Abstract

Nematodes are important parasites of humans and other animals. Nematode parasitism is thought to have evolved by free‐living, facultatively developing, arrested larvae becoming associated with animals, ultimately becoming parasites. The formation of free‐living arrested larvae of the nematode Caenorhabditis elegans is controlled by the environment, and involves dafachronic acid (DA) and transforming growth factor (TGF)‐β signalling. Recent data have shown that DA acid signalling plays a conserved role in controlling larval development in both free‐living and parasitic species. In contrast, TGF‐β signalling does not seem to be conserved; this difference perhaps points to how nematode parasitism did evolve.