The life cycle of the nematode Caenorhabditis elegans: II. A simplified method for mutant characterization

Abstract

A simple method for characterizing the development and reproduction of mutant strains of the small nematode Caenorhabditis elegans has been developed. “3-egg” populations of nematodes, started with three synchronously laid eggs and allowed to develop undisturbed for about two generations, are measured on the electronic nematode counter, and the resulting size distributions are interpreted by a computer. The computer compares the observed distribution to an expected distribution, generated by assuming the developmental curves previously measured for the wild-type C. elegans; if the distributions do not agree, the computer independently varies scale factors for developmental rate, size, egg-laying rate, and spread until the expected distribution best approximates the observed one. The resulting factors quantify any mutant defect of growth or reproduction, and the poorness of fit tells how greatly the mutant's development differs from that of the wild-type in ways other than those allowed for by the four scale changes. The computer program is shown to be able to fit wild-type C. elegans 3-egg populations grown for various lengths of time at 20°C. Three-egg populations of wild-type animals grown at 16 and 25°C are fitted by the computer and give altered developmental parameters consistent with those previously measured by more direct means. Nine behavioral and morphological mutants have been analyzed by this method. All show some developmental alterations from the wild-type. Fertility seems to be more adversely affected than growth. One mutant has been studied in more detail to determine the specific ways in which it differs from the wild-type.