Eastern Voalavo
Encyclopedia
Voalavo antsahabensis, also known as the Eastern Voalavo, is a rodent
in the family Nesomyidae
which occurs in the Anjozorobe
forest of eastern Madagascar
. Although surveys before 2002 failed to record the species, it is common in some places. However, it is threatened by habitat loss because of slash-and-burn agriculture. The species was formally described in 2005 and is most closely related to the only other species of Voalavo
, Voalavo gymnocaudus from northern Madagascar.
The two species of Voalavo are only subtly different in morphology. With a body mass of 20.7 to 22.6 g (0.73 to 0.8 oz), V. antsahabensis is a small rodent. It has a longer tail than V. gymnocaudus, as well as a longer rostrum (front part of the skull) and diastema
(gap between the incisor
s and molars
), but shorter molar rows. The two species also differ in details of the configuration of the palate
.
forest. In 2005, the species was formally described by Steven Goodman
and colleagues as Voalavo antsahabensis, the second species in the genus Voalavo
. The only previously known species, Voalavo gymnocaudus, occurs further to the north, in the Northern Highlands
. The sequences
of the cytochrome b
gene
differ by about 10% in these two species. The specific name, antsahabensis, derives from the name of the village of Antsahabe
, which is near the place where the holotype
was found. The common name
"Eastern Voalavo" has been used for this species.
). V. antsahabensis is similar to V. gymnocaudus and differs only in subtle characters. The tail is shorter in V. antsahabensis, but the head and body is slightly longer, as is the ear. However, the latter two apparent contrasts may be the result of differences in measurement technique. In both species, the final 25 to 30 mm (1 to 1.2 in) of the tail are covered with white hairs. In three specimens of V. antsahabensis, head and body length ranges from 88 to 91 mm (3.5 to 3.6 in), tail length is 106 to 114 mm (4.2 to 4.5 in), hindfoot length 19 to 20 mm (0.75 to 0.79 in), ear length 15 to 16 mm (0.59 to 0.63 in), and body mass 20.7 to 22.6 g (0.73 to 0.8 oz).
In the skull, Voalavo antsahabensis has a significantly longer rostrum (the front part of the skull) and diastema
(the gap between the incisor
s and the molars
). Furthermore, V. antsahabensis has shorter molar rows in both the upper and lower jaws. The back end of the incisive foramina (openings in the front part of the palate
), which is located in front of the first molars, is rounded in V. antsahabensis, but angular in V. gymnocaudus. The sutures of the maxilla
ry and palatine
bones (the line where the two bones, part of the skull, join) are straight and parallel to each other, the toothrows, and the midline of the skull in V. antsahabensis; in V. gymnocaudus, in contrast, they are more curved. Statistical analysis of measurements of the skull and teeth clearly separates the two species of Voalavo.
, on the eastern margin of Madagascar's Central Highlands
. Among the specimens found in 2002, two were captured at 1425 m (4680 ft) altitude on a Uapaca densifolia branch, about 1.5 m (4.9 ft) over the ground, in moist montane forest, and a third was caught on the ground at 1275 m (4180 ft) altitude. This last specimen, a male, had its testicles located in the scrotum, and therefore was reproductively mature, even though its skull bones were not completely fused, indicating it was not yet osteologically
mature. Before it was collected in 2002, the species was not recorded in earlier biological surveys of Anjozorobe, taking place in 1977–1986 and 1996; whether this is because the animal is difficult to collect, because its abundance varies from year to year, or because its distribution is patchy is unknown. Goodman and colleagues argued on the basis of this example that rapid surveys may not necessarily yield complete inventories of the fauna of an area. Later surveys in 2005 and 2006 did find it at several other sites in the region, at some of which it was abundant. Anjozorobe is about 450 km (280 mi) from the nearest occurrence of V. gymnocaudus, and most of the intervening area contains montane forest. However, this forest zone is bisected by the low-lying Mandritsara Window, which may serve as a barrier between the two species of Voalavo.
because of its small, vulnerable range; the Anjozorobe forest is threatened by the practice of slash-and-burn agriculture
(tavy). However, its habitat has been designated as a protected area
, the Couloir Forestier d'Anjozorobe-Angavo.
Rodent
Rodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....
in the family Nesomyidae
Nesomyidae
Nesomyidae is a family of African rodents in the large and complex superfamily Muroidea. It includes several subfamilies, all of which are native to either continental Africa or to Madagascar...
which occurs in the Anjozorobe
Anjozorobe
Anjozorobe is a large town in Analamanga Region, Madagascar, approximately 90 kilometres north-east of the capital Antananarivo.Anjozorobe is famous with its corridor and with a pilgrim city of Anosivolakely where the Virgin Maria is reported to have appeared in 1990.Anjozorobe Forest Corridor is...
forest of eastern Madagascar
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...
