Quantifying the Neural and Behavioral Correlates of Repeated Social Competition in the Fighting Fish Betta splendens

Abstract

The fighting fish Betta splendens, long studied for their aggressive territorial competitions, has the potential to be a tractable and relevant model for studying the intersection of cognitive ecology and social neuroscience. Yet, few studies have comprehensively assessed Betta behavior across both social and nonsocial contexts. Furthermore, the present study is the first to quantify the expression of phosphorylated ribosomal protein S6 (PS6), a proxy for neural response, in the Betta telencephalon. Here, we assessed male Betta behavior across a suite of tasks and found that response to a mirror, but not neophilia (a novel object) nor anxiety (scototaxis), predicted behavior in a social competition. To then explore the cognitive aspects of social competition, we exposed Betta to either a familiar or novel opponent and compared their competitive behavior as well as their neural responses in the teleost homologs of the hippocampus, basolateral amygdala, and lateral septum. We did not detect any differences between familiar-exposed and novel-exposed individuals, but by implementing the first use of a habituation–dishabituation competition design in a study of Betta, we were able to observe remarkable consistency in competitive outcomes across repeated exposures. Taken together, the present study lays the groundwork for expanding the use of Betta to explore integrative and multidimensional questions of social cognition.

Coordination and persistence of aggressive visual communication in Siamese fighting fish

“…To that end, we began by performing a brain-wide screen for neurons that were active when fish were engaged in an aggressive display ( Fig 6A,B and SFig 7 ). We used phosphorylation of the ribosomal S6 protein (pS6) as a proxy for neuronal activity during display 31,32 . Four out of the 28 brain regions assessed had a significant (p<0.05) increase in the number of pS6+ neurons in displaying animals compared to unexposed controls ( SFig 7 ).…”