The sable, Martes zibellina, is an active and agile predator slightly smaller than a house cat. It has excellent hearing and vision thanks to its big ears and eyes, and a keen sense of smell. With its flexible body and long strong legs, the sable feels equally comfortable on the ground, under the snow, and high up in tree crowns. Its color is quite variable – from pale greyish-buff to rich brown to jet black, usually with a paler face, darker dorsal stripe, tail and paws, and a contrasting irregular-shaped throat patch, which is sometimes small or absent; some individuals have white guard hairs uniformly “sprinkled” all over their bodies. Most of its range lies in Siberia, from the Ural mountains to the Kamchatka peninsula; there are some sables in northeastern Kazakhstan, in Mongolia and northeastern China, and on a number of islands off the Pacific coast of Eurasia, including Sakhalin, some of the Kurils, and the island of Hokkaido.
Like other martens, the sable gravitates towards large contiguous areas of old-stand, mainly coniferous forests with lots of dead wood to provide shelter, nesting and a good supply of small rodents, including its main target – the red-backed vole (Clethrinomys spp.). However, it can take down prey several times its size and weight, such as capercaillies, mountain hares, and small ungulates such as the Siberian musk deer or even roe deer trapped in deep snow. It will use any calories it can find: in years with a good crop of Siberian pine cones, it will feed almost exclusively on pine seeds, and in some years, it will venture out into peatbogs and eat cranberries until the snow becomes too deep. It thrives in a variety of habitats and climates, be it the forest-tundras of the Yamal peninsula, bogged coniferous taiga of Yugra, birch-covered forest-steppes of Southwest Siberia, larch hills of Yakutia, or coastal rainforests of northern Japan. Still, the sable is a quintessential cold-climate animal and is extremely well-adapted to life in deep snow: by late October, it grows a thick, soft winter coat that protects it from extreme temperatures, and long bristles on its well-furred feet that allow it to cover long distances in deep fluffy snow, looking for food; thick snow cover provides shelter from the elements, and during cold spells, when temperatures drop below -40 F, sables are known to spend up to two weeks in the snow without surfacing. How they do it is a bit of a mystery, as they have fast metabolism, do not have any significant fat deposits, and cannot hibernate.
In the western part of its range, east of the Urals and across the West Siberian plain, the sable occurs together with the closely related pine marten (Martes martes), a similarly sized, more uniformly-colored mustelid with coarser fur and longer, fuzzier tail, which is believed to be adapted to slightly warmer climates and more arboreal lifestyle; the two species often produce apparently fertile hybrids; such a hybrid is called a kidus, or kidas, in Russian, and usually has mixed morphological features from both parents.
The crave for the silky-furred mustelid was the driving force behind the conquest of Siberia by the Russian Empire; sable pelts were a royal luxury, commanding sky-high prices, and remained a key export of the state well into the Soviet times. This illustration shows a natural tax imposed upon hunters by the Bolshevik government: a single sable skin equaled three snow leopards or 1000 squirrels! Even nowadays, harvested sustainably, sable fur remains a major source of sustenance for thousands of people in Siberia, especially in areas such as Evenkia and Yakutia, where the climate is too harsh and unpredictable for dependable agriculture.
Early in the XX century, a catastrophic decline of the species occurred throughout its range, caused by hunting pressure and quite possibly other factors, because simultaneously, a similar decline happened with the North American marten even in areas where trapping pressure was insignificant. In 1935-1940, the Soviet government imposed a total ban on sable hunting and trapping and launched a massive reintroduction program. Hundreds of sables were live-trapped, primarily East of Baikal, in Yakutia and on Kamchatka, where the darkest and thus the most valuable forms of the sable occur, transported over thousands of miles by air, by train, and even on reindeer sleds, and released in various locations all over Siberia. This worked, and within a decade, the numbers of the species rebounded back to healthy levels. Unfortunately, the wildlife management science of the time had little concern for the well-being of infraspecific taxa, and some subspecies of the sable were probably lost or dissolved in the progeny of those introduced individuals. We are yet to understand the impact of the reintroduction program on the morphological and genetic diversity of the sable – a challenge where this study will come in so handy!
