The determinants of aggression in male Siamese fighting fish,Betta splendens

Abstract

1Siamese fighting fish, Betta splendens, have been extensively studied due to their aggression 2 and stereotypical displays. Many studies have focused on their characteristic opercular 3 flaring, while the less aggressive and less energetically costly lateral display have been 4 comparatively understudied. Many factors have been shown to influence aggression in 5Bettas, notably body length and the personality trait of boldness, however, the role that colour 6 plays in determining an individual's aggressiveness is much less clear. The role of colour has 7 only been briefly studied, and based on human interpretations of colour, i.e. limited to what 8 the receivers' eyes and sensory systems actually can process and discriminate, with results 9 suggesting blue males are more aggressive than red males. Using male-male interactions, 10 measuring opercular flaring and lateral display we found that colour and personality do play a 11 role in determining the degree of aggressiveness in Betta splendens. Blue-finned males were 12 more aggressive, performing longer lateral displays more frequently. Blue fins are a 13 phenotype observed in wild type males and is likely selected for to allow visual cues to travel 14 through the murky water they inhabit. Body mass was positively correlated with lateral 15 display frequency, and opercular flare frequency and duration. Finally, neophobic individuals 16 -individuals that were less willing to approach a novel object -were more aggressive, 17 performing significantly more lateral displays. This indicates that personality may impact 18 fighting strategy, with males either choosing to end conflicts quickly with more aggressive 19 displays or to outlast their opponent with less energetically costly displays. 20 21

The ornamental fighting fish is the next model organism for genetic studies

“…The frequency and duration of lateral displays, as well as opercular flares, were all positively linked with body mass 34 . Finally, neophobic (i.e., unfamiliar) males were more aggressive and produced many more lateral displays than non‐phobic males, who were less inclined to approach a novel object 52 . This suggests that personality traits may influence fighting tactics 52 .…”

“…34 Finally, neophobic (i.e., unfamiliar) males were more aggressive and produced many more lateral displays than non-phobic males, who were less inclined to approach a novel object. 52 This suggests that personality traits may influence fighting tactics. 52 Long-term selection for fighting winners suggests that selection favoured high-frequency and metabolically demanding aggressive displays in males.…”

“…52 This suggests that personality traits may influence fighting tactics. 52 Long-term selection for fighting winners suggests that selection favoured high-frequency and metabolically demanding aggressive displays in males. This selection also increased female aggression, opening up many testable hypotheses about the ultimate and proximate mechanisms of male and female aggression in B. splendens.…”