We developed a quantitative assay for Caenorhabditis elegans avoidance behavior. This was then used to demonstrate that the worm moved away from toxic concentrations of Cd2+ and Cu2+, but not Ni2+, all ions that prevented development from larval to adult stages. Mutants that have structural defects in ciliated neurons (che-2 and osm-3) as well as worms with three laser-operated neurons (ADL, ASE, and ASH), showed no avoidance behavior from Cd2+ and Cu2+. These results suggest that the avoidance from Cd2+ and Cu2+ are mediated through multiple neural pathways including ADL, ASE, and ASH neurons. We hypothesize that the three sensing neurons provide increased accuracy of the sensory response and a survival advantage in the natural environment of the worm.
1Division of Biological Sciences, The Institute of Scientific and Industrial Research, Osaka University, CREST of Japan Science and Technology Corporation, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan
2Present address: Department of Microbiology, Xian Medical University, Xian Shaanxi 710061, China
3Corresponding Author: Masamitsu Futai
ACKNOWLEDGEMENTS: We thank Takeshi Ishihara and Isao Katsura for teaching us the laser microbeam surgical operation and Robert K. Nakamoto for critical reading of this manuscript. The wild-type and mutant strains were from Caenorhabditis Genetic Center which is supported by the National Center for Research Resources (NCRR). This work was supported partly by the Japanese Ministry of Education, Science, and Culture.
Received 2 December 1998; accepted 11 January 1999