Family Cricetidae

Last modified on August 21, 2010

For a list of rule-outs for infectious disease in rodents, click here.

Hamsters

Gerbils

Cotton rats

White-footed mice (Peromyscus) (warning, might be Muridae)

Voles (Microtus)

Hamsters

Taxonomy    Genetics/Nomenclature    Anatomy    Physiology    Uses in Research

Taxonomy

Hamsters belong to the order Rodentia, family Cricetidae{3989}. This family is characterized by thick bodies, short tails, cheek pouches, incisors that grow continuously and molars that do not. They are nocturnal.{3566} There is debate over whether hamsters belong in the family Muridae with mice or the family Cricetidae. Arguments against inclusion in the Muridae include the fact that the tail is different (no scales, no bristles, no length), molar cusp differences (hamsters have two parallel rows of cusps, mice have three rows in transverse ridges). The ACLAM text places hamsters in a subfamily of the family Cricetidae called Cricetinae. There are 7 genera: Cricetus, Cricetulus, Mesocricetus, Phodopus, Tscherskia, Mystomys and Calomyscus. The genus Mesocricetus was finally established in 1940; they differ from Cricetus by having shorter tails, smaller size, and more mammary glands. Hamster karyotyping has been extensive.{3995}

The Syrian or Golden hamster is Mesocricetus auratus, weighing 110-140 gm, 2N=44. Most of the following information relates to Syrian hamsters, as the others are very rarely used in research.

Turkish hamster = Mesocricetus brandti, look like Syrians but hard to breed, used in hibernation and comparative studies with Syrians{3988}.

Chinese hamster = Cricet(ul)us griseus or C. barabensis{3995}: gray-black, 30-35 gm, very aggressive and solitary; low diploid number, 2N=22; naturally occurring diabetes mellitus{3988}. CHO cells are the "E. coli of the mammalian world" because of their use to produce therapeutic recombinant proteins.

Armenian or gray hamster = Cricetulus migratorius, 2n=22, cytogenetics and oncology. {3988}

European or black-bellied hamster = Cricetus cricetus, very large, almost the size of a guinea pig {3988}. Adults weigh 300-400 grams. Used for smoke-inhalation studies, but there are no breeding colonies available in the US.  Most studies involve hibernation, as they are "true hibernators". Despite their cuteness, they are very aggressive, especially the females. {4758}According to Wikipedia, these "common hamsters" were a real farm pest since they eat so much. They are found from Belgium and Alsace eastward to Russia and south to Romania. However, the war on hamsters was so successful that they are now on the International Union for the Conservation of Nature and Natural Resources (IUCN) Red List of Threatened Species, and are designated as Critically Endangered, meaning that their numbers will decrease by 80% within three generations. The last remaining colony in Alsace was suffering because farmers were growing maize instead of cabbage, and when the hamsters emerge from hibernation in March there is nothing for them to eat.

Dzungarian (Siberian) hamster = Phodopus sungorus, gray with a midline black stripe on the back, relatively tame.{3988} Another reference {4091} calls these "dwarf hamsters" of two different species. P. sungorus is the Siberian hamster, and P. campbelli is the Djungarian hamster. They are small, <40gm, native to the steppes of Siberia, have thick fur, short limbs, and a short tail. They differ in the importance of the male parent for survival and growth because of "physiologic constraints on female reproduction." Dwarf hamsters have also been studied for the endocrinology of the photoperiod, puberty, maternal endocrinology, and separation stress. According to LAM2 this species has "the most compressed reproductive cycle of any eutherian mammal" (aka good test question). Females have a fertile post-partum estrus, unlike most hamsters, and the gestation period is 18 days. They can therefore have a second litter while weaning the first, in 36 days. Females are quite non-aggressive and mating pairs can remain together for life. The critical photoperiod is 13 hours (12.5 hr for Syrians and 15.5 for Europeans). They do NOT hibernate, even if exposed to temperatures of -40C.{4758}

South African hamster = Mystromys albicaudatus, estivates, nocturnal, gray on the back with whitish belly, long tails, no cheek pouches and no gall bladder; used in diabetes and leishmaniasis research{3988}.

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Genetics and Nomenclature

Several genetic variants are available for study. 

