Amblysomus[1] (also narrow-headed golden mole or South African golden mole) is a genus of the golden mole family, Chrysochloridae,[2] comprising five species of the small, insect-eating, burrowing mammals endemic to Southern Africa. All five species can be found in South Africa and some are also found in Eswatini and Lesotho.[3]
The order of golden moles and tenrecs, Afrosoricida, is part of Afrotheria, one of the four main divisions of placental mammals, along with elephant shrews, aardvarks, hyraxes, sirenians and elephants.[4] Golden moles are not all golden. Some have black to pale tawny-yellow fur.; the name and family name “Chrysochloridae” (meaning green-gold), refers to the coppery gold, green, purple or bronze sheen of their dense fur.[5]
Description
They all have differences in size and color, but have a similar appearance” with compact fusiform or lozenge-shaped bodies, short and powerful forelimbs containing pick-like claws, and no external eyes, ears or tail”. Their fur consists of guard hairs that are moisture repellent. They have a woolly underfur for insulation. Their skin is thick and tough, especially on the head, containing a wedge-shaped muzzle with a leathery nosepad protecting its nostrils. upward thrust of their dorsally-flattened head and powerful down thrusts of the foreclaws help them tunnel through the soil during subsurface foraging. This creates raised visible ridges of soil. Genera Amblysomus and Neamblysomus use the head and webbed hind feet to move soil and evict it on the surface.[5]
Similarities to fossorial mammals resulted from ecological convergence, not ancestry. The eyes are vestigial and that is why they are covered by skin. The optic nerve is degenerate because they live underground where there is little use of them. The external ear pinnae are absent as well as the external tail. The body has a streamlined shape which facilitates movement through dense substratum.[5] On the outside, they are similar to other fossorial small mammals, but the golden moles show highly specialized characters like “a unique hyoid-dentary articulation. Some also have hypertrophied malleus bones in the middle ear that permits great sensitivity to underground vibrations and airborne sounds. They have a third bone in the forearm (i.e. ossified tendon) and a reduction of phalanges in the fore- and hindfeet. Muscle arrangements are not paralleled in the Mammalia. Most anatomical specializations shown in extant species are found in 3 fossil species (dating back to the Miocene). Chrysochlorids have been described as "spectacularly autapomorphic" due to how unusual and numerous they are.[5]
They are blind, subterranean small mammals[5] with small ears, tails and eyes that are all covered by skin and fur. They have unique cranial and nasal morphology.[5] On their nose is a large leathery pad to help them burrow. They have powerful forearms and claws, but use mainly their snout to burrow. The golden mole thrusts its forearms from under its body to help it burrow deeper into the earth.
Both the male and female have a cloaca. They have tabulars in the occipital which is not found in other mammals. Their zygomatic arches form elongations of the maxillae. Their malleus is enlarged and helps in hearing under the ground. Golden moles do not have a fifth finger on their front paws. Instead, they have a huge claw on the third or second finger. Their fur has an iridescent sheen.
