This article needs additional citations for verification .(November 2007) |
Blesmols Temporal range: | |
---|---|
![]() | |
Damaraland mole-rat | |
Scientific classification ![]() | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Mammalia |
Order: | Rodentia |
Parvorder: | Phiomorpha |
Family: | Bathyergidae Waterhouse, 1841 |
Type genus | |
Bathyergus Illiger, 1811 | |
Genera | |
|
The blesmols, also known as mole-rats, or African mole-rats, are burrowing rodents of the family Bathyergidae. They represent a distinct evolution of a subterranean life among rodents much like the pocket gophers of North America, the tuco-tucos in South America, or the Spalacidae from Eurasia.
Modern blesmols are found strictly in sub-Saharan Africa. Fossil forms are also restricted almost exclusively to Africa, although a few specimens of the Pleistocene species Cryptomys asiaticus have been found in Israel. [1] Nowak (1999) also reports that †Gypsorhychus has been found in fossil deposits of Mongolia.
Blesmols are somewhat mole-like animals with cylindrical bodies and short limbs. They range from 9 to 30 cm (3.5 to 11.8 in) in length, and from 30 to 1,800 g (1.1 to 63.5 oz) in weight, depending on the species. Blesmols, like many other fossorial mammals, have greatly reduced eyes and ear pinnae, a relatively short tail, loose skin, and (aside from the hairless naked mole rat) velvety fur. Blesmols have very poor vision, although they may use the surfaces of their eyes for sensing air currents. Despite their small or absent pinnae, they have a good sense of hearing, although their most important sense appears to be that of touch. Like other rodents, they have an excellent sense of smell, and they are also able to close their nostrils during digging to prevent them from clogging with dirt. [2]
The eyes of blesmols are structurally normal, despite their relatively small size, and include normal light-sensitive cells. However, the visual centres of their brains are reduced in certain respects, especially in those centres concerned with localising objects in the visual field. Research has shown that at least two species of blesmol ( Fukomys mechowii and Heliophobius argenteocinereus ) are not blind, as commonly believed, and will actively avoid blue or green-yellow light. They do not appear able to detect the presence of red light, and can probably not distinguish between different colours. The ability to sense the presence of light is probably useful in allowing them to detect breaches in their tunnel systems and repair them promptly. [3]
Most blesmol species dig using their powerful incisors and, to a lesser extent, the foreclaws, although dune blesmols dig primarily with their feet, restricting them to soft, sandy soil. [2] Dune blesmols aside, some species have been reported to be able to extend their burrows by an inch (2.5 cm (0.98 in)) into the walls of concrete enclosures.[ citation needed ] Their unique skull shape is associated with delivering sheer power to the lateral masseter muscle which is responsible for the powerful bite of the anterior portion of the mouth. The incisors of blesmols are projected forward and protrude from the mouth even when the mouth is closed. This condition allows the animals to burrow with their teeth without getting dirt in their mouths. The number of cheek teeth varies greatly between species, an unusual feature among rodents, so that the dental formula for the family is:
Dentition |
---|
1.0.2-3.0-3 |
1.0.2-3.0-3 |
The skull morphology of blesmols sets them apart from all other rodents. As with all members of their suborder, their jaws are hystricognathous, but, unlike their relatives, they have a highly reduced infraorbital foramen. The medial masseter muscle shows only minimal passage through the infraorbital foramen leading most authorities to consider them protrogomorphous. They are therefore the only protrogomorphous hystricognaths.
Blesmols live in elaborate burrow systems and different species exhibit varying degrees of sociality. Most species are solitary, but one species, the damaraland blesmol (Fukomys damarensis) is one of only two eusocial mammals, the other being the naked mole rat.[ citation needed ] These species are characterized by having a single reproductively active male and female in a colony where the remaining animals are sterile.
These animals prefer loose, sandy soils and are often associated with arid habitats. They rarely come to the surface, spending their entire life underground. Blesmols are herbivorous, and primarily eat roots, tubers, and bulbs. They are even able to pull smaller plants underground by their roots, without having to leave their burrows, enabling them to eat leaves, stems, and other parts of the plant that would otherwise be inaccessible. Blesmols burrow in search of food, and the great majority of their tunnel complex consists of these foraging burrows, surrounding a smaller number of storage areas, nests, and latrine chambers. [2]
Most species breed only once or twice during the year, although some breed all year round. They generally have small litters of two to five young, perhaps because their environment is sufficiently safe that they do not need to rapidly replace their population as many other rodents do. However, some species have much larger litters, averaging twelve young in the naked mole rat, and sometimes much larger. [2]
The Bathyergidae are monophyletic, with all taxa tracing back to a single common ancestor. [4] Although there is some controversy, the closest living relatives of the blesmols appear to be other African hystricognaths in the families Thryonomyidae (cane rats) and Petromuridae (dassie rats). Together these three living families along with their fossil relatives represent the infraorder Phiomorpha. [5]
At present 21 species of blesmols from 5 genera are accepted, [6] [7] [8] but this number is likely to increase. Like other fossorial rodents such as pocket gophers, tuco-tucos, and blind mole rats, blesmols appear to speciate rapidly. They become geographically isolated easily, leading to various chromosomal forms and genetically distinct races. Some studies have suggested that the genus Bathyergus represents the basal-most lineage; while many researchers had posited that the Naked mole-rat, Heterocephalus , held that position, [6] [7] [9] more recent investigation has placed that genus in a separate family, Heterocephalidae. [10] [11] [12]
Mole-rat or mole rat can refer to several groups of burrowing Old World rodents:
The rodent subfamily Rhizomyinae includes the Asian bamboo rats and certain of the African mole-rats. The subfamily is grouped with the Spalacinae and the Myospalacinae into a family of fossorial muroid rodents basal to the other Muroidea.
