Blesmol
Encyclopedia
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 gopher
s of North America, the tuco-tuco
s in South America, or the Spalacidae
.
. Fossil
forms are also restricted almost exclusively to Africa
, although a few specimens have been found in Israel
. Nowak (1999) also reports that †Gypsorhynchus has been found in fossil deposits of Mongolia
.
-like animals with cylindrical bodies and short limbs. They range from 9 centimetre in length, and from 30 gram 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.
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.
Most blesmol species dig using their powerful incisors and, to a lesser extent, the foreclaws, although dune blesmol
s dig primarily with their feet, restricting them to soft, sandy soil. Dune blesmols aside, some species have been reported to be able to extend their burrows by an inch (2.5 cm (0.984251968503937 in)) into the walls of concrete enclosures. 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:
, 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.
(Fukomys damarensis) and the naked mole rat
(Heterocephalus glaber) are considered to be the only two eusocial mammals. 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.
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.
.
At present 22 species of blesmols from 6 genera are accepted, but this number is likely to increase. Like other fossorial rodents such as pocket gophers, tuco-tucos, and blind mole rat
s, 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, but most researchers accept that Heterocephalus holds that position.
Pocket gopher
The pocket gophers are burrowing rodents of the family Geomyidae. These are the "true" gophers, though several ground squirrels of the family Sciuridae are often called gophers as well...
s of North America, the tuco-tuco
Tuco-tuco
The tuco-tucos are members of a group of rodents that belong to the family Ctenomyidae. The tuco-tucos belong to a single genus: Ctenomys, but they include some 60 different species. The relationships among the species are debated by taxonomists. Their closest relatives are degus and other...
s in South America, or the Spalacidae
Spalacidae
The Spalacidae, or spalacids are a family of rodents in the large and complex superfamily Muroidea. They are native to eastern Asia, the Horn of Africa, the Middle East, and south-eastern Europe. It includes the blind mole rats, bamboo rats, root rats, and zokors...
.
Distribution
Modern blesmols are found strictly in sub-Saharan AfricaSub-Saharan Africa
Sub-Saharan Africa as a geographical term refers to the area of the African continent which lies south of the Sahara. A political definition of Sub-Saharan Africa, instead, covers all African countries which are fully or partially located south of the Sahara...
. Fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
forms are also restricted almost exclusively to Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
, although a few specimens have been found in Israel
Israel
The State of Israel is a parliamentary republic located in the Middle East, along the eastern shore of the Mediterranean Sea...
. Nowak (1999) also reports that †Gypsorhynchus has been found in fossil deposits of Mongolia
Mongolia
Mongolia is a landlocked country in East and Central Asia. It is bordered by Russia to the north and China to the south, east and west. Although Mongolia does not share a border with Kazakhstan, its western-most point is only from Kazakhstan's eastern tip. Ulan Bator, the capital and largest...
.
Anatomy
Blesmols are somewhat moleMole (animal)
Moles are small cylindrical mammals adapted to a subterranean lifestyle. They have velvety fur; tiny or invisible ears and eyes; and short, powerful limbs with large paws oriented for digging. The term is especially and most properly used for the true moles, those of the Talpidae family in the...
-like animals with cylindrical bodies and short limbs. They range from 9 centimetre in length, and from 30 gram 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
Somatosensory system
The somatosensory system is a diverse sensory system composed of the receptors and processing centres to produce the sensory modalities such as touch, temperature, proprioception , and nociception . The sensory receptors cover the skin and epithelia, skeletal muscles, bones and joints, internal...
. 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.
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.
Most blesmol species dig using their powerful incisors and, to a lesser extent, the foreclaws, although dune blesmol
Bathyergus
Bathyergus is the genus of dune mole rats endemic to South Africa. It contains two species — B. janetta, the Namaqua Dune Mole Rat, and B. suillus, the Cape Dune Mole Rat.-References:...
s dig primarily with their feet, restricting them to soft, sandy soil. Dune blesmols aside, some species have been reported to be able to extend their burrows by an inch (2.5 cm (0.984251968503937 in)) into the walls of concrete enclosures. 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
Dentition
Dentition pertains to the development of teeth and their arrangement in the mouth. In particular, the characteristic arrangement, kind, and number of teeth in a given species at a given age...
for the family is:
Technical characters
The skull morphology of blesmols sets them apart from all other rodents. As with all members of their suborderHystricognathi
Hystricognathi is an infraorder of rodents. Hystricognaths are distinguished from other rodents by the bone structure of their skulls. The masseter medialis passes partially through the infraorbital foramen and connects to the bone on the opposite side...
, their jaws are hystricognathous
Hystricognathi
Hystricognathi is an infraorder of rodents. Hystricognaths are distinguished from other rodents by the bone structure of their skulls. The masseter medialis passes partially through the infraorbital foramen and connects to the bone on the opposite side...
