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Scientists Discover First Fluorescent Frog

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#1 JCDowdy

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Posted 16 March 2017 - 22:23

Scientists Discover First Fluorescent Frog, TheScientist, March 15, 2017

If you don't live somewhere with scorpions, perhaps tree frogs?

And because inquiring minds want to know.....

This is from a recent PNAS article.
Carlos Taboada, Andrés E. Brunetti, Federico N. Pedron, Fausto Carnevale Neto, Darío A. Estrin, Sara E. Bari, Lucía B. Chemes, Norberto Peporine Lopes, María G. Lagorio, and Julián Faivovich. Naturally occurring fluorescence in frogs, PNAS 2017 ; published ahead of print March 13, 2017

The photos shown on TheScientist website are form Fig 1B which are described in the figure legend as, "... taken with a band-pass excitation filter attached to the flash and a long-pass emission filter (516 nm) attached to the lens."

The article further states ".... spectral profiles presented excitation maxima of 390−430 nm and emission maxima at 450−470 nm (blue), with a shoulder at 505−515 nm (green) giving an overall cyan coloration ...."

Edited by JCDowdy, 16 March 2017 - 22:50.


#2 Mark

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Posted 17 March 2017 - 10:58

While I think this is very cool in an aesthetic sense, I also think the commenter on that page completely nailed it.

That being said, I'll probably be out this spring with a portable UVIVF setup :)

Edited by Mark, 17 March 2017 - 10:58.


#3 Andrea B.

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Posted 17 March 2017 - 16:10

I wanted to understand more about frog vision. So here is a nice reference.

Frog Vision: http://archives.ever...ml#Color_Vision

Rods:
  • green @ 502 nm from rhodopsin pigment
  • blue @ 433 nm (pigment not given)
  • uv from porphyropsin pigments (wavelength not given)
    Perception of UV is adaptive because higher energy wavelengths travel further through water
    and enable frogs to hunt prey. Not all amphibians have porphyropsin pigments.
Cones:
  • yellow @ 580 nm (pigment not given) [yellow-green?]
  • double cone with rhodopsin+yellow
**********

So, how would fluorescence between 450-470 nm from sunlight appear to the frog's eyes during the day if the frog is underwater ?? The frog rods would be in use in the lower light underwater. So the cyan fluorescence would be visible to the frog. My guess is that froggy fluorescence helps the frog distinguish between friends and prey.

What do you think?? :D

Nothing is accidental in nature. That frog species evolved to fluoresce cyan for a reason. Our human eyes may not understand.
Andrea G. Blum
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#4 Alex H

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Posted 18 March 2017 - 06:28

View PostAndrea B., on 17 March 2017 - 16:10, said:

Nothing is accidental in nature. That frog species evolved to fluoresce cyan for a reason. Our human eyes may not understand.

Than can you explain what is the reason for so many plants to fluoresce?

#5 Cadmium

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Posted 18 March 2017 - 08:03

There is perhaps a paradox to what is accidental in nature. I think on one hand, every new life brings with it much accident.

Edited by Cadmium, 18 March 2017 - 08:18.


#6 Andrea B.

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Posted 18 March 2017 - 19:01

Than can you explain what is the reason for so many plants to fluoresce?

The generally accepted answers are that fluorescence might be used for signaling or for camouflage. Or it might simply be a dissipation of unwanted energy in the form of light. (IIRC, plants don't really use UV in photosynthesis but they do absorb some to protect some plant parts.) Just because we humans do not see plant fluorescence in strong sunlight doesn't mean that other creatures don't make use of it.

So, what do you all think?
BTW, has anyone ever looked for a correlation between UV-absorbing/reflecting plant areas and UV induced visibly fluorescing areas?
Andrea G. Blum
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#7 Alex H

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Posted 18 March 2017 - 19:05

My opinion was expressed here: http://dx.doi.org/10.1080/14688417.2015.1078121

Statements that animals can actually see UV-induced visible fluorescence under normal daylight conditions are not substantiated by any hard evidence, at least in the literature that I reviewed in the past.

#8 Andy Perrin

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Posted 18 March 2017 - 20:28

I don't know anything about frogs, but I have a real problem with the statement that "Nothing is accidental in nature." Anything that neither helps nor hurts a species can't possibly be selected for by natural selection (or even epigenetics, not that I claim to know much about either one). Even in human designs, which I know quite a lot more about since I'm a mechanical engineer, we have many situations where design tradeoffs must be made, often based on somewhat arbitrary factors.