Their dental formula is 3,1,3,2/3,1,3,2. The first incisor is enlarged. The lateral incisors and first premolars are like canines. The molars are zalmbdodont (have v-shaped crest) like tenrecs. Zalambdodonty has arisen independently. This implies that it is due to morphological convergence, because they are not closely allied to any other family of extant mammals.[5]
Studies show that tenrecs and golden moles should be separated from Insectivora and placed in Afrotheria which include the elephant shrews and hyraxes.[4] They share few morphological synapomorphies. Mitochondrial/nuclear gene sequences and rare genomic changes demonstrated that chrysochlorids and tenrecs form their own clade, Afrosoricida (African shrew-like mammals). It contains no soricids (shrews) and is sometimes confused with the shrew subgenus Afrosorex. Alternative names were "Tenrecoidea" and "Tenrecomorpha”. Divergence between golden-moles and tenrecs occurred about 50million years ago. They are now classified as Chrysochloridea instead of a specialized members of Order Insectivora.[5]
Natural history
Golden moles are common throughout southern Africa. There are 7 genera and 18 species known. They resemble the Talpidae (true moles) and Notoryctidae (marsupial moles).[4] Two subfamilies may be recognized: the Chrysochlorinae, in which the malleus bone of the middle ear is enlarged with a spherical or club-like shape and the Amblysominae, in which the malleus is not expanded and has the typical mammalian shape (i.e. Amblysomus).[5]
All 21 species of golden moles are endemic to subSaharan Africa. They inhabit a wide altitudinal, climatic and vegetational spectrum of subterrestrial habitats. The highest diversity is found in southern Africa. Only three species occur outside the region (i.e. Calcochloris leucorhinus; Chrysochloris; and Calcochloris tytonis). The South African species fall into two ecological groups: semi-desert (Eremitalpa granti, Cryptochloris zyli and C. wintoni), karroid (Chrysochloris visagiei) or fynbos habitats (Chrysochloris asiatica) along the south-west coast; and indigenous forests, savanna woodlands and temperate grasslands in the eastern part of the subregion (Chrysospalax, Chlorotalpa, Calcochloris, Neamblysomus and Amblysomus).[5]
Only the Hottentot golden mole (Amblysomus hottentotus) and the Cape golden mole (Chrysochloris asiatica) are widespread. The Stuhlmann's golden mole (Chrysochloris stuhlmanni) and Juliana's golden mole Neamblysomus julianae), are known from scattered localities situated hundreds of kilometres apart, but connected by continuous favourable habitat. These may be more widespread than is indicated by the scant distribution data currently available. Other species, such as Sclater's golden mole (Chlorotalpa sclateri), probably have more restricted ranges than general texts indicate, since the few populations known to exist occur at localities separated by wide expanses of seemingly inhospitable habitat. Geographical continuity between these isolates seems unlikely.[5]
Despite a high thermal conductance, the golden mole has a low basal metabolic rate. They reduce their thermoregulatory energy requirements and enter torpor, (i.e. either daily or in the cold). Body temperature in the thermal neutral zone is lower than in other small mammals. Efficient renal function effectively reduces water requirements so that they do not need to drink. Specializations allow them to survive in extreme habitats and where food is seasonally or perennially scarce.[5]
Most golden mole species are restricted to a narrow range of habitats and environmental conditions. They have very limited mobility and dispersal abilities. They are specialized K-selected strategists, opportunistic insectivores. They eat primarily invertebrates they find.[4] They feed on earthworms, termites and millipedes. Their diets may vary due to the abundance of prey items.[5]
Most are solitary and subterrestrial. They construct semi-permanent tunnel systems. Their tunnels consists of an upper tier of burrows used for foraging and a lower tier with inter-connecting chambers used for resting and raising young (except the Namib (Eremitalpa granti namibensis) who “swims" through the desert in search for termite nests.[5]
Populations of golden moles are restricted to patches of habitat with friable soils and abundant invertebrates. Their distribution is clumped and sympatric. Different species rarely coexist to compete for resources. If two species occur in the same area they tend to occupy different microhabitats due to ecological displacement.[5]
In courtship the male chirrups, bobs his head and stomps his foot and the female rasps and squeals. Reproductive data suggests that golden moles breed throughout the year, but peaks in the wetter months when food is more abundant. Some think they are polyoestrous. Litter sizes are usually 2. Post-natal development reaches up to 45.[5]
