4 The Anatomy

Abstract

I. INTRODUCTION
The complete cellular architecture of Caenorhabditis elegans is now known. Much of this knowledge was obtained from reconstructions of electron micrographs of serial sections and is therefore quite detailed. The invariance of cell number and cell fate within the somatic tissues of C. elegans has enabled every cell in the animal to be identified and assigned a unique label. This information has been related to the cell lineages (Sulston et al. 1983), thereby providing, for the first time, a comprehensive description of the ontogeny and ultimate differentiated state of all the various cells that comprise a metazoan.

One of the original motivations for undertaking ultrastructural reconstructions of C. elegans was to deduce the structure and connectivity of the nervous system, which is dealt with more fully in Chapter 11. This chapter presents a general anatomical description of the somatic tissues of the animal. It begins by describing some features of the somatic tissue types and then goes on to describe the major organs of the body.

II. TISSUES
A. Epithelia
Epithelial cells, together with the cuticle that they secrete, establish the basic body form of C. elegans. In common with all epithelial cells, those of C. elegans have two distinct regions in their plasma membranes: the basolateral surface and the apical surface. Cuticle is always laid down adjacent to the apical surface, and there is usually a basement membrane adjacent to the basal surface. It is likely that the apparatus for secreting the material of the cuticle is...