Scientists clear air on crocodiles

BRITISH and Japanese scientists reported recently that they had found the quirk of nature that lets crocodiles lurk underwater for hours and said this could someday be bred into humans.

Alligators, crocodiles and related reptiles have unique haemoglobin - the molecule in red blood cells that carries oxygen - which lets them stay underwater without breathing for long periods of time. It is different from the method used by porpoises, whales and other marine mammals.

Professor Kiyoshi Nagai of Britain's Medical Research Council's Laboratory of Molecular Biology and colleagues at Osaka University said they had created a cross between human and crocodile haemoglobin that had the same qualities.

They wrote in the science journal Nature that in the process, they had discovered exactly how crocodile haemoglobin works. When crocodiles hold their breath, bicarbonate ions in their blood attach themselves to the haemoglobin and cause it to release more oxygen into the blood.

By creating the crocodile-human haemoglobin, the researchers found the precise site on the molecule where this happens.

'In this case, crocodile haemoglobin has a superior property in delivering oxygen to hard-working tissue,' Professor Nagai said.