Rats, Mice, and Relatives: Muridae
The Murids are classified in four subfamilies, and about 140 genera. The family name Muridae is sometimes used in a broader sense to include all members of the superfamily Muroidea. The rat is commonly transmitted poison from the bark of the poison arrow tree, Acokanthera schimperi, on which it eats, on these hairs, forming a defensive mechanism that can sicken or even kill predators that try to bite it. The forefeet are big, and digit 1 does not have a claw, but digits 2–5 have a well-developed claw. The maned rat, also known as the (African) crested rat (Lophiomys imhausi), is a nocturnal, long-haired, bushy-tailed East African rodent with a porcupine-like appearance. Rats, mice, and relatives are found throughout the world except for the extreme polar regions of Earth.
They are thought to have developed from hamster-like creatures in tropical Asia during the early Miocene and have only generated species that can survive in colder regions since then. As a result of hitching a ride alongside human migrations throughout the current geological age, they have grown notably abundant globally. Another large group, restricted to Africa and the Middle East to Central Asia. Most species inhabit dry areas with sparse vegetation, including deserts. Granivorous and herbivorous, but some also consume large numbers of insects.
A molecular phylogenetic investigation of several of the taxa now classified as Murinae or Dendromurinae has never been performed. All of the genera are found in Africa, implying that the deomyines originated there. The subfamily Deomyinae includes four mouse-like rodent genera that were previously classified in the subfamilies Murinae and Dendromurinae. They are frequently referred to as the Acomyinae, especially in references that before the finding that Deomys ferruginous, the link rat, is a member of a group.
The rare Ethiopian water mouse (Nilopegamys plumbeus) is known only from a mountain tributary of the Blue Nile, and is critically endangered (IUCN, 2006); it may even be extinct. It is the only African rodent to show the degree of adaptation to aquatic life and swimming ability evident in the Neotropical Ichthyomyinae and in the Australian Hydromyinae (Peterhans and Patterson, 1995). Goslingi or Malacomys spp., which belong to the ‘wading murid’ niche and have feet that are elongated and thin. They serve the purpose of raising the body so that these animals can hunt by wading in shallow water (Kingdon, 1974). The Muridae, or murids, are the biggest rodent and mammal family in the world, with over 700 species including many mice, rats, and gerbils found in Eurasia, Africa, and Australia.
They occupy ecosystems ranging from dry desert to wet tropical forest, from tundra to savanna to temperate woodland. Some species are semiaquatic; others live underground; yet others spend their entire lives in the canopy of tropical forest. Their food habits range from true omnivores to specialists on earthworms, subterranean fungi, even aquatic invertebrates. Some species cause millions of damage to agricultural lands and stored foods. Others are the vectors or reservoirs of a number of diseases that have periodically devasted human populations (and continue to do so). Some are important biological controls of pestiferous insects.
Mammals display the full range of lung maturity at birth from the Muridae and dogs, where alveolarization is entirely postnatal, to the guinea pig where the full complement of alveoli appears to be present at birth. Likewise, it is clear that in some species (mice, rats, primates, pigs, rabbits) new alveoli form into early adulthood while in other species postnatal neoalveolarization is limited (guinea pigs, sheep) (Figure 1). There still remain significant gaps in our knowledge of species-specific changes in lung structure with age, and research is required in this field. In particular, studies on the “normal” changes in lung structure into senescence are warranted. In contrast, in species where environmental exposures and infection are not controlled (e.g., dog, nonhuman primates), there is evidence of emphysematous changes in lung structure in the latter stages of life (Figure 1).
Research animal vendors sell a variety of outbred stocks and inbred strains of the laboratory mouse (Mus domesticus). Different mouse strains have different coat colours and other traits. Commercially accessible mice come in a variety of species and genera.
Above, the animal is dark to grey-brown, and below, it is pale grey-brown. The zygomatic plate is massive, the snout is long and wide, and the interorbital breadth is broad). The Togo mouse is thought to be insectivorous based on its skull anatomy. Mice are members of the Rodentia order’s Muridae rat family.
