Althouse: "It wasn’t until he examined the frogs under a microscope that he discovered that the spines on their upper lips were covered in poison glands."

August 10, 2015

"It wasn’t until he examined the frogs under a microscope that he discovered that the spines on their upper lips were covered in poison glands."

"'It took me a long time to realize that the pain had a relationship with the intense and careless collection of these animals hitting the palm of my hands,' he said. When the frog head-butted him, it envenomed him too."

12 comments:

Eric the Fruit Bat said...: Hmmmmm. Maybe I should take a closer look at my wife's vagina.; 8/10/15, 1:47 PM
Rob said...: I've looked at it, Eric. Nothing much to see there.; 8/10/15, 2:19 PM
lgv said...: Well, it did make me click on the tag "frogs" to see how many actual frog posts there were. More than I imagined.; 8/10/15, 3:19 PM
YoungHegelian said...: Frogs. Rotten, little, sneaky bastards, the lot of 'em.; 8/10/15, 3:32 PM
PackerBronco said...: I always knew that you couldn't trust the frogs, but I didn't think that it applied to the amphibians as well.; 8/10/15, 4:44 PM
traditionalguy said...: Ever since the 2010 Rose Bowl the Wisconsin Folks have been afraid of Frogs using poisonous head butts.; 8/10/15, 8:03 PM
Ann Althouse said...: You got me looking back into the frog tag. I love when something that specific has a big accumulation.; 8/10/15, 8:34 PM
Quaestor said...: This comment has been removed by the author.; 8/11/15, 12:47 AM
Quaestor said...: The amazing thing about those frogs is the lethality of the venom. This disproportionally between the envenomator and the envenomed has lots of examples in nature. Consider the female black widow spider (Latrodectus mactans). The amount of venom one spider can produce over its entire lifetime is a few dozen μgrams, yet one bite can kill an adult human. It eats flies. The box jelly, perhaps the most venomous creature to ever evolve, eats plankton.

Or perhaps it not so perplexing. Amphibians, especially frogs, have evolved toxic skin secretions thousands of times, mostly in the form of passive defense. For a passive defense to work predators need to be deterred rather than killed, since killing the predator involves the death of the defender. In the case of amphibians it's color that deters, yellow and red specifically. (Interestingly many yellow fish are toxic, which suggests a possible evolutionary history of toxic skin. Perhaps amphibians inherited their toxin genes from distant fish ancestors in the Devonian Period.) The most toxic are bright yellow, or bright yellow with a contrasting color. The problem of the passive strategy is mimicry. Other non-toxic frogs evolve yellow skin displays to gain protection without going to the trouble of evolving the whole gamut of toxin + coloration. This in turn leads to another problem, the predators (birds and snakes mostly) cope with the increased number of apparently toxic frogs by eating them anyway, death by toxic shock or death by starvation is still death. Some of the predators die by eating the poison frogs, but most don't because they eat the mimics. Those that eat non-toxic mimics won't be deterred when they encounter the real mccoy.

Over time the whole passive defense strategy becomes problematic, which puts evolutionary pressure on the toxic frogs to evolve a different way to use their expensive weaponry. Spines covered with toxic slime would be easy to evolve in a genus of frogs that already had the toxic slime genes. That head-butting behavior is the obvious tactic to use. When a predatory appears, attack immediately, hesitation invites death. And why is the venom so toxic? Its because the enemies are so large compared to the frog. The threat must be driven away with the first thrust, else the frog dies whether the predator dies or not. Snakes are a particular challenge to any venom-powered defense. Snake metabolisms are so low and their circulation so sluggish that any venom that could have an immediate effect would have to be extraordinary potent.; 8/11/15, 12:55 AM
rcommal said...: "'It took me a long time to realize that the pain had a relationship with the intense and careless collection of these animals hitting the palm of my hands,' he said. When the frog head-butted him, it envenomed him too."

Too long, I would say.; 8/11/15, 1:00 AM
mikee said...: I learned long ago from some exotic nature show that one could ingest some kinds of snake venom without damage. (Thanks, National Geographic,IIRC.)

I did not know that male platypuses had spurs on their rear legs that could inject venom into unwary platypus handlers until just a few years ago. (Thanks, Patrick O'Brian, for that, and so much more in your Aubrey/Maturin novels.)

My question now is, what happens if one licks these venomous frogs? Anything similar to the hallucinogenic frogs/toads of urban myth and scientific trivia?

And after that, what happens if one licks the male platypus (ingests the venom)?

So much to learn, so little time left....; 8/11/15, 10:24 AM
Michelle Dulak Thomson said...: Quaestor, can snakes see colors? Birds can, of course, but for your passive defense to work against reptiles they would also need color vision.; 8/12/15, 10:22 AM