Snakes cross poisonous newts in the evolutionary race

Although snakes don't know fugu - a delicious seafood made from blowfish that is known for its extremely toxic substance; But if a non-poisonous snake with a long stripe wanders to a sushi store, it won't hesitate to order a fugu feast.

This snake has evolved its resistance to blowfish poison - the poison tetrodotoxin (TTX) - by hunting rough-skinned newts that can also release this toxin. Meanwhile some newts are so toxic that TTX in their bodies can kill dozens of adults.

Why could such a small animal release such a large amount of poison? The answer lies right in the evolutionary relationship between newts and non-toxic striped snakes. Within the common territory of the two species, both newts and snakes are kept in the pursuit circle: the TTX-resistant snakes make natural selection to create increasingly toxic newts; In contrast, evolutionary newts require natural selection to enhance the poison resistance of snakes.

In an article published March 11 in Library of Science : Biology, Charles Hanifin, a postdoctoral researcher at the Hopkins Marine Research Center at Standford, wrote that in some areas, snakes has prevailed in the ' arms race ' to evolve in the relationship between predators and prey. Surprisingly, in some geographic areas snakes have developed the ability to resist TTX poison to a limit where newt toxins cannot catch up .

The most unique amphibian in the world

Some ' residents ' in newts can produce TTX toxins enough to kill thousands of rats or take 10 to 20 lives. According to Hanifin, this newt is more poisonous than the famous poisonous frog of South America.

Hanifin said: 'Some newts are particularly representative of the most unique amphibian species on our planet.'

There have been deaths due to newt's poison. The American Medical Association published an article about a 29-year-old man who died after swallowing an 8-inch-long newts when challenged. The newspaper also stated another case in Oregon state, the 26-year-old man struggled to survive after he swallowed 5 newts to win the bet. Soon after, he felt dizzy, gagging, and then exhausted he could not walk a step; Although he was eventually rescued by a doctor.

A snake Thamnophis sirtalis is eating tetrodotoxic Taricha granluosa newt . (Photo: Edmund D. Brodie III)

Without considering the above cases, newts rarely harm humans.You can safely hold the newts with your bare hands because its toxins are not absorbed through the skin. Only when eating newts is poison . According to Hanifin, the animal often releases a strong smell to warn animals and children not to eat it.

Get rid of the " arms race "

At first glance, the number of newts and snakes seems to be in balance. The most toxic newts coexist with the highest poison resistant snakes. Non-toxic newts are home to snakes that are not resistant to poison.

Data on Hanifin's long-striped snakes, including Edmund Brodie Jr. collected from Utah State University and Edmund Brodie III of the University of Virginia. They identified the TTX resistance of snakes by injecting toxins into the animal's body and then see how fast the snake could crawl.Although TTX poison cannot kill snakes, it makes animals slow for a certain period of time . Low poison resistant snakes move more slowly after injecting TTX, some are even temporarily paralyzed.

To learn more about the relationship between snakes and newts, Hanifin and his colleagues experimented with 383 sauces from different regions where the Brodie brothers conducted a test. TTX poison resistance of striped snake species. Newt finding sites stretch along the west coast from British Columbia (Canada's westernmost province) to central California (USA).

Hanifin found that striped snakes have taken the upper hand against newts. In one third of the study sites, the only newts can still be eaten by the lowest poison resistant snakes. This means that all snakes can hunt newts without taking into account their TTX resistance. Because of this, they also do not suffer from any evolutionary pressure in enhancing their resistance to poison.

Hanifin said: 'I think snakes have won the race at these survey sites'.

How can snakes achieve such high levels of TTX resistance, while newt's poison must be backward? According to Hanifin, it seems that there are many genes in the snake genome that are involved in this antitumor ability; means that TTX resistance in snakes evolves extremely fast and leaps and bounds. Besides, newts' genomes work according to another mechanism. Newt's toxicity increases in proportion to its size.

Moreover, newts are also limited by its own biological characteristics. They can only resist TTX but cannot be immune to it.Just injecting a few milligrams of TTX into the newt intestine can cause it to die , so it must keep toxins in the skin. The most toxic newts contain between 14 and 15 milligrams of TTX, while some striped snakes can resist up to 100 milligrams of TTX. In order to contain such a large amount of TTX in the body, the body structure of newts needs to ensure a ratio of 1 part toxic / 9 parts of skin. This is something that cannot be realized.

According to Hanifin, although snakes have won the race, its fortunes may not last forever. There is some evidence that TTX resistance also requires price. The higher the snake resistance, the slower its crawling rate compared to those with little or no toxicity. Assuming that the snake's super strong antitoxin does not benefit it, it is this ability that brings the price of evolution. The snake must eventually reduce its resistance to poison so that the ratio of toxins in the newts may be more dominant. Although Hanifin said the hypothesis sounds credible, it is still necessary to conduct many years of research to confirm the hypothesis.

Collect and conduct experiments with newts

Together with his father, who is a dermatologist, Hanifin studied a method to determine newt levels of toxins by using surgical pliers to remove the skin for a biopsy. Hanifin took a 0.5-centimeter-diameter circular piece of skin on the anesthetized newt, then rolled the skin sample to analyze the amount of toxin in it.

It is very difficult to get the correct numbers. Hanifin spent two months studying techniques from blowfish researchers in Japan. After resolving the procedure, Hanifin and his colleagues took 5 years to collect a sufficient number of newts for research.

Hanifin said, newts are quite easy to find.'They are very gentle. They are usually not uncomfortable when touched. If you look for them in ponds, they seem to be floating around you. '

The toxin of the saucer breeds them without having to hide from rubber boots researchers. Hanifin captured most of the newts by hand. He said he was not jealous of snakes when they had to chase the animals that crawled on grass and bushes.

In the process of collecting newts, Hanifin received the help of everyone in his lab, colleagues at Oregon State University, Oregon University, Washington, California researchers and scientists. Learn California Fish and Wildlife.

Hanifin said: 'A dozen people have contributed to this research. It is indeed a great support. '

Hanifin's future research direction includes learning more about human diseases by exploring the genome of poison-resistant snake stripes. TTX poison has prevented electronic signals from nerve cells by inhibiting the activity of sodium tubes. TTX-resistant snakes have altered sodium tubes that make them unrecognizable. In humans, defects in sodium tubes can cause many serious illnesses, including several forms of epilepsy. Biological knowledge of sodium tubes can help treat these diseases.