Programmed cell death in nematode development.

The phenomenon of programmed cell death, which occurs during the normal development of many organisms and is particularly common in neural development, is intriquing. Why should organisms generate cells only to destroy them? We believe that studies of the cell deaths that occur in nematodes have provided some answers to this question. Programmed cell death is a prominent feature of nematode development. For example, the generation of the 816 nongonadal cells of the hermaphroditic free-living nematode Caenorhabditis elegans is accompanied by the generation and death of an additional 131 cells. Most of these deaths appear to involve cells that are neural in character. Neural cell death is similarly common during the development of C. elegans males and during the postembryonic development of both females and males of another nematode species, Panagrellus redivivus. Overall, for both sexes of these two nematode species, approximately 20% of all presumptive neural cells produced undergo