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The Biological Bulletin, Vol 185, Issue 3 335-345, Copyright © 1993 by Marine Biological Laboratory

CELL BIOLOGY

Direct Monitoring of Intracellular Calcium Ions in Sea Anemone Tentacles Suggests Regulation of Nematocyst Discharge by Remote, Rare Epidermal Cells

P. Mire-Thibodeaux and G. M. Watson
Department of Biology, The University of Southwestern Louisiana, Lafayette, Louisiana 70504-2451

In tentacles of sea anemones, cnidocytes and adjacent supporting cells are believed to be independent receptor-effector complexes that regulate nematocyst discharge in response to exogenous N-acetylated sugars. When sugar chemoreceptors on supporting cells are activated, nematocyst discharge is two- to threefold greater than discharge without chemosensitization. To examine the role of Ca2+ as a second messenger in chemodetection of sugars, we used fluo-3 to monitor Ca2+ levels in epidermal cells of intact anemone tentacles. Certain epidermal cells exhibit relatively high Ca2+ both with and without chemosensitization. With chemosensitization, a two-to threefold increase occurs in the abundance of relatively rare cells exhibiting the highest Ca2+ levels. Timecourses depicting abundances of these rare cells in chemosensitized specimens show positive correlations to timecourses for nematocyst discharge from chemosensitized specimens and for labeling of chemoreceptors. Cnidocyte/supporting-cell complexes discharging nematocysts are about three times more abundant than the rare cells exhibiting the highest intracellular Ca2+ levels. One interpretation of these data is that the Ca2+-dependent regulation of nematocyst discharge occurring with chemosensitization involves intense Ca2+ signaling by remote, rare cells. This interpretation is inconsistent with the current model that portrays cnidocyte/supporting-cell complexes as independent effectors of nematocyst discharge.


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V. H. Ozacmak, G. U. Thorington, W. H. Fletcher, and D. A. Hessinger
N-Acetylneuraminic Acid (NANA) Stimulates in situ cyclic AMP Production in Tentacles of Sea Anemone (Aiptasia pallida): Possible Role in Chemosensitization of Nematocyst Discharge
J. Exp. Biol., January 6, 2001; 204(11): 2011 - 2020.
[Abstract] [Full Text] [PDF]


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Copyright © 1993 by the Marine Biological Laboratory.