The naked mole-rat, also known as the sand puppy, is a burrowing rodent native to the Horn of Africa and parts of Kenya, notably in Somali regions. It is closely related to the blesmols and is the only species in the genus Heterocephalus.
Caviomorpha is the rodent infraorder or parvorder that unites all New World hystricognaths. It is supported by both fossil and molecular evidence. The Caviomorpha was for a time considered to be a separate order outside the Rodentia, but is now accepted as a genuine part of the rodents. Caviomorphs include the extinct Heptaxodontidae, the extinct Josephoartigasia monesi and extant families of chinchilla rats, hutias, guinea pigs and the capybara, chinchillas and viscachas, tuco-tucos, agoutis, pacas, pacaranas, spiny rats, New World porcupines, coypu and octodonts.
The Hystricognathi are an infraorder of rodents, distinguished from other rodents by the bone structure of their skulls. The masseter medialis passes partially through a hole below each eye socket and connects to the bone on the opposite side. This, together with their lack of an infraorbital plate and the relative size of the infraorbital foramen, distinguishes hystricognaths from other rodent groups.
The rodent parvorder or infraorder Phiomorpha comprises several living and extinct families found wholly or largely in Africa. Along with Anomaluromorpha and perhaps the extinct Zegdoumyidae, it represents one of the few early colonizations of Africa by rodents.
The term Hystricomorpha has had many definitions throughout its history. In the broadest sense, it refers to any rodent with a hystricomorphous zygomasseteric system. This includes the Hystricognathi, Ctenodactylidae, Anomaluridae, and Pedetidae. Molecular and morphological results suggest the inclusion of the Anomaluridae and Pedetidae in Hystricomorpha may be suspect. Based on Carleton & Musser 2005, these two families are discussed here as representing a distinct suborder Anomaluromorpha.
The Damaraland mole-rat, Damara mole rat or Damaraland blesmol, is a burrowing rodent found in southern Africa. Along with the smaller, less hairy, naked mole rat, it is a species of eusocial mammal.
Cryptomys is the genus of mole-rats, endemic to Africa. Most of the species formerly placed in this genus were moved to the genus Fukomys in 2006.
The Cape mole-rat is a species of mole-rat endemic to South Africa. It is the only extant species currently described as belonging to the genus Georychus.
The Cape dune mole-rat is a species of solitary burrowing rodent in the family Bathyergidae. It is endemic to South Africa and named for the Cape of Good Hope.
Ansell's mole-rat is a species of rodent in the family Bathyergidae. It is endemic to Zambia. Its natural habitats are moist savanna and miombo forests. It is noted for its very long tunnels, up to 2.8 km (1.7 mi) for a single colony of only ten individuals. The colonies are made of a eusocial system. They include a main reproductive king and queen that are thought to be faithful to one another.
The Nigerian mole-rat is a species of rodent in the family Bathyergidae. It is found in northern Nigeria and Cameroon. A colonial, subterranean species, its natural habitats are tropical dry lowland grassland, riverside woodland and rocky places.
Mechow's mole-rat is a species of rodent in the family Bathyergidae. It is found in Angola, Democratic Republic of the Congo, Zambia, and possibly Malawi. Its natural habitats are moist savanna, subtropical or tropical dry shrubland, and subtropical or tropical dry lowland grassland. This mole-rat was first described by the German naturalist Wilhelm Peters in 1881. The specific epithet honours the Prussian explorer and naturalist Friedrich Wilhelm Alexander von Mechow.
The Ghana mole-rat or Togo mole-rat is a species of rodent in the family Bathyergidae. It is endemic to Ghana.
The Zambian mole-rat is a species of rodent in the family Bathyergidae. It is found in Zambia and the Democratic Republic of the Congo. It was formerly considered a subspecies of Cryptomys hottentotus.
Rodents are mammals of the order Rodentia, which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are native to all major land masses except for New Zealand, Antarctica, and several oceanic islands, though they have subsequently been introduced to most of these land masses by human activity.
The common mole-rat, African mole-rat, or Hottentot mole-rat, is a burrowing rodent found in Southern Africa, in particular in the Western Cape province of South Africa. It also occurs in Eswatini, Lesotho, Malawi, Mozambique, Tanzania, Zambia, and Zimbabwe. It is a species in the subfamily Bathyerginae.
Fukomys is a genus described in 2006 of common mole-rats, containing several species that were formerly placed in the genus Cryptomys; its species are endemic to Africa. The species contained in the genus includes :