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New Research Suggests That Clownfish Aren’t As Nice As Nemo, And They Actually Use Counting To Differentiate Between Allies And Adversaries

Past studies have indicated that coral reef fish, clownfish included, evolve stripe patterns as a means of recognition in large groups. Yet, the focus of this research was to explore how anemonefish differentiate themselves from other species.

So, Dr. Hayashi nurtured a group of clownfish right from their egg stage, making sure they weren’t exposed to other anemonefish species. Then, when the clownfish were six months old, the researchers observed how they reacted to various species, such as Clarke’s anemonefish, saddleback clownfish, and orange skunk clownfish, in addition to their own kind.

This revealed that the common clownfish displayed significant aggression towards their own three-banded species, getting into confrontations as much as 80% of the time. Members of other species encountered varying levels of aggression. For instance, the orange skunk clownfish, which is recognizable by its single white stripe and lacking sidebars, was met with the least resistance.

On the other hand, the Clarke’s and saddleback clownfish, each adorned with two and three white bars, respectively, were subject to a moderate amount of harassment.

“Common clownfish attacked their own species most frequently,” said Dr. Hayashi.

Even though the researchers frequently witnessed their own kind being attacked, they were still curious about how clownfish could tell the difference between their own species and others.

To explore this, they conducted additional experiments, introducing young clownfish to various models that had different numbers of white stripes. The fish largely ignored a plain orange model, much like their response to the orange skunk clownfish.

Then, they showed some aggression towards a model with a single stripe but were more hostile towards the models with three stripes, suggesting they’re not keen on sharing their space with fish that look similar to them. The model with two stripes was also met with hostility.

According to Dr. Hayashi, the reluctance towards two-striped fish could be connected to their growth stages. Since typical clownfish first develop two stripes and later acquire a third, it’s possible they see two-striped fish as rivals.

“Anemonefish are interesting to study because of their unique, symbiotic relationship with sea anemones. But what this study shows is that there is much we don’t know about life in the marine ecosystems in general,” Dr. Hayashi concluded.

To read the study’s complete findings, which have since been published in the Journal of Experimental Biology, visit the link here.

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