Voalavo

Voalavo is a type of rodent in the Nesomyinae family, found only in Madagascar. There are two kinds, both living in mountain forests above 1250 meters (4100 feet). The northern voalavo lives in the north of Madagascar, and the eastern voalavo lives in a small area in the middle of the island. Scientists found the genus in 1994 and gave it a name in 1998. Voalavo is closely related to Eliurus in the Nesomyinae family, and DNA studies suggest the way these two groups are defined may need changes.

Voalavo rodents are small, gray, and look like mice. They are some of the smallest nesomyines. Unlike Eliurus, they do not have a bunch of long hairs at the end of their tails. Their tails are long, and female voalavos have six nipples. Male voalavos have two scent glands on their chest that make a sweet-smelling musk during breeding time, which Eliurus does not have. Their skulls have a long front part and a smooth back part. The incisive foramina (holes in the front of the palate) are long, and the palate bone is smooth. Their molars are high-crowned but not as much as Eliurus. The third molars are smaller and simpler.

 Taxonomy 
A sample of the genus was first found in 1994 in Anjanaharibe-Sud, northern Madagascar. The genus was named Voalavo in 1998 by Michael Carleton and Steven Goodman, with one species, northern voalavo, living only in the Northern Highlands of Madagascar. The name Voalavo comes from a Malagasy word meaning "rodent." A second species, eastern voalavo, was named by Goodman and others in 2005 from the Anjozorobe area in the Central Highlands. The two Voalavo species are very closely related and look alike, but they have small differences in body size and shape (mainly measurements) and are 10% different in the mitochondrial cytochrome b gene.

Voalavo belongs to the Nesomyinae subfamily, which has nine genera found only in Madagascar. Before Monticolomys (described in 1996) and Voalavo (1998) were discovered, all known Nesomyinae genera were very different from each other, making it hard to understand how they were related. Like Monticolomys (which is similar to Macrotarsomys), Voalavo has clear similarities to the Eliurus genus. Carleton and Goodman said in their Voalavo description that Eliurus and Voalavo are closely related but separate groups. In 1999, Sharon Jansa and others studied cytochrome b sequences from nesomyines and other rodents. They found that northern voalavo is more closely related to Grandidier's tufted-tailed rat than to Eliurus species, making Voalavo's status as a separate genus unclear. However, they could not study Petter's tufted-tailed rat, another species believed to be close to Grandidier's tufted-tailed rat, since no tissue samples were available.

Studies of nuclear genes also show a link between northern voalavo and Grandidier's tufted-tailed rat, but Petter's tufted-tailed rat has not been studied yet, so the taxonomic question is still open. Nuclear DNA studies suggest that Eliurus, Voalavo, Gymnuromys, and Brachytarsomys are closely related. These four genera are less closely related to other nesomyine genera and even more distantly related to other subfamilies of Nesomyidae, found in mainland Africa.

Category:Rodents