. Although surveys before 2002 failed to record the species, it is common in some places. However, it is threatened by habitat loss because of slash-and-burn agriculture. The species was formally described in 2005 and is most closely related to the only other species of Voalavo
Voalavo
Voalavo is a genus of rodent in the subfamily Nesomyinae, found only in Madagascar. Two species are known, both of which occur in mountain forest above 1250 m altitude; Voalavo gymnocaudus lives in northern Madagascar and Voalavo antsahabensis is restricted to a small area in the central part...
, Voalavo gymnocaudus from northern Madagascar.
The two species of Voalavo are only subtly different in morphology. With a body mass of 20.7 to 22.6 g (0.73 to 0.8 oz), V. antsahabensis is a small rodent. It has a longer tail than V. gymnocaudus, as well as a longer rostrum (front part of the skull) and diastema
Diastema (dentistry)
Diastema is a space or gap between two teeth. Many species of mammals have diastemata as a normal feature, most commonly between the incisors and molars.-In humans:...
(gap between the incisor
Incisor
Incisors are the first kind of tooth in heterodont mammals. They are located in the premaxilla above and mandible below.-Function:...
s and molars
Molar (tooth)
Molars are the rearmost and most complicated kind of tooth in most mammals. In many mammals they grind food; hence the Latin name mola, "millstone"....
), but shorter molar rows. The two species also differ in details of the configuration of the palate
Palate
The palate is the roof of the mouth in humans and other mammals. It separates the oral cavity from the nasal cavity. A similar structure is found in crocodilians, but, in most other tetrapods, the oral and nasal cavities are not truly separate. The palate is divided into two parts, the anterior...
.
Taxonomy
Voalavo antsahabensis was first recorded in 2002, when three individuals were captured in Madagascar's AnjozorobeAnjozorobe
Anjozorobe is a large town in Analamanga Region, Madagascar, approximately 90 kilometres north-east of the capital Antananarivo.Anjozorobe is famous with its corridor and with a pilgrim city of Anosivolakely where the Virgin Maria is reported to have appeared in 1990.Anjozorobe Forest Corridor is...
forest. In 2005, the species was formally described by Steven Goodman
Steven Goodman
Steven Goodman is an American Conservation Biologist, and field biologist on staff in the Department of Zoology at the Field Museum of Natural History....
and colleagues as Voalavo antsahabensis, the second species in the genus Voalavo
Voalavo
Voalavo is a genus of rodent in the subfamily Nesomyinae, found only in Madagascar. Two species are known, both of which occur in mountain forest above 1250 m altitude; Voalavo gymnocaudus lives in northern Madagascar and Voalavo antsahabensis is restricted to a small area in the central part...
. The only previously known species, Voalavo gymnocaudus, occurs further to the north, in the Northern Highlands
Northern Highlands
The Northern Highlands are a mountainous biogeographical region of northern Madagascar. The region includes the Tsaratanana Massif and smaller nearby massifs such as Marojejy, Anjanaharibe-Sud, and Manongarivo...
. The sequences
DNA sequence
The sequence or primary structure of a nucleic acid is the composition of atoms that make up the nucleic acid and the chemical bonds that bond those atoms. Because nucleic acids, such as DNA and RNA, are unbranched polymers, this specification is equivalent to specifying the sequence of...
of the cytochrome b
Cytochrome b
Cytochrome b/b6 is the main subunit of transmembrane cytochrome bc1 and b6f complexes. In addition, it commonly refers to a region of mtDNA used for population genetics and phylogenetics.- Function :...
gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
differ by about 10% in these two species. The specific name, antsahabensis, derives from the name of the village of Antsahabe
Antsahabe
Antsahabe is a town and commune in Madagascar. It belongs to the district of Antsohihy, which is a part of Sofia Region. The population of the commune was estimated to be approximately 11,000 in 2001 commune census....
, which is near the place where the holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
was found. The common name
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
"Eastern Voalavo" has been used for this species.
Description
Species of Voalavo are small rodents with a delicate skull and without a tuft at the tip of the tail (as present in the closely related genus EliurusEliurus
Eliurus is a genus of rodent in the family Nesomyidae.It contains the following species:* Tsingy Tufted-tailed Rat * Ankarana Special Reserve Tufted-tailed Rat...
). V. antsahabensis is similar to V. gymnocaudus and differs only in subtle characters. The tail is shorter in V. antsahabensis, but the head and body is slightly longer, as is the ear. However, the latter two apparent contrasts may be the result of differences in measurement technique. In both species, the final 25 to 30 mm (1 to 1.2 in) of the tail are covered with white hairs. In three specimens of V. antsahabensis, head and body length ranges from 88 to 91 mm (3.5 to 3.6 in), tail length is 106 to 114 mm (4.2 to 4.5 in), hindfoot length 19 to 20 mm (0.75 to 0.79 in), ear length 15 to 16 mm (0.59 to 0.63 in), and body mass 20.7 to 22.6 g (0.73 to 0.8 oz).
In the skull, Voalavo antsahabensis has a significantly longer rostrum (the front part of the skull) and diastema
Diastema (dentistry)
Diastema is a space or gap between two teeth. Many species of mammals have diastemata as a normal feature, most commonly between the incisors and molars.-In humans:...
