Clownfish, the orange and white fish famously featured in Disney’s Finding Nemo, may possess the ability to count up to three, according to new research.
A study conducted by Japan’s Okinawa Institute of Science and Technology reveals that clownfish exhibit selective aggression towards intruders based on the number of white bars they possess. The research indicates that clownfish are more aggressive towards those with three stripes, similar to their own markings.
Officially known as clown anemonefish (Amphiprion ocellaris), these species tend to cohabitate with various types of anemonefish but display territorial behavior towards other adults of their kind, employing aggressive actions such as chasing and biting.
In the initial phase of the study, individual clownfish were placed in separate tanks, with a flowerpot serving as a surrogate home base. The researchers observed the reactions of the clownfish when an ‘intruder’ fish, including Clark’s anemonefish (A. clarkii), Orange skunk clownfish (A. Sandaracinos), Saddleback clownfish (A. polymnus), and clown anemonefish, were introduced into the tank within a transparent water-filled box.
The study found that the clownfish exhibited more frequent aggression towards intruders with a greater number of white bars, particularly towards their own species.
Unable to physically engage with the intruder due to the transparent box, the clownfish employed alternative aggressive tactics such as rushing at the intruder or following it while facing it. The least aggression was directed towards the Orange skunk clownfish, a species lacking vertical white bars and featuring only one white stripe along its back.
Dr. Kina Hayashi, the author of the study, explained, “The frequency and duration of aggressive behaviors in clown anemonefish was highest toward fish with three bars like themselves.”
In the second stage of the study, 120 immature clownfish were placed in groups of three in tanks and given eight days to establish social relationships. These colorful creatures typically form small groups on a host anemone, comprising an alpha female, beta male, and several juveniles.
In each tank, researchers introduced a model – a clownfish puppet made from resin clay, adorned with a set of white bars ranging from 0 to 3 drawn using a marker. The clownfish responded to the model intruder in a similar pattern, displaying increased aggression towards models with three white bars and minimal aggression towards fish without vertical stripes.
The 28 species of anemonefish exhibit various colors such as black, red, orange, or yellow, patterned with a series of white stripes or bars ranging from 0 to 3.
The researchers argue that the findings, published in the Journal of Experimental Biology, suggest that clown anemonefish can distinguish between different types of fish by counting the number of white bars.
Source of the news: https://cosmosmagazine.com
