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Rana temporaria - White tadpoles.


During August 2013 in the B d Col lake I noticed some white tadpoles. I was not aware of the existence of any white larva of amphibian in this area, so I decided to get in contact with my friend Daniele Seglie, an herpetologist, asking him if I should look for help from him or if and optician would be better….
I learnt that albino specimen happen also in Rana temporaria and usually lead to the death of the animal.
As I was caught by enthusiasm I involved more friends that I supposed could help me in some ways.
Then I increased the frequency of my trips to the lake and the attention I paid to it.
Over the remaining months of 2013 I made many visits and took many pictures that allowed me to put together a proper description of facts and to develop some hypothesis
Let me be clear on a point. Within this text, I will use the words “white tadpoles” or “white frog” just to be clear on the specimen I refer to. Strictly speaking, the term is not fully correct but it is straightforward and clear.

Tadpole Rana temporaria albino white Prali Praly
White tadpole with rear legs.
September 2013.

Tadpole Rana temporaria albino white Prali Praly
Group of white individuals seen on artificial background and a normal specimen to highlight the difference.
August 2013.

Tadpole Rana temporaria albino white Prali Praly
Individual at the latest stage of the metamorphosis. Only the tadpole tail remains.
September 2013.

Tadpole Rana temporaria albino white Prali Praly
As far as it can be observed with this picture, the eyes are black. If it were an albino, they would be red. Therefore it should be a matter of abnormal color rather than completely missing melanin.
August 2013.

Tadpole Rana temporaria albino white Prali Praly
Detail of the body.
Picture form Daniele Seglie.
August 2013.

White specimen were visible in a relatively large number. I could physically see at once about 50 while in the rest of the lake other individuals could be seen anywhere. As this has happen in the advanced season when surrounding green fields were already populated by myriads of just metamorphosed frogs, it can be reasonably argued that many more were present at hatching phase. Possibly thousands.
Therefore, it cannot be an accidental issue but a phenomenon that happens quite frequently.

“White” color.
40% of “white” individuals miss one eye, occasionally both. As I noticed this late in the season I and no means to check if the normal dark population suffered the same disease or not.
The observed individuals show a certain degree of neotenism. Many individuals can hardly metamorphose into a complete frog.
The ones we captured before freezing and moved into an artificially warm environment did not metamorphose for the time being.
A similar phenomenon was not visible at all with dark specimen. When autumn was approaching, only white individuals were still active in the lake. Last observation of a live individual apparently in good health was made on September 29th, 2013.
Looking at the eyes with microscope, I noticed that they are black. As albinos have red eyes, this phenomenon should be different. A lack of melatonin triggered by other factors than the albino gene.
Following step.
The large number of individuals triggered the attempt to find adults with the same color feature that could hatch large quantity of tadpoles with the “special” feature.
The problem was complex because Rana temporaria lives mostly in the grass where finding them is terribly difficult. However, I needed to observe a large number of them, which was a “tragic” need.
The approaching autumn helped me.
When temperature is decreasing, frogs come back in the water, as they will hibernate at the bottom of the lake to survive the winter. So, many adults become visible in the water with each visit.
After some failed attempts, I had the feeling to see a white adult. However, it was just an instant view as the animal saw me before I saw it, and escaped. This reinforced my hypothesis. I kept visiting the lake and I finally was able to see adults and take pictures.
The color of Rana temporaria is variable so we have to pay attention to avoid easy conclusions based on the available observations. However the photographed individuals are clearly “whiter” the normal one. Describing them in words we could say that they show the same pattern of normal individuals but drawn on a white background.
The adults I photographed were adult size. Therefore, they were aged probably between 3 and 5 years. A precise statement could be achieved by means of proper laboratory analysis.
The presence of many white individuals make it possible that two adults mate together and generate all or many white individuals. Which seems have happened already.
A genetically based accident should lead to a single individual, as frogs are not monozygotic twins.
All of this can be verified in the next years on the condition that the lake is not artificially dried as it used to in the past.

Tadpole Rana temporaria albino white Prali Praly
Adult with regular pattern and color.
September 2013.

Tadpole Rana temporaria albino white Prali Praly
Adult with “white” background and about regular pattern.
September 2013.

Tadpole Rana temporaria albino white Prali Praly
Adult with regular pattern and color.
September 2013.

