Variation in social feeding behaviors and interactions among Caenorhabditis nematodes

The ability to respond to complex stimuli and environmental cues is
essential for organisms to survive and reproduce. Evolution of behaviors
occurs ubiquitously in most established ecological niches, even among
closely related species. We have taken advantage of the large and
relatively ancient divergence in the Caenorhabditis genus to ask how
different Caenorhabditis nematodes respond to environmental stimuli and
whether behavioral traits are shared or distinct. Here, we assayed
foraging behaviors of twelve members of the Caenorhabditis clade. 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 a wide
variation in social aggregate feeding and bordering behaviors of
hermaphrodite and female animals, but the variation did not correlate with
evolutionary relatedness of the species. Addition of male animals with
female or hermaphrodite animals of the same species increased aggregation
behavior of a subset of species. Combination of a second species with C.
elegans significantly reduced aggregate feeding behavior of C. elegans.
Overall, we find that foraging and social feeding behaviors vary widely
across Caenorhabditis species and that intraspecies and interspecies
interactions modify behavioral paradigms. In general, the clade represents
a compelling model to dissect evolution of behavior across diverse
environments and a large timescale.