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HystricomorphaLast modified on June 5, 2010 Guinea PigsTaxonomy Genetics/Nomenclature Anatomy Physiology Behavior TaxonomyGuinea pigs (Cavia porcellus) are hystricomorph rodents. The family, Cavidae, are tailless South American rodents with four toes on the front feet and three toes on the back, and a single pair of mammary glands.{3559}They are hypsodonts. Genetics/NomenclatureOutbred guinea pigs are usually of the American or English shorthair, Dunkan-Hartley, or Hartley strains. Dunkan-Hartley and Hartley pigs are albino. Pet guinea pigs include Abyssinian (which has a rosette hair pattern) and Peruvian (which has very long hair). Inbred strains are strain 2 and strain 13, and both are tricolor (white, red and black). A revised listing of available stocks is periodically published by the NRC{3559}
This is an American or English shorthair guinea pig, which can be any of several coat colors. This pig has an enlarged cervical lymph node characteristic of infection with Streptococcus zooepidemicus {3559} Anatomy
Guinea pigs are used as models for histocompatibility studies; although the thymus is easily removed surgically there may be accessory islets in the contiguous fascia. Guinea pig serum is also a good source of complement.{3559,4652} The dental formula in the guinea pig varies from that of most rodents; it
is Nutritional requirements{3983}
PhysiologyNormal physiologic values are compared in rodents in table form. Use the Back button to return here. Penicillin use in guinea pigs and hamsters has been linked to fatal enterocolitis, possibly related to Clostridium difficile. Procaine, used to alleviate discomfort in some penicillin-streptomycin preparations, is toxic to guinea pigs, rabbits and mice. In fact, the Blue Book states that "most antimicrobial agents are lethal for hamsters and guinea pigs."{4177} Like ferrets and primates, guinea pigs are relatively resistant to the effects of steroids. {4652} Reproduction{3983, }
Vaginal cytology has been used for years in the guinea pig to determine the stage of estrus (in fact, the Papanicolaou stain was first described during studies of guinea pig estrus{2588}). Electrical impedance can also be used, and correlates well with histologic assessment{3870}. Impedance peaks at the beginning of metestrus, then declines for 2 days. During the estrous cycle, the cell types seen on smears change as follows:
Breeding systems used for guinea pigs are usually either monogamous or polygamous (1 boar per 4-6 sows or even more), and the boars can be left in the cage with the neonates if convenient. Sows begin breeding at 2-3 months when they weigh 350-450 gm; boars are ready to breed at 3-4 months and 600-700 gm. Females display lordosis when in estrus, as well as a perforate vaginal membrane (common to hystricomorphs), vaginal vascular congestion and a cornified vaginal smear. A vaginal plug forms from the ejaculate and remains in the vagina for several hours. During the last 30 days of pregnancy the pubic symphysis relaxes, allowing the pelvic canal to separate by 3 cm. Labor is brief, with pups born every 3-7 minutes in litters of 2-5. The mother does not build a nest. Dystocia is common, as indicated by greenish-brown or hemorrhagic vaginal discharge. Cesarean section is frequently required. The sow’s breeding life lasts generally for 4-5 litters, until she is approximately 18-20 months of age. Guinea pigs are born precocious after a 59-72 day gestation period. This makes hand raising and cesarean derivation relatively easy if it is necessary. The young may not nurse for 12-24 hours postpartum. They begin to eat solid food in the first few days of life. They are usually weaned at 21 days of age or when they weigh 180 gm.{3559} Obese sows can develop pregnancy toxemia during the last 2 weeks of pregnancy. It is similar to pre-eclampsia in women, in that the cause is thought to be uteroplacental ischemia due to the large uterus. There is an abrupt onset of anorexia and sluggishness, leading to prostration and dyspnea. Death occurs in 2-5 days if not treated. Laboratory signs include hypoglycemia, hyperlipidemia, proteinuria, ketonemia and acid urine. Sows are mildly anemic, thrombocytopenic, hyperkalemic, hyponatremic, and hypochloremic with elevated liver enzymes and fatty liver.{3559} RespiratoryThe guinea pig is a very useful model for studying lung function and bronchial reactions. Together with the Basenji breed of dogs, it is the best-characterized animal that manifests airway hyperresponsiveness and reactions that resemble asthma in humans. Salient features of the guinea pig's respiratory system, accounting for its susceptibility to anaphylaxis, are:{4121}
Uses in researchThe guinea pig is a model for evaluation of vaccines against Coxiella burnetii, the agent of Q fever. The following information is from the 1999 POLA notes and is a nice summary of the uses of the guinea pig over the preceding 3 years.{3775}(Publications from last three years surveyed in Pub Med 5/99) Toxicology
Surgery: Otolaryngology, cardiology, implants, mastectomy, transplantation, device infection Bone/Cartilage Disease (Osteoarthritis, Vitamins C, D, and A, rotator cuff, osteopenia) Immunology: Viral, complement, IgE, asthma, autoimmune encephalitis, DHT Stress: Adrenocortical function, corticosteroids, renal hypertension, thermoregulation Hematology, Coagulation: Thrombosis, complement, eosinophilia, PAF Nutrition: Fatty acids, vitamins Neoplasia: Carcinogens: aflatoxin (liver), bracken fern (urinary bladder), reproductive Physiology: Cardiac, hearing, nerve conduction Infectious models