The behavior of all golden moles is primarily solitary and territorial. They live in deserts and swamps. The Golden mole digs and lives in burrows.[4] Territorial golden moles fight viciously when confined together. Studies show that small groups may hibernate together, but only in the giant golden mole. Burrows used by more than one mole. The Hottentot golden mole will fight aggressively with either sex by using their foreclaws to wrestle, and biting at the abdomen. Fighting is accompanied by high-pitched squeaks. The golden mole actively defends its burrow systems range overlap, and the dominant mole take over neighbouring burrows to increase its home range.[5]
The IUCN Red List of Threatened Species includes 10 South African golden mole species. The De Winton's golden mole (Cryptochloris wintoni) is critically endangered. Marley's golden mole (Amblysomus marleyi), Giant golden mole (Chrysospalax trevelyani), Van Zyl's golden mole (Cryptochloris zyli), Gunning's golden mole (Neamblysomus gunningi), and Juliana's golden mole (Neamblysomus julianae) are endangered. The topotypical population of Juliana's golden mole is critically endangered. Robust golden mole (Amblysomus robustus), Arend's golden mole (Carpitalpa arendsi), Duthie's golden mole (Chlorotalpa duthieae), Rough-haired golden mole (Chrysospalax villosus) are vulnerable. Grant's golden mole (Eremitalpa granti), Fynbos golden mole (Amblysomus corriae), and Highveld golden mole (Amblysomus septentrionalis) are near threatened. Congo golden mole (Calcochloris leucorhinus) Somali golden mole (Calcochloris tytonis), Visagie's golden mole (Chrysochloris visagiei) are listed as Data Deficient.[6]
Threatened species have restricted or fragmented distributions. Populations subjected to habitat degradation due to human activities like mining, urbanization, agriculture and the poor forest management.[5] Husbandry projects have been conducted on the Golden mole. This included captivity for a few weeks up to nearly two years. Individuals were housed separately in containers of rich soil/sand. They were fed daily with insects and earthworms. Water was provided ad libitum because they do not drink in the wild. Some get pinky mice and frozen day-old chicks (Bronner) Room temperature is okay, but not below 15°C or above 30°C. This range does not disrupt their endogenous torpor rhythms. Torpor reduces the amount of food intake. DO not handle them as they sleep. They will awaken and the stress will cause them to stop eating and physiological decline others.[5]
Research review
The question of higher-level relationships among placental mammal centers on the order Inserctivora. Huxley argued that insectivores retain many primitive features. They are closer to their ancestor mammals than the living groups. Cladistic analysis suggests that living insectivores are “united by derived anatomical features”. Insectivores are not monophyletic, golden moles included. This clade also includes hyraxes, manatees, elephants, elephant shrews and aardvarks. They are from an African origin. Suggested from 12S ribosomal RNA transversions, African radiation came from a single common ancestor and gave rise to divergence during Cretaceous period. This is before the land connections were developed with Europe in the early Cenozoic era.[7]
The middle ear of nine families of golden moles (family Chrysochloridae) were examined to see the ossicular apparatus. The Amblysomus species have ossicles typical of mammals. The Chrysospalax, Chrysochloris, Cryptochloris and Eremitalpa species do not. They ”have enormously hypertrophied mallei. Golden moles differ in the nature and extent of the interbullar connection, the shape of the tympanic membrane and that of the manubrium. The stapes has an unusual orientation, projecting dorsomedially from the incus. It has been proposed that hypertrophied ossicles in golden moles are adapted towards the detection of seismic vibrations. The functional morphology of the middle ear apparatus is reconsidered in this light, and it is proposed that adaptations towards low-frequency airborne hearing might have predisposed golden moles towards the evolution of seismic sensitivity through inertial bone conduction. The morphology of the middle ear apparatus sheds little light on the disputed ordinal position of the Chrysochloridae.”[8]
Abstract: The densities of middle ear ossicles of golden moles (family Chrysochloridae, order Afrosoricida) were measured using the buoyancy method. The internal structure of the malleus was examined by high-resolution computed tomography, and solid-state NMR was used to determine relative phosphorus content. The malleus density of the desert golden mole Eremitalpa granti (2.44g/cm3) was found to be higher than that reported in the literature for any other terrestrial mammal, whereas the ossicles of other golden mole species are not unusually dense. The increased density in Eremitalpa mallei is apparently related both to a relative paucity of internal vascularization and to a high level of mineralization. This high density is expected to augment inertial bone conduction, used for the detection of seismic vibrations, while limiting the skull modifications needed to accommodate the disproportionately large malleus. The mallei of the two subspecies of E. granti, E. g. granti and E. g. namibensis, were found to differ considerably from one another in both size and shape.[9]
