New study unifies major theories on what controls animal body size

What is it about?

Ecologists are a step closer to understanding what controls body size in cold blooded animals, identifying major differences between species that live in water and on land. The new research, conducted by ecologists at Queen Mary University of London and the University of Liverpool, compared existing data from across the world to identify major patterns in the sensitivity of body size to temperature and latitude. Cold blooded animals frequently grow to a smaller adult size in the warm than in the cold. Curiously, aquatic animals reduce their body size much more with warming than those on land. For the first time, these differences have been shown to closely match body size patterns seen across latitudes. Within single species, aquatic animals tend to get smaller towards the equator, whilst most animals on land show much weaker or even opposite patterns. For example, marine and freshwater crustaceans shrink by 3% for every 1°C increase in temperature on average, and increase in size by around 4% for every 1 degree latitude shift away from the equator. Crickets and grasshoppers, on the other hand, grow larger with warming, and reduce their size with distance from the equator. The findings, which focused on arthropods, including economically important species of insects and marine plankton, provide support for the idea that oxygen limitation in the warm is a major restriction on body size in water-living animals, but not land-dwellers, as oxygen availability is much lower in water than in air.

Featured Image

Why is it important?

Body size controls a multitude of biological rates and processes, and hence changes in animal size can have implications on, for example, the productivity of species and their ability to sustain higher predators. Changes in size with warming may have important implications on food webs and goods and services from the ecosystems we depend upon.