Akodon caenosus

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Akodon caenosus

Data Deficient  (IUCN 3.1)[1]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Rodentia
Family: Cricetidae
Subfamily: Sigmodontinae
Genus: Akodon
Species:
A. caenosus
Binomial name
Akodon caenosus
Thomas, 1918
Scattered localities in a narrow strip from northwestern Argentina to south-central Bolivia
Distribution in Argentina and Bolivia.[2]
Synonyms[6]
  • Akodon puer cænosus Thomas, 1918[3][fn 1]
  • Akodon caenosus: Thomas, 1920[5]
  • Akodon diminutus Barquez, Díaz, and Goytia, 1994[fn 2]
  • Akodon lutescens caenosus: Anderson, 1997[7]
  • Akodon aliquantulus Díaz, Barquez, Braun, and Mares, 1999[8]

Akodon caenosus is a

Akodon lutescens (formerly Akodon puer). The species Akodon aliquantulus, described from some very small Argentine specimens in 1999, is now recognized as a synonym
of A. caenosus.

Akodon caenosus is very small, averaging 19.3 g (0.68 oz) in weight, and variable in coloration, but generally brown. The underparts are sharply different in color from the upperparts. The skull has a short rostrum (front part), broad

braincase. The karyotype includes 34 chromosomes. A. caenosus mostly occurs in Yungas vegetation and breeds mainly during the winter. It shares its range with many other sigmodontine
rodents, including three other species of Akodon.

Taxonomy

E. Budin collected the first specimen of the species on August 21, 1917, in

Principle of Priority; therefore, he utilized the combination Akodon lutescens caenosus for the Argentine subspecies.[7] Through the 1990s and 2000s, authors continued to differ on the classification of caenosus as either a full species or a subspecies or puer (=lutescens).[11]

Two small Akodon collected in 1993 in Tucumán Province, northwestern Argentina, were given the name Akodon diminutus in 1994, but that name is a nomen nudum and therefore not available for use under the International Code of Zoological Nomenclature.[15] In 1999, Mónica Díaz and others described these animals more fully as a new species, Akodon aliquantulus, which they considered closely related to A. puer caenosus.[16] The specific name means "how little" or "how few" in Latin and refers to the small size of the species and the small sample Díaz and colleagues could use.[17] In the 2005 third edition of Mammal Species of the World, Guy Musser and Michael Carleton termed the differentiation between A. aliquantulus and A. lutescens (=puer) "unimpressive" and recommended further taxonomic research.[18] Common names proposed for A. aliquantulus include "Diminutive Akodont"[19] and "Tucumán Grass Mouse".[20]

Akodon boliviensis group

Akodon caenosus

Akodon lutescens

Akodon subfuscus

Relationships within the Akodon boliviensis species group according to analysis of cytochrome b data.[21]

In 2010, Pablo Jayat and colleagues reviewed the members of the Akodon boliviensis group in Argentina. On the basis of

morphometrical differentiation between the two and could not replicate the characters Díaz and colleagues had noted as diagnostic for A. aliquantulus.[11]

Description

Akodon caenosus is the smallest of the Argentine members of the A. boliviensis group[6]–indeed, among the smallest of all species of Akodon.[25] The upperparts are uniformly colored, but their tone is variable: generally ochraceous brown, but approaching yellow, red, or olivaceous in some individuals.[6] Reddish tones occur mostly in lactating females. High-altitude animals are generally lighter, but there is also conspicuous variation within populations.[26] The ears are similar to the upperparts, but some individuals have the sides more rich and clear in color. The underparts are clearly different in color, varying from light gray to yellowish or reddish.[6] There are yellowish rings around the eyes,[27] which are more highly developed in high-altitude populations.[6] There are white to yellowish hairs on the fore- and hindfeet.[28] The tail is variably covered with hair and is dark brown above and white to buffy below.[26]

In the skull, the rostrum (front part) is short, the

mesoloph on the first and second upper molar.[26]

In twelve adult Argentine A. caenosus, total length is 124 to 169 mm (4.9 to 6.7 in), averaging 151 mm (5.9 in); tail length is 46 to 75 mm (1.8 to 3.0 in), averaging 62 mm (2.4 in); hindfoot length is 20 to 26 mm (0.79 to 1.02 in), averaging 21 mm (0.83 in); ear length is 12 to 15 mm (0.47 to 0.59 in), averaging 13 mm (0.51 in); and weight is 10.5 to 27.5 g (0.37 to 0.97 oz), averaging 19.3 g (0.68 oz).

