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Biological Chemistry

Why don’t poison frogs poison themselves?

Researchers reveal protein mutations that protect these poisonous amphibians

by Emma Hiolski
February 9, 2018 | APPEARED IN VOLUME 96, ISSUE 7

Credit: C&EN/ACS Productions

Poison frogs have evolved to resist the deadly effects of the toxins they carry. But these changes come with a cost. Learn more about how these tiny, colorful critters keep themselves one step ahead of their poisons in the latest episode of Speaking of Chemistry.



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Ju feng (February 14, 2018 4:21 PM)
Good topic.
Craig A Perman (February 14, 2018 6:17 PM)
"Poison frogs have evolved to resist the deadly effects of the toxins they carry." Does this mean that before they evolved this resistance they died? If so, then there should not be any frogs. Seems like twisted logic.
Hernandez Maria Alcira (February 15, 2018 11:48 AM)
As the young scientist explained, the mutation involved a single aminoacid in a protein key for survival. Such "simple" mutations can happen in a relatively short span of time. Natural selection makes it possible for the frogs with ability to make such change to survive. Survival of the fittest. Yes, maybe a few generation died and the ones that remained were the ones with the survival trait...
Phil Hultin (February 15, 2018 11:49 AM)
The toxins originate in the insects that the frogs eat. Presumably, when the first frogs ate these bugs, most of them DID die, but those that had the mutation did not and thus the mutation spread.
Rebecca Tarvin (March 12, 2018 11:32 AM)
Before the frogs evolved the ability to sequester toxins, they were consuming these toxins in low quantities. So, resistance presumably evolved prior to sequestration, which would allow the frogs to manage consuming and sequestering toxins at first until higher amounts of resistance evolved. There may also be plastic responses to increased toxin exposure (for example, upregulation of detoxification enzymes) that also ameliorate the initial costs of exposure. Evolving toxic defenses is costly and does require other adaptations like resitance, but it has happened many times in many animals, not just the frogs.
Patrick Dansette (February 15, 2018 4:42 AM)
It would be nice not just to put a contributor name on the picture but to add a list of references of the major fact cited in this good review.
Otherwise you have to look in pubmed and take time to select the original or most important papers.
Hernandez Maria Alcira (February 15, 2018 11:52 AM)
Obviously your task to do if the topic motivates you. PubMed also tells you how many times the author was cited and you can always filter results by the impact factor of the scientific magazine.
Rebecca Tarvin (March 12, 2018 11:33 AM)
Here is the publication most of this information is from:
Walter J. Freeman (February 15, 2018 9:38 AM)
I loved the topic and the information. But may I suggest that you slow down your speech, Emma? A more measured pace would make this easier to follow as would leaving the structures on screen a bit longer.

Though I understood generally what you were saying, I did not get any feeling of why the particular poisons worked in the sense of structure-property relationships that is of more interest to a chemist.
Hernandez Maria Alcira (February 16, 2018 9:30 PM)
"Speaking of Chemistry" and "Pretty in poison" clearly state the purpose of this communication. It is a light, introductory presentation of an interesting topic that involves chemistry, selective toxicity, and natural selection. Even the receptors that mediate the response were mentioned. Discussing SAR is outside of the scope of this communication. I think Emma did a great job.
Bjarne Gabrielsen Ph.D. (February 17, 2018 9:08 PM)
I love the example of how "nature" has somehow just "evolved" these critical mutations at just the right places for many different creatures. To my simple but scientific mind, it sounds like some "intelligent designer" behind such a delicately balanced ecosystem. Keep up the great illustrations.
John Cross (February 21, 2018 5:17 PM)
Possession of these mutations allowed certain frog in the population of frogs to eat insects that they could not otherwise eat. That provided a selective advantage to those that could take advantage of this nutrition, while others without the mutation had to be more choosey and spend more time finding food.
Rebecca Tarvin (March 12, 2018 11:38 AM)
Epibatidine is a potent toxin and thus exerts strong levels of natural selection on organisms that are exposed to it. It is no wonder that they evolved resistance. As for why the same mutation evolved in the same place three separate times, there is constraint in how the protein functions that limits the sites at which replacements can appear without severely (i.e. lethally) compromising the protein's function. There is also the idea that convergent phenotypes in closely related animals are likely to have the same genetic basis while convergent phenotypes in distantly related organisms are likely to have a distinct genetic basis, given other evolutionary changes. In the grand scheme of things, these frogs are closely related (less than 20 million years), and thus it is not so surprising that they have the same changes. (Here is the citation for that idea:

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