Not so long ago, there was a lot of uncertainty regarding how clades of living mammals were interrelated. Many mammalian systematists believed that golden moles (Chrysochloridae) were “insectivorans” along with shrews and hedgehogs. It appears in most studies as the sister taxon to Tenrecidae-Chrysochloridae-Macroscelididae, but has also been placed as sister taxon to Chrysochloridae, Tenrecidae, or to a macroscelidid-chrysochlorid clade. Relatedly, tenrecids and chrysochlorids are generally reconstructed as sister taxa, except for those studies just noted. Different resolutions of intra-afrotherian phylogeny, particularly the intriguing possibility that tenrecids, chrysochlorids, and macroscelidids are more basal than paenungulates have important implications for understanding the afrotherian common ancestor as occupying either an ungulate- or insectivoran-grade niche. The quality of the fossil record of some afrotherian lineages, such as proboscideans, hyracoids and sirenians, is relatively good, and while that of other afrotherians is much poorer, it too is benefiting from a steady pace of discovery. ... Afrotheria (paenungulates, aardvarks, tenrecs, golden moles) comprising a single clade (Atlantogenata) at the base of Placentalia, and with all other placentals in the clade Boreoeutheria, has received relatively consistent support since 2007. Hence, there now is good phylogenetic reason to scrutinize a major division within Placentalia: afrotherians and xenarthrans (“southern” placentals) on the one hand, and boreoeutherians (“northern” placentals) on the other. For example, Leche argued that in tenrecs and golden moles, “der Zahnwechsel in eine sehr späte Lebensphase fällt” (“tooth replacement occurs in a very late period of life”) based on the observation that individuals of adult size retain deciduous teeth and/or have not yet erupted their permanent successors”.[10]
Related Research Articles
Moles are small mammals adapted to a subterranean lifestyle. They have cylindrical bodies, velvety fur, very small, inconspicuous eyes and ears, reduced hindlimbs, and short, powerful forelimbs with large paws adapted for digging.
Placental mammals are one of the three extant subdivisions of the class Mammalia, the other two being Monotremata and Marsupialia. Placentalia contains the vast majority of extant mammals, which are partly distinguished from monotremes and marsupials in that the fetus is carried in the uterus of its mother to a relatively late stage of development. The name is something of a misnomer considering that marsupials also nourish their fetuses via a placenta, though for a relatively briefer period, giving birth to less developed young which are then nurtured for a period inside the mother's pouch. Placentalia represents the only living group within Eutheria, which contains all mammals more closely related to placentals than to marsupials.
The order Insectivora is a now-abandoned biological grouping within the class of mammals. Some species have now been moved out, leaving the remaining ones in the order Eulipotyphla within the larger clade Laurasiatheria, which makes up one of the basal clades of placental mammals.
Golden moles are small insectivorous burrowing mammals endemic to Sub-Saharan Africa. They comprise the family Chrysochloridae and as such they are taxonomically distinct from the true moles, family Talpidae, and other mole-like families, all of which, to various degrees, they resemble as a result of evolutionary convergence. There are 21 species. Some are relatively common, whereas others are rare and endangered.
The clade Afrosoricida contains the golden moles of Southern Africa, the otter shrews of equatorial Africa and the tenrecs of Madagascar. These three groups of small mammals were for most of the 19th and 20th centuries regarded as a part of the Insectivora or Lipotyphla, but both of those groups, as traditionally used, are polyphyletic.
A tenrec is any species of mammal within the afrotherian family Tenrecidae, which is endemic to Madagascar. Tenrecs are a very diverse group; as a result of convergent evolution some resemble hedgehogs, shrews, opossums, rats, and mice. They occupy aquatic, arboreal, terrestrial, and fossorial environments. Some of these species, including the greater hedgehog tenrec, can be found in the Madagascar dry deciduous forests. However, the speciation rate in this group has been higher in humid forests.
