For fish that can change sex, losing a big fight is actually the 'trauma' that flips the switch to make them transform.
March 20, 2026
Original Paper
Loser effects orchestrate dominance hierarchies in socially-controlled sex change
bioRxiv · 10.64898/2026.03.16.712238
The Takeaway
While sex change in fish is known to be socially controlled, this study shows that 'loser effects'—the increased likelihood of losing again after a single defeat—are the primary driver of dominance hierarchies. This behavioral feedback loop ultimately dictates which females will transition into males.
From the abstract
Socially-controlled sex changing fishes provide powerful model systems for investigating sexual development and phenotypic plasticity in both behavior and physiology. The remarkable sexual transformation these fishes undertake is strongly influenced by their position in dominance hierarchies. However, the behavioral mechanisms underlying hierarchical formation remain understudied, particularly among female groups. Here, we investigated the role of winner-loser effects among females in establishi