We are interested in identifying genes that control dynamic behavior modification underlying exploratory search in C. elegans. Immediately following removal from food, worms engage in an area-restricted search (ARS), characterized by an initial high frequency of sharp turns that then decays over time. This causes the search path to shift over time from local and overlapping to globally directed with infrequent overlap. ARS is found in a wide variety of animals and is theoretically supported as an efficient search strategy for finding resources that are distributed in patches. Using motion-sensitive computer analysis, we observed worms immediately after removal from food and quantified the temporal dynamics of their search paths including such features as velocity, radial displacement, and turning angle distribution. These features change continuously with time, but stabilize by approximately 40 minutes. This search behavior is experience dependent, changing significantly in a predictable way across worms reared in different resource distributions. Worms grown in liquid also display ARS, suggesting a genetic predisposition for the behavior. To identify genes controlling this dynamic behavior modification, we quantified ARS in worms with mutations in candidate genes. Mutations in the glutamate receptor
glr-1 and the amino acid decarboxylase
bas-1 cause significant changes in the dynamic aspects of ARS, suggesting that the dynamics of ARS are modified by mutations in a single gene. To further identify genes controlling this behavior, we are developing a genetic screen to isolate mutants that lack the local search following removal from food. We are isolating worms that disperse to a point significantly farther than wild type following removal from food.
bas-1 mutants, which lack the local search, are being used to calibrate the distance and time that provides the most efficient separation between wild type and potential mutants. In conclusion, the area-restricted search phenotype has been quantified in C. elegans, shows predictable interactions with the environment, and appears to be under the control of specific genes which we are currently in the process of identifying.