Scientists reveal how snakes 'see' at night

March 15, 2010 by Marlowe Hood
Scientists revealed Sunday for the first time how some snakes can detect the faint body heat exuded by a mouse a metre (three feet) away with enough precision and speed to hunt in the dark.

Scientists revealed Sunday for the first time how some snakes can detect the faint body heat exuded by a mouse a metre (three feet) away with enough precision and speed to hunt in the dark.

It has been known for decades that rattlesnakes, boas and pythons have so-called pit organs between the eye and the nostril that can sense even tiny amounts of infrared radiation -- heat -- in their surroundings.

Among pit vipers, the western diamondback rattlesnake, native to northern Mexico and southwestern United States, is in a class of its own, its heat-seeking ability up to 10 times keener than any of its cousins.

Even with tiny patches covering its eyes, the has shown the ability to track and kill prey blindfolded.

But exactly how these reptiles detect and convert infrared signals into has remained a mystery, and the subject of sharp debate.

One candidate was the photochemical process underlying vision, whereby the eye sees -- visible light for humans -- in the form of photons that activate , which in turn convert the energy into a biochemical signal to the brain.

Some fish, for example, can see into the of the .

But David Julius, a molecular biologist at the University of California in San Francisco, demonstrated in laboratory experiments that a different neurological pathway was at work for the serpentine "sixth sense."

"In this case, the is actually detected inside the pit organ as heat," Julius said in a phone interview. "We found the molecule responsible."

A very thin membrane inside the pit organ -- essentially a hollow, bony cavity -- warms up as the radiation enters through an opening in the skin, he explained.

Because the membrane is in a hollow space, it is exquisitely sensitive to changes in temperature.

"The heated tissue then imparts a signal to to activate the receptors we have identified," known as TRPA1 channels.

The neurochemical pathway involved suggests that snakes feel heat rather than see it.

"The molecule we found belongs to a family of receptors related to pain pathways in mammals," Julius said.

In humans, the equivalent mechanism is called the "wasabi receptor" because it allows our sensory nervous system to detect irritants -- such as the Japanese condiment -- that belong to the mustard family.

It is not, however, activated by heat.

The discovery, published in Nature, may also shed light on how snakes, which have been slithering across the planet for more than 100 million years, evolved.

"Studying change in sensory molecules is an interesting way to look at evolution because as animals inhabit different niches, smell and taste different things, hunt different animals, their sensory systems have to adapt," Julius said.

The findings also suggest that the forces of natural selection yielded the same remarkable heat-seeking mechanism in reptiles on separate occasions.

Unlike boas and pythons, which also have pit organs, vipers -- including rattlesnakes -- are relatively recent arrivals, in evolutionary terms, and thus must have developed the same capacity independently.

"It is amazing to think that random mutation could have come up with the same kind of solution more than once," Julius said.

Explore further: Researchers discover paradox about general anesthesia: It can increase post-surgical pain

Related Stories

Squirrels use snake scent

December 19, 2007

California ground squirrels and rock squirrels chew up rattlesnake skin and smear it on their fur to mask their scent from predators, according to a new study by researchers at UC Davis.

Heat halts pain inside the body

July 5, 2006

The old wives' tale that heat relieves abdominal pain, such as colic or menstrual pain, has been scientifically proven by a UCL (University College London) scientist, who will present the findings today at the Physiological ...

Burmese pythons slithering their way north?

June 24, 2009

(AP) -- One by one, seven slithering Burmese pythons were dumped into a snake pit surrounded by 400 feet of reinforced fence at the Savannah River Ecology Lab in South Carolina.

Recommended for you

Knowledge gap on the origin of sex

May 26, 2017

There are significant gaps in our knowledge on the evolution of sex, according to a research review on sex chromosomes from Lund University in Sweden. Even after more than a century of study, researchers do not know enough ...

The high cost of communication among social bees

May 26, 2017

(Phys.org)—Eusocial insects are predominantly dependent on chemosensory communication to coordinate social organization and define group membership. As the social complexity of a species increases, individual members require ...

Darwin was right: Females prefer sex with good listeners

May 26, 2017

Almost 150 years after Charles Darwin first proposed a little-known prediction from his theory of sexual selection, researchers have found that male moths with larger antennae are better at detecting female signals.

Why communication is vital—even among plants and funghi

May 26, 2017

Plant scientists at the University of Cambridge have found a plant protein indispensable for communication early in the formation of symbiosis - the mutually beneficial relationship between plants and fungi. Symbiosis significantly ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.