Study offers insight into evolution of fish gills

London, January 14 (ANI): Biologists appear to be one step closer in solving the mystery behind the evolution of fish gills after researchers observed that regulating chemicals in their bodies may be a probable explanation.

Principal investigator Clarice Fu, a zoologist from the University of British Columbia in Canada, and her colleagues based their observation on the development of gills in rainbow trout larvae and measured the uptake of ions, which are charged chemical particles, such as sodium.

The team discovered as the larvae matured, their gills developed the ability to regulate the chemicals in their blood earlier than they began to take up oxygen.

"In freshwater fish, like rainbow trout, they tend to lose ions from their blood to the water, because the ion concentration in blood is greater than that of freshwater," the BBC quoted Clarice as saying.

She added: "When the gills are still immature, a significant portion of ion uptake occurs at the skin. As the fish get older and the gills mature, [this] can gradually shift to... the gills," said Ms Fu.

"We found that ion uptake shifted from the skin to the gills earlier than oxygen uptake. This led us to propose that the gills are needed for ion regulation earlier than they are needed for oxygen uptake."

Professor Rick Gonzalez, who studies the physiology of aquatic animals, the University of San Diego, tagged the study as a "very interesting first step" but added more research was needed to determine the mystery of why fish evolved gills.

He said: "Gills combine some of the functions of the lungs and kidneys in mammals, which leads to interesting interactions of function.

"The physical and chemical nature of the water can play an important role in their function. So how these all work together to get the various jobs done is very interesting and offers insight into how natural selection works."

The report was published in the Royal Society journal Proceedings B. (ANI)