Crocodile's blood bypasses lungs to boost digestion

Sydney, February 11 : Crocodiles and alligators' consume such a heavy meal in one sitting that they require diverting gas-rich blood away from their lungs into their stomachs to digest it, say US researchers.

C. G. Farmer, an assistant professor of biology at the University of Utah, says that a study of American alligators suggests that they can eat 23 per cent of their own mass at once. She believes that the finding is applicable to all crocodilians.

The researcher says that the study also appears to have solved the mystery as to why alligators and crocodiles often find a warm place to quietly recline after consuming a huge meal.

Farmer says that, though this behaviour of crocodilians seems quite sedate, an extraordinary activity remains active inside their body.

During the study, she and her colleagues focussed on the extra left aorta that crocodilians have on the side of their otherwise very mammal-like hearts.

Normally, blood pumped by the right side of the heart flows through the reptile's pulmonary artery into the lungs, where a transfer of carbon dioxide occurs. However, this blood is shunted to the stomach when a crocodile or alligator gorges, say the researchers.

The carbon dioxide then gets converted into gastric acid, a digestive juice, and bicarbonate, which in turn function as a kind of antacid for the reptile, they add.

Farmer says crocodilians produce 10 times more digestive juice than the highest rates measured in mammals. Without this, she says, the enormous quantity of food they eat would rot in their guts.

She says that if conditions are warm to support fluid flow in crocodilians, digestion can take 10 to 20 days, and mostly eliminate the possibility of rotten food.

James Hicks, a University of California at Irvine professor of ecology and evolutionary biology whose laboratory is studying crocodilian circulation, says that the two most common theories are that the process contributes "to the croc's capacity for extended, underwater dives" and that it helps with digestion.

"Dr Farmer's paper provides the first experimental test and supporting evidence for one of these hypotheses," ABC Online quoted him as telling Discovery News.

However impressive crocodilian digestion is, says Farmer, they just cannot stomach hair.

"They can't digest hair. The hair of their prey forms small pellets, and these are regurgitated," Farmer says.

ANI