Afrotheria is a superorder of mammals, the living members of which belong to groups that are either currently living in Africa or of African origin: golden moles, elephant shrews, otter shrews, tenrecs, aardvarks, hyraxes, elephants, sea cows, and several extinct clades. Most groups of afrotheres share little or no superficial resemblance, and their similarities have only become known in recent times because of genetics and molecular studies. Many afrothere groups are found mostly or exclusively in Africa, reflecting the fact that Africa was an island continent from the Cretaceous until the early Miocene around 20 million years ago, when Afro-Arabia collided with Eurasia.
The web-footed tenrec, Malagasy otter shrew, or aquatic tenrec is the only known semiaquatic tenrec, and is found in eastern Madagascar, especially in and around Ranomafana National Park. It grows to between 25 and 39 cm, and was once thought to be extinct. It feeds on crabs, aquatic insects, and crayfish. The population is considered vulnerable. It was formerly placed in the monotypic genus Limnogale, but has been moved to Microgale based on molecular data showing it to be deeply nested within the latter.
Juliana's golden mole is a golden mole endemic to South Africa. It is listed as an endangered species due to habitat loss and a restricted range. Golden moles are an ancient group of mammals that live mostly below ground. The eponymous Juliana is Juliana Meester, the wife of the South African zoologist who named this species.
The Afroinsectiphilia is a clade that has been proposed based on the results of recent molecular phylogenetic studies. Many of the taxa within it were once regarded as part of the order Insectivora, but Insectivora is now considered to be polyphyletic and obsolete. This proposed classification is based on molecular studies only, and there is no morphological evidence for it.
Pseudoungulata, or "false hoofed mammals", is a possible clade made up of two subgroups, aardvarks and paenungulates. Before this group was proposed, it was thought that aardvarks were more closely related to xenarthrans. However, all of these mammals are now considered to be part of Afrotheria, which also includes elephant shrews and afrosoricidans. Other positions of aardvarks within Afrotheria are possible, such as being closest relatives of elephant shrews and/or afrosoricidans.
Marley's golden mole is a species of burrowing mammal in the golden mole family, Chrysochloridae. It is found in South Africa and possibly Eswatini. It has been separated from Amblysomus hottentotus by Bronner. Its natural habitat is indigenous forests and moist grassland, and also gardens. It is classified as Endangered in the IUCN Red List of Threatened Species. The main threats it faces are habitat degradation, either through overgrazing by cattle or the removal of vegetation for firewood, and urbanization.
The Congo golden mole is a species of mammal in the family Chrysochloridae. It is found in Angola, Cameroon, Central African Republic, Republic of the Congo, and Democratic Republic of the Congo. Its natural habitats are subtropical or tropical forest, arable land, pastureland, plantations, and rural gardens.
The rough-haired golden mole is a species of mammal that live mostly below ground. They have shiny coats of dense fur and a streamlined, formless appearance. They have no visible eyes or ears; in fact, they are blind - the small eyes are covered with hairy skin. The ears are small and are hidden in the animal's fur.
De Winton's golden mole is a species of mammal in the family Chrysochloridae. It is endemic to South Africa. Its natural habitats are subtropical dry shrubland, Mediterranean-type shrubby vegetation, and sandy shores. It is threatened by habitat destruction and is "critically endangered". It was named after British zoologist William Edward de Winton.
Potamogalidae is the family of "otter shrews", a group of semiaquatic riverine afrotherian mammals indigenous to sub-Saharan Africa. They are most closely related to the tenrecs of Madagascar, from which they are thought to have split about 47–53 million years ago. They were formerly considered a subfamily of Tenrecidae.
Afroinsectivora is a clade of mammals that includes the macroscelideans and afrosoricidans. This clade includes the elephant shrews, golden moles and tenrecs.
↑ Mason, MJ (2006). "Morphology of the middle ear of golden moles (Chrysochloridae)". Journal of Zoology. 260 (4): 391–403. doi:10.1017/S095283690300387X.
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