Lizard Secretes Heat

Researchers confirm the unprecedented endothermic abilities of a South American reptile.

By Bob Grant | January 25, 2016

WIKIMEDIA, BJORN CHRISTIAN TORRISONThe Argentine black and white tegu (Salvator merianae) is unique among its reptilian kin, according to researchers who recently confirmed that the lizard can regulate its body temperature, in some seasons raising it a full 10°C above its surroundings. The tegu’s feat of endothermy is special among the typically ectothermic Class Reptilia—only a few other species are known to purposefully alter their body temperatures above that of the surrounding environment, and none achieve such a dramatic difference.

Researchers from Canada and Brazil reported last week (January 22) in Science Advances that tegu lizards behave like other reptiles for most of the year—sunning themselves to stay warm during cold periods and seeking shade to lower their body temps—but act more like endotherms, such as birds and mammals, during their mating season (September to December). In the coldest, early morning hours of that season, the tegu can produce heat sufficient to warm its body about 10°C above its surroundings. “We would expect them to be as cold as they possibly could be at that time,” study coauthor Glenn Tattersall of Brock University in Canada told New Scientist.

Although Tattersall and his colleagues could not pinpoint a physiological mechanism that allows the tegu to produce and sustain that body heat, they did note that the lizards’ breathing and heart rates increased as they warmed up.

The findings—along with similar research into the endothermic abilities of a fish, the opah—may hold clues as to how endothermy evolved. “The fully warm-blooded conditions of birds and mammals may have evolved gradually as their ancestors tinkered with their metabolic systems and went through a hybrid phase like this new lizard shows,” Stephen Brusatte, a palaeontologist at the University of Edinburgh in the U.K. who was not involved with the study, told New Scientist.

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Avatar of: v sitaramam

v sitaramam

Posts: 4

January 26, 2016

I tend to think that endothermy, homeothermy etc are rather romantic notion overstayed in biologial literature. If you fully section a vertebrate spinal cord at c7-c8, the sympathetic denervation rebders the animal poikilothermic. Some four decades ago I did Arrhenius kineticsof enzyme induction in vivo in rat livers by keeping these poikilothermic rats at various temperatures. Antibodies to nerve growth factor  were too expensive for the lab those days. 

There is really no constancy of body temperature but varies all the time and the limits only differ. A little extrastimulation of the symaptheric nervous system via mid brain together with a moderate vasoconsriction can shoot up the body temperature  very easily. Far less plausible is that the gut secrets into the body some pyrogens conveniently.

Since mechanisms can only play around metabolsim and control of heat dissipation, endothermy is a far less rewarding a thought than one presumes.

What is realy interesting in these animals is that inspite their grossly simple nervous sysetm interconnections, a simulable model of thermoregulation has not been achieved as far as I know. So much for systems biology!

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