(the gap between the incisor
Incisor
Incisors are the first kind of tooth in heterodont mammals. They are located in the premaxilla above and mandible below.-Function:...
s and the molars
Molar (tooth)
Molars are the rearmost and most complicated kind of tooth in most mammals. In many mammals they grind food; hence the Latin name mola, "millstone"....
). Furthermore, V. antsahabensis has shorter molar rows in both the upper and lower jaws. The back end of the incisive foramina (openings in the front part of the palate
Palate
The palate is the roof of the mouth in humans and other mammals. It separates the oral cavity from the nasal cavity. A similar structure is found in crocodilians, but, in most other tetrapods, the oral and nasal cavities are not truly separate. The palate is divided into two parts, the anterior...
), which is located in front of the first molars, is rounded in V. antsahabensis, but angular in V. gymnocaudus. The sutures of the maxilla
Maxilla
The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...
ry and palatine
Palatine bone
The palatine bone is a bone in many species of the animal kingdom, commonly termed the palatum .-Human anatomy:...
bones (the line where the two bones, part of the skull, join) are straight and parallel to each other, the toothrows, and the midline of the skull in V. antsahabensis; in V. gymnocaudus, in contrast, they are more curved. Statistical analysis of measurements of the skull and teeth clearly separates the two species of Voalavo.
Distribution and ecology
Voalavo antsahabensis is only known from the forests at AnjozorobeAnjozorobe
Anjozorobe is a large town in Analamanga Region, Madagascar, approximately 90 kilometres north-east of the capital Antananarivo.Anjozorobe is famous with its corridor and with a pilgrim city of Anosivolakely where the Virgin Maria is reported to have appeared in 1990.Anjozorobe Forest Corridor is...
, on the eastern margin of Madagascar's Central Highlands
Central Highlands (Madagascar)
The Central Highlands, Central High Plateau, or Hauts-Plateaux are a mountainous biogeographical region in central Madagascar. They include the contiguous part of the island's interior above 800 m altitude...
. Among the specimens found in 2002, two were captured at 1425 m (4680 ft) altitude on a Uapaca densifolia branch, about 1.5 m (4.9 ft) over the ground, in moist montane forest, and a third was caught on the ground at 1275 m (4180 ft) altitude. This last specimen, a male, had its testicles located in the scrotum, and therefore was reproductively mature, even though its skull bones were not completely fused, indicating it was not yet osteologically
Osteology
Osteology is the scientific study of bones. A subdiscipline of anatomy, anthropology, and archeology, osteology is a detailed study of the structure of bones, skeletal elements, teeth, morphology, function, disease, pathology, the process of ossification , the resistance and hardness of bones , etc...
mature. Before it was collected in 2002, the species was not recorded in earlier biological surveys of Anjozorobe, taking place in 1977–1986 and 1996; whether this is because the animal is difficult to collect, because its abundance varies from year to year, or because its distribution is patchy is unknown. Goodman and colleagues argued on the basis of this example that rapid surveys may not necessarily yield complete inventories of the fauna of an area. Later surveys in 2005 and 2006 did find it at several other sites in the region, at some of which it was abundant. Anjozorobe is about 450 km (280 mi) from the nearest occurrence of V. gymnocaudus, and most of the intervening area contains montane forest. However, this forest zone is bisected by the low-lying Mandritsara Window, which may serve as a barrier between the two species of Voalavo.
Conservation status
Voalavo antsahabensis is listed as "Endangered" on the IUCN Red ListIUCN Red List
The IUCN Red List of Threatened Species , founded in 1963, is the world's most comprehensive inventory of the global conservation status of biological species. The International Union for Conservation of Nature is the world's main authority on the conservation status of species...
because of its small, vulnerable range; the Anjozorobe forest is threatened by the practice of slash-and-burn agriculture
Slash and burn
Slash-and-burn is an agricultural technique which involves cutting and burning of forests or woodlands to create fields. It is subsistence agriculture that typically uses little technology or other tools. It is typically part of shifting cultivation agriculture, and of transhumance livestock...
(tavy). However, its habitat has been designated as a protected area
Protected area
Protected areas are locations which receive protection because of their recognised natural, ecological and/or cultural values. There are several kinds of protected areas, which vary by level of protection depending on the enabling laws of each country or the regulations of the international...
, the Couloir Forestier d'Anjozorobe-Angavo.
Literature cited
- Goodman, S. 2009. . In IUCN. IUCN Red List of Threatened Species. Version 2010.2. <www.iucnredlist.org>. Downloaded on January 8, 2011.
- Goodman, S.M., Rakotondravony, D., Randriamanantsoa, H.N. and Rakotomalala-Razanahoeraa, M. 2005. A new species of rodent from the montane forest of central eastern Madagascar (Muridae: Nesomyinae: Voalavo) (subscription required). Proceedings of the Biological Society of Washington 118(4):863–873.