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At hatching, the nematode Caenorhabditis elegans contains about 550 nongonadal nuclei; during postembryonic development the number increases to about 810 in the hermaphrodite and to about 970 in the male. The cell lineages leading to these increases were described by Sulston and Horvitz (1977), but at that time the fates of the male specific cells were largely unknown. We have now followed the nongonadal cellular development of the male up to maturity, and have reconstructed the posterior anatomy of the adult from electron micrographs; thus the migration, differentiation, and ultimate fate of each cell in the tail is now known. The development of the gonad has been elucidated by Kimble and Hirsh (1979), and its connection to the somatic structures will be described. We have mapped the nervous system only as far as is necessary to define each cell uniquely.
The development of the male is of interest both for its complexity and for its genetic accessibility. Since the principal sexual form of C. elegans is a self fertilising hermaphrodite, functional males are not required for strain propagation, and male-specific mutants can be maintained without difficulty. Hodgkin (1974) has isolated a number of strains in which hermaphrodites are fertile but males are defective. In another class of mutant, transformer (Klass et al, 1976; Hodgkin and Brenner, 1977), animals bearing two X chromosomes are male rather than hermaphrodite.
The study of such mutant strains is one approach to understanding the control of the developmental events described below. Another approach is selective cell ablation by means of a laser microbeam; experiments using this technique are described both in this and in the following paper.
Adapted by Yusuf KARABEY for WORMATLAS, 2003