MH
12,03,08, 03:50
http://www.timesonline.co.uk/multimedia/archive/00301/newt-385_301255a.jpg
It may be one of the most toxic amphibians, but a rough skinned newt has little chance against this garter snake
From The Times
March 11, 2008
Mark Henderson, Science Editor
http://www.timesonline.co.uk/tol/news/environment/article3525429.ece?token=null&offset=0
An evolutionary arms race between a species of North American snake and the newts on which they prey has been decisively won by the reptiles, in a remarkable example of natural selection in action.
Though rough-skinned newts ward off predators with a toxin so deadly that a single animal can make enough to kill a roomful of people, some garter snakes have developed total resistance that allows them to eat the amphibians with impunity.
This extreme resistance has been caused by a mutation that has altered just a single DNA letter of the snakes’ genomes, illustrating clearly how tiny and random genetic copying mistakes can drive evolution forward if they confer a major survival advantage.
Natural selection would have greatly favoured super-resistant snakes, which would have had more and more offspring until their progeny came to dominate entire local populations.
The skin of the rough-skinned newt secretes a poison called terodotoxin (TTX), which is lethal to most animals in very small quantities. The same poison is also made by the puffer-fish, and is responsible for the infamous toxic qualities of the sushi delicacy fugu when it is not expertly prepared.
Some newts produce enough TTX to kill up to 20 people, or more than a thousand mice. “Some populations of these newts may very well represent the most toxic amphibians on the planet,” said Charles Hanifin, of Stanford University in California, who has led new research into their interaction with snakes.
Human deaths are rare, as the newts must be eaten for the poison to work. At least one death is known, of a 29-year-old American man who swallowed a rough-skinned newt for a dare. A second man survived eating five to win a bet, though he became too weak to walk before recovering.
On the West Coast of North America, the newts live alongside garter snakes, a non-venomous species that hunts insects, worms and small birds, rodents, amphibians and fish.
Over many generations, the snakes have evolved a resistance to the TTX poison, as those that were capable of eating newts without dying or being incapacitated had a major advantage, and consequently had more offspring.
The newts, however, struck back, evolving greater and greater toxicity in response to the snakes’ resistance. As partially resistant snakes ate more poisonous newts, they would have been killed or put off pursuing them.
Snakes, in turn, have evolved greater resistance, in what scientists often describe as an evolutionary arms race.
In the new study, published in the journal Public Library of Science Biology, Dr Hanifin has now examined this arms race in detail.
His team tested the toxicity of newts and the resistance of snakes in 28 locations. They found that most areas with the most toxic newts also had the most resistant snakes, as would be expected from this tit-for-tat pattern of natural selection.
In about a third of the sites, however, even the least resistant snake was able to eat the most toxic newt. “In these areas, I think the snakes have won,” Dr Hanifin said.
The victory has gone to the garter snakes because only a few genetic changes are needed to confer substantial resistance, while the genetic mutations needed to boost TTX production among newts are more complicated.
On top of that, there are natural limits to TTX synthesis among the newts that seem to have been reached in some places.
It is possible, however, that the garter snakes will eventually lose some of their resistance, bringing the newt toxins back into play again.
The most resistant snakes are also a little slower than the less resistant reptiles, which puts them at an evolutionary disadvantage.
In the areas where all the snakes can eat newts, the slightly less resistant ones will be favoured by natural selection, and should become more common over time.
Toxic table-toppers
— The poison in the puffer-fish is said to be about 1,000 times deadlier than cyanide. The fish is considered a delicacy, known as fugu, in Japanese cuisine and chefs must be specially trained to prepare it
— The skin of the adult golden poison frog, the deadliest of the poison dart frogs, has enough toxin to kill 100 adult humans
— The venom from one bite from the taipan snake could in theory kill 100 fully grown men, but there have been no known fatalities
— The Brazilian wandering spider’s venom is more potent than that of the black widow. Strangely, a side-effect of being bitten has led scientists to consider adapting the venom as a natural Viagra
It may be one of the most toxic amphibians, but a rough skinned newt has little chance against this garter snake
From The Times
March 11, 2008
Mark Henderson, Science Editor
http://www.timesonline.co.uk/tol/news/environment/article3525429.ece?token=null&offset=0
An evolutionary arms race between a species of North American snake and the newts on which they prey has been decisively won by the reptiles, in a remarkable example of natural selection in action.