#9 Shane

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Posted 18 March 2017 - 22:02

Quote

Nothing is accidental in nature.

I also disagree with this statement. I think much in nature is coincidental.

Many schemochromic structures in nature are just a byproduct of the building blocks and serve no other purpose than providing strength to the subject. Take pearl oysters with the iridescent surfaces, on the inside of the shell underneath the fleshy mantle, never to be seen by anything. Some of the inner lips of the oyster fluoresce red, not really serving any purpose. Pearls produced by some pearl oysters can exhibit iridescence and fluorescence but they are inanimate objects and fluorescence serves no purpose.

Quote

Statements that animals can actually see UV-induced visible fluorescence under normal daylight conditions are not substantiated by any hard evidence, at least in the literature that I reviewed in the past.

While I tend to agree, if the fluorescence is polarized, "maybe" an animal could distinguish polarized colors from unpolarized colors if their vision permits detection of polarized light.

#10 Hornblende

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Posted 19 March 2017 - 03:58

Quote

While I tend to agree, if the fluorescence is polarized, "maybe" an animal could distinguish polarized colors from unpolarized colors if their vision permits detection of polarized light.

Also, humans can perceive polarized light but it serve absolutely no purpose, unfortunately!

#11 Andrea B.

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Posted 20 March 2017 - 05:44

The benefit of pigment fluorescence in plants may not lie in its visibility (or lack thereof) to bees, etc. The plant receives more energy than it can use for its biochemical processes and must dissipate the excess in the form of either heat or light. Light is probably the less damaging option. Ergo fluorescence?
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#12 Cadmium

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Posted 20 March 2017 - 08:02

Imagine, a glowing frog. :-)

Edited by Cadmium, 20 March 2017 - 09:33.


#13 Mark

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Posted 20 March 2017 - 10:54

I agree that, for your example @Andrea, it would be beneficial for a plant to absorb excess radiation and convert/release it as less harmful longer wavelengths/heat. But a plant could also opt to block excess radiation as well. Either option serves the same purpose. So, whether the fluorescence is intentional or not, who knows (I don't know that "intentional" is the right word there, but you know what I mean). Consider also that many things/materials fluoresce - completely inanimate things. Surely there is no intention there. In many (most, I'd bet) instances it may just be one of the coincidental results of the interaction of light with matter (among transmission, absorption, reflection, degradation, etc, and so on).

What would be interesting (though unethical in my opinion) is to genetically engineer some of these 'fluorescent frogs' without [whatever compound is fluorescing], then raise them side by side with unaltered frogs to see what, if any, effects/differences are observed (breeding/mating success, longevity, prey/predation success, etc).

In the absence of actual proof/supporting data I can only say - it just plain looks cool. And I'm going to shoot every frog species I can get my lens on this spring! Which is probably only a few. But still!

#14 Andrea B.

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Posted 20 March 2017 - 16:23

Consider also that many things/materials fluoresce - completely inanimate things. Surely there is no intention there.

Of course not. But then inanimate things do not evolve. So their fluorescence is simply* a matter of optics/physics.
And whether the nature of matter is accidental or not, well, I leave that up to the physicists, cosmologists ---- and theologians. :D

Perhaps I should go back and add a word to my sentence: Nothing is accidental in "living" nature. I was attempting to refer to living plants and animals and not to rocks. :lol:

Pigment fluorescence in living plants or animals is most likely a kind of adaptive mechanism which benefits the plant or animal. [Is it better if I give the claim a probablistic twist?] We already know pigment fluorescence in plants is beneficial for dissipating energy. And may have other values. And observations have shown the benefits of pigment fluorescence in some animals -- like fish or frogs using pigment fluor for recognition underwater. Just one little example. (BTW, I'm not talking about internally produced bioluminescence.)

Of course there are evolutionary leftovers. Some feature was beneficial in some eon to some animal, then the world changed and that feature is no longer used. But when a feature is so widely present -- as is pigment fluorescence -- then it is hard to argue that it is some kiind of evolutionary leftover even though we might not know what its exact benefit is to the particular plant or animal.

It sort of makes me happy that we don't know everything yet about plants and animals. :rolleyes: B) :lol:


*simply. <lol> Nothing is ever simple, is it?
Andrea G. Blum
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