Polymodal sensory perception drives settlement and metamorphosis of Ciona larvae

The Earth’s oceans brim with an incredible diversity of microscopic lifeforms, including motile planktonic larvae, whose survival critically depends on effective dispersal in the water column and subsequent exploration of the seafloor to identify a suitable settlement site. How their nervous systems mediate sensing of diverse multimodal cues remains enigmatic. Here, we uncover that the tunicate Ciona intestinalis larvae employ ectodermal sensory cells to sense various mechanical and chemical cues. Combining whole-brain imaging and chemogenetics, we demonstrate that stimuli encoded at the periphery are sufficient to drive global brain-state changes to promote or impede both larval attachment and metamorphosis behaviors. The ability of C. intestinalis larvae to leverage polymodal sensory perception to support information coding and chemotactile behaviors may explain how marine larvae make complex decisions despite streamlined nervous systems. [Display omitted] •Long- and short-range chemical cues influence larval attachment and metamorphosis•Ciona larvae use polymodal sensory cells to sense mechanical and chemical cues•Individual sensory neurons can encode stimulus-specific information•Brain dynamics act as a framework for stimulus-driven behavioral action choice Ciona is a marine chordate with a biphasic life cycle. Hoyer et al. identify a set of short- and long-range chemical cues that influence attachment and metamorphosis of Ciona larvae. These cues are detected by polymodal sensory cells, which encode the valence of the stimulus and drive brain-wide dynamics to elicit robust behavioral actions.