In the animal kingdom, there are various grand examples of species that make sense of their world by expertly deciphering even weak indicators from their environment.
An eagle hovering above the bottom spies a river fish down under, about to swallow a bug; a hungry black bear smells a morsel of meals two miles away in a dense thicket; a duck-billed platypus, swimming in a freshwater creek, closes its eyes and detects the electrical impulses of a tasty tadpole close by.
Then there are the pit vipers.
Found in all kinds of habitats, from jungles to deserts, these snakes use highly effective infrared sensors positioned close to their nostrils to hunt for prey within the darkness by sensing even the tiniest temperature change — they usually accomplish this with thermally-sensitive ion channels which are solely on par with the sensory equipment of people.
How do pit vipers do that? A pair of Yale physicists could have found the reply in a brand new mathematical mannequin, described in a brand new examine within the journal Proceedings of the National Academy of Sciences.
“To locate their prey, pit vipers need to detect milli-Kelvin changes in temperature with their sensory organ, requiring the whole organ to be 1,000 times more sensitive than their underlying molecular sensors,” stated Isabella Graf, a postdoctoral fellow in physics in Yale’s Faculty of Arts and Sciences (FAS).
A Kelvin is the internationally accepted base unit for measuring temperature.
“What is more, these snakes sometimes live in deserts where the ambient temperature changes dramatically between day and night,” Graf added. “How is it possible that milli-Kelvin changes in temperature can be robustly detected by vastly less-sensitive sensors in widely varying environments?”
Graf and Benjamin Machta, an assistant professor of physics at FAS and a member of the Yale Quantitative Biology Institute, say the reason could also be a organic mechanism that permits pit vipers to amplify small indicators and transmit them to their mind with excessive constancy.
For the examine, the researchers created a mathematical mannequin that makes use of ideas from statistical physics and data concept to know how the incoming temperature sign from a pit viper’s individual ion channels collectively impacts the neuronal response. Within the mathematical mannequin, there’s a “bifurcation” — some extent the place the neuronal response qualitatively modifications and the individual, less-sensitive temperature sensors exhibit a excessive diploma of cooperation.
“Near this bifurcation point, we show that the snake’s brain can get almost as much information about temperature as if it could read out the measurement from each individual sensor and then average them together perfectly to get one, optimally accurate measurement,” Machta stated.
This is how a pit viper finds its dinner at midnight.
The new examine additionally accounts for the best way pit vipers keep their thermal sensitivity amid sweeping shifts in temperature between day and evening. The researchers stated their mathematical mannequin features a “feedback” function that mechanically protects the general sensitivity of the system all through temperature swings.
Graf and Machta stated their new mannequin could have functions past the nocturnal wanderings of the pit viper.
“Similar feedback and design principles might be found in other sensory systems which also need to detect tiny signals in a varying environment,” Graf stated.
The analysis was supported by the National Institutes of Health, a Simons Investigator award, and the German Research Foundation.
