Northern voalavo

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Northern voalavo

Least Concern  (IUCN 3.1)[1]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Rodentia
Family: Nesomyidae
Genus: Voalavo
Species:
V. gymnocaudus
Binomial name
Voalavo gymnocaudus
Known records of Voalavo gymnocaudus (red) and
Voalavo antsahabensis
 (green)

The northern voalavo

least concern because it lacks obvious threats and much of its range is within protected areas
.

The northern voalavo is a small, mouse-like rodent with soft, grey fur that is only slightly darker above than below. The ears are short and rounded. The long tail appears mostly naked and lacks a distinct

braincase. The molars are relatively high-crowned (hypsodont
). It has a body mass of 17 to 25.5 g (0.60 to 0.90 oz).

Taxonomy

The rodent fauna of the

generic name, Voalavo, is a general Malagasy word for rodent, and the specific name, gymnocaudus, refers to the naked tail, which distinguishes the northern voalavo from the related tufted-tailed rats (Eliurus).[5] In 2000, the species was also recorded from the nearby Marojejy National Park.[6]

Meanwhile, in 1999, Sharon Jansa and colleagues published a molecular phylogenetic study of the Nesomyinae, the native Malagasy rodents, using the mitochondrial gene cytochrome b. Their results suggested that the current definitions of Eliurus and Voalavo may not be correct, because they found that northern voalavo and Grandidier's tufted-tailed rat are more closely related to each other than to the remaining species of Eliurus. However, the DNA of Petter's tufted-tailed rat, a possible close relative of northern voalavo, could not be sampled, so Jansa and colleagues recommended further evaluation of the problem.[7] According to a 2003 report, data from nuclear genes also support the relationship between northern voalavo and Grandidier's tufted-tailed rat, but Petter's tufted-tailed rat remains genetically unstudied and the taxonomic issue has not been resolved.[8]

A second species of Voalavo,

cryptic species.[11]

Description

External morphology

Measurements of northern voalavo[12]
Locality n Head-body Tail Hindfoot Ear Mass
Anjanaharibe-Sud 4 86–90 119–120 20–21 – 20.5–23.5
Marojejy 5 80–90 113–126 17–20 15–15 17.0–25.5
n: Number of specimens measured.
All measurements are in millimeters, except body mass in grams.

The northern voalavo is a small, mouse-like rodent.[13] It differs from the very similar eastern voalavo mainly in some measurements, such as a greater tail length.[14] It also resembles small species of Eliurus, but the fur is darker and there is no tail tuft.[3] The fur is soft, short, and thick,[15] and appears dark grey on most of the upperparts, but more brownish on the sides.[16] On the back, the cover hairs, which form the main part of the fur, are three-colored: most of the hair is grey, followed by a narrow light buff band and a black tip. The longer guard hairs are black.[15] The fur of the underparts is not different in overall color, but the individual hairs are gray for about three quarters of their length and white at the tips, except for those at the chin, which are white throughout.[16]

The

hallux) is much shorter. The tail is longer than the head and body and appears naked for most of its length, but fine hairs are visible near the tip. Although the lower side is slightly lighter, there is no clear difference in coloration between the upper and lower sides.[16] The skin of the tail is grey, and it is covered lightly by fine hairs that are dark brown over most of the length of the tail but white near the tip.[16]

Skeleton

The skull is delicate and lightly built. The rostrum, the front part of the skull, is narrow and fairly long;

braincase also lacks such ridges.[17]

The

tegmen tympani, the roof of the tympanic cavity, is reduced.[19]

The root of the lower incisor is visible at the back of the

caudal (tail) vertebrae. The humerus (upper arm bone) lacks an entepicondylar foramen.[19]