, but, unlike their relatives, they have a highly reduced infraorbital foramen
Infraorbital foramen
Above the canine fossa is the infraorbital foramen, the end of the infraorbital canal; it transmits the infraorbital artery, vein, and infraorbital nerve.-External links: *...
. 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.
Behavior
Blesmols live in elaborate burrow systems and different species exhibit varying degrees of sociality. Most species are solitary, but two species, the damaraland blesmolDamaraland Mole Rat
The Damaraland Mole Rat, or Damaraland blesmol is a burrowing rodent found in sub-Saharan Africa. Along with the smaller, less hairy Naked Mole Rat, it is one of only two known eusocial mammals....
(Fukomys damarensis) and the naked mole rat
Naked Mole Rat
The naked mole rat , also known as the sand puppy or desert mole rat, is a burrowing rodent native to parts of East Africa and the only species currently classified in the genus Heterocephalus...
(Heterocephalus glaber) are considered to be the only two eusocial mammals. 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
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
, 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.
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.
Classification
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 PhiomorphaPhiomorpha
The rodent parvorder or infraorder Phiomorpha comprises several living and extinct families found wholly or largely in Africa. Along with the Anomaluromorpha and perhaps the †Zegdoumyidae, they represent one of the few early colonizations of Africa by rodents....
.
At present 22 species of blesmols from 6 genera are accepted, but this number is likely to increase. Like other fossorial rodents such as pocket gophers, tuco-tucos, and blind mole rat
Blind mole rat
The genus Spalax contains the blind, fossorial, or subterranean mole rats, which are one of several types of rodents that are called mole rats. The hystricognath mole rats of the family Bathyergidae are completely unrelated, but some other forms are also in the family Spalacidae...
s, blesmols appear to speciate
Speciation
Speciation is the evolutionary process by which new biological species arise. The biologist Orator F. Cook seems to have been the first to coin the term 'speciation' for the splitting of lineages or 'cladogenesis,' as opposed to 'anagenesis' or 'phyletic evolution' occurring within lineages...
rapidly. They become geographically isolated easily, leading to various chromosomal
Chromosome
A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...
forms and genetically distinct races. Some studies have suggested that the genus Bathyergus
Bathyergus
Bathyergus is the genus of dune mole rats endemic to South Africa. It contains two species — B. janetta, the Namaqua Dune Mole Rat, and B. suillus, the Cape Dune Mole Rat.-References:...
represents the basal
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
-most lineage, but most researchers accept that Heterocephalus holds that position.
- Family Bathyergidae
- Subfamily Bathyerginae
- Georychus - Cape Blesmol
- Georychus capensis - Cape Blesmol
- CryptomysCryptomysCryptomys is the genus of common mole rats, endemic to Africa. Most of the species formerly placed in this genus were moved to the genus Fukomys in 2006.-References:...
- Cryptomys anomalus - no common name
- Cryptomys holosericeus - no common name
- Cryptomys hottentotus - Common Mole Rat
- Cryptomys natalensis - no common name
- Cryptomys nimrodi - Matabeleland Mole Rat
- FukomysFukomysFukomys is a recently-described genus of common mole rats, containing several species that were formerly placed in the genus Cryptomys; its species are endemic to Africa.-References:...
- Fukomys amatus - Zambian Blesmol
- Fukomys anselli - Ansell's Blesmol
- Fukomys bocagei - Bocage's Blesmol
- Fukomys damarensis - Damaraland Blesmol
- Fukomys darlingi - Mashona Blesmol
- Fukomys foxi - Nigerian Blesmol
- Fukomys ilariae - Somali striped Mole Rat
- Fukomys kafuensis - Kafue Blesmol
- Fukomys mechowii - Mechow's Blesmol
- Fukomys micklemi - Kataba Blesmol
- Fukomys occlusus - no common name
- Fukomys ochraceocinereus - Ochre Blesmol
- Fukomys whytei - Malawian Blesmol
- Fukomys zechi - Ghana Blesmol
- Heliophobius - Silvery Blesmol
- Heliophobius argenteocinereus - Silvery Blesmol
- BathyergusBathyergusBathyergus is the genus of dune mole rats endemic to South Africa. It contains two species — B. janetta, the Namaqua Dune Mole Rat, and B. suillus, the Cape Dune Mole Rat.-References:...
- Dune blesmols- Bathyergus janetta - Namaqua Dune Mole Rat
- Bathyergus suillus - Cape Dune Mole Rat
- Georychus - Cape Blesmol
- Subfamily Heterocephalinae - Naked Mole Rat
- Heterocephalus - Naked Mole Rat
- Heterocephalus glaber - Naked Mole Rat
- Heterocephalus - Naked Mole Rat
- Subfamily Bathyerginae