acrocentric pairs, which have a long and a very short arm. The X chromosome is medium-sized and subtelocentric, with a long and a short arm, and the Y chromosome is very small and is acrocentric in Jujuy specimens, but metacentric in those from Tucumán. The karyotype is separated from that of A. lutescens by three Robertsonian translocations.[14]

Members of the Akodon boliviensis group, including A. caenosus, are generally similar and difficult to separate,[27] but they differ in relative cranial measurements and some other characters.[30] A. spegazzinii is larger than A. caenosus;[26] A. sylvanus is darker and has less contrast between the upper- and underparts and less well-developed eye-rings;[11] A. polopi has a squared interorbital region and more well-developed ridges on its skull;[31] and A. boliviensis is paler and has more densely furred ears.[32]

Distribution and ecology

Akodon caenosus is found from northwestern Argentina into south-central Bolivia.

oestrid fly Cuterebra apicalis[35] and the flea Hectopsylla gracilis have been recorded from A. caenosus.[36] The mites Androlaelaps fahrenholzi, Androlaelaps rotundus, and Eulaelaps stabularis have been found on A. aliquantulus.[37]

Conservation status

The

Least Concern" because of its wide distribution, large population, and ability to persist in disturbed habitats. However, habitat loss may threaten Yungas populations.[39]

Footnotes

  1. ligature such as æ are to be corrected.[4]
  2. ^ Nomen nudum (naked name, not fulfilling the requirements of the International Code of Zoological Nomenclature).[6]

References

  1. ^ Jayat, J; Pardinas, U. (2019). "Akodon caenosus". IUCN Red List of Threatened Species. 2019: e.T114956458A22380244. Retrieved 31 January 2020.
  2. ^ Anderson, 1997, p. 422; Jayat et al., 2010, p. 25
  3. ^ Thomas, 1918, p. 189
  4. ^ International Commission on Zoological Nomenclature, 1999, Art. 32.5.2
  5. ^ Thomas, 1920, p. 192
  6. ^ a b c d e f Jayat et al., 2010, p. 23
  7. ^ a b Anderson, 1997, p. 421
  8. ^ Díaz et al., 1999, p. 788
  9. ^ Thomas, 1918, pp. 189–190
  10. ^ Thomas, 1920, p. 193
  11. ^ a b c d e Jayat et al., 2010, p. 25
  12. ^ Myers et al., 1990, p. 66
  13. ^ Myers et al., 1990, p. 73
  14. ^ a b Myers et al., 1990, p. 74
  15. ^ Díaz et al., 1999, p. 795; Jayat et al., 2010, p. 23
  16. ^ Díaz et al., 1999, p. 786
  17. ^ Díaz et al., 1999, p. 794
  18. ^ Musser and Carleton, 2005, p. 1093
  19. ^ Musser and Carleton, 2005, p. 1092
  20. ^ Duff and Lawson, 2004, p. 59
  21. ^ Jayat et al., 2010, fig. 1
  22. ^ Jayat et al., 2010, p. 5
  23. ^ Jayat et al., 2010, fig. 1, p. 9
  24. ^ Jayat et al., 2010, p. 43, fig. 1
  25. ^ Díaz et al., 1999, p. 795
  26. ^ a b c d e Jayat et al., 2010, p. 24
  27. ^ a b Jayat et al., 2010, p. 18
  28. ^ Jayat et al., 2010, pp. 23–24
  29. ^ Jayat et al., 2010, table 1
  30. ^ Jayat et al., 2010, pp. 24, 25, 41
  31. ^ Jayat et al., 2010, p. 41
  32. ^ Jayat et al., 2010, p. 21
  33. ^ Jayat et al., 2010, p. 25; Anderson, 1997, p. 422
  34. ^ Anderson, 1997, p. 422
  35. ^ Pinto and Claps, 2005, p. 572
  36. ^ Lareschi et al., 2010, p. 212
  37. ^ Lareschi et al., 2003, p. 60
  38. ^ Pardinas and Jayat, 2008
  39. ^ Dunnum et al., 2008

Literature cited

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