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Color variants

There are endless, possible alternatives to normal, or better, to the most widespread colors that are found in nature. These colors are usually the ones that have guaranteed the best chance of survival to a particular species and/or subspecies. Nevertheless, normally random mutations occur, which may also affect the genes controlling traits such as the patterm shape and distribution as well as its colors. The evolution based on these random mutations, actually never stops, and the environment is the  sole force that may intervene, intended as climate, predators or competitors for food and/or resources exploitation. Actually, any pattern or color entailing a benefit for the animal will be positively selected and gradually spread across the population. Man has always intervened in this system, by exploiting these random mutations for his own purposes or for mere aesthetic pleasure, implementing endless selections and combinations in any biological field.
Testudo marginata albino caramel

    
This is the first and successful selection of a color variant in the Testudo species. Even though albino variants have been known for over a century and preserved in the Museo di Storia Naturale in Milano, up to two decades ago nobody was able to select it so as to have a reproducer group that could generate these specimens in a steady and continuous manner.
The presence in nature of specimens that are carriers of this mutation has repeatedly given birth to mutated specimens. However, due to the long time required to reach the age of reproduction and to the fact that not everyone is capable of recognizing a similar event and relating  it to a selectable mutation, only today specimens with this particular mutation has become available in a continuous and reliable manner.
It has in fact proved to be a recessive homozygous mutation  with the characteristics of an albinism defined as  tyrosinase-positive (T+). Babies are born completely colorless and red-eyed: however, over time, they show a soft caramel shade that becomes increasingly vibrant over the years, although it remains quite different from specimens’ typical color.
Besides a slow initial growth, probably due to a slower metabolism resulting from a lower ability to get warm compared to a normal tortoise, this color variant reaches the species’ typical adult size and has proved to be very productive from reproduction standpoint. This type of tortoise is currently kept in our breeding, in addition to the first ancestral mutant which the selection started from and other three generations, of which two are adult and reproductive.




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Testudo hermanni hermanni albino
Testudo hermanni hermanni albino

    

The most famous and loved mutation is the one causing total albinims, in which the deficit in melanin pigment production is total and, as happens with reptiles, the animal features a yellowish color usually combined with a pattern typical of melanin-devoid species, ie similar to a photographic negative.
Thanks to their much faster reproductive cycle, in scales-skinned reptiles, this mutation is already fixed in many species and some of them are so widespread that the mutated specimens on sale often exceed those normally colored. Although not strictly related to albinism, the yellow canary is an eloquent example we can refer to. In the wild, canary is normally green with dark streaks, but today the number of yellow specimens with the endless  color variations that have been added over time, far outnumber specimens free in nature.
The recently discovered Testudo hermanni hermanni’s mutation is under investigation in order to fix it and create a progeny and offsprings as reliable as in the case of Testudo marginata. This will take some time though. From initial observations, babies easily and regularly grow under natural conditions, although more slowly compared to normal colored specimens, reaching an adult size slightly smaller compared to the average. Despite bright lights cause visual disturbances in young animals, these tortoises need the sun just as normal specimens do. During adulthood, they positively reproduce. Recessive homozygous tyrosinase-negative (T-) mutation. Similar mutations have been positively selected for some years now in Testudo hermanni boettgeri.

 




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Testudo hermanni hermanni isabel form
Testudo hermanni hermanni isabella

    

This mutation mainly occurs in birds, and it is normally defined in reptiles as pastel. The shape and distribution of the typical pattern of the species is maintained, however with more nuanced and less sharp and vibrant shades. In this case, pattern’s color fading strongly highlights the lively background color, in this case a beautiful solid yellow. As in the case of Testudo marginata albino caramel, mutation occurred and widespread in nature across the Apulian populations of this species, even though Balearic Islands’ populations are mentioned as well. Recently, I have seen photos of a specimen found in Sardinia. In this case, the number of adult specimens found in nature and included in private collections in the past, has not required any selection. Mutation affects a single recessive gene and intervened presumably before it occurred in Testudo marginata, where the albino specimens are small, sporadic and never adults documented with certainty as in this case. This could be explained by a crucial difference, as opposed to albinism T- o T+, that babies upon birth are only a little lighter compared to normal ones and therefore certainly less recognizable by a predator: as a result, they survive up to adulthood more easily than the other two color variants.
Growth rate and adult size are quite similar to normal specimens, even though with a different pattern’s color shade.

 




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Other not common color variants
Other unusual color variants

    

Since the genes involved in pattern and color determination are many, also color variants possibilities are equally numerous. The only limit is compatibility with life: in fact the expression of a gene may be multifaceted, which may affect vital processes. Where this problem does not exist, we have many expression variables, which often are not all easy to classify. As far as I know, in the case of tortoises we always talk about homozygous recessive mutations, contrary to what is observed in other areas where co-dominant or dominant mutations occur. In the case of tortoises, we are therefore dealing with relatively few variations. Beside those mentioned above, opposite to albinism, we find melanism, i.e. animals very dark or even completely black or leucism, i.e. animals completely white but with black eyes, or real chimeras in which you can identify a basic leucism, with black spot here and there. Some tortoises may feature red colors that follow a genesis parallel to melanin’s, which can give birth to other variants, just like albinism. Finally, we can find pattern variants, very common in snakes and geckos, but probably extremely rare in tortoises.




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