Summary
The nervous system of juvenile and adult Ceriantheopsis americanus has been examined with the electron microscope. The nervous system is exclusively ectodermal, forming a plexus of fibres lying between the epithelium and the muscle layer. The plexus consists of three types of nerve fibre that vary in diameter from 0.1 to 20 μ, and a fourth type of fibre of uncertain nature. The reticulum, previously thought to be the ectodermal nervous system, is redescribed as the peduncles of epithelial supporting cells.
Intraneural and neuromuscular synapses are described. About 97% of the interneural are polarized. The unpolarized synapses are a variety not previously described, consisting of a series of polarized zones, for which the name multipolarized synapse is proposed. Structurally, the interneural synapses are more complex than those previously seen in the Cnidaria. Presynaptic projections, periodic cleft densities, and a postsynaptic web are described. By contrast, the neuromuscular synapses bear no membrane specializations.
On the basis of observed synaptic interactions of its components a preliminary model of the functional organization of the nervous system is proposed.
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This work was supported by grant MH-11218 from the U. S. Public Health Service and by grant A-1445 from the Candian National Research Council.
The author wishes to thank Drs. M. N. Arai, G. O. Mackie, and D. M. Ross for their critical reading of earlier manuscripts.
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Peteya, D.J. A light and electron microscope study of the nervous system of Ceriantheopsis americanus (cnidaria, ceriantharia). Z.Zellforsch 141, 301–317 (1973). https://doi.org/10.1007/BF00307408
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DOI: https://doi.org/10.1007/BF00307408