Among Aesop’s Fables are The Cat and the Mice and The Frog and the Mouse. In James Herbert’s first novel, The Rats, (1974), a vagrant is attacked and eaten alive by a pack of giant rats; further attacks follow. The name Muridae comes from the Latin mus (genitive muris), meaning “mouse”, since all true mice belong to the family, with the more typical mice belonging to the genus Mus. Four clawed digits are found on each forefoot (the pollex or “thumb” is small and bears a nail); the hind foot in most has five clawed digits (but sometimes the hallux or first toe has a nail). Other external features (ears, eyes, tail, pelage, etc.) are extremely variable.
Having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. The mane erects when the animal is scared or agitated, stripping portions and exposing the glandular region.
Although none of them is native to the Americas, a few species, notably the house mouse and black rat, have been introduced worldwide. Fossorial, arboreal, and semiaquatic murid species occur, though most are terrestrial. The extensive list of niches filled by murids helps to explain their relative abundance.
Murids have sciurognathous jaws (a rodent ancestral trait), as well as a diastema. Three molars are usually present (but one or two are occasionally seen), and the nature of the molars varies by genus and eating style. They have a head and body length of 2.4 to 11.4 inches (6.1 to 29.0 centimeters); tail length of 1 to 6.3 inches (3 to 16 centimeters); and weight of 0.4 to 18 ounces (12 to 510 grams). An apparent coevolution of hantaviruses with their reservoir hosts is evident by the commonly observed close association of each hantavirus species with a certain rodent species. Depending on the population density, up to 50% of any given population of rodents are seropostive and considered as silent carriers for hantaviruses.
Nemirov et al. (2002) have examined the phylogenetic trees of hantaviruses and compared these to the D-loop region of mitochondrial DNA. These studies show a remarkable concordance between murine evolution and the evolution of hantaviruses. Focusing on the divergence of Saaremaa virus from Dobrava virus, Nemirov et al. have speculated that Saaremaa virus has evolved as a result of Dobrava virus switching host from the yellow-striped field mouse (Apodemus flavicollis) to A. The result is a virus with a reduced pathogenicity for humans compared to Dubrova virus, although there are some qualifications as to just how pathogenic the latter virus really is. Other examples include transmission of Monongahella virus from Peromyscus maniculatus to P. leucopus, eventually leading to the evolution of New York virus (Morzunov et al., 1998).
Murids are found nearly everywhere in the world, though many subfamilies have narrower ranges. Although none of them are native to the Americas, a few species, notably the house mouse and black rat, have been introduced worldwide. Murids occupy a broad range of ecosystems from tropical forests to tundras. Fossorial, arboreal, and semiaquatic murid species occur, though most are terrestrial animals.[4] The extensive list of niches filled by murids helps to explain their relative abundance.
They have front paws with four digits and a short thumb, and hind feet with five digits. Their soft, thick fur varies in color (depending on the species) from gray to reddish brown, and their underparts can be white, gray, or black. Check this for Doeat.top Omnivorous animals They have excellent senses of hearing and smell, but poor eyesight (even though they have large, round eyes). Adults are 2 to 13.4 inches (5 to 34 centimeters) long and weigh between 0.9 and 31.7 ounces (25 to 900 grams).
The taxonomy of southern African gerbils is still under revision as chromosomal and molecular data are expanded. Recent studies have suggested that the genus Gerbillurus should be incorporated into the genus Gerbilliscus (Colangelo et al., 2007), based on their analyses of mitochondrial genes. Knight et al. (2013) adopted the new nomenclature, naming all former Gerbillurus species as Gerbilliscus. Setzeri specimen used for the molecular analyses in the studies by Chevret and Dobigny (2005), Colangelo et al. (2007), and Granjon et al. (2012) is given as Western Cape, South Africa, whereas G. Setzeri is endemic to the Namib Desert with the southern limit of its distribution being the Kuiseb River, about 1500 km distant from the Western Cape (Dempster, Perrin, Downs, & Griffin, 1998). Setzeri used in the analyses of Colangelo et al. (2007), Chevret and Dobigny (2005), and Granjon et al. (2012).
Some groups are known to be monophyletic (hamsters, voles, African pouched rats, gerbils, Old World rats and mice, African spiny mice, platacanthomyines, zokors, blind mole rats, and bamboo rats). Other groups, however, cannot be classified with certainty and may or may not be a hodgepodge of unrelated genera and species (New World rats and mice, dendromurines, and Malagasy rats and mice). Also unresolved are the affinities of subfamilies containing only one genus (mouselike hamsters, the maned rat). The Muridae is the largest family of mammals (numbering over 1300 species), with a great variety of adaptations to life in and around water. Oddly, however, there are no water rats in the Asian tropics.
