Cheek pouches are pockets on both sides of the head of some mammals between the jaw and the cheek. They can be found on mammals including the platypus, some rodents, and most monkeys, [1] [2] as well as the marsupial koala. [3] The cheek pouches of chipmunks can reach the size of their body when full.
Cheek pouches are located in the thickness of the flange on both sides of the head of some mammals. Monkeys have open cheek pouches within the oral cavity, but they open out in some rodents of America. Hence the name "diplostomes" is associated with them, which means "two mouths." In some rodents, such as hamsters, the cheek pouches are remarkably developed; they form two bags ranging from the mouth to the front of the shoulders. [4] Étienne Geoffroy Saint-Hilaire described that some bats of the genus Nycteris have an amazing form of cheek pouches, as they have a narrow opening, through which the bat can introduce air, closing the nasal canal through a special mechanism and pushing air under the skin, so they expire in the tissue, which unites the very loose skin to the underlying muscles. [4]
Cheek pouches have several roles; they allow the rapid collection of food, but also serve as temporary storage and transport. In monkeys of the subfamily of Cercopithecinae, they allow for more predigested food. [5] Cheek pouches contribute to the protection of animals by allowing them to carry their food in the pouches to shelter, allowing them to transport their food to safer locations, as they are pressing these pouches to the back of the mouth with the back of the leg, or moving the jaw. [5] [6] The females of some species of hamster are known to hide their young in their cheek pouches to carry them away when they fear danger. [7] Other species of hamsters are known to fill their pouches with air, allowing them to float better while they swim. [7] [8]
The cheek pouches can become infected as a result of an injury caused by a sharp object inserted into them or a fight. An abscess can form, which can be confused with protuberance with stored food. If the abscess bursts and the pus contained therein is absorbed by the animal, it can develop sepsis and die of the poisonous toxins. [9] [10] [11] [12] The cheek pouches can also turn outwards. [9] [13]
The cheek pouches of hamsters have been studied in laboratories to understand vascular membranes and healing better. [14] They are also useful for the study of the immune system, notably in the development of abscesses or tumours. [15] [16] [17]
Chipmunks (Tamias) have large cheek pouches that allow them to transport food. [18] These pouches can reach the size of their body when they are full. [7] [18] [19]
Below is the introduction of the legume (pod) of peanut in the cheek pouch of a chipmunk:
One of the classic behavioral characteristics of hamsters (subfamily Cricetinae) is food hoarding. Hamsters carry food to their underground storage chambers using their spacious cheek pouches. [20] A hamster "can literally fill its face with food." [21] When full, the pouches can make the hamsters' heads double, or even triple in size. [20]
The platypus feeds on annelid worms, insect larvae, freshwater shrimps, and yabbies (freshwater crayfish) that it digs out of the riverbed with its snout or catches while swimming. It uses its cheek pouches to carry prey to the surface for eating. [22]
The cheek pouch is a specific morphological feature that is evident in particular subgroups of rodents (e.g. Heteromyidae and Geomyidae, or gopher), yet a common misconception is that certain families, such as Muridae (including the common black and brown rats), contain this structure when in fact their cheeks are merely elastic due to a high degree of musculature and innervation in the region. The true cheek pouch, however, is evident in the former Heteromyidae and Geomyidae groups. [23]
Cheek pouches are more pronounced in certain rodents, such as hamsters, yet this structure is also distinguishable on certain species of rat, like the Gambian pouched rat, of which extensive morphological investigations have been conducted. [23] Aspects including rat pouch musculature, vascularization, and innervation were all explored and compiled through this and other studies. The widely distributed Rattus rattus is an example of the rodent family Muridae that lacks a true cheek pouch; rather, they exhibit more elastic cheeks (not true pouches) due to the organization of their cheek musculature.
