A porcupine fish (Diodon hypertrix) is being cleaned by cleaner fishes (Labroides dimidiatus), near Bali, Indonesia Hans Gert Broeder/Alamy
While cleaning client fish, female cleaner fish can be sensitive to the needs of their partners. They may also have theory of mind. This concept is often linked to humans and other primates.
Labroides dimidiatus, cleaner wrasse, is a species of wrasse that works in pairs. They clean clients' fish by eating their skin parasites and dead skin cells. Although the wrasse prefer to eat the mucus from client fish, clients have the option to terminate the relationship and leave the cleaners without food.
When a male-female cleaner washes wrasse team works together, there is a lot at stake. One fish may cheat by trying to eat mucus, while the other fish is working with the client. This could leave both fish starving. Katherine McAuliffe, Boston College, Massachusetts, states that if a male cleaner fish learns his female partner is cheating, he may chase and even attempt to bite her.
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Continue reading: A fish species has passed the mirror test.
McAuliffe and her coworkers wondered if females could cheat on their male partners without their knowledge. We had reason to believe that cheating could be punished and females would gain from being able to get away with it, McAuliffe says.
In an experiment, the females were given the option of eating in transparent or opaque barriers. Their male partner had to eat in a separate tank that contained either a transparent partition or an opaque one. Researchers found that female cleaner fish are more likely to cheat if their male partners are not visible. Researchers also discovered that females who were paired with punitive males were more likely to cheat by hiding behind opaque barriers.
This suggests that cleaner wrasse may have developed cognitive abilities to solve their problems at a level with other animals like primates and corvids.
This is controversial because primates are able to do things that are not possible for other animals (especially fishes) according to Alex Jordan from the Max Planck Institute of Animal Behavior, Germany. This paper's greatest message is that humans cannot sit on the top of any ladder. Then there are primates, and then there's another.
Journal reference: Communications Biology, DOI: 10.1038/s42003-021-02584-2
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