Tadpole Rana temporaria albino white Prali Praly
On the left a “white” adult; on the right a regular one.
September 2013.

Tadpole Rana temporaria albino white Prali Praly
“White” adult partially submerged in the mud.
September 2013.

Tadpole Rana temporaria albino white Prali Praly
“White” adult while hiding in the mud.
September 2013.

Tadpole Rana temporaria albino white Prali Praly
On October 13th, 2013, after the first snow come and cows were still waiting to go back in the plain, a white tadpole was still swimming and looked healthy.

Tadpole Rana temporaria albino white Prali Praly
Spetember 2013. Two captive individuals just metamorphosed.
The normal one on the left; the white one showing the missing eye on the right.
One picture does not have statistical relevance but shows that the white one is even less visible than the ordinary one.
It is important to highlight that the animals, in this case the predators, do not see as humans do and that Rana temporaria spends more time in the grass than in the water. It is necessary to make further studies but the first look is like that.

Test on the effect of the background colour.

As amphibians, within limits, adapt their skin colour to the background, on suggestion of an herpetologist  I covered the normal sand of my aquarium with 100% black artificial aquarium sand.
Four weeks after the sand addition no relevant colour changes were visible.
My feeling was that some darkening actually happened, but within limits that I was not able to document. This could be logic if the white specimen kept the adoption capability although based on a different starting point.
The experiment took place in January/February 2014. In this season tadpoles usually don't exist at all. I cannot separate the effect of the background form the one of the abnormal season.

February 2014. White tadpole some weeks after the black sand was used to darked the background.

Some hypothesis to work on.
The color of the Rana temporaria, as any other characteristic of any live specimen, went through a natural selection that promoted the ones that helped individuals to reproduce most.
Mating, by its very nature, produces always-different individuals with the only exceptions of monozygotic twins. It is statistically almost impossible that two individuals carry identical genome.
Only survivors were able to transfer their genes to the future.
A new advantageous characteristic generated by a random genetic accident, takes a relatively short time to spread into the all population; geologically speaking… But in terms of human life it takes a very long time.
In this case something has happened quite quickly. Probably less than a decade as the lake used to be dried earlier… What could have triggered this?
The correct answer is “I don’t know”.
However, as I have been working until this point, let me go on with more hypothesis.

I have no means to forecast if it will be correct on not; not if it will be just a loss of time. By sure I dedicate it to Charles Darwin. With almost no scientific tools besides a block notes and a pen, he was able to understand the very essence of how life works and allowed to understand anything happen in the life on hearth.

The fact that white individuals are so common means that that color – at least – is not a major disadvantage. I mean that if it made the animal more visible to predators, they would disappear.

These options can be imagined:
There is an ongoing selection mechanism that promotes the color for some reason
The selection factor that used to keep the color away is not working which trigger the so-called “de-selection” of the genes that operate in that area.

The B d Col lake – in natural condition – is a closed lake. Water comes from a spring a few meter away from the lake rising form a calcareous rock.
Most of the year the water only evaporates or is absorbed by the ground, as there is not a visible permanent emissary. The water should be very transparent and clean as it normally is in mountain lakes.
In this case, the lake is in the center of a large cattle farm and widely used form caws as drinking water; but the consequence is that a significant amount of excrements drops into the water.
Therefore, one hypothesis can be that the modified chemical, physical and biological characteristics of the water generate a new situation, which is favorable to the diffusion of the color feature.
The kind of reproductive cycle of the frog, combined with the high number of individuals generated each year by each couple could help the quick diffusion of the characteristic, which normally needs longer time.
What triggers this effect? Hard to say… But an option could be that the human activities generate a slight color change in the lake which makes more visible to predators the “normal” individuals, thus promoting the others.
With those observations and hypothesis as a background, I made some Internet research.
The “white” individuals are like this because of the lack of melatonin (it is obvious but it is the starting point).
They also show, to a certain extent, neotenism. I.e. a portion of them can hardly complete the metamorphosis or they do very late.
Some damages to the epiphysis can trigger both these problems.
The epiphysis suffers damages if the water shows high concentration of fluorine, phosphorus and calcium.
The spring that supplies water to the lake is in a calcareous are (otherwise rare in the valley) so there may be a high concentration of calcium.
The massive presence of caws may increase the concentration of phosphorus and fluorine.
If this was confirmed, it could be that the special chemical characteristics of the water trigger the change. As this would happen on a large scale and on a population subject to an extremely high natural mortality, it could be that the inconveniences do not show up as they disappear in the natural casualties allowing the survival of a certain number of individuals.
None of this gives explanation about the missing eyes. One hypothesis for which I am grateful to Daniele is that they are damaged during attack of the dragonfly larvae, which could see the black eyes better on a white background. We need the next season to make more observations.
I go on.
Feel free to contact me on this subject on my mail.