They are most commonly some shade of brown in colour, although many have black, grey, or white markings. A broad range of feeding habits is found in murids, ranging from herbivorous and omnivorous species to specialists that consume strictly earthworms, certain species of fungi, or aquatic insects. Most genera consume plant matter and small invertebrates, often storing seeds and other plant matter for winter consumption. Murids have sciurognathous jaws (an ancestral character in rodents) and a diastema is present. Generally, three molars (though sometimes only one or two) are found, and the nature of the molars varies by genus and feeding habit. Murids have sciurognathous jaws (an ancestral character in rodents) and a diastema is present.[5] Murids lack canines and premolars.
One study reported that this species had an abnormally high occurrence of gastric adenocarcinoma (Oettle, 1957). Further studies have determined these masses to be gastric carcinoids (Snell and Stewart, 1969). As a result, this species is actively used in the study of mechanisms of gastric hyperplasia and carcinoid formation (Kidd et al., 2000). Around 1150 living species of murid rodents have been described, but surely many more remain to be discovered. These are placed in around 260 genera, which are distributed among 17 subfamilies.
Whether recognized as the family Muridae or the superfamily Muroidea, the living members of these 18 groups show an impressive range of variation in body form, locomotion, and ecology. Colangelo et al. (2007) estimated the times of divergence of taxonomic groups included in their study. Auricularis is separated from all Gerbilliscus species occurring in Africa. The southern Gerbilliscus clades split from the western clades about 5.5 million years ago, with the origin of the hairy-footed gerbils being 3.4 million years ago. The origin of the southern Gerbilliscus clade (G. afra, G. brantsii, and G. leucogaster) occurred about 2.8 million years ago, with G.
Monophyletic groupings are known to exist (hamsters, voles, African pouched rats, gerbils, Old World rats and mice, African spiny mice, platacanthomyines, zokors, blind mole rats, and bamboo rats). Other groupings, on the other hand, are difficult to classify and may or may not be a jumble of unrelated genera and species (New World rats and mice, dendromurines, and Malagasy rats and mice). The affiliations of subfamilies with only one genus are also unknown (mouselike hamsters, the maned rat).
A perforated plastic top with a filter that serves as a microbiologic barrier may be placed over the assembled shoebox unit. Automatic water delivery and active cage ventilation are available as options for the mouse shoebox cage. An average adult laboratory mouse weighs around 25 g and requires 97 cm2 of cage floorspace. The average lifespan for most stocks and strains of the laboratory mouse is under 2 years. Murids have a diverse range of dietary patterns, including herbivorous and omnivorous species as well as specialists who eat only earthworms, fungus, or aquatic insects. Plant materials and tiny invertebrates are consumed by most species, with seeds and other plant matter being stored for winter use.
Relative to standard laboratory rats, Mastomys appear to be more resistant to the hepatotoxic affects of aflatoxins (Kumagai et al., 1998) and the nephrotoxic effects of mercury II chloride (Holmes et al., 1996). One study reported on stereotypic behavior in laboratory-housed animals (Gulatti et al., 1988). African climbing mice, gerbil mice, fat mice, and forest mice.
Mastomys has been promoted as a model of other types of neoplasia as well. Madarame et al. (1995) reported on spontaneous rhabdomyosarcomas, and Pruthi et al. (1983) described intracutaneous cornifying epitheliomas. Papillomavirus has been used to experimentally induce keratoacanthomas and squamous cell carcinomas, although the classification of these lesions has been questioned (Rudolph and Busse, 1981; Rudolph et al., 1981). A histopathological survey of aged Mastomys displayed a wide range of spontaneous neoplastic and preneoplastic lesions (Solleveld et al., 1982). Overgrown incisors are treated by physically reducing the length of the tooth or teeth involved. Clippers or rongeurs may be used to quickly treat conscious rats, but must be used with caution as the teeth tend to split longitudinally, producing jagged edges and predisposing to apical abscess formation (Emily, 1991).
