Sunday, September 26

Fish are altruistic or selfish depending on the context

Fish are altruistic or selfish depending on the context

Fish are altruistic or selfish depending on the context

Researchers at the University of Osaka in Japan have discovered that fish can develop specific social behaviors according to context and their own convenience: they can be altruistic and cooperative, as well as selfish and antisocial. Now, scientists will seek to discover how the minds of these fish evolved to produce complex social behaviors.

Under pressure to take food solely for themselves or share it with others, male convict cichlid fish reacted differently depending on the situation. Members of the Cichlidae family, this species of fish is characterized by its territorial and aggressive behavior during spawning, protecting its space from any possible intruder.

In the framework of research carried out by Japanese scientists, the fish chose the altruistic and prosocial option when they shared space with other known fish or potential mates. Instead, they chose to be selfish and not share food when living with females who already had a partner or with other males who could be rivals.

According to a Press release, the researchers obtained experimental evidence about these behaviors in the fish: they distinguish between reproductive females, unknown females and rival males, adjusting their actions to provide food to both them and the females or avoid giving food to competing males. Is there a brain evolution unknown in fish until today, taking into account this kind of behavior?

Unknown behaviors

During the experiment, the scientists studied the reactions of a male convict cichlid when receiving food. In the first place, they introduced him to another male fish with whom he had shared breeding experiences. On that occasion, he chose the prosocial option without hesitation and shared the food with his partner.

However, when the fish was placed with other male specimens that it did not know and could be rivals, it did not share its food. To delve into these types of reactions, the researchers later mixed it with females. Some were breeders and potential mates, while others already had a mate.

Again, the fish reacted according to its convenience: it shared its food with the unmated females, but not with those who were already “engaged.” As the scientists establish in the conclusions of their study, recently published in the journal Nature Communications, these results are identical to those recorded in similar experiments with primates.

Brain evolution

For Dr. Shun Satoh, one of the directors of the research, “it is the first time that this type of selfish or altruistic attitudes have been observed in fish. No one would have ever expected such sophisticated and complex social behavior from such a small fish, “he said.

Now, the researchers will develop new behavioral experiments seeking to clarify whether these fish really have an evolved psychosocial structure and what are the real motivations for their reactions. Ultimately, they will try to discover how the brain evolution took place that made it possible to produce this kind of behavior.

The hypotheses are varied and include different scenarios, including the possibility of the existence of a hitherto unexplored kind of union between fish, primates and humans throughout the history of evolution, which would connect us based on these cooperative or selfish behaviors. An incognito that opens and that perhaps will be able to be answered in future investigations.


Prosocial and antisocial choices in a monogamous cichlid with biparental care. Shun Satoh, Redouan Bshary, Momoko Shibasaki, Seishiro Inaba, Shumpei Sogawa, Takashi Hotta, Satoshi Awata and Masanori Kohda. Nature Communications (2021). DOI:


The convict cichlid fish used during the experiments. He demonstrated prosocial or antisocial behaviors according to different situations and contexts. Credit: Shun Satoh, Masanori Kohda.

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