After the first part devoted to endemic plants from Balkans, today you will find out something about the national symbol of Slovenia - "The Baby Dragon".
Since the ancient times, people used to find mysterious little creatures, just downstream from the caves.
Their body was narrow, it had some kind of little wings, but it was also fragile, thus it must be some kind of a dragon.
And the big dragons were living in the caves - very logical...
Valvasor gave it a scientific name, Proteus, and it happened in 1689, some 50 years before the Linnaeus.
It was also the first animal described as the real cave animal once it was confirmed in Postojna cave.
Today, it's a symbol of basketball club Olimpia, and the key element of the Ljubljana's coat of arms. And there is the bridge that it protects, also in Ljubljana.
(Source and about the bridge)
What is that animal?
There are two species, the regular "white" one Proteus anguinus, and the new "black" sub-species discovered in 1994 [1], Proteus anguinus parkelj.
The black one has numerous different morphological characteristics and can be clearly distinguished from the white subspecies using the PCA plot. PCA plot is used for the reduction of dimensionality. Basically, you measure 10 or 20 parameters and calculate the new set of parameters that describe most of the characteristics with only 2 or 3 new parameters. Think about it as the image compression.
Screenshot from the reference [1], publicly available
Image and text in Slovenian
More photos and the text in German
Studies suggest that the Proteus entered the cave system during the last glaciation period, some 10.000 years ago.
It probably happened separately, on several locations, and the convergent evolution of the initially same species lead to the formation of local populations that are distinguishable, but still represent a single species [2].
Today, Proteus can be found from Isonzo River on the west (Italy/ Slovenia), Southern Croatia, parts of Bosnia and maybe even in Montenegro, but it should be confirmed by catching the living specimens.
Up to date, it was proven by the analysis of the environmental DNA (eDNA), and the markers in the sequence DQ494754.1- DQ494786.1. Incredible now method, if you want to read more about it, check the reference 4.
Does it have any cousins?
Proteus anguinus, olm, or the human-fish as we call it, is the amphibian, and as you can see it has the tail, thus it's classified as the Urodela (salamander).
Now it becomes interesting because it is the member of the family Proteide and they can be found in the USA and the Balkans *(strangely similar with the Trump family...).
Its American cousins are known as the "waterdogs" or the "mudpuppies".
Source and a short text
As you can see, the American cousin from the open waters needed to adapt itself to a much different environment and it became more agile and more robust, while the cave version is very slow, boring animal that is not wasting the energy.
Depending on the age, they spend somewhere between 5-15 % of its time moving. And they don't really care what is the time of the day (what a non-surprise... [6]]
Image from the Reference 6, freely available via ResearchGate
Tough life in the caves
Living in the cave often means one thing - starvation. Keep in mind that there is no sunlight, thus no plants, no photosynthesis, no initial food source.
Proteus can survive long periods without any food ingestion. In the study I found, it stayed without the food for 240 days (8 months!) and it lost only about 13 % of body weight [3].
You are probably wondering what is going on with its glycogen reserves. How can it move? Well, that's interesting. During the first 3 months, the glycogen level falls to 80% of the original value and then - in increases.
Catabolism of the musculature begins only after 180 days.
Proteus is also very well adapted to anoxia with the responses of oxidative stress enzymes not typical for other animals (measured SOD, GPx, CAT) [7]
Surprisingly, they have an incredibly long lifespan of 100 years!
age at sexual maturity of 15.6 years and lays, on average, 35 eggs every 12.5 years [5]
References, the highest number ever found in my post:
- Sket, B., and J. W. Arntzen. "Proteus anguinus parkelj n. ssp.(Urodela: Proteidae)." Bijdragen tot de Dierkunde 64.1 (1994): 33-53. link
- Sket, Boris. "Distribution of Proteus (Amphibia: Urodela: Proteidae) and its possible explanation." Journal of Biogeography 24.3 (1997): 263-280. link
- Hervant, F. R. É. D. É. R. I. C., J. A. C. Q. U. E. S. Mathieu, and J. A. C. Q. U. E. S. Durand. "Behavioural, physiological and metabolic responses to long-term starvation and refeeding in a blind cave-dwelling (Proteus anguinus) and a surface-dwelling (Euproctus asper) salamander." Journal of Experimental Biology 204.2 (2001): 269-281. link
- Vörös, Judit, et al. "Surveying Europe’s only cave-dwelling chordate species (Proteus anguinus) using environmental DNA." PloS one 12.1 (2017): e0170945. link
- Voituron, Yann, et al. "Extreme lifespan of the human fish (Proteus anguinus): a challenge for ageing mechanisms." Biology letters (2010): rsbl20100539. link
- Hervant, F., J. Mathieu, and J. P. Durand. "Metabolism and circadian rhythms of the European blind cave salamander Proteus anguinus and a facultative cave dweller, the Pyrenean newt (Euproctus asper)." Canadian Journal of Zoology 78.8 (2000): 1427-1432. link
- Issartel, Julien, et al. "High anoxia tolerance in the subterranean salamander Proteus anguinus without oxidative stress nor activation of antioxidant defenses during reoxygenation." Journal of Comparative Physiology B 179.4 (2009): 543-551. link
If you want to see it...
Visit Slovenia, lovely country easily accessible by low-cost flights and less expensive than the most of Europe.
You can the "baby dragon" in Postojna cave which is incredible with the train inside. Yes, train, in the cave...
And there are many great things to see above the ground as well, like Bled