Study says cold-blooded animals grow larger, not smaller, in warmer waters Premium
The Hindu
Scientists expected cold-blooded animals would grow to have smaller bodies as adults. This may not be true, according to a new study of Eurasian perch over 24 years.
Scientists have called into question an idea that the bodies of cold-blooded marine animals, such as fish, will shrink in a warming world.
A study published last week said that aquatic animals such as fish would actually grow larger due to warm water pollution, i.e. water heated by warm pollutants.
As the planet warms, scientists had expected that cold-blooded animals, or ectotherms, would grow faster at a younger age but reach smaller body sizes as adults. They had observed this pattern in small-scale studies, including in natural settings.
The new study, published in the journal eLife, was conducted by researchers from the Swedish University of Agricultural Sciences, Uppsala. They studied samples of fish called Eurasian perch ( Perca fluviatilis) collected over 24 years, to investigate the effects of warming on the ‘body sizes’ of ectotherms.
These fish were taken from an enclosed bay into which a nuclear power plant nearby discharged water. This water heated the bay by 5-10° C over its surroundings.
They collated older data to estimate the ‘normal’ death rates, population size, and distribution for this fish, at various ages. Then they compared this to the corresponding data for perch from the bay as well as perch from a water-body nearby that wasn’t being heated by nuclear discharge. Finally, they combined this with knowledge of the fishes’ sizes at different ages.
According to the paper, the researchers studied only female fish because male and female perch usually have different body sizes, making direct comparisons harder.