In this area, there is an urban legend that states that radioactivity is tremendously high due to the leaks form the neighboring French nuclear power station stating that “they” get rid of nuclear waste in the environment as then it comes all by “us”.
To prevent idiot hypothesis I travelled around in the valley with a Geiger. The value almost everywhere is about 0,2 μSievert which is the natural background.
At the bottom of small channels where debris tend to deposit sometimes, a minimum increase can be detected. In no case, the display shown number worth reading…

Tadpole Rana temporaria albino white Prali Praly Geiger
Measurement made on the side of the lake on September 29th, 2013: 0,196 μSievert.

What happened to the captive individuals born in 2013?
In August 2014, when wild tadpoles were beginning to metamorphose,  the individuals from 2013 spawning were still in my aquarium. Some died. The ones still alive look healthy.
Death normally happen after the individual has slimmed very badly. It looks they cannot feed anymore.
Over summer, one year old individuals begun to show small back legs which never grew over 2 to 4 mm.

Starting in February 2014, when the lake was still 100% frozen, I followed closely what was going on.
With the arrival of spring and milder temperatures the ice begun to melt. Then adults laid the eggs and spawning happened. During mating hundreds of adults were present. Their colours ranged between brown and grey as usual.
With newly born tadpoles, I could not see any white specimen. Of course, checking the all population was impossible. However, if a number of white individuals were present amongst the mass of black ones, I assume they would have been very visible.
When they were big enough to be able to see with bare eye if they had both eyes or not, I sampled some hundreds over 3 weeks and detected no visible problems.

I could not visit the site over July 2014.

On August 10, 2014, I visited again the lake. Metamorphosis was going on. Tadpoles are very large and many small frogs are already jumping in the grass surrounding the lake.
I made 2 full tours of the lake at different times in the afternoon.
On the first tour I saw 4 white individuals of which 3 sure and one very quickly.
On the second tour, I saw 6.
From that day onwards, I visited the lake until winter. Each time I found white specimen. Apparently, the phenomenon was substantially the same as the preceding year.

September 14, 2014. White individuals. Top left: asymmetrical eyes. Top centre: undersized symmetrical eyes. Top right: one eye.

Resume of the observed effect of the unknown problem:
  • alters the skin colour
  • makes the individuals neotenic
  • creates “one eyed” individuals and/or eye size modifications.
  • generates some risk to have 3 legs only
I found all combinations of disease but I was missing the black one-eyed neotenic individuals.
I have been looking for them over the summer with no results. I thought it could have been a visibility issue. Spotting a one-eyed individual amongst tens of thousands of normal one is just impossible. I developed another idea: if it exists, most likely it should be also neotenic. Therefore, I could more easily spot them after most individuals already metamorphosed.
In autumn, when all normal individuals had disappeared already, some tadpoles were still swimming and shown no legs. Two of them were black. One of those had one eye!

September 28, 2014. One eyed, black, neotenic individual.

The “white tadpoles” phenomenon happened already 2 years under my eyes.
The numbers are large enough that good observation can be made at any time and any day.
It seems that all individuals hatch black. Whitening happens sometimes in July.
During mating, I could not observe abnormal specimen. I was there only one day. I assume mating lasted at least some days.
I wander if there could be a non-genetic reason for all of that. The problem arises during summer. There could be an issue that develops its effects over time. Fungi? Anything else?

Last minute remark.
At the end of the summer season, I noticed also some “white” specimen of insects swimming in the water.
There is a relevant number of them. I moved some in my aquarium to observe them. They seem normal individuals almost completely white.
At the moment I don’t know it this is a normal colour or not.

July 28, 2014. Two individuals of different colour.


The extremely warm summer shortened a lot the breeding cycle. Combined with limited time from my side, I was not able to make effective observations.
I spotted only one white individual when no other tadpoles were around any more but I was to ale to take a picture.


Same situation as preceding year but I saw no white specimen. Short breeding season and limited time make the remarks of little relevance.

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