Scientists have discovered that clownfish decrease their body size in response to ocean warming. This is a survival strategy that allows them to optimize their energy consumption amid intense ocean heatwaves.
The phenomenon was observed in Papua New Guinea, where some orange-striped fish slimmed down during a heatwave, increasing their chances of survival.
Impact of climate change on coral reefs
Submarine heatwaves are becoming more frequent and intense, causing the bleaching of sea anemones, the natural habitat of clownfish.
The study, published in Science Advances, monitored 134 fish in Kimbe Bay during the 2023 heatwave, revealing that 101 individuals reduced their length in response to thermal stress.
A biological mechanism still under study
Scientists have not yet determined how clownfish shrink, although one hypothesis suggests they may reabsorb their own bone matter.
By decreasing their size, fish require less food, helping them conserve energy in extreme conditions.
Moreover, some breeding pairs synchronized their shrinking, maintaining the social hierarchy where females are larger than males.
Similar adaptations in other species
While this phenomenon had not been observed before in reef fish, other species also reduce their size in response to environmental stress, such as:
- Marine iguanas, which shrink during El Niño events in the Galapagos.
A reversible shrinking process
Despite the impact of heatwaves, researchers found that the size reduction was temporary.
According to Melissa Versteeg from the University of Newcastle, clownfish can recover and regrow when water conditions become less stressful.
This finding reinforces the importance of biological flexibility in combating the effects of global warming in the oceans.
