Phagocytic activities of the gorgonian coral Swiftia exserta

The cellular response component of body defense in gorgonians and other cni darians is thought to be carried out by cells with phagocytic capabilities. To test for the phagocytic character of cells, the introduction of foreign particles was employed and observed in both living cells and histological preparations of the gorgonian coral Swiftia exserta. Observations of untrea ted tissues revealed normal cells and tissue morphologies. A microscopic ob servation of living cells following the introduction of particles in a cut revealed that only a mixed population of colorless cells phagocytized the p articles. Also particles or clumps of particles were seen on the surface of the colorless cells. Subsequent histological observations allowed identity of colorless cells to be inferred as granular amoebocytes, ectodermal cell s, and gastrodermal cells. Cells stained for localization of peroxidase (in dicative of phagocytic activity) demonstrated the presence of peroxidase-po sitive cells. Histological preparations revealed that major phagocytosis of particles was associated with tissue trauma. When particles were introduce d by means of a cut or inserted thread, phagocytic activity was detected wi thin 2 h. However, it was confined to the granular amoebocytes in the immed iate site of trauma. After 24 h, extensive phagocytosis spread throughout a relatively large area surrounding the wound. At that later time, phagocyti c cell types included granular amoebocytes, epidermal cells, sclerocytes, m esogleal cells, and gastrodermal cells of the solenia. Observations suggest that trauma induces phagocytosis in cells not normally phagocytic in S. ex serta. No localization of phagocytic cells and no mitotic cells were observ ed at either 2 or 24 h after particle introduction. (C) 2000 Academic Press .