Dentition

The upper incisors are

orthodont (with their cutting edge perpendicular to the plane formed by the molars) and have yellow to light orange enamel. On the lower incisor, the enamel contains series of fine ridges.[19] The toothrows are longer than in eastern voalavo.[14] As in Eliurus, the molars are incipiently hypsodont (high-crowned) and the individual cusps have lost their identities, having merged into transverse laminae not connected longitudinally. There are three laminae on each first and second molar, two on the third lower molar, and the laminae cannot be differentiated on the third upper molar. Although the first and second molars are similar to each other in size, the third (upper and lower) molars are conspicuously smaller. There are three roots below each upper and two below each lower molar.[19]

Distribution and ecology

The northern voalavo has been found only in two massifs of the

Marojejy, but may range more widely.[2] At Anjanaharibe-Sud, the species has been found in wet mountain forest at 1,950 m (6,400 ft), where it occurred with the indigenous rodents Major's tufted-tailed rat and island mouse as well as the introduced black rat (Rattus rattus), and in drier forest at about 1,300 m (4,300 ft), where it may live alongside other species of Eliurus and Voalavoanala.[20] The Marojejy records come from similar habitats at 1,250 to 1,875 m (4,101 to 6,152 ft) above sea level.[6]
The northern voalavo probably largely lives on the ground, but is able to climb in vegetation.[6] It likes areas with dense networks of roots, among which it moves using runways and natural tunnels.[3] The species is nocturnal (active during the night), is solitary, probably eats fruits and seeds, and bears up to three young per litter.[21] A variety of parasitic arthropods have been recorded on northern voalavo: mites from the families Laelapidae and Trombiculidae (both Marojejy and Anjanaharibe-Sud), the demodecid mite Demodex (Marojejy only), the atopomelid mite Listrophoroides (both Marojejy and Anjanaharibe-Sud), and unidentified sucking lice (Anjanaharibe-Sud only).[22] In 2007, a laelapid mite found on V. gymnocaudus in Anjanaharibe-Sud was described as a new species, Andreacarus voalavo.[23] The apicomplexan parasite Eimeria has also been recorded in Anjanaharibe-Sud.[24]

Conservation status

Although it has a small range and is uncommon even within that range, no major threats are known and virtually all of its distribution is within

Least Concern" on the IUCN Red List.[1]

Notes

  1. ^ a b c Kennerley 2016.
  2. ^ a b Musser & Carleton 2005, p. 953.
  3. ^ a b c Garbutt 2007, p. 234.
  4. ^ Carleton & Goodman 1998, p. 164.
  5. ^ Carleton & Goodman 1998, p. 189.
  6. ^ a b c d Carleton & Goodman 2000, p. 251.
  7. ^ Jansa, Goodman & Tucker 1999, p. 262.
  8. ^ Jansa & Carleton 2003, pp. 1263–1264; Carleton & Goodman 2007, p. 17.
  9. ^ Goodman et al. 2005, p. 163.
  10. ^ Goodman et al. 2005, pp. 870–871.
  11. ^ Baker & Bradley 2006, p. 653.
  12. ^ Carleton & Goodman 1998, table 11-7; Carleton & Goodman 2000, table 12-5.
  13. ^ Carleton & Goodman 1998, p. 182.
  14. ^ a b c d Goodman et al. 2005, p. 866.
  15. ^ a b Carleton & Goodman 1998, p. 185.
  16. ^ a b c d e f Carleton & Goodman 1998, p. 186.
  17. ^ a b c Carleton & Goodman 1998, p. 187.
  18. ^ Goodman et al. 2005, p. 869.
  19. ^ a b c d Carleton & Goodman 1998, p. 188.
  20. ^ Carleton & Goodman 1998, p. 188; Goodman & Carleton 1998, p. 211.
  21. ^ Goodman, Ganzhorn & Rakotondravony 2003, table 13.4.
  22. ^ OConnor 1998, p. 76; OConnor 2000, p. 140.
  23. ^ Dowling, Bochkov & OConnor 2007, p. 413.
  24. ^ Laakkonen & Goodman 2003, p. 1196.

References

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