Warm blooded lizards that switch on heat at will

One of the most unique organisms amongst the reptile species is the warm blooded lizard, Tegu. These lizards have the capability of heating themselves 10 degree Celsius more than their surrounding temperature.

Tegu usually switch on their unique heating mechanism only at a certain time of the year. This discovery has given rise to a controversy pertaining to the body temperature of dinosaurs, whether they were warm blooded or cold blooded or something in between like the lizards. Reptiles, amphibians and fish usually absorb heat from their surroundings, unlike mammals and birds which can heat themselves up.

Glenn Tattersall of Brock University in Canada who co-led the research along with Cleo Leite at the Federal University of Sao Carlos in Brazil says that “It may also provide a clue to how warm-bloodedness, or endothermy, first evolved.”

Glenn and his team studied the Argentinian black and white Tegu, which are 60-90cm long and found mostly across South America. These lizards were further spotted in Florida where they were pilfering eggs from their fellow reptiles. During this intensive study, it was seen that the Tegu cooled down its body temperature as the sun set, reaching a temperature similar to its burrow.

The months of September-December are the reproductive time for the lizards and it was seen that their heart rates and breathing spiked up and their temperatures reached 10 degrees higher than that of their burrows. This phenomenon was not only seen in the females, but the males as well. The discovery was so unexpected that the scientists took a further three years to confirm it, said Tattersall.

“We would expect them to be as cold as they possibly could be at that time,” he said. The scientists went one step ahead and removed any access to sunshine or food, but yet the Tegu warmed itself up before dawn.

Opah, a warm blooded fish was reported to generate heat by flapping its fins by another group of researchers. These fishes usually used their swim muscles to heat up their heart and brain which helps them increase their metabolic function in deep cold waters, allowing them to compete with other cold water species. Other reptiles like female pythons, shiver to heat their eggs. But in the case of Tegu, how this heat generation happens is still unknown. Glenn believes that there could be a possibility that the lizard secretes a hormone that causes increased hyperactivity or concentration in the tissues, possibly those of the liver, heart or muscles which produces heat as a result.

Evolution of the regulation of body temperature by means of metabolism, also called as endothermy is another mystery because it requires so much extra energy and time.

This work could explain the rise of the endothermal phenomenon and the body temperature associated with dinosaurs. At the same time a more detailed study needs to be carried out for the same.

Source: New Scientist.

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