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Anatomy

When performing studies with infectious organisms it is important to know how intraperitoneally-administered particulates are distributed. This has been studied in mice, rats, rabbits, cats, dogs, sheep, cattle, swine, monkeys, and recently hamsters. The lymphatics of the peritoneal side of the diaphragm have stomata that overlie lacunae which can accommodate particles at least up to 22 microns in size. Trans-diaphragmatic transport of solutions is considered the main route of fluid drainage from the peritoneal cavity. The absorbed material arrives by lymphatic transport in the cranial and caudal mediastinal lymph nodes within a few minutes. Much of it is taken up by macrophages there, leading to a "clogging up" and perhaps slowing further transport. Some marker leaks past the RE cells and gets into the blood, ending up in the spleen and liver. Interestingly, it also goes to the bone marrow. Another route of passage is in the vaginal tunic to the testis. This may explain the occurrence of Strauss phenomenon (described in 1907), fulminant orchitis in hamsters and guinea pigs after ip bacterial inoculation with Burkholderia mallei, the causative agent of glanders.{4133}

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Physiology

Blood volume of a male dwarf hamster (Phodopus)=3.0-3.5ml. One to 1.2ml can be removed from the retro-orbital sinus in a single sample, and the hematocrit will return to normal immediately, suggesting splenic replenishment. With repeated sampling, a 5-day rest period may be needed if hematocrit declines to 70% of original values.{4091}

They hibernate if the temperature reaches 5°C, although since they do not store large amounts of energy they must wake up periodically to eat.{4758}

Although hamsters are not plagued with many infectious diseases, they do develop a number of spontaneous and viral-induced tumors and display chemical carcinogenic sensitivities that are useful in research. For example, renal carcinoma, urinary bladder tumors, estrogen-linked pituitary adenomas, pancreatic tumors, bile duct carcinomas, papillomas and adenocarcinomas in the forestomach and intestines, and adenomatous polyps in the colon have all been described.{3566} Renal cell carcinoma is rare in Siberian hamsters (Phodopus sungorus); rather, more common neoplasms include tumors of the mammary gland, skin, lungs, and thyroid gland{3789}.

Hamsters can harbor viruses from other species (a sarcoma became a carrier of LCMV which infected other hamsters and humans). Adenoviruses from many species (man, NHP, bovine, chicken) cause tumors (sarcomas at site of injection) in newborn hamsters. This has been exploited for oncology research. In particular, these studies have led to the discovery of early genes, produced within hours of infection. The gene products (of genes E1A and E1B) are seen as intranuclear flecks in T cells, but are not involved in T-cell-mediated immunity. The proteins bind to and inactivate tumor suppressor genes p53 and Rb, thereby causing malignant transformation{3777}. This can be useful as a screening tool in humans, to see if the tumors are of viral etiology. However, the system gets very complicated when examining whether adenovirus-transformed cells grow in an older hamster, or in an immunodeficient mouse or rat.{3771}

The immune system of the hamster is very interesting because it is less susceptible to alloantigens; also hamsters have no IgD and are deficient in the sixth component of complement.

Reproduction

1.      Trial period: house individually until single male housed with single female, checking for lordosis. Introduce male to female 3 days after appearance of post-ovulatory discharge, 1 hour before start of dark cycle{3989}

2.      Harem: House 1 male with 1-2 females for 7-14 days, and remove females before parturition

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Use in research{3988, 4758}

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Gerbils

Gerbils are any member of the subfamily Gerbillinae, containing at least 10 genera and 100 species. They belong to the family Cricetidae of the suborder Myomorpha. The Mongolian gerbil, Meriones unguiculatus, is the species most often used in research in the US and Japan. The first 20 pairs were trapped in eastern Mongolia in 1935 and taken to Japan. Eleven pairs were imported to the US in 1954. Common names for M. unguiculatus include jird, sand rat, desert rat, and antelope rat. Most are brownish or gray with pale bellies, but black and albino mutants occur. Most gerbils are outbred; however there is one inbred strain, MON/Tum.{3560, 4635} For a list of infectious diseases in gerbils, click here.

Anatomy

Physiology

Reproduction

Behavior

Iatrogenic, neoplastic and age-related problems {4635}

Dihydrostreptomycin (in a penicillin/dihydrostreptomycin/procaine combo) caused death in 80-100% of gerbils in a 1980 report.

