text | "China Science News" reporter Hu Minqi
Snakes are important and representative ectothermic vertebrates. Due to their low metabolism, they cannot produce enough heat to maintain a constant body temperature. They usually need to use external temperatures to increase their body temperature.
There is a unique snake in our country, which can adapt to the high and cold Qinghai-Tibet Plateau , and has settled on the plateau at an altitude of 3700 to 4850 meters, becoming one of the snakes with the highest distribution in the world.
The reason why they become the "alternatives" of the family is because they have a very special survival strategy and survive by "bathing" in hot springs.
Researchers from the Chengdu Institute of Biology, Chinese Academy of Sciences, have revealed the mystery of the hot spring adaptation of this special species, the Tibetan hot spring snake. Relevant results were recently published in "Innovation".
Tibetan hot spring snake. Photo by Guo Junfeng
The only snake that uses geothermal resources to survive
Scientists have discovered three kinds of hot spring snakes in my country, namely the Tibetan hot spring snake, the Sichuan hot spring snake and the Shangri-La hot spring snake. They are endemic species to the Qinghai-Tibet Plateau and are the only snakes that use geothermal resources to survive.
Among them, the Tibetan hot spring snake is a species endemic to Tibet.
The hot spring snake species gradually differentiated and formed about 28 million years ago, when the Tibetan Plateau was in a relatively early period of uplift.
Today, Tibetan hot spring snakes are mainly distributed in areas rich in geothermal resources in the middle and lower reaches of the Yarlung Zangbo River, including Lhasa, Shannan, Shigatse, Nyingchi, and other places.
"The species of the genus Hot Spring Snake belong to the family Snail Snake. Its closely related groups, except for the Ningshan Linear Snake distributed in my country, are currently only distributed in the Americas, and mainly in tropical America. Their living environments are very different." Paper Communication Li Jiatang, the author of and a researcher at the Chengdu Institute of Biology, Chinese Academy of Sciences, said.
However, the reason why Tibetan hot spring snakes can survive in the high-cold Qinghai-Tibet Plateau is not because they are really "freeze-resistant", but because they have a strong ability to find heat sources.
The Tibetan Plateau was formed due to the collision of the Indian Plate and the Eurasian Plate. This violent surface movement not only formed fault zones, but also brought countless geothermal resources, such as hot springs, to the plateau.
The Yangbajing , Yangyi, Nagqu Town and other places in Lhasa, Tibet, have very rich hot spring resources.
Hot springs bring heat from the center of the earth directly to the surface, so the surface and soil temperatures near the hot springs are higher than elsewhere.
"In fact, Tibetan hot spring snakes will not really 'soak' in the hot springs for a long time. Instead, they use the geothermal heat around the hot springs to increase their body temperature and resist the severe cold." Li Jiatang told " China Science Journal " that the warmer areas around the hot springs Habitats such as rock piles and meadows are suitable for their survival.
Sometimes, after raising their own body temperature, they will enter cold water such as streams, rivers or still ponds near hot springs, and prey on alpine frogs , plateau loaches, heterodont Schizothorax, etc.
Mutation of star gene TRPA1
In the long evolutionary history, how did the Tibetan hot spring snake successfully adapt to this unique natural environment? In order to answer this question, Li Jiatang's team conducted a detailed multi-dimensional integrated study on hot spring snakes in the Yangbajing area of Tibet.
They first conducted a thermotaxis behavior experiment. The results found that compared to corn snakes and Mengla blunt-headed snakes, Tibetan hot spring snakes can locate high-temperature areas faster and show a strong preference for high-temperature areas.
Therefore, researchers believe that Tibetan hot spring snakes have an efficient temperature sensing system, which enhances their ability to detect warm environments under cold stimulation.
Scientists have found evidence of the molecular biology behind this ability.
Researchers found through comparative genomic analysis that genes related to the temperature sensing and regulatory abilities of Tibetan hot spring snakes have undergone evolutionary changes, including multiple temperature-related transient receptor potential (TRP) ion channels.
For example, TRPV3, which is related to the sense of temperature, has undergone rapid evolution, and TRPM8, which is related to the sense of cold, shows rapid evolution shared with other plateau species.
"The most important thing is that we found a unique mutation in the star gene - TRPA1 in Tibetan hot spring snakes." Li Jiatang said.
David Julius, winner of the 2021 Nobel Prize in Physiology or Medicine,’s research on TRPV1 and its family has opened up human exploration of the temperature sensing mechanism.
TRPA1 is a transient receptor potential ion channel, which is related to temperature sensing, pain, itching, etc.
In reptiles , TRPA1 will participate in the thermal detection of some snakes, including infrared detection behavior.
Li Jiatang explained that in infrared snakes with lip pit/cheek pit structures, this gene is one of the important molecular elements for them to sense infrared heat sources.
Infrared Snakes sense infrared mainly through unique mutations of TRPA1, which changes their response threshold to temperature.
In this study, scientists identified that TRPA1 contains three non-synonymous mutations unique to hot spring snakes. "But unlike infrared snakes, changes in these three sites do not lead to changes in the temperature response threshold of TRPA1, but enhance the thermal sensitivity and heat-induced opening of the ion channel, which may help "Hot spring snakes respond quickly to warm environments. At the same time, the study suggests that hot spring snakes and infrared snakes adopt two different temperature sensing strategies," Li Jiatang said.
After long-term adaptation, the Tibetan hot spring snake has evolved an ingenious survival strategy of relying on geothermal resources to provide heat energy.
Li Jiatang also called for protecting the local geothermal resources in Tibet to protect the natural sanctuary of hot spring snakes.
Resistance to hypoxia and strong ultraviolet radiation
In addition to being highly sensitive to heat sources, Tibetan hot spring snakes also have special abilities in resisting the extreme living environment of hypoxia and strong ultraviolet radiation.
Previously, Li Jiatang's team published results in the Proceedings of the National Academy of Sciences of the United States. By sequencing the entire genome of the hot spring snake , they discovered 27 substitutions of amino acids.
Among them, they found that the mutant form of the FEN1 gene related to DNA repair is more stable under ultraviolet irradiation than the genotype of low-altitude species.
This mutation helps the hot spring snake resist ultraviolet radiation in high-altitude environments.
In addition, the EPAS1 gene is considered to be an important gene in the hypoxia-induced regulatory pathway.
Scientists have discovered mutations in this gene in the Tibetan population and mammals on the Qinghai-Tibet Plateau.
Li Jiatang's team discovered a mutation in the EPAS1 gene in hot spring snakes, which weakens its ability to regulate the expression of the downstream gene erythropoietin , resulting in a lower hemoglobin concentration of in hot spring snakes .
This is also an important reason why hot spring snakes adapt to low-oxygen conditions at high altitudes.
Li Jiatang said that extreme plateau environments may cause severe altitude sickness in people entering the plateau, and even cause altitude sickness. Research on the genetic mechanisms of plateau animals in extreme environments can help prevent and treat altitude diseases in humans.
related paper information:
https://doi.org/10.1016/j.xinn.2022.100295
