The colorful anemonefish–aka clownfish–that call the carnivorous and stingy anemones on coral reefs home have a happy and carefree reputation among humans. However, their real personalities aren’t always appropriate for a Pixar movie. They will very aggressively bully and defend their space from other anemonefish that they perceive as an enemy and not part of their colony. Some new research suggests that they can recognize fish that they don’t want around them based on the number of white bars on the intruding fish’s body. The findings are detailed in a study published February 1 in the Journal of Experimental Biology.
[Related: Baby anemonefish can rapidly change their genes to survive in the sea.]
There are 28 described species of anemonefish. They live in warmer waters in the Indian and Pacific Ocean. These fish are only about four inches long and have anywhere between zero and three white bars on their bodies. Scientists have observed the clownfish allowing other anemonefish species to visit their home. However, if a member of their own species that is not part of their colony enters their home, the largest fish–or alpha fish–will chase and bite at the intruder.
Counting bars
To determine how these fish can tell who they want in their clique (and who they don’t), a team at the Okinawa Institute of Science and Technology in Japan conducted two experiments with immature lab-raised common clownfish (Amphiprion ocellaris) that had never seen any other species. The team then recorded the fishes’ reactions to intruders of their own species and other anemonefish species–including Clarke’s anemonefish (A. clarkii), orange skunk clownfish (A. sandaracinos), and saddleback clownfish (A. polymnus).
In the first experiment, they placed different species of anemonefish that had different numbers of white bars in small cases inside a tank. They watched for how often and for how long the fish would stare at the case and…
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