Evolutionary shift from fighting to foraging in blind cavefish through changes in the serotonin network

Area of Science:

• Neuroscience
• Evolutionary Biology
• Genetics

Background:

• Investigates the origins of adaptations in interfertile sighted surface fish and blind cavefish populations of Astyanax mexicanus.
• Focuses on the neural, genetic, and developmental underpinnings of aggressive behavior evolution.

Purpose of the Study:

• To compare aggressive behavior between surface and cave populations of Astyanax mexicanus.
• To identify the neural and genetic mechanisms controlling aggression and its evolutionary loss in cavefish.

Main Methods:

• Utilized an intruder-resident behavioral assay to quantitatively and qualitatively assess aggressiveness.
• Analyzed the role of serotonergic neurons and Sonic Hedgehog signaling in behavioral evolution.

Main Results:

• Surface fish exhibit genetically influenced aggressive behavior controlled by raphe serotonergic neurons, establishing dominance.
• Cavefish have lost aggressive/dominance behavior, displaying food-seeking actions instead.
• Cavefish food-seeking behavior is driven by hypothalamic serotonergic neurons, influenced by Sonic Hedgehog signaling.

Conclusions:

• Evolutionary adaptation to cave environments involved a behavioral shift in cavefish, modifying their serotonergic neuronal networks.
• Cavefish lost aggressive behavior, developing advantageous food-seeking behaviors for survival in darkness.
• Demonstrated a direct link between neuronal network development and adaptive behaviors controlled by these networks.