Though rough-skinned newts ward off predators with a toxin so deadly that a single animal can make enough to kill a roomful of people, some garter snakes have developed total resistance that allows them to eat the amphibians with impunity.
This extreme resistance has been caused by a mutation that has altered just a single DNA letter of the snakes’ genomes, illustrating clearly how tiny and random genetic copying mistakes can drive evolution forward if they confer a major survival advantage.
Natural selection would have greatly favoured super-resistant snakes, which would have had more and more offspring until their progeny came to dominate entire local populations.
The skin of the rough-skinned newt secretes a poison called terodotoxin (TTX), which is lethal to most animals in very small quantities. The same poison is also made by the puffer-fish, and is responsible for the infamous toxic qualities of the sushi delicacy fugu when it is not expertly prepared.
Some newts produce enough TTX to kill up to 20 people, or more than a thousand mice. “Some populations of these newts may very well represent the most toxic amphibians on the planet,” said Charles Hanifin, of Stanford University in California, who has led new research into their interaction with snakes.
Human deaths are rare, as the newts must be eaten for the poison to work. At least one death is known, of a 29-year-old American man who swallowed a rough-skinned newt for a dare. A second man survived eating five to win a bet, though he became too weak to walk before recovering.
On the West Coast of North America, the newts live alongside garter snakes, a non-venomous species that hunts insects, worms and small birds, rodents, amphibians and fish.
Over many generations, the snakes have evolved a resistance to the TTX poison, as those that were capable of eating newts without dying or being incapacitated had a major advantage, and consequently had more offspring.
The newts, however, struck back, evolving greater and greater toxicity in response to the snakes’ resistance. As partially resistant snakes ate more poisonous newts, they would have been killed or put off pursuing them.
Snakes, in turn, have evolved greater resistance, in what scientists often describe as an evolutionary arms race.
In the new study, published in the journal Public Library of Science Biology, Dr Hanifin has now examined this arms race in detail.
His team tested the toxicity of newts and the resistance of snakes in 28 locations. They found that most areas with the most toxic newts also had the most resistant snakes, as would be expected from this tit-for-tat pattern of natural selection.
In about a third of the sites, however, even the least resistant snake was able to eat the most toxic newt. “In these areas, I think the snakes have won,” Dr Hanifin said.
The victory has gone to the garter snakes because only a few genetic changes are needed to confer substantial resistance, while the genetic mutations needed to boost TTX production among newts are more complicated.
On top of that, there are natural limits to TTX synthesis among the newts that seem to have been reached in some places.
It is possible, however, that the garter snakes will eventually lose some of their resistance, bringing the newt toxins back into play again.
The most resistant snakes are also a little slower than the less resistant reptiles, which puts them at an evolutionary disadvantage.
In the areas where all the snakes can eat newts, the slightly less resistant ones will be favoured by natural selection, and should become more common over time.
Toxic table-toppers
— The poison in the puffer-fish is said to be about 1,000 times deadlier than cyanide. The fish is considered a delicacy, known as fugu, in Japanese cuisine and chefs must be specially trained to prepare it
— The skin of the adult golden poison frog, the deadliest of the poison dart frogs, has enough toxin to kill 100 adult humans
— The venom from one bite from the taipan snake could in theory kill 100 fully grown men, but there have been no known fatalities
— The Brazilian wandering spider’s venom is more potent than that of the black widow. Strangely, a side-effect of being bitten has led scientists to consider adapting the venom as a natural Viagra