The Preoptic Area and Dorsal Habenula Jointly Support Homeostatic Navigation in Larval Zebrafish

Animals must maintain physiological processes within an optimal temperature range despite changes in their environment. While the preoptic area of the hypothalamus (PoA) acts as a thermostat in mammals through autonomic and behavioral adaptations, its role in temperature regulation of animals lacking internal homeostatic mechanisms is not known. Through novel behavioral assays, wholebrain functional imaging and neural ablations, we show that larval zebrafish achieve thermoregulation through movement and a neural network connecting the PoA to brain areas enabling spatial navigation. PoA drives reorientation when thermal conditions are worsening and conveys this information for instructing future motor actions to the navigation-controlling habenula (Hb) - interpeduncular nucleus (IPN) circuit. These results suggest a conserved function of the PoA in thermoregulation acting through species- specific neural networks. We propose that homeostatic navigation arose from an ancient chemotaxis navigation circuit that was subsequently extended to serve in other sensory modalities.