Cleaner wrasse (Labroides dimidiatus) are small fish found in coral reefs that provide a valuable service to other fish by removing parasites and dead tissue from their bodies. Despite the benefits that cleaner fish provide, they often face aggression from the fish they clean, which can be seen as a cost to the cleaner fish. However, a new study suggests that cleaner fish may actually benefit from this aggression, as it helps them to maintain their status as the dominant cleaner fish in their territory.

The study, published in the journal "Biology Letters," found that cleaner fish that were subjected to aggression from other fish were more likely to maintain their status as the dominant cleaner fish in their territory. This suggests that aggression may help cleaner fish to establish and maintain their dominance, which in turn allows them to access more food resources and reproduce more successfully.

The researchers believe that aggression may serve as a form of "payment" from the fish that are cleaned to the cleaner fish. By allowing the cleaner fish to remove parasites and dead tissue, the fish that are cleaned benefit from improved health and survival. In return, they may tolerate or even reward the cleaner fish with food or other resources.

The study's findings suggest that cleaner fish may not be as reluctant to provide their services as previously thought. Instead, they may be motivated by the benefits that they receive from their interactions with other fish, including the opportunity to maintain their status as the dominant cleaner fish in their territory.

This study provides new insights into the complex social interactions between cleaner fish and the fish that they clean. It suggests that cleaner fish may not be simply altruistic, but may instead be acting in their own self-interest when they provide their services.