Image Credit-CGtrader
Poison dart frogs, tiny, colorful frogs in the family Dendrobatidae that dwell in the rainforests of Central and South America, are among the most deadly animals on the planet. One frog can carry enough poison to kill ten adults. These frogs aren't born deadly; they pick up the dangerous toxin from insects and other arthropods they eat.
But, if this poison is so lethal, why don't the frogs die when they consume it?
The ability of these frogs to avoid autointoxication has long mystified scientists, according to Fayal Abderemane-Ali, a researcher at the University of California San Francisco's Cardiovascular Research Institute and the lead author of a new study published in the Journal of General Physiology that investigates the phenomenon.
The researchers looked into poison frogs from the genus Phyllobates that use a toxin called batrachotoxin, which disrupts sodium ion movement in and out of cells, one of the body's most fundamental physiological activities. When your brain transmits signals to your body, it uses electricity to do so. These signals send commands to various parts of the body, such as your limbs telling them to move, muscles telling them to contract, and the heart telling them to pump.
The passage of positively charged ions, such as sodium, into negatively charged cells, allows for these electrical signals.
Ion channels are protein doorways that allow ions to move in and out of cells. Electrical signals cannot flow through the body when these ion channels are disturbed.
Batrachotoxin keeps ion channels open, allowing a free flow of positively charged ions into cells, according to Abderemane-Ali of Live Science. If they fail to close, the system as a whole loses the ability to transmit electrical impulses.
"These channels must open and close for electricity to flow through our brain and heart muscles," Abderemane-Ali explained. "There is no heart action, neural activity, or contractive activity" if the channels remain open.
If you eat one of these frogs, you will almost immediately die.
So, how do these frogs, as well as other dangerous species, avoid a similar fate? To stop autointoxication, poisonous creatures employ three tactics, according to Abderemane-Ali. The most frequent include a genetic mutation that alters the structure of the toxin's target protein, the sodium-ion door, preventing it from binding to it. A poison frog species named Dendrobates tinctorius Azureus, for example, carries a toxin called epibatidine that mimics the useful signaling molecule acetylcholine.
These frogs evolved changes in their cholinergic receptors that slightly modified the geometry of those receptors, rendering them resistant to the toxin, according to a 2017 study published in the journal Science.
Another approach utilized by dangerous animal predators is the ability to eliminate the toxin from the body, according to Abderemane-Ali. This isn't the same as preventing autointoxication; it's simply another strategy for animals to avoid getting poisoned by the foods they eat.
"Sequestration" is the name given to the third strategy.
"The animal will evolve ways to collect [or] soak up the toxin so that it does not cause difficulties," Adberemane-Ali added.
He cloned sodium-ion channels from Phyllobates frogs and treated them with the poison in Adberemane-study. Ali He was shocked to learn that the poison did not affect sodium-ion channels.
Alderman-Ali stated, "These beasts should be dead." The frogs should not survive with this toxin in their systems since their sodium-ion channels were not resistant to the toxin's disrupting effects.
Based on those findings, Abderemane-Ali believes that these frogs are most likely using a "protein sponge" to avoid autointoxication as part of their sequestration strategy. The frogs most likely create a protein that can absorb and store the poison, preventing it from reaching the susceptible protein channels in the first place.
Sequestration is also used by American bullfrogs (Rana catesbeiana), according to Abderemane-Ali. Saxiphilin, a protein produced by these frogs, can bind to and inhibit the toxin saxitoxin. Saxiphilin is being researched as a possible remedy for neutralizing toxins introduced into our water supply by toxic algal blooms.
You must be logged in to post a comment.