Variable stress-responsiveness in wild type and domesticated fighting fish

Area of Science:

• Animal behavior
• Comparative physiology
• Stress endocrinology

Background:

• Betta splendens, commonly known as the Siamese fighting fish, exhibits distinct behavioral differences between wild-type and domesticated strains bred for fighting.
• Previous research indicates higher aggression in the fighter strain compared to the wild type under fight-simulating conditions.

Purpose of the Study:

• To compare the coping styles of wild-type and fighter strain Betta splendens when exposed to non-social stressors.
• To investigate whether the fighter strain displays a more proactive coping style, characterized by lower cortisol and higher sympathetic responses.

Main Methods:

• Utilized a combination of behavioral and physiological measures to assess stress responses in both strains.
• Developed a non-invasive assay for repeated measurement of water-borne cortisol levels.
• Estimated sympathetic activation via opercular beat rate and recorded behavioral immobility duration.
• Introduced non-social challenges: an unfamiliar environment and spatial confinement.

Main Results:

• Exposure to an unfamiliar environment increased cortisol in the wild type but not the fighter strain.
• Confinement elevated cortisol levels in both strains.
• Opercular beat rates decreased in both strains during later stages of confinement.
• The fighter strain, unlike the wild type, exhibited immobility from the onset of confinement.

Conclusions:

• The fighter strain of Betta splendens demonstrates a more proactive coping style, particularly in response to novel environments, compared to the wild type.
• Selective breeding for fighting may influence stress physiology and coping strategies in Betta splendens.
• These findings contribute to understanding the neuroendocrine and behavioral adaptations associated with domestication and aggression.