Gerbils are prone to epileptiform seizures from a young age, seen more commonly in some lines than others. About 20-40% can show seizures, which are induced by noise or stress. They are usually fairly short and have no lasting effects.

Age-related problems have been reported as neoplasia and chronic interstitial nephritis. Gerbils also have a high incidence of aural cholesteatoma.

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Cotton Rat

Taxonomy    Genetics/Nomenclature    Physiology    Behavior    Uses in Research

Taxonomy

There are seven species of cotton rats, but the most common laboratory species are either Sigmodon hispidus (at left) or Sigmodon fulviventer (at right). The name Sigmodon refers to S-shaped enamel loops on the grinding surfaces of the cheek teeth. These animals are widely distributed in the wild from the southern US, north to Virginia, west to California, and south to Mexico, Central America, and northern south America. Cotton rats are members of the family Cricetidae, and are nest building rodents living in burrows or dense clumps of vegetation.{3841}

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Genetics/Nomenclature

The number of chromosomes varies among species from 22 to 52.  Anatomy is similar to other rodents. 

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Physiology

These animals may be nocturnal, diurnal, or crepuscular in activity. Social groups consist of males dominating females and adults dominating the young. Generally they live as solitary animals, forming groups for reproduction. Young can survive in the wild by 5 days of age.{3841}

There are four life stages:  juvenile (1-75 days); young adults (76-200 days); adults (201-300 days); and old adults (>300 days). Captive-bred animals have an average lifespan of 2-3 years.

Breeding is seasonal in the wild, but not in the lab. They may be harem bred, or placed in monogamous pairs. Pairs should be established when the female has reached puberty. Earlier pairing seems to delay puberty. The estrous cycle averages 9 days, there is a postpartum estrus, gestation is about 27 days, young are born haired and eat solid food by one week of age. Normally they are weaned at 3-5 weeks of age, but they can be weaned as young as 5-10 days.{3841} House the males separately to avoid fighting. Ideal temperature range is 60-80; below that they hunch up and above it they pant. Moving them to a clean cage can be done by tipping them towards the clean cage while covering the rest of the opening with the other hand; they can be picked up by scruffing or whole-body holds.{4174}

Test sentinels for bacteria, viruses (PVM, Reo3, MEV, Sendai, LCMV, SDAV, KRV, hantavirus), protozoa (Spironucleus, Giardia, Entamoeba, trichomonads, Eimeria), ectoparasites (Myobia, Myocoptes, Radfordia, Polyplax, Psorergates, Notoedres, Demodex, Liponyssus) and helminths (Syphacia, Aspiculuris, Hymenolepis, Trichosomoides).{4174}

Blood can be collected from the retro-orbital sinus, or with terminal cardiac puncture. Use isoflurane or ketamine (25mg/kg)/xylazine (7.5mg/kg)/acepromazine (2.5mg/kg).{4174}

For a comparative table of reproductive values in several non-traditional rodents, click here.

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Behavior

Cotton rats can be housed in large polycarbonate rat cages. They should have locking lids, and bedding for nesting. Nutritional requirements are similar to those for rats. A high-fat chow (i.e. Teklad 7004) can be used for nursing mothers. They are also best handled like rats; some people prefer to wear leather gloves. Avoid picking them up by the tail as the tail skin easily degloves.{3841, 4174}

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Uses in Research

The cotton rat is susceptible to many human pathogens, thus making it a valuable model in biomedical research. They were originally used to model human polio since it is the only small animal permissive for it. Now they are used for respiratory syncytial virus, human parainfluenza virus 3, human adenoviruses, and pineal gland studies.{4174} They have been used as a recipient of adenovirus vectored human genes for cystic fibrosis and a 1-antitrypsin in the lung.{3929} Female cotton rats also develop gastric adenocarcinomas, which have been compared with human enterochromaffin-like cell (ECL) carcinomas.{4203}

Anesthesia, blood sampling, and light cycles can be the same as for other rodents such as rats.{3841} The orbital plexus can be used for survival procedures, and cardiac puncture for terminal bleeding. IV injections can be given directly IC since there are no readily accessible peripheral veins.{4174}