BehaviorGuinea pigs are herbivorous and crepuscular. They learn very early which foods to eat, so if special diets are planned they should be introduced before the pigs become accustomed to standard pelleted chow. They tend to pack water bottle sippers with saliva and ingesta, and they will defecate in food bowls, so special equipment is often used. Guinea pigs are also coprophagous. They are posterior fermenters with a large cecum. The most important behavioral feature of guinea pigs is the "scatter or freeze" response to sudden stimuli. In some situations the pigs will scatter in a stampede or circle wildly, whereas in other situations they will remain immobile for up to 20 minutes. Either of these is an indicator of stress and may make research in some areas, i.e. pain, nearly impossible.{3559} Normally pigs interact well socially in groups. There is a male-dominated hierarchy in normal colonies of animals, supported by anal and supracaudal gland secretions, urine, vocalization, displays and occasionally combat.{3559} Chinchillas
Chinchillas are widely used in hearing research. They have large, accessible tympanic bullae. They do not develop presbycusis despite their long life span (12-20 years). They are relatively free from middle ear infections. They are, however, highly susceptible to Chagas' disease, and invariably die if infected. Female reproductive anatomy is unique in that the vagina opens onto the perineum separately from the urethra and anus. It remains closed except during estrus and at parturition.{3560} Adult female chinchillas are very aggressive, perhaps requiring individual housing. In most circumstances, however, one male can be housed with several females as long as the enclosure is sufficiently large and there are several nest boxes. Often there are several interconnected cages, with each female restricted to her own cage by wearing a collar that is too large to fit through the opening. Kits are born onto the floor, as the mother does not build a nest; therefore solid flooring should be provided. Chinchillas are often housed in rabbit cages in laboratories. Although they can tolerate cold, they are very susceptible to heat stress. They are fanatical groomers, requiring a daily dust bath of silver sand mixed with Fuller's earth. If overstressed during handling, chinchillas release fur from their follicles, a phenomenon referred to as "fur slip".{3560}
Degu (Octodon degus)
Cataract development is related to unusually high aldose reductase activity in the lens. This has been prevented with a drug called sorbinil, an aldose reductase inhibitor. Degus have a high spontaneous incidence of diabetes mellitus with islet amyloidosis. Pregnant females can develop pregnancy toxemia and fatty liver, similar to guinea pigs.{4602} The degu is a native of Chile. They eat fruit and nuts in nature but in the lab can be fed guinea pig chow without added sugar, as they are prone to diabetes mellitus. They can be supplemented with fresh vegetables, but not fruit. To avoid obesity, breeding animals should be fed to maintain a weight of 250 grams.{4602} Feeding bowls are acceptable. They are diurnal, which accounts for their popularity as laboratory animals. Their incisor teeth are normally orange in color; if they turn white, they may be diseased. They do not normally drink much water.{3996} Newborns are precocious, born fully haired and with teeth, but they do not undergo puberty until the age of 3-4 months. They begin their breeding lives at 4-9 months, and are best housed in breeding pairs or else in same-sex pairs. Females are induced ovulators; however in the absence of a male there is some indication of an estrous cycle. The vagina opens early in estrus and during early pregnancy. Palpation for pregnancy may endanger the fetuses. Instead, a reddish discharge from the vulva combined with weight gain are used to diagnose pregnancy. Gestation period is 90 days, and litter size ranges from 3-8 pups. The female has 4 pairs of mammary glands. Weaning age is approximately 5 weeks. Lifespan averages 5-7 years.{3996} Degus should not be picked up by the tail, as it degloves easily. They may jump if picked up by hand; a fishnet works better for transfer. They are social animals like guinea pigs. They enjoy a dust bath occasionally, and will use running wheels if provided.{3996} |
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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 |
There are three major features of guinea pigs that are of comparative
significance{
Chinchillas
bred in captivity are nearly all descended from 11 animals saved from
extinction in the 1920s by an American engineer. At that time, chinchilla fur
was so sought after that they had been hunted almost to extinction in the Andes
mountains. There are two species: short-tailed (Chinchilla brevicaudata)
and long-tailed (C. laniger, at left). Some taxonomists consider both to
be the same species.{
The
degu (trumpet-tailed rat) is a member of the suborder Hystricomorpha (aka Histricognatha), family
Octodontidae. The term "octodont" refers to the figure 8 shape of
their molar teeth. Degus are covered under the Animal Welfare Act, but there
are no specific guidelines published for their care or housing. They are used
in studies of sleep, diurnal cycles, diabetes mellitus and diabetic cataracts,
puberty and aging. In particular, the relationship between puberty and sleep
patterns has been studied in the degu as a model for man.{