Dwarf comb rat

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Dwarf comb rat
Tuco-tuco, Tiny Tuco Tuco (Ctenomys minutus) .jpg

Dwarf crested rat ( Ctenomys minutus )

Systematics
Subordination : Porcupine relatives (Hystricomorpha)
Partial order : Hystricognathi
without rank: Guinea Pig Relatives (Caviomorpha)
Family : Comb rats (Ctenomyidae)
Genre : Comb rats ( Ctenomys )
Type : Dwarf comb rat
Scientific name
Ctenomys minutus
Nehring , 1887

The dwarf crested rat or little crested rat ( Ctenomys minutus ) is a type of crested rat . The species is endemic to the south of Brazil and occurs there in the states of Santa Catarina and Rio Grande do Sul .

features

External features

The dwarf crested rat reaches an average total length of 14.1 centimeters in the males and 15.7 centimeters in the females with an average tail length of 7.4 centimeters and a weight of about 190 grams. The rear foot length is 32 millimeters. It is a small to medium-sized species of the genus. The back color ranges from medium brown to dark brown, the belly side is lighter brown. Young animals are usually lighter than adult animals.

Features of the skull

The skull is small. The upper incisors are slightly protruding ( proodont ). The tympanic bubbles are enlarged. The area between the eyes is comparatively wide, the cranium has an only slightly pronounced crest.

Genetic traits

The karyotype consists of a double set of chromosomes of 2n = 42, 46, 48 or 50 (FN = 68 to 80) chromosomes, whereby the haplotypes within the species concentrate on two types and the species thus before the lami-comb rat ( Ctenomys lami ) possesses the highest variability of the karyotypes within the comb rats. The polymorphism is due to the various changes in the chromosomal structure and indicates three population nuclei , a northern one with 2n = 49 and 50, a central one with 2n = 46a, 47 and 48, and a southern one with 2n = 42, 45 and 46b. These results suggest isolation as the start of speciation .

The sperm are symmetrical.

distribution

The distribution area of ​​the dwarf crested rat is limited to the south of Brazil , where the species is endemic from Laguna Beach in the state of Santa Catarina to São José do Norte in Rio Grande do Sul .

Way of life

The dwarf crested rat, like all crested rats, lives largely underground in duct systems. As a habitat, it uses open sandy areas of the flatlands and in dune areas, and it typically lives in the highest areas of sandy and dry fields and pastures not far from water. In a generalist vegetarian manner, it feeds on the available vegetation, especially grass and leaves. A DNA analysis of the diet composition of the dwarf crested rat identified plants from 13 different plant families, mainly grasses (Poaceae), Araliaceae , daisy family (Asteraceae) and legumes (Fabaceae). Using the dwarf crested rat as an example, the effects of colonization by the animals on the soil conditions and vegetation in the habitats in which the animals occur were examined. It was found that in these areas the total biomass is decreasing, but the vegetation coverage of the area remains the same. In the areas used, the soil is much looser and softer, both at a depth of 10 and 20 centimeters, the phosphorus and potassium content is significantly higher and the pH value is significantly lower than in regions not populated by crested rats.

The animals are loners (solitary); the population density is between 7 and 42 individuals per hectare, whereby the gender distribution is slightly shifted in favor of the female animals. The mating of the animals takes place from June to October; the females give birth to the young from September to December or January after a gestation period of about 90 days. The litters each consist of one to three young animals. The animals reach sexual maturity after about six months .

Systematics

The dwarf crested rat is classified as an independent species within the genus of the crested rats ( Ctenomys ), which consists of about 70 species. The first scientific description of the species comes from the German zoologist Alfred Nehring from 1887, who described it using individuals "from the Campos east of Mundo Novo"; the Terra typica was in the 1970s in the coastal area near the mouth of the Rio Tramandahy, about 98 kilometers east of Porto Alegre , limited. In 2001, the lami-comb rat ( Ctenomys lami ) was distinguished from the dwarf- comb rat . Based on molecular biological data, it is assigned to the torquatus group around the collar-comb rat ( Ctenomys torquatus ).

