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martedì 18 agosto 2015


(in Eng?ish)

Hello dear English-thinking-speaking-reading visitor! Welcome back to this obscure blog usually frequented only by ghosts of ancient mariners looking for a safe heaven where to chill out and finally digest in peace that gristly bird in company of their mascot, Tom Cat, which has found here a perfect hideout even if it is not necessary anymore given the fact that it's arch-enemy, Curiosity, has been sent no less than to another planet (NASA is in fact ruled by a secret congregation devoted to cartoon cats. And smart paillettes. Whatever they be.)

by sciencemug
by sciencemug

Sooo once upon a time, like... now, there were and are two species of hylid frogs named Corythomantis greeningi and Aparasphenodon brunoi. They live happily ever always in Brazil and they don't want to be grabbed (they are less than ten centimeters big indeed and therefore their size fits perfectly that of the shaky hands of the corny dreamers I’m talking about in four words) and kissed (two…) by any sloppy fairy tales junkie to become some Prince Charming who spends all his time running away from the paparazzi and all his considerable PC’s fortune (he's one of the biggest shareholder of Packard Bell) on H75 Chardonnay hair dyes and long expensive trips to his dermatologist (an Inuk who receives exclusively on his personal iceberg off Uummannaq) to nurse a chronic rash caused by too tight cheap long johns.

To protect themselves from the serial-kissers, the two anti-monarchist amphibians have flat heads full of tiny (not even half of a millimeter) bony spines concentrated in the rear part of their skulls and in the nasal and jaw zones where these pointy little things form a sort of provocative lusty stinging upper lip (yeah, those frogs are leaping saucepots...). But it's not this that make these couple of Brazilian Kermits so special to become the main characters of a report just published on the science journal Current Biology (and of such a useless post like this). Nope.

lipstick frog (by sciencemug)
C. greeningi (sort of)'s maquillage (by sciencemug)

The fact is that the frogs’ heads’ pointy little bony thingies are associated with minuscule (about 1/10 to 3/10 of a millimeter in size) skin glands. The spines indeed “pierce the epidermis in areas of the skin well supplied with […] glands(Carlos et al, 2015 aka P) and end up all poulticed with these glands’ secretion which is – X-Files-the reboot (by the way HELL YEEEEEEESSS!)-suspence-generating-like music- toxic stuff.
Actually it is stuff made of stuff (enzymes) that cripple the normal process of coagulation of the blood (the kind of stuff that used to freak out Buffy and her gang in other words) and crumble proteins. In the secreted stuff, besides, there's other stuff (the name is hyaluronidase, and it’s an enzyme too) which enhances the transport and delivery of those above mentioned toxic stuff. So, well, the glands' stuff is bad stuff (is it discreet and dissimulated enough the sponsorship I got form “Stuff” the auto-repair and dental prosthesis shop?). At least for a wanna-be frog predator (and for the serial-kissers running dry).

by sciencemug
“Stuff” the auto-repair and dental prosthesis shop (by sciencemug)

Soooooo, that’s the reason why Carlos Jared and other six biologists and zoologists from US and Brazilian universities take their science clever lab time to study 15 frogs of both C. greeningi and A. brunoi.
They do it ‘cause toxic stuff+stinging stuff+animal-equal-venomous thug. Aaand the Brazilian leapers are the first frogs, and amphibians, to be classified as venomous and not poisonous.

That’s the scientific scoop!

I mean, yes, it is commonly known that most of amphibians are poisonous, ‘cause they have their skin covered with toxic glands-spitted whatever to protect themselves from predators. But till our Carlitos labcoated bunch’s discover, well, no species of this class of animals had been found to be venomous, that is not only to be able to produce toxic compounds, but to be also equipped with a delivery mechanism that can shoot the toxins straight into another animal.
I mean, that’s usually snakes’ (especially on a plane) weaponry, like the fangs.

So now, to recap, thanks to Jared and colleagues, the world is aware of the fact that there’re at least two venomous species of frogs which have a venom delivery system consisting of spines which are covered with toxins produced by skin glands, placed in correspondence of the spines. Spines that cover the frogs’ head. Head that is therefore, as a matter of fact, well, the ultimate Kermit’s weapon.

by sciencemug
by sciencemug

C. greeningi and A. brunoi defense strategy is indeed based on their ability, unusual in amphibians, to flex a lot the head both laterally and vertically. Once grabbed or constrained, the Brazilian Kermits release their stiky venom and move “the head, jabbing and rubbing the spines” (P) so to sting/cut the predator and deliver, like this, their toxic secretion into the wound.

And Jared is positive that the strategy works. He himself accidentally ends up with a hand injured by the spines of one C. greeningi frog, and feels an “intense pain radiating up the arm, lasting about 5 hr.(P) So, the sore researcher and his probably still mercilessly laughing colleagues think that their frogs’ “jubbing and rubbing the flexible venomous stinging head” defense strategy that impairs the arm of a human being for hours “should be even more effective on the mouth lining of an attacking predator”.(P)

Moreover the researchers test the lethality of the frogs' venoms in the lab, on some mouses, and they find that just a hint of them (about 3 to 50 millionths of a gram) is sufficient to kill the rodents.

Basically, the Carlitos say, the frogs’ from Brazil venoms are 2 (C. greeningi) to 25 (A. brunoi) times more lethal than the Central and South American vipers’ (genus Bothrops) one.

Good news for the frogs, bad news for the "Union of serial-kissers&predators&fried frogs’ French (and also other non French individuals of the world) eaters".

To sum up Jared and colleagues close their report (and I this post useless as a pair of sneakers for Jabba the Hutt) with these lines: “There are other amphibians that probably should be considered as venomous, including salamanders with ribs that pierce through the skin […] and frogs with spines in the head region […], but information on the toxicity of their skin secretions is lacking. […] It is likely that venomous amphibians are more toxic and common than previously assumed.

- Jared, C., Mailho-Fontana, P. L., Antoniazzi, M. M., Mendes, V. A., Barbaro, K. C., Rodrigues, M. T., and Brodie, E. D., Jr. (2015). Venomous Frogs Use Heads as Weapons. Curr Biol 25, 2166–2170.

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