The amazing ability of the fish from Finding Nemo to count stripes has been revealed

The study shows that the cute clownfish made famous by the cartoon Finding Nemo scare away species with the same stripes.

Unlike the star of the Disney film Finding Nemo, ordinary clownfish in real life do not tend to share their home with members of their own species, writes The Guardian.

Researchers say they figured out how the fish chase away intruders by counting the stranger’s vertical white markings.

According to previous research, sea anemones that house the common clownfish may also provide temporary shelter for other species – provided they have horizontal stripes or no stripes at all.

However, common clownfish do not tend to cohabitate with fish that have vertical markings similar to their own, and instead experiments have shown that they are more aggressive towards fish species painted with such patterns.

Now scientists have discovered that not only the presence of vertical stripes, but also their number helps the common clownfish recognize its fellow fish.

Dr Kina Hayashi from the Okinawa Institute of Science and Technology, first author of the study, said: “It is possible that there are other factors besides white vertical lines that are important for distinguishing the same species. But this experiment at least suggested that the number of white vertical lines is important for distinguishing between the same species and deciding whether to attack or not.”

In a paper published in the Journal of Experimental Biology, researchers from Japan describe how they took young common clownfish that had never seen another species and placed a small transparent box in their tanks. The box contained either a fish of the same species—an orange body with three vertical white stripes—or a different species of clownfish with different markings.

The results showed that common clownfish exhibited a greater amount and frequency of aggressive behavior towards members of their own species than towards the orange skunk clownfish, which has only a single white horizontal stripe on its back. However, no significant differences in behavior were observed in relation to other clownfish species, which all had one or more vertical stripes.

The team then exposed common clownfish to model fish that were colored orange and lacked one, two or three vertical white stripes.

The scientists found that the frequency of these groups’ aggressive behavior towards the model was much lower when they were painted without stripes, compared to the models with stripes.

However, based on the behavior of individual fish, the team found that the fish were more aggressive towards the model with three vertical stripes than the one with one stripe.

Hayashi notes that the results are interesting because the ecological role of the white stripe pattern in clownfish, also known as anemonefish, was not previously clear.

“This result supports the idea that anemonefish are able to distinguish between different numbers of white stripes, and differences in the number of white stripes help anemonefish differentiate between their own species,” she said.