Chemotactic behavior of mutants of the nematodeCaenorhabditis elegans that are defective in osmotic avoidance

Summary Wild-typeC. elegans and seven derivative strains previously selected for absence of the wild-type tendency to avoid highly concentrated solutions (Culotti and Russell, 1978) were tested for responsiveness in 11 assays of chemotaxis, including 6 attractant and 3 repellent stimuli. The two strains altered in the geneosm-1 (P808 and P816) did not respond in any test except, possibly, one or two weak responses. Strain P801 responded to one attractant and two repellents. Strain P802 made moderately strong responses to most stimuli and avoided CO₂ in phosphate buffer as strongly as the wild-type. Of particular interest, this strain avoided OH^– which is attractive to wild-type. Strain P821 avoided CO₂ in phosphate buffer weakly, if at all, but did respond to the attractants Na⁺ and Cl^–. Conversely, strains P813 and P811 made little if any response to any attractant but did respond to the two strong repellents. Taken together with other results, these findings suggest that the osmotic response has more gene requirements in common with both attractive and repellent chemical stimuli than with thermal or mechanical stimuli. In addition, they indicate that the known chemical stimuli and the osmotic stimulus are probably mediated by at least 9 different receptors.This research was supported by the National Science Foundation and the National Institutes of Health. I would also like to thank Ms. Georgann Hardin, Mr. Kirt Rusenko, and Ms. Deborah Higgins for their assistance in carrying out the experiments. Drs. J.G. Culotti and R.L. Russell generously provided the mutant strains they had isolated.