Concerning the musculature, the cheek pouch is composed primarily of a developed masseter (cheek) muscle that exhibits a high tensile ability. The masseter muscle has been shown to insert into the pectoralis muscles, allowing for a higher degree of food retention. The pouch is clearly divided between a buccal (cheek) and sublingual (below the tongue) portion. Volumetric analyses within this study attributed the differences in net cheek volume between male and female rats to the average size of the respective sexes. [24]
Due to muscle's high nutritional demand, this muscle exhibits vascularization that has been highly studied. Dissections at Boston University by Frank Brodie describe the various bifurcations (or splittings) of the common carotid. This artery splits into an internal and external branch, of which the latter extends dorsally and divides into five branches that supply the general cheek region. The branch that extends dorsally to the ear is known as the auricular branch. [25]
As for innervation of this structure, the associated nerve branches were all found to originate from the facial (CN VII of XII) nerve that initiates at the medulla and passes into the facial canal via the stylomastoid foramen. The primary aforementioned muscle, the masseter, is supplied by two large neural branches known as the temporalis and zygomatic nerves. [25] The buccal divisions of this nerve supply much of the masseter muscle, which ultimately facilitates the voluntary retention of food within the cheek pouch.
Hamsters are rodents belonging to the subfamily Cricetinae, which contains 19 species classified in seven genera. They have become established as popular small pets. The best-known species of hamster is the golden or Syrian hamster, which is the type most commonly kept as a pet. Other hamster species commonly kept as pets are the three species of dwarf hamster, Campbell's dwarf hamster, the winter white dwarf hamster and the Roborovski hamster.
Whiskers or vibrissae are a type of stiff, functional hair used by most mammals to sense their environment. These hairs are finely specialised for this purpose, whereas other types of hair are coarser as tactile sensors. Although whiskers are specifically those found around the face, vibrissae are known to grow in clusters at various places around the body. Most mammals have them, including all non-human primates and especially nocturnal mammals.
The Muroidea are a large superfamily of rodents, including mice, rats, voles, hamsters, lemmings, gerbils, and many other relatives. Although the Muroidea originated in Eurasia, they occupy a vast variety of habitats on every continent except Antarctica. Some authorities have placed all members of this group into a single family, Muridae, due to difficulties in determining how the subfamilies are related to one another. Many of the families within the Muroidea superfamily have more variations between the families than between the different clades. A possible explanation for the variations in rodents is because of the location of these rodents; these changes could have been due to radiation or the overall environment they migrated to or originated in. The following taxonomy is based on recent well-supported molecular phylogenies.
Heteromyidae is a family of rodents consisting of kangaroo rats, kangaroo mice, pocket mice and spiny pocket mice. Most heteromyids live in complex burrows within the deserts and grasslands of western North America, though species within the genus Heteromys are also found in forests and their range extends as far south as northern South America. They feed mostly on seeds and other plant parts, which they carry in their fur-lined cheek pouches to their burrows.
The white-tailed rat also known as the white-tailed mouse, is the only member of the subfamily Mystromyinae in the family Nesomyidae. This species is sometimes placed in the subfamily Cricetinae due to similarities in appearance between the white-tailed rat and hamsters, but molecular phylogenetic studies have confirmed that the two groups are not closely related. The subfamily Mystromyinae is sometimes placed within the family Muridae along with all other subfamilies of muroids.
The giant pouched rats of sub-Saharan Africa are large muroid rodents.
Mammalia is a class of animal within the phylum Chordata. Mammal classification has been through several iterations since Carl Linnaeus initially defined the class. No classification system is universally accepted; McKenna & Bell (1997) and Wilson & Reader (2005) provide useful recent compendiums. Many earlier ideas from Linnaeus et al. have been completely abandoned by modern taxonomists, among these are the idea that bats are related to birds or that humans represent a group outside of other living things. Competing ideas about the relationships of mammal orders do persist and are currently in development. Most significantly in recent years, cladistic thinking has led to an effort to ensure that all taxonomic designations represent monophyletic groups. The field has also seen a recent surge in interest and modification due to the results of molecular phylogenetics.
