QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by MUNOZ, D. P. Articles by CHASE, R. Search for Related Content PubMed Articles by MUNOZ, D. P. Articles by CHASE, R.

Journal of Experimental Biology 107,147-161 (1983)
Published by Company of Biologists 1983

Symmetrical Giant Neurones in Asymmetrical Ganglia: Implications for Evolution of the Nervous System in Pulmonate Molluscs

DOUGLAS P. MUNOZ ¹, PETER A. PAWSON ¹, and RONALD CHASE ¹

¹ Department of Biology, McGill University, 1205, Avenue Docteur Penfield, Montreal, Quebec, H3A 1B1, Canada

Two of the largest neurones in the terrestrial snail Achatina fulica are RPrl, located in the right parietal ganglion, and V1, located in the visceral ganglion. Several characteristics of these cells were studied in detail, including morphology, passive and active electrical properties, synaptic inputs, sensory inputs, motor outputs and sensitivity to transmitter substances. The results suggest that RPrl and V1 form a bilaterally homologous pair of cells, yet they reside in asymmetrically placed ganglia. An explanation of this paradox is offered in the proposal that RPrl and V1 were formerly locatedin the bilaterally symmetrical intestinal ganglia. Their contemporary asymmetrical locations are accounted for by the hypothesis that, during the evolution of the pulmonate nervous system, the supraintestinal ganglion fused with the right pallial ganglion and the subintestinal ganglion fused with the visceral ganglion.