An ancient battle between snakes and their prey could be over 鈥� with the snake victorious. The outcome could have ominous implications for the battles playing out between humans and the microbes that infect us.
Garter snakes along the west coast of North America have evolved 鈥渟uper-immunity鈥� against a newt armed with a poison so deadly that a single animal can kill a dozen people. The poison has escalated in power as the snake 鈥� the newt鈥檚 main predator 鈥� has evolved resistance.
Charles Hanifin of , California, US, and colleagues measured the toxicity of 383 rough-skinned newts (newts of the genus ) at 28 sites from British Columbia to central California.
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The newts carry extremely high levels of tetrodotoxin (TTX) 鈥� the same deadly poison found in blowfish.
鈥淥unce for ounce, some of these populations are the most toxic amphibians on the planet,鈥� Hanifin says.
鈥楿ntouchable鈥� snakes
They compared this toxin data to the resistance found in (Thamnophis sirtalis) throughout the region.
In most locations, the snakes鈥� level of resistance closely matched newt toxicity. In such cases, the poison temporarily slows the snakes down but isn鈥檛 enough to kill them. This supports 鈥渁rms race鈥� theories explaining how toxicity and resistance co-evolve.
But in some areas where newt toxicity was relatively high, the poison had no measurable affect on snake mobility.
The team found that resistant snakes had a single genetic mutation on TTX receptor sites on their neural and muscle cells, which prevented the toxin from binding. It made snakes with this mutation 鈥渦ntouchable鈥�.
鈥淚t is pretty much biologically impossible for the newts to ever catch up,鈥� Hanifin says.
Microbe warning
While the snakes achieved this super-immunity from a single mutation, Hanifin says that increases in toxicity only occur in smaller incremental changes in a number of genes. And Hanifin thinks microbes infecting humans could also develop super-immunity.
鈥淭he rapid evolution of resistance in snakes doesn鈥檛 bode all that well [for humans],鈥� Hanifin says. 鈥淲hen you have relatively simple toxins or simple drugs you can get this rapid, extreme resistance 鈥� and it doesn鈥檛 take that long to happen.鈥�
However, Craig Benkman of the University of Wyoming cautions against extrapolating from snakes and newts to antibiotics and microbes.
鈥淚t might apply to these examples that they are alluding to, but it may not,鈥� he says, noting that there is great variation in the molecular pathways and number of genes controlling chemical receptors on microbes.
鈥淚f there are a lot of genes with small affect than this analogy won鈥檛 apply,鈥� Benkman adds.
Journal Reference:
Evolution 鈥� Learn more about the struggle to survive in our comprehensive special report.