Campbell's dwarf hamster is a species of hamster in the genus Phodopus. It was given its common name by Oldfield Thomas in honor of Charles William Campbell, who collected the first specimen in Mongolia on July 1, 1902. It is distinguished from the closely related Djungarian hamster as it has smaller ears and no dark fur on its crown. Campbell's dwarf hamster typically has a narrow dorsal stripe compared to the Djungarian hamster and brown or gray fur on the stomach. This hamster may be raised in captivity and kept as a small pet.
Phodopus, a genus of rodents in the hamster subfamily Cricetinae—a division of the larger family Cricetidae—is a lineage of small hamsters native to central Asia that display unusual adaptations to extreme temperatures. They are the only known hamsters that live in groups and, in some cases, rely on significant contributions by males to the raising of offspring. They are nocturnal and active throughout the year; they do not hibernate. Species of Phodopus, together with members of the genera Cricetulus, Allocricetulus and Tscherskia are called dwarf hamsters because of their small size relative to other hamsters.
Sciuromorpha ( 'squirrel-like') is a rodent clade that includes several rodent families. It includes all members of the Sciuridae as well as the mountain beaver species.
The suborder Myomorpha contains 1,524 species of mouse-like rodents, nearly a quarter of all mammal species. Included are mice, rats, gerbils, hamsters, lemmings, and voles. They are grouped according to the structure of their jaws and molar teeth. They are characterized by their myomorphous zygomasseteric system, which means that both their medial and lateral masseter muscles are displaced forward, making them adept at gnawing. As in the hystricognathous rodents, the medial masseter muscle goes through the eye socket, a feature unique among mammals. Myomorphs are found worldwide in almost all land habitats. They are usually nocturnal seed-eaters.
The Texas kangaroo rat is a rodent of the family Heteromyidae. It is found in Texas and Oklahoma in the United States, where it often lives in association with brush species, like mesquite and lotebush, growing in areas with firm clay-loam soils. The species is listed as threatened by the Texas Parks and Wildlife Department and the IUCN lists the species as vulnerable.
Geomyoidea is a superfamily of rodent that contains the pocket gophers (Geomyidae), the kangaroo rats and mice (Heteromyidae), and their fossil relatives.
Perognathinae is a subfamily of rodents consisting of two genera of pocket mice. Most species live in complex burrows within the deserts and grasslands of western North America, They feed mostly on seeds and other plant parts, which they carry in their fur-lined cheek pouches to their burrows.
The Gambian pouched rat, also commonly known as the African giant pouched rat, is a species of nocturnal pouched rat of the giant pouched rat genus Cricetomys, in the family Nesomyidae. It is among the largest muroids in the world, growing to about 0.9 m (3 ft) long, including the tail, which makes up half of its total length. It is widespread in sub-Saharan Africa, ranging from Senegal to Kenya and from Angola to Mozambique from sea level to 2,000 m (6,600 ft).
The Gulf Coast kangaroo rat is a species of rodent in the family Heteromyidae found in Mexico and the state of Texas in the United States. Its appearance and ecology are very similar to those of its putative sister species, Ord's kangaroo rat.
Merriam's kangaroo rat is a species of rodent in the family Heteromyidae. The species name commemorates Clinton Hart Merriam. It is found in the Upper and Lower Sonoran life zones of the southwestern United States, Baja California, and northern Mexico.
The Panamint kangaroo rat is a species of rodent in the family Heteromyidae. It is endemic to the Mojave Desert in eastern California and western Nevada, in the United States.
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 Antarctica, and several oceanic islands, though they have subsequently been introduced to most of these land masses by human activity.
Handbook of the Mammals of the World (HMW) is a book series from the publisher Lynx Edicions. The nine volumes were published from 2009 to 2019. Each mammal family is assessed in a full text introduction with photographs and each species has a text account with a distribution map and illustrations on a plate. This is the second major project by Lynx Edicions since the release of the Handbook of the Birds of the World in 1992. The chief editors are Russell Mittermeier and Don E. Wilson in association with Conservation International, the Texas A&M University and the IUCN. Don E. Wilson is also editor of the reference work Mammal Species of the World.
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