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Oncillary function

The oncilla (Leopardus tigrinus), aka the “small jaguar”, graciously walks the neotropical rainforests from Costa Rica in Central America down south to Northern Argentina. It is also commonly called tigrillo, tigrina, or tiger cat. Highly adaptive, this small cat also lives in savannas (pushed there by deforestation) and in mountains up to the snow-line. Unlike many other felids, oncillas enjoy swimming. Previously hunted for beautiful pelt with rosettes and ringed tail, now this species is listed as vulnerable, with a population of about 10,000.

Profile of an oncilla, photo by Tambako The Jaguar, [CC BY-ND 2.0], via Flickr.com

Oncilla is a bit bigger than a house cat with a small muzzle and slender body. It scouts the ground for small rodents and lizards and likes to rest safely on trees. Birds and eggs are also on the menu, including farm birds that make oncillas a target for farmers intruding into the oncilla’s habitat. Otherwise, these secretive solitaire hunters are rarely seen by humans.


The genus Leopardus is a distinct phylogenetic lineage (so-called - Ocelot lineage) that split off about 10 million years ago from other felids (Johnson et al., 2006) and 6 million later started to form different species. Oncilla still hybridizes with its cousins in the genus Leopardus such as the Pampas cat and Geoffroy's cat.


In general, we know very little about these mostly nocturnal cats. The oncilla phylo-geography is still poorly studied due to a lack of sampling across the species range. Recent comparative molecular studies of small cats from the Leopardus genus revealed a fascinating picture of multiple ancient and modern interspecific hybridizations. Genetic distances indicate that many current subspecies are eligible for the species rank. In fact, the whole species of oncilla is paraphyletic, with the Costa-Rican cat (L.t. oncillus) possibly being a separate species. Interestingly, North-eastern L. tigrinus possesses a mitochondrial genome of an entirely different species - that of a pampas cat! (Li et al., 2016; Trindade et al., 2021). The southern subspecies of oncilla already earned the species rank, L. guttulus. Oncillas vary in fur coloring patterns throughout the range, with differences in background color and spots indicating at least three distinct groups (Nascimento and Feijo, 2017). Many oncillas are melanistic (black cats with black spots).

Oncilla, photo by Tambako The Jaguar, [CC BY-ND 2.0], via Flickr.com

To help study the species today we release the chromosome-length assembly for the oncilla (Leopardus tigrinus)! The skin biopsy used for this assembly was collected from a captive female tiger cat at the zoo on April 21, 1982. The primary fibroblast cell line (LTI-3) was established by Mary Thompson at the Laboratory of Genomic Diversity (LGD), led by Dr. Stephen O’Brien. We sincerely acknowledge Dr. Stephen J. O’Brien for providing the cell line for this study. We are grateful to Drs. Melody Roelke-Parker, Carlos Driscoll, Christina Barr, as well as David Goldman and Stephen Lindell for the preservation of the LGD cell line collection. Passage 4 was used to make the WGS and Hi-C library.


The assembly suggests a karyotype, 2n=36, that is rather unusual for cats that are typically very conservative with a 2n=38. This is consistent with prior studies that showed that Leopardus is the only genus with a lower diploid number of chromosomes (2n=36) in the entire felid family. The 2n is lower because the fusion of felid chromosomes F1 and F2 forms unique metacentric chromosome C3 - ancestral for the whole genus. Browse the chromosomes of the oncilla in the interactive Juicebox.js session below!

References

  1. Graphodatsky AS, Perelman PL, O’Brien SJ. Atlas of mammalian chromosomes. 2nd ed. Wiley-Blackwell; 2020. pp. 727-732

  2. Li G, Davis BW, Eizirik E, Murphy WJ. Phylogenomic evidence for ancient hybridization in the genomes of living cats (Felidae). Genome Res. 2016 Jan;26(1):1-11. doi: 10.1101/gr.186668.114.

  3. Nascimento, FO, Feijo, A. Taxonomic revision of the tigrina Leopardus tigrinus (Schreber, 1775) species group (Carnivora, Felidae). Pap. Avulsos Zool. 57 (19), 2017, https://doi.org/10.11606/0031-1049.2017.57.19

  4. Trindade FJ, Rodrigues MR, Figueiró HV, Li G, Murphy WJ, Eizirik E. Genome-Wide SNPs Clarify a Complex Radiation and Support Recognition of an Additional Cat Species. Mol Biol Evol. 2021 Oct 27;38(11):4987-4991. doi: 10.1093/molbev/msab222.


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