Variation in social feeding behavior and interactions among Caenorhabditis nematodes.

Abstract

The ability to respond to complex stimuli and environmental cues is essential for organisms to survive and reproduce. Responding to a wide range of stimuli requires a neuronal network that can integrate cues and execute behavioral responses. Evolution of behaviors occurs ubiquitously in most established ecological niches, especially among closely related species. To uncover the genetic and neuronal drivers of evolving behaviors, we have taken advantage of the large and ancient divergence in the Caenorhabditis clade of nematodes to ask how different Caenorhabditis nematodes respond to environmental stimuli and are behavioral traits shared or distinct. Here, we assayed foraging behaviors of twelve members of the Caenorhabditis clade, including members of both the elegans and japonica supergroup, and the basal taxon C. monodelphis. For each species, we analyzed social feeding and bordering behaviors, which are well characterized in C. elegans. These behaviors are the functional readout of complex sensory integration of multiple sensory cues including pheromones, touch, O2/CO2 concentration, and attractive and noxious stimuli. We hypothesized that the evolutionary divergence between species would correlate to divergence in these behaviors. We observed wide variation in aggregate social feeding and bordering behaviors of hermaphrodite and female animals, but the variation did not correlate with evolutionary relatedness of the species. Combination of both sexes of individual species increased aggregation behavior of select species that had lower levels of aggregation in single sex assays. Combination of C. elegans with a second species in the same assay altered aggregate feeding behavior of C. elegans in a species-specific manner. Intraspecies and interspecies interactions can modify behavioral paradigms. Overall, we find that foraging and social feeding behaviors vary widely across Caenorhabditis species, likely due to species-specific responses and integration of context sensory cues.