Agonistic Behaviors of The Anemonefish Amphiprion ocellaris Living with Their Host Anemones

¹ Sorbonne Paris Nord University, 99 av Jean Baptiste Clément, 93430 Villetaneuse, Paris, France
² Institute for Biotechnology and Environment, Nha Trang University, Nha Trang, Viet Nam

^* Corresponding author: thanhnth@ntu.edu.vn

Abstract

Agonistic behaviours, defined as an individual’s aggressive behavior towards a conspecific, facilitate a social ranking throughout the animal kingdom, particularly within anemonefish group. In this study, we investigated the agonistic behaviors of the specialist anemonefish Amphiprion ocellaris living with different host anemones. Juvenile fish were exposed to their natural and unnatural host anemones in laboratory, and their agonistic behaviors were assessed through the occurrence of bites, the occurrence of chases, and the time spent in chilling behavior. The fish exhibited a higher frequency of bites and spent more time in chilling behavior (p<0.01) when residing within their natural anemone host, Stichodactyla gigantea. In contrast, when living within S. haddoni, where survival was less assured, fish exhibited more chases (p<0.05), which were less likely to injure conspecifics. The fish also engaged more in biting behavior (p<0.001) once establishing symbiosis within the natural host S. gigantea. These results suggest that biting is important to the establishment of the social hierarchy, while the chasing behavior is crucial for maintaining the hierarchy across time, which is important for reproduction potential. These findings imply that by adjusting their agonistic behavior, coral reef fish could make a trade-off between survival and reproduction in unfavorable environmental conditions.