Poster abstracts
Poster number 64 submitted by Kaarthik Abhinav Balakrishnan
Thermoregulation in larval zebrafish is characterized by navigational modes that are represented in the brainstem
Kaarthik Abhinav Balakrishnan (Interdisciplinary Biophysics Graduate Program)
Abstract:
Ectotherms, such as zebrafish, lack physiological mechanisms to modulate their body temperature and need to regulate their internal temperature using behavioral mechanisms. This makes them an excellent model for investigating how ectotherms integrate external stimuli to generate behavioral responses. The larval zebrafish seeks out moderate temperatures by biasing individual movements away from temperature extremes. Their behavior is highly tractable, characterized by discrete swim bouts in which direction selection and modulation of swim speed occur. Previous research suggests that larval zebrafish raise their swim speeds in warmer water and execute larger turns to avoid hot temperatures. Our current work extends that observation to cold temperatures and proposes a parametric model to describe behavior as a function of temperature and context. We combined behavioral recording, modeling and functional calcium imaging in larval zebrafish to gain insight into how vertebrates seek out preferred temperatures through the interaction of two competing drives: the avoidance of hot and cold temperatures. A key insight was the characterization of behavior over longer timescales as strings of bouts that make up a trajectory. Using Markov models, we identified three distinct swim modes—reversal, persistent, and general—and quantified state transitions in response to temperature stimuli. This description shows a significant improvement over existing models of navigation based on individual bout parameters. Additionally, two-photon calcium imaging of the zebrafish medulla revealed neurons encoding hot and cold temperatures, forming a 'place code'-like representation of thermal stimuli. Our findings provide a foundational description of larval zebrafish thermoregulatory behavior, linking neural activity to navigational strategies that accurately predict observed behavior.
Keywords: Neural circuits, Thermoregulation, Behavior