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Selection for winners impacts the endocrine system in the Siamese fighting fish
1Institute of Science and Environment, University of Saint Joseph, Rua de Londres 16, Macao.
General and Comparative Endocrinology
|February 13, 2022
Summary
Aggression in Siamese fighting fish (Betta splendens) is linked to hormone levels. Fighter strains show lower cortisol and higher 11-ketotestosterone responses, suggesting selection impacts endocrine systems related to aggression.
Area of Science:
- Behavioral Endocrinology
- Animal Behavior
- Evolutionary Biology
Background:
- Siamese fighting fish (Betta splendens) males are selectively bred for aggression.
- Previous studies indicate fighter strains are more aggressive than wild-types.
- Selection for winning likely targeted aggression-related endocrine systems.
Purpose of the Study:
- Compare plasma levels of 11-ketotestosterone (KT) and cortisol (F) between fighter and wild-type Betta splendens strains.
- Investigate the hormonal basis of aggression differences.
- Determine the impact of selection on endocrine axes.
Main Methods:
- Measured plasma KT and F levels in F2 males of fighter and wild-type strains under laboratory conditions.
- Assessed hormonal responses to a mirror-induced aggressive challenge.
- Compared hormonal levels in socially housed versus isolated fish.
Main Results:
- Fighter males generally had lower cortisol (F) than wild-type males.
- No overall difference in 11-ketotestosterone (KT) between strains initially.
- Post-challenge, cortisol (F) increased significantly more in wild-type males; KT increased in both strains.
- Fighter males had higher post-challenge KT and lower F than wild-type males.
- Social isolation affected hormones differently: F decreased in wild-types, KT decreased in fighters.
Conclusions:
- Wild-type males showed increased androgens and corticosteroids during aggression.
- Fighter males exhibited a blunted cortisol response but increased 11-ketotestosterone.
- High androgens and low corticosteroids correlate with high aggression.
- Selection for winning appears to have a greater impact on the hypothalamus-pituitary-interrenal axis than the hypothalamus-pituitary-gonadal axis in Betta splendens.
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