Ctenomys rionegrensis Langguth & Abella 1970
Creators: name: Don E. Wilson
name: Thomas E. Lacher, Jr
name: Russell A. Mittermeier
Publisher: name: Lynx Edicions
Year: 2016
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Mammalia
Rodentia
Ctenomyidae
Ctenomys
Ctenomys rionegrensis

description: 36.
Rio Negro Tuco-tuco
Ctenomys rionegrensis
French: Tuco-tuco du Rio Negro / German: Rio-Negro-Kammratte / Spanish: Tuco tuco de Rio Negro
Taxonomy. Ctenomys rionegrensis Langguth & Abella, 1970,
“Balneario Las Canas, boca del Arroyo Las Canas, 7 km al Sudoeste de Fray Bentos, Rio Negro, Uruguay,” c. 100 m, 33°06’ S, 58°20’ W.
Ctenomys rionegrensis was first classified in the Eastern group based on biogeography, and based on mtDNA, it was classified in the mendocinusspecies group. It was initially considered a subspecies of C. minutus. Its karyotype was described as 2n = b0, but there is chromosomal variation from 40 to 56 that includes species from Argentine and Uruguay. Morphometric variation was studied in C. rionegrensis in relation to geographical distribution, and no correlation between geographical and morphological distances was found. Sperm morphology is simple asymmetric. Monotypic.
Distribution. SW Uruguay (Rio Negro Department) and NE Argentina (Entre Rios Province).
Descriptive notes. Head-body 178-190 mm (males) and 162-190 mm (females), tail 71-83 mm (males) and 65-83 mm (females), hindfoot 30-33 mm (males) and 29-33 mm (females). No specific data are available for body weight. The Rio Negro Tuco-tuco is relatively small. Greatest skull length is 45-9-47-9 mm (males) and 41-44-6 mm (females), and condylobasal length is 41-42-8 mm (males) and 37-1-40 mm (females). Dorsal color varies extensively: light brownish orange, darkbacked, or melanistic individuals to “agouti” individuals, with small yellow paraunicular spots and yellowish venters. There are no axillary or inguinal spots. Bases of all body hairs are dark gray. Tail is bicolored, with dorsal dark brown line along its length. From above, sides of rostrum are parallel, and temporal crests of parietal are almost parallel. Frontal and parietal have flat dorsal faces. The most external point of zygomatic arch is near its posterior end; vertex of mandibular process of zygoma 1s more rostral with respect to vertex of frontal process; longitudinal crest running along external surface of zygomatic bone is almost straight. Upper incisors are opisthodont.
Habitat. Sand dunes between Rio Negro and Rio Uruguay.
Food and Feeding. The Rio Negro Tuco-tuco likely feeds on annual grasses and woody shrubs.
Breeding. Reproduction of the Rio Negro Tuco-tuco is seasonal, with mating in austral autumn. First litters are born in early spring.
Activity patterns. There is no information available for this species.
Movements, Home range and Social organization. Although the Rio Negro Tuco-tuco is not social like the Colonial Tuco-tuco (C. sociabilis), many individuals were captured in the same burrow. Telemetry studies suggest solitary behavior, but the Rio Negro Tuco-tuco might have an intermediary social pattern. Densities are quite high, reaching 40 ind/ha.
Status and Conservation. Classified as Endangered species on The [UCN Red List. Populations of Rio Negro Tuco-tucos from Argentina and Uruguay are separated by the Uruguay River.
Bibliography. Altuna & Lessa (1985), Bidau (2015), Contreras & Bidau (1999), D'Elia et al. (1998), D’Anatro & Lessa (2006), Garcia et al. (2000), Kiblisky et al. (1977), Lacey (2000), Lacey et al. (1997), Parada et al. (2011), Reig et al. (1992), Rossi et al. (1995), Tassino et al. (2011), Wlasiuk et al. (2003).
description: Published as part of Don E. Wilson, Thomas E. Lacher, Jr & Russell A. Mittermeier, 2016, Ctenomyidae, pp. 498-534 in Handbook of the Mammals of the World – Volume 6 Lagomorphs and Rodents I, Barcelona :Lynx Edicions on page 524, DOI: 10.5281/zenodo.6588177