The Ultrastructural Basis for the Electrical Coordination Between Epithelia of Hydra
Previously published electrophysiological and ultrastructural studies suggest that the coordinated behavior of Hydra depends on both nervous and non-nervous conduction (c. f. Josephson and Macklin, 1967; Kass-Simon, 1972; Wood, 1961; Hand and Gobel, 1972). As discussed in another paper in this volume (Kass-Simon, 1976), hydra’s behavioral repertoire seems to require the controlled passage of information between the two muscular cell layers, the ectoderm and the endoderm, which are separated from each other by a thick acellular layer, the mesoglea. To help reveal a morphological basis for this interaction, we undertook a light and electron microscopic study of Hydra, directed exclusively toward defining how the two cell layers interact morphologically. Three separate but related topics were addressed: 1) direct interaction of muscular cells of the two epithelia via gap junctions; 2) bridging of the mesoglea by nerve cell processes, and 3) a third type of cellular process which has been reported to occur within the mesoglea of Hydra, but which is actually a bacterial symbiont.
KeywordsCell Process Nerve Cell Process Central Cylinder Outer Sheath Axial Filament
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- Bonnefoy, A-M. and X. Kolenkine, 1975. Ultrastructure et signification des “corps tubulaires” et “particules” de la mesoglee chez les Hydres. C. R. Acad. Sc. Paris, Ser D, 280: 2673–2676.Google Scholar
- Hadzi, J., 1909. Ueber das Nervensystem von Hydra. Arb. zool. Inst. Wien, 17:225–268.Google Scholar
- Hand, A. R., 1971. Observations on the substructure of septate and gap junctions in Hydra. Anat. Rec. 169: 333–334 (abstr).Google Scholar
- Hufnagel, L., D. Borsay and G. Kass-Simon, 1975. Ultrastructural basis for direct electrical coordination of ectodermal and endodermal epitheliomuscular cells in Hydra. J. Cell Biol. 67:185a.Google Scholar
- Kass-Simon, G., 1972. Longitudinal conduction of contraction burst pulses from hypostomal excitation loci in Hydra attenuata. J. comp. Physiol. 80:5.Google Scholar
- Lentz, T. L., 1966. The Cell Biology of Hydra, North-Holland, AmsterdamGoogle Scholar
- Wood, R. L., 1961. The fine structure of intercellular and mesogleal attachments of epithelial cells in Hydra. Lenhoff, H. M. and Loomis, W. F., Eds., pages 51–67 in The Biology of Hydra. Univ. Miami Press, Coral Gables, Florida.Google Scholar