The Nerve Ring of the Nematode Caenorhabditis elegans: Sensory Input and Motor Output

<-- back to wormatlas home

Table of contents  -  Abstract  -   Introduction  -   Materials & Methods  -   Results  -   Discussion  -   References

Introduction

Nematodes have simple nervous systems composed of only a few hundred neurons. Seventy years ago, R. Goldschmidt made a detailed study of the nervous system of Ascaris by reconstruction from serial sections using optical microscopy. (Goldschmidt, '03, '08, '09). Among his elegant anatomical drawings he produced a set of enigmatic wiring diagrams which have never been interpreted. It is likely that some of the bizarre connections shown in the diagrams were simply the outcome of the low resolution of the method Goldschmidt used. A smaller nematode would offer the possibility of determining the complete structure of a nervous system by electron microscopy allowing reliable identification of connections. This would open the way to understanding how the nematode's behavior could be generated by the nervous structure.

We have chosen the small soil nematode Caenorhabditis elegans for electron microscopical reconstruction of its nervous system. C. elegans is a favorable organism for studying the gentics of complex processes and many behavioral mutants have been isolated (Brenner, '73; Ward, '73; Brenner, '74). Reconstruction of the wild-type nervous system will make it possible to recognize anatomical lesions in such mutants. Such lesions should aid the task of understanding nervous system function by allowing correlation of behavioral and anatomical defects. In addition, the study of genetically induced lesions may help to understand how nervous system structure is specified gentically.

This paper is the first of a series which will describe the structure of the nervous system of C. elegans. It deals with the anterior sensory nervous system. Although, in volume, this is only a small part of the nematode it accounts for 58 of the 300 or so neurons found in the animal. The neurons are relatively simple and the reconstruction, though laborious, has not posed any special problems.


Web adaptation, Thomas Boulin, for Wormatlas, 2002