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School of Biological and Behavioural Sciences

Cold-blooded animals grow bigger in the warm on land, but smaller in warm water

Scientists studying arthropods, the group of cold-blooded animals that includes crabs and insects, have found that individuals within species living on land tend to grow to a larger size in the warm and nearer the equator, but that the reverse is true of species found in water.


The findings strongly support the idea that reduced oxygen availability in water causes aquatic animals to reduce their body size much more with warming than those on land.

The new research, which appears in Ecology Letters, gathered together existing global data to gain the best picture yet of how arthropod body sizes change with temperature and latitude, revealing a close match between the sensitivity of body size to temperature measured in the lab, and body size trends seen in nature.

This new information could be significant in analysing the impact of climate change on animal species, as changes in body size with warming could affect many aspects of an animal’s health, as well as alter the composition of ecologically and economically  important ecosystems.

Lead author of the research, Curtis Horne, said:

Increasing our understanding of what influences how big animals grow will mean we can start to make better predictions about how different groups of species will cope with climate change.

We see a really close match between lab experiments and patterns observed in nature, which suggests that the same factors are at play. It brings us a significant step closer to solving a problem that has long puzzled biologists.

The work was undertaken as a collaboration between Queen Mary University of London and the University of Liverpool.

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