Chemosensory neurons with overlapping functions direct chemotaxis to multiple chemicals in C. elegans.

The functions of the 11 classes of exposed chemosensory neurons of C. elegans were tested by killing cells with a laser microbeam. One pair of neurons, the ASE neurons, is uniquely important for chemotaxis: killing the ASE neurons greatly reduced chemotaxis to cAMP, biotin, Cl-, and Na+. Additional chemosensory function is distributed among several other cell types. Thus, 3 pairs of chemosensory neurons (ADF, ASG, and ASI) contribute to a residual response to cAMP, biotin, Cl-, and Na+ after ASE is killed. Chemotaxis to lysine similarly depends on the partly redundant functions of 4 pairs of chemosensory neurons (ASE, ASG, ASI, and ASK). The combined activity of several neuron types that act in parallel might increase the fidelity of chemotaxis.