. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. CELL DETACHMENT IN SYMBIOTIC CNIDARIANS 325 Host Cell Endoderm Cellular Product Mechanism. EXOCYTOSIS APOPTOSIS NECROSIS PINCHING OFF HOST CELL DETACHMENT Figure 1. A schematic representation of five potential mechanisms by which zooxanthellae could be released from the endoderm of cni- danans. and the cellular entities associated with each mechanism, m, mesoglea; vm, host vacuolar membrane; hn, host cell nucleus; zx, zoox- anthella (shaded for clarity of presentation). zooxanthellae associated with remnants of the host cell
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. CELL DETACHMENT IN SYMBIOTIC CNIDARIANS 325 Host Cell Endoderm Cellular Product Mechanism. EXOCYTOSIS APOPTOSIS NECROSIS PINCHING OFF HOST CELL DETACHMENT Figure 1. A schematic representation of five potential mechanisms by which zooxanthellae could be released from the endoderm of cni- danans. and the cellular entities associated with each mechanism, m, mesoglea; vm, host vacuolar membrane; hn, host cell nucleus; zx, zoox- anthella (shaded for clarity of presentation). zooxanthellae associated with remnants of the host cell (Searle a ai, 1982); (d) pinching off of the distal portion of the host cell, resulting in the release of zooxanthellae surrounded by the vacuolar and pinched off plasma membrane (Glider, 1983); and (e) detachment of endo- derm cells from the host and release of these intact cells containing their complement of zooxanthellae. Because cnidarians can be readily bleached in the lab- oratory by brief exposure to low (Steen and Muscatine, 1987; Muscatine el ai, 1991) or high (Hoegh-Guldberg and Smith, 1989; Glynn and D'Croz, 1990) seawater temperature, the mechanism of bleaching and the mor- phology of the cellular entities released can be investigated experimentally. This approach, together with scanning electron microscopy of endoderm of the Hawaiian sea anemone A. pulchella after experimental cold shock, re- vealed profiles that were interpreted as evidence of exo- cytosis of zooxanthellae (Steen and Muscatine, 1987). In- deed, examination of the cellular entities released 24 h after cold stress revealed abundant isolated zooxanthellae. In this paper, we describe the cellular entity released by A. piilclielld and the Hawaiian coral Pocillopora dam- icornis immediately after a brief exposure to low or high temperature. P. damicornis is one of several coral genera that have undergone extensive bleaching in the tropical eastern Pacific during the elevated temperature of the El Nino
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
