[
International C. elegans Meeting,
2001]
Chemotaxis and thermotaxis, the two sensory mechanisms that C. elegans uses to interact with its environment have been reported in detail. However little is known of phototaxis, another operative sensory mechanism. To investigate photoresponse in the worm, we used two approaches. In (1), phototaxis of wild type worms were observed on NGA plates using two different light sources and (2) photoresponse of a single worm was determined under limited light conditions. Phototaxis is shown as phototaxis rate (PR) = Number of worms in area after irradiation/ worms before irradiation. In 30 independent assays using white light, PR ranged between 3.0 and 0.8. Using a thermostat filter to maintain constant temperature, PR decreased to between 1.35 and 0.75. This result indicates that the worm is sensitive to temperature increase during irradiation. We are yet to obtain clear results with a light source of 533 nm filter and we are trying other approaches for precise determination. Photoresponse was observed after irradiation shift from weak to strong light and percentage of responsive animals were classified as avoidance, weak avoidance and no response. In 15 independent tests, 25% of the worms responded to irradiation. Using mutant worms of chemotaxis and thermotaxis, the percentage irradiation response was decreased proportionally to the morphology of the amphid cilia. This suggests that some molecules in the amphid cilia could respond to light. The relationship between phototaxis and photoresponse and its link to chemotaxis and thermotaxis are still underway.