In addition to the nominate form, no subspecies are distinguished within the species , although Wilson & Reeder named two subspecies in 2005: Ctenomys minutus minutus and Ctenomys minutus bicolor . The two-colored crested rat ( Ctenomys bicolor ) in Bolivia is now regarded as a separate species.

Status, threat and protection

The International Union for Conservation of Nature and Natural Resources (IUCN) does not classify the dwarf crested rat in a hazard category, but instead lists it as "data deficient" due to insufficient data. The habitats in the coastal plain where this species lives suffer from constant changes due to urbanization , livestock and agricultural land use, as well as drainage measures related to rice cultivation.

A hybrid zone was identified between the populations of the dwarf crested rat and the closely related lami crested rat ( Ctenomys minutus ) . Originally both species were separated by a wide wetland zone; however, rice cultivation reduced the swamp to an arid region and the two species were merged.

supporting documents

  1. ↑ a b c d e f g h i j k Minute Tuco-tuco. In: TRO Freitas: Family Ctenomyidae In: Don E. Wilson, TE Lacher, Jr., Russell A. Mittermeier (editor): Handbook of the Mammals of the World: Lagomorphs and Rodents 1. (HMW, Volume 6) Lynx Edicions, Barcelona 2016, pp. 521-522. ISBN 978-84-941892-3-4 .
  2. ↑ a b Thales Renato O. de Freitas: Ctenomys lami: The highest chromosome variability in Ctenomys (Rodentia, Ctenomyidae) due to a centric fusion / fission and pericentric inversion system. Acta Theriologica 52, 2007; Pp. 171-180. doi : 10.1007 / BF03194212
  3. ↑ Thales Renato O. de Freitas: Chromosome polymorphism in Ctenomys minutus (Rodentia-Octodontidae). Brazilian Journal of Genetics 20 (1), March 1997. doi : 10.1590 / S0100-84551997000100001
  4. ↑ Cristina Claumann Freygang, Jorge Reppold Marinho, Thales RO de Freitas: New Karyotypes and Some Considerations about the Chromosomal Diversification of Ctenomys minutus (Rodentia: Ctenomyidae) on the Coastal Plain of the Brazilian State of Rio Grande do Sul. Genetica 121, 2004; Pp. 125-132. doi : 10.1023 / B: GENE.0000040376.56321.be
  5. ↑ a b c Ctenomys minutus in the endangered Red List species the IUCN 2019 Posted by: J. Dunnum, N. Bernal, 2016. Accessed April 26, 2020th
  6. ^ Daniel Galiano, Bruno B. Kubiak, Gerhard E. Overbeck, Thales RO de Freitas: Effects of rodents on plant cover, soil hardness, and soil nutrient content: a case study on tuco-tucos (Ctenomys minutus). Acta Theriologica, July 2014. doi : 10.1007 / s13364-014-0193-x .
  7. ↑ a b c Ctenomys minutus . In: Don E. Wilson , DeeAnn M. Reeder (Eds.): Mammal Species of the World. A taxonomic and geographic Reference. 2 volumes. 3. Edition. Johns Hopkins University Press, Baltimore MD 2005, ISBN 0-8018-8221-4 .
  8. ↑ Thales Renato O. de Freitas: Tuco-tucos (Rodentia, Octodontidae) in Southern Brazil: Ctenomys lami spec. nov. Separated from C. minutus Nehring 1887. Studies on Neotropical Fauna and Environment 36 (1), 2001; Pp. 1-8.
  9. ↑ Ctenomys lami in the endangered Red List species the IUCN 2019. Posted by: CJ Bidau, 2016. Accessed April 24, 2020th

literature

  • Minute Tuco-tuco. In: TRO Freitas: Family Ctenomyidae In: Don E. Wilson, TE Lacher, Jr., Russell A. Mittermeier (editor): Handbook of the Mammals of the World: Lagomorphs and Rodents 1. (HMW, Volume 6) Lynx Edicions, Barcelona 2016, pp. 521-522. ISBN 978-84-941892-3-4 .

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