Today, we present the chromosome level assembly for the sable marten, Martes zibellina. This is the fourth species in the genus Martes we have released here on the DNA Zoo. All C-scaffolds of the sable were assigned to the corresponding chromosomes via a Zoo-FISH experiment with the stone marten chromosomes used as probes. Both the sable and stone marten have the same diploid number of chromosomes (2n=38) with no detected translocations, so we arranged the sable chromosomes in the same order as in the stone marten karyotype. Among other types of rearrangements several inversions were observed (Fig. 2).
Check out the interactive Juicebox.js session below for a Hi-C contact map of the 19 sable chromosomes, and don't forget to visit the assembly page for more details about the assembly procedure!
This work was performed with funding from Dr. Rogell Powell (North Carolina State University) for 10x Genomics linked-read sequencing for the draft assembly. Dr. Klaus Koepfli (Smithsonian-Mason School of Conservation) and Dr. Alexander Graphodatsky (Institute of Molecular and Cellular Biology, Russia; IMCB) organized and brought all of the collaborators together to achieve chromosome-length genome assembly for the sable. Samples from a female M. zibellina were provided by Tatiana Bulyonkova. The fibroblast cell line was established by Dr. Polina Perelman (IMCB). Cultured cells (passage 3) were used for both DNA extraction for linked read sequencing and for Hi-C experiments (passage 9). High-molecular weight DNA was extracted by Natalia Serdyukova (IMCB). Zoo-FISH experiments were performed by Dr. Violetta Beklemisheva (IMCB). The initial assembly was performed by Sergei Kliver (IMCB). Hi-C experiments and scaffolding to chromosomes were done by Ruqayya Khan, David Weisz and Olga Dudchenko. The genome annotation and a paper describing this research is in progress. IMCB work was supported by RFBR grant № 20-04-00808 and grants to A.S. Graphodatsky: RSF 19-14-00034 and Program of fundamental research of state academies of sciences 0246-2021-0015.
There is a massive body of studies on sable ecology, physiology and genetics conducted by many prominent Russian scientists: D.V. Ternovsky (“Biology of mustelids”, 1977), Yu.G. Ternovskaya, A. S. Graphodatsky (Novosibirsk), G.I. Monahov, V.G. Monahov (Ekaterinburg), A.V. Abramov (St. Petersburg), V.V. Rozhnov (Moscow), K.G. Abramov (St. Petersburg), P.B. Yurgenson (Moscow), S.I. Ognev (Moscow) and many others. Sable has 2n=38 with relatively small amount of heterochromatin compared to other mustelids (Graphodatsky et al., 1976, 1977, 2020; Orlov, Malygin, 1969).
And finally, if you're interested in more marten genomes, please check out the assembly pages for the pine marten, stone marten, and the yellow-throated marten. This is the 5th species lead by the DNA Novosibirsk team, be on the look out for many more to come!
Citations:
Atlas of mammalian chromosomes (2nd edition). eds. Graphodatsky AS, Perelman PL, O’Brien SJ. Wiley-Blackwell, USA, 2020, 1008 p.
Graphodatsky A.S., Volobuev V.T., Ternovsky D.V., Radjabli S.I., 1976. G-staining of chromosomes of seven mustelidae species (Carnivora, Mustelidae). "Zool. J.", 55: 1704-1711.
Graphodatsky A.S., Ternovskaia Ju.G., Ternovsky D.V., Radjabli S.I., 1977. G- and C-bands and amount of DNA in sable. "Tsitol. Genet.", 11: 483-485. (Rus.)
Graphodatsky A.S., Radjabli S.I., 1988. Chromosomes of rural and laboratory mammals. Atlas. “Nauka”, Novosibirsk. (Rus.)
Orlov V.N., Malygin B.M., 1969. In: Mammals, N.N.Vorontsov, Ed., Novosibirsk. (Rus).
Ternovsky D.V. Biology of mustelids. Ed. Maksimov A.A., Nauka (Novosibirsk), 1977, 280 pp.