THE ULTRASTRUCTURE OF COELOMOCYTES OF THE SEA STAR DERMASTERIAS IMBRICATA

¹ Department of Biological Sciences, University of Cincinnati, Cincinnati, Ohio 45221

1. The structure of coelomocytes from Dermasterias imbricata was characterized by light microscopy and scanning and transmission electron microscopy. The petaloid or lamellipodial configurations were the prevalent forms in freshly drawn coelomic fluid. Cells produced filopodia when they adhered to glass slides.

2. Lysosomes were stained with neutral red and observed by light microscopy, and variations in density and structures of their matrices described by TEM.

3. Animals injected with a bacterial suspension cleared the bacteria from their coelomic fluid within 2-3 days. Ultrastructure of coelomocytes in these animals indicated that phagocytosis and digestion of bacteria were rapid and involved lysosomes.

4. With TEM numerous bacteria were observed within cells of Tiedemann's bodies from untreated animals, indicating that this organ may play an important role in clearing the coelomic fluid and water vascular system of foreign particles.

5. Giemsa-stained coelomocytes of untreated animals and animals recovering from coelomic fluid removal indicated that coelomocytes did not undergo mitosis within the coelomic fluid. Removal of coelomic fluid resulted in recovery or increase in total body weights and coelomocyte concentrations. Hence, circulating coelomocytes must be recruited from other tissue sources in the animal.

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