Mice of the genus Peromyscus

There are at least 40-50 different species in this genus, many of which are commonly called white-footed mice because the abdominal fur is white, and the dorsal fur ranges from gray to brown. Their natural range encompasses all of North America and extends south as far as Colombia. Within this range, individual species generally inhabit a limited portion, with the exception of the deer mouse (P. maniculatus) which inhabits most of the total range. Some species that have been maintained in the laboratory include P. leucopus, P. maniculatus, P. floridanus, P. bairdi, and P. polionotus.{3560} 

A recent article in Comparative Medicine places deer mice in the family Muridae, subfamily Sigmodontineae. Deer mice (Peromyscus) are "the most widely distributed indigenous small mammal on the continent." They are claimed to be very easy to maintain in captivity, and are furthermore the natural reservoir of several human pathogens: Lyme disease, granulocytic ehrlichiosis, babesiosis, bartonellosis, and hantavirus. They are the predominant carrier of the Sin Nombre strain of hantavirus, which is highly pathogenic. This led to a CDC recommendation for new, safer handling of the mice. Wild-caught mice should be quarantined and tested for SN after 5 weeks. Breeding pairs are best left alone; use highly-absorbent bedding and change it only about every 2-3 weeks.{4579}

Peromyscus leucopus (right)

Peromyscus maniculatus (left), which is used in studies of Hanta virus.

Peromyscus mexicanus nudipes (right), the naked-footed deer mouse.

Peromyscus behavior that has been studied includes food hoarding, maternal care, feeding patterns and light preference. Several species exhibit idiopathic epileptic seizures, and the clonic and tonic phases, recovery and post-seizure behavior are reported to be almost identical to those in man.{3560}

The mice can be housed in similar style as Mus, but care must be taken during cage transfers as they may jump. Animal transfer is best managed in a box with sides at least 30cm high.{3560} When used in studies of hanta virus infection, they must be housed using ABSL4 procedures.{3950}

Like most New World rodents, the demarcation between the cardiac and pyloric portions of the stomach is not as distinct as it is in Old World rodents (such as Mesocricetus and Mystromys). Stratified squamous epithelium in the cardiac portion is thought to protect the stomach from abrasion caused by rough feed.{3560}

Reproduction

White-footed mice have been successfully bred in captivity. They can be caged in groups. In their natural habitat their reproductive peak is during long days (spring, summer and early fall), so in the lab a light: dark ratio of 15-16: 8-9 works best. After about three litters, reproductive performance declines.{3560}

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Voles (Microtus)

There are around 50 species of voles, and they are found throughout the world. Microtus pennsylvanicus, the Eastern meadow vole or field mouse, has been raised in the laboratory. Its natural habitat is the eastern US, Canada, and Alaska. The common vole (M. arvalis) is a very common European mammal. Like some other wild rodents, they tend to be escape artists, very excitable, and rarely become tame. More secure caging and more care during cage changes is necessary. Dim red light may help with handling nocturnal animals, which have a high percentage of rods in their retinas that are not sensitive to red light.{3560}

Some voles are exceedingly prolific. M. arvalis females mature as early as 14 days of age, have 4-7 young per litter and have a new litter every 3 weeks.{3560}

This is Microtus pennsylvanicus, the Eastern meadow vole, at right.

Meadow voles are reported to be good bioassay animals for digestibility of forages and for protein content of feeds. Females are induced ovulators, with ovulation occurring 12-18 hours after mating.{3560}

 

This is Microtus agrestis, the field vole, at left.

 

 

 

 

 

 

 

This is Microtus chrotorrhinus, the rock vole or yellow-nosed vole, at right.

	Adult weight: 40-60 gm
	Life span: 33 weeks, 124 weeks maximum
	Food consumption: 7-10 gm/day
	Chromosome number: 46
	Puberty: 42 days in males, 25 days in females
	Estrous cycle length: 5 days
	Gestation: 21 days (19-22)
	Litter size: 4 (1-11)
	Birth weight: 2 gm
	Eyes open: 8 days
	Weaning: 14 days{3560}

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©1999, Janet Becker Rodgers, DVM, MS, DipACLAM, MRCVS

All rights reserved.

Comments? Send an email to janet.rodgers@vet.ox.ac.uk