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Animals must robustly execute behaviors while remaining flexible enough to adapt when circumstances change. Over longer timescales, the circuits underlying behavior must evolve to match the animal’s needs. Crucially, what makes a nervous system capable of this at both scales remains an open question.
We study foraging behavior in nematodes to investigate these questions. Specifically, we use a grazing bacteriovore, the model nematode C. elegans, alongside an omnivorous species, P. pacificus that can prey on other nematodes. Despite their large large evolutionary divergence of over 100 My, the coarse structure of the nervous system remains sufficiently similar, allowing us to compare which structural and which neuromodulatory changes contribute to the behavioral divergence. We could recently show that changes in noradrenergic signaling underlie the evolution of predatory aggression, demonstrating that flexibility in the extrasynaptic modulatory signaling can be a powerful way to adapt and evolve novel behaviors. Theoretical modeling further supports this insight by showing that a biophysically inspired model of neuromodulation generates more robust and diverse states than models without neuromodulation. Building on this, we now investigate how coordinated changes in both synaptic and neuromodulatory signaling together shape the evolvability of behavior using behavioral assays, whole-brain functional imaging and computational models.