In situ Chemotaxis Assay in Caenorhabditis elegans (for the Study of Circadian Rhythms)

Abstract

Olfaction is a well-studied sensory mechanism in Caenorhabditis elegans (C. elegans). The nematodes respond to a wide range of chemicals by either attraction, repulsion or a mixture thereof (Bargmann et al., 1993). We have used olfaction to characterize behavioural and molecular circadian rhythms in C. elegans. The circadian clock is a biological oscillator that provides an endogenous temporal structure that approximately matches the 24-hour periodicity in the environment (due to the rotational movement of the Earth). Circadian rhythms are present in most organisms from cyanobacteria to humans and they typically regulate sensory functions among many other processes. Olfaction is under circadian control in many animals (Granados-Fuentes et al., 2006; Granados-Fuentes et al., 2011; Tanoue et al., 2008; Krishnan et al., 1999). This protocol was designed to allow the assessment of olfaction for a population of worms within a short time interval, in the same plate where the worms grew (to avoid washing steps that may disturb the rhythms), and in the presence of food.