Blue inner thighs

[Didiman]

Im just curious in wanting to know what the blue colouring on the inner thighs of L.Aurea and L.Raniformis are for. My guess is that its a breeding display as it is most visual when the frog is in the water with its back legs spread out. Does anyone know?

Heres a couple of pics of one of my frogs (still not 100% what they are yet) thats shows the blue colourings.

[Evan]

It is flash colouration. When they are chased by a predator, they hop, and the bright colours (in this case blue) are visible for a fraction of a second. This can confuse the predators, giving them enough time to get away.

[Didiman]

Cheers evan, never thought of that!

[samehada]

wow thats great colouration, ive heard about that colour flash thing the chloris and gracilenta do it too.

[Edgee]

I have never noticed anything on my chloris but 2 of 3 of my gracis have blue inner thighs 24/7.

[Gulper]

I think that flash colour might be associated with breeding- the frogs flash at each other prior to amplexus to ensure they have the right species. As a frog "predator" with good colour vision, I rarely notice the bright colour as a frog jumps away. But I guess I don't have my beak as close to a frog as a heron might.. It is a damn fine question, given that most frogs are nocturnal, probably don't have colour vision, (I don't think snakes have colour vision either) and locate one another on the sound of the male's call. One would wonder why the flash colours are so species-specific if all that was required was a flash of bright colour to confuse a predator. Another idea just popped up in my excuse for a brain- given that the green in frog's skin is a combination of two different chemicals, (one blue, one yellow, as demonstrated by the blue colouration of these species in alcohol) maybe there is no need to produce the expensive yellow pigment where it isn't going to provide camoufage, in those areas of the frog invisible while the frog is at rest. Any other theories?

Cheers!

Alex.

[Evan]

But look at L. peronii. It uses yellow, which it doesn't even use on the rest of its body. Also, you say that snakes probably don't have colour vision, does more primitive frog?

But you do make a good point, it is very variable between species, and there is no reason speciation should take place if a population has different flash colours. But, then again. It is something which has effect on the frog if it changed, so there is more likelihood to be large variability. It wouldn't matter if it changed to a different pattern or colour, as long as it still works. A good experiment would be to see whether L. wilcoxi and L. lesueuri mate in the wild (which I think they do from memory of the paper). As they probably have the same call, but different flash colourations.

[Gulper]

Of course there is no reason to suppose that flash colouration might not serve both purposes to varying degrees. Obviously the breeding thing doesn't always work. I once saw a male Limnodynates (Platyplectrum) ornatus in amplexus with a Litoria (Pelodryas) cearulea. Maybe he had been underground for a bit too long.

[samehada]

chloris do naturally have blue in their thighs i talked to groo about it and he says that usually captive breed ones dont have it all the times

[Evan]

Did you get a photo of that Alex? That would look pretty funny. In "Austrailan Frogs A Natural History", by Tyler, there is a male L. nasuta in amplexus with a Notaden melanoscaphus.

[Gulper]

Unfortunately it was on 17 December 1983 (near Mangrove Mountain NSW), and I didn't get a camera until August 1984. Since then I have been hoping to see something similar so I can get a picture. Does that mean there is something wrong with me?

[Evan]

No, but don't go 'round telling people.

[Gerry Marantelli]

Flash coloration does not need to be species specific to work but evolution is. So once a suitable direction has been taken and is working it tends only to be refined. Since change to another color or mix of colors has no benefit, it is unlikely that a single species sharing gene flow would evolve different colors.
Once gene flow is cut or reduced however a color that has no purpose or does not need to be maintained as the same color to achieve the same purpose can easily drift.
Look at closely related species it is often the ventral, groin and thigh paterns that differentiate them - it may be that there is pressure to maintain the dorsal colors and patterns for the very reasons they evolved - but less pressure to maintain the same color or pattern for flash or belly.

[Brad M]

Gerry, is 100% correct. Look at Uperoleia. U.tyleri, U.fusca and U.laevigata are very hard to tell apart from dorsal colouration and call. From my experience the best way to distinguish them is the groin flash colours.

