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Earresistable puzzle: decoding the plains vizcacha

The South American plains vizcacha (Lagostomus maximus, Desmarest, 1817) is a rodent that inhabits the Southern area of the Neotropical region, mainly distributed in Argentina, from the North of Patagonia throughout the Pampean region and reaching the South of Bolivia and Paraguay (Jackson et al. 1996). The species belongs to the order Caviomorpha, suborder Hystricomorpha, family Chinchillidae (Voloch et al. 2013, Steppan and Schenk 2017), which comprises three living species: the chinchilla (Chinchilla lanigera), the mountain vizcacha (Lagidium viscascia), and the plains vizcacha (Lagostomus maximus).

The South American plains vizcacha, drawing by Patricia Saragüeta

Three subspecies of L. maximus are recognized: L. m. petilidens (Hollister, 1914), distributed in southern Buenos Aires, La Pampa, and Río Negro provinces in Argentina, L. m. maximus (Desmarest, 1817), in central Argentina, and L. m. immollis (Thomas, 1910), spreading from northern Argentina to Paraguay and Bolivia (Llanos and Crespo 1952, Redford and Eisenberg 1992). Its widespread distribution in the Argentinean pampas contributes to the cultural symbolic value of this species.


Phenotypically, plains vizcachas show a strong occipital crest, a noticeable facial pattern consisting of two parallel black bands, one passing through the eyes and the second across the nose, separated by a white stripe, two pairs of bi-laminate molars, hind limbs with three digits, and a strong tail used as a third leg (Pocock 1922, Jackson et al. 1996). Sexual dimorphism is very pronounced. Males are much larger, have a bigger head, and a more pronounced facial mask than females. This large herbivore species is highly social and shows polygynous behavior. It lives in communal burrow systems and indulges in nocturnal foraging outings (Llanos and Crespo 1952).

The South American plains vizcacha, photo by by Adrián Grilli

Like other packrats, Vizcachas in North Patagonia are in the habit of collecting “souvenirs”. For this reason, they function as a marker species in Paleoecology in South America, revealing the secrets of peculiar places such as the Huemul cave (Llano 2020). It is very difficult to determine the rodent species inhabiting these caves; then, genomic information could contribute to precise the species in the past of the Earth.


Female plains vizcacha is a seasonal breeder that shows unusual reproductive features, distinguishing it from other mammals, representing the highest polyovulation rate so far recorded for a mammal (Weir 1971) and the second longest gestation for a rodent, only exceeded by the pacarana (Dinomys branickii), another caviomorph rodent. Neonates are precocious and, despite suckling for a couple of weeks, can feed and move independently from birth. The unusual physiology of the ovary makes L. maximus a unique alternative research model, especially to understand the regulatory mechanisms of oogenesis (Leopardo and Vitullo, 2017).


Today we release the chromosome-length assembly for the South American plains vizcacha. The sample used for this genome assembly came from an adult female plains vizcacha from ECAS (Estación de Cría de Animales Silvestres, Wild Animal Breeding Station, Fauna and Flora Department, Ministry of Agrarian Development, Buenos Aires Province, Argentina). The capture of the specimen was approved by the Fauna and Flora Department, Ministry of Agrarian Development and CICUAE (Comité Institucional de Cuidado y Uso de Animales de Experimentación) at Universidad Maimónides. The sample was collected by Dr. Alfredo Vitullo and his scientific team at CEBBAD (Centro de Estudios Biomédicos Básicos, Aplicados y Desarrollo, Universidad Maimónides, Buenos Aires, Argentina) and processed by Clara Campos at Saragüeta´s team at IBYME-CONICET (Instituto de Biología y Medicina Experimental, Buenos Aires, Argentina). Browse the Hi-C contact map for the 28 L. maximus chromosomes below, and visit the assembly page for more details about the data model and sequencing.

Blog post by Patricia Saragüeta, IBYME-CONICET, Buenos Aires Argentina, saraguetalab@gmail.com

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