed that the colloidal gold was localized in organelles which, on the basis of fine-structure morphology and histochemical tests, we ascertain to be lysosomes.

4. Pinocytosis, occurring as a result of the pinching-off of the bases of the microvilli is a prominent activity of these cells. The micropinocytotic vesicles arising by this process apparently give rise to large vacuoles and lysosomes.

5. The intracellular mechanism by means of which ingestion by the mantle cells occurs has not previously been recorded. The significance of this activity awaits further study.