[Tereza Tantar]

Does the blue colouration on the inner thighs on L.raniformis serve as an indication of toxins present in the frog? As a deterant for predators but also a true (not pseudo) indication of a high level of toxin?

Also, how dangerous is the toxin if present? If rubbed into the eyes of a human, will it sting or be more severe? I once rubbed (by accident) secretions from a banjo frog's skin into my eye and it was hideously painful but it went away after about an hour or so.
Or perhaps how dangerous would it be to a kookaburra for example?

I would appreciate it if anyone knew the answer to this.

T

[Brad M]

The flash colouration is used as a "confusion" mechanism. When the frog hops the colours are visible, this may startle the predator and may give the frog enough time to escape. Colouration more like that of Psuedophyrne and Dendrobates (poison arrow frogs) etc are an indicator of poison. The colours are visible all the time, so the predator may not go near the frog in the first place. However, I do know that the skin secretions of L.aurea (and probably L.raniformis) does cause irritation with some people.
Cheers,
Brad

[Eipper]

Hi all,

A good friend of mine working on Litoria raniformis, once rubbed her eyes after processing a frog, The eyelids became swollen and the eye became irritated and painful. These symptoms progressivly decreased over the following 2 days.

Moral of the story...wash before and after touching a frog!

I have had similar from Pseudophyrne semimarmorata (painful, swollen fingers and frozen joints).

As for snakes lacking colour vision.....American Vine Snakes, and the oriental vines (both rear fanged colubrids) are thought to have binocular colour vision.

You cannot use flash colours on all Uperoleia...eg U. martini and U. tyleri

Regards,
Scott Eipper

[Didiman]

Im not to sure if its the actual skin that gives off this irritation. When removing my forgs (pretty sure they are L.Raniformis now) from their enclosure for cleaning, they will often squirt from their backside when trying to avoid me. I am careful to wash my hands after so i couldnt tell you the ill effects from this is, but no doubt its part of their defence mechanism.

[Evan]

I've noticed that with my ''L. splendida'', and I thought it was just expelling excess water. They do whenever they come out from a swim.

[Brad M]

Definetly not all species of Upe. Call is easiest to seperate U.martini and U.tyleri. Uperoleia are probably one of the hardest genus (in Aus) to distinguish between each species. Most of the genus was only described in the 80s, and I'm sure there are more out there that haven't been named.

Cheers,
Brad

[GrantW]

Another example of a frog using its flash colours to indicate poison is Pseudophryne bibronii, which is known to cause severe irritation when it comes in contact with people eyes (and death to snakes which eat it), so the flash colouring under the armpit (red, orange or yellow) and the belly marbling I guess would be an indication that it is toxic.

Cheers,
Grant

[Evan]

Not neccesarily. Just because something evolves poison, does not require them to evolve amposmetism. The toads (mainly Bufo, as I don't know much about the other genera) are a great example, many of them are extremely poisonous but show no indication of it.

[GrantW]

I know that it doesn't have to represent that the frog is toxic, but it is at least a logical explanation for it. Pseudophryne bibronii wouldn't have much other use for flash colours (as they tend to move slowly, a quick flash of colour isn't going to distract the predator long enough for the frog to escape). Bufo is a good example at that for poison not being represent by colour but just look at the Dendrobatids, they are a clear example of colour being used as a warning.

Cheers,
Grant

[Evan]

Obviously, but I still doubt having colourful thighs has anything to do with its toxicity. P. corroboree uses aposematism, as the colour is on the back. All P. bibronii has to do is make the colour visible to confuse the predator. Animals can do amazing things when their life is in danger, otherwise they would be extinct. It wouldn't surprise me if they have a movement which exploits their flash colouring.

[GrantW]

Okay then, even if the armpit colouring has nothing to do with toxicity, then what does the ventral surface indicate? It is very strong marbling, and I have never encountered a Pseudophryne that flips itself over in a defensive postion. Maybe a combination of the two represents its toxicity, if the predator doesn't see the armpit first, it may see the ventral surface afterwards.