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Mongolian Gerbil Meriones unguiculatus. The Mongolian gerbil is also known as the jird , clawed jird , sand rat, or desert rat. It is native to China and Mongolia and was introduced into the United States in 1954.
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The Mongolian gerbil is also known as the jird, clawed jird, sand rat, or desert rat. It is native to China and Mongolia and was introduced into the United States in 1954. • The most common color is the agouti, shown here: light buff to white ventrum, with mixed white, yellow and black hairs dorsally, giving an overall brown fur color.
Appearance • Gerbils may also be black, gray, white, or piebald. They are characterized by a long, fully furred tail, strong claws for burrowing, and elongated hindlimbs, used for jumping and for maintaining a semi-erect posture. • The body and the tail are each about 11-15 centimeters in length, with the body slightly longer than the tail. Adults weigh 70-150 grams, with males slightly larger than females.
Taxonomy • The Mongolian gerbil, Merionesunguiculatus,is in the order Rodentia, suborder Myomorpha and the family Cricetidae - the same family as the hamster.
Dental and vertebral formulas Their dental formula is typical of rodents. Gerbils have a single maxillary and mandibular incisor on each side. There are no canines or premolars. The gerbil has 3 maxillary and 3 mandibular molars on each side. 2 ( I 1/1 C 0/0 PO/O M3/3 ) = 16 • They have 7 cervical vertebrae, 13 thoracic, 6 lumbar, 4 sacral and 7 or more coccygeal vertebrae. ( C7 T13 L6 S4 Cy7+)
Facts • Life Span: 3-4 years on average (up to 8 reported, though this is exceptional!) • Mongolian gerbils are not nocturnal although they are sometimes active at night; they go through several sleep/active cycles in the course of 24 hours
They are very curious and will explore anything, and can be quite entertaining.
Sexual dimorphism • Gerbils have a prominent, elliptical ventral marking gland, composed of sebaceous glands and overlying coarse hair. • The marking gland is more prominent in males than in females and is helpful in sexing mature animals. • The males also have a prominent, darkly pigmented scrotum.
Adrenal glands • The adrenal glands (arrow) are large for their body weight.
Breeding and reproduction • Female gerbils are polyestrous, spontaneous ovulators with an estrous cycle of 4-6 days. • They may display a slight winter breeding depression. Males and females that are paired before seven weeks of age bond in lifelong monogamous pairs. Remating is difficult if one dies or is removed. Housing of two females with a single male is another acceptable mating system.
Reproduction • Gestation lasts 24-26 days; but if the female is bred during the postpartum estrus, implantation may be delayed, increasing gestation to a total length of 42 days. • The male gerbil should not be removed from the cage when the young are born, because fighting may occur when he is reintroduced.
Reproduction cont.. • The average litter consists of 3-7 blind, hairless pups weighing 3-4 grams each. • The ears of the newborn will open at 3-7 days postpartum. • The young will be covered with fur by 7-1 0 days and their eyes will open at 2-3 weeks.
Maturation/ life cycle • Gerbils are ready to be weaned at 20-30 days of age. • They reach puberty at 65-85 days. • The reproductive lifespan of the female lasts until about 12-17 months of age and the male until two years of age.
HUSBANDRY • Satisfactory housing in a research setting includes polycarbonate "shoebox" cages, as shown here. They should be at least 15 centimeters (6 inches) high. • Each gerbil should have a minimum of 116 sq. centimeters (1 8 sq. in.) of floor space. • A breeding pair with their litter should have a minimum of 900 sq. centimeters (140 sq. in.) of floor space.
Management Cages should be constructed with rounded corners to discourage chewing. Optimal temperature range for gerbils is between 65 and 80° F, with babies doing best at 70 to 75° F. The relative humidity should be between 30 and 50%.
Bedding and nesting materials • Absorbent bedding for burrowing should be provided in the cage. Opaque tubes or boxes for hiding provide environmental enrichment and soft shreddable materials for nesting may improve reproductive performance.
Food • Gerbils should be fed ad libitum from feed hoppers that have wide openings for easy accessibility. The feed hopper should be mounted low as newborns will begin to consume solid food at about 2 weeks of age. Each adult gerbil will consume approximately 5-8 grams of pelleted rodent ration per day.
Water • Captive gerbils need a water supply - either a water bottle or an automatic watering device
USES IN RESEARCH • One of the first uses of gerbils in research was in radiation studies, because they can tolerate much greater whole-body radiation exposure than other animal species. • They have also been used in studies of endocrine gland metabolism, as they have one of the largest ratios of adrenal weight to body weight of all animals. • Gerbils have a high incidence of spontaneous epileptiform seizures, usually precipitated by being startled or by a novel environment. This makes them an important animal model for study of epilepsy.
USES IN RESEARCH • They have been used in reproduction studies to evaluate antifertility drugs and in auditory research, because their hearing curve is closer to man's than most common laboratory animals. • In toxicology research, gerbils have been used in studies of food additives, pesticides, industrial solvents and heavy metals. • Gerbils are also useful in infectious disease research. Although they are relatively free of spontaneous diseases, they are susceptible to agents from other species. • And finally, they are used in parasitology research, as they have been successfully infected with parasites common to other species.
HANDLING • To physically restrain a gerbil, grasp it at the base of the tail - not the tip. If the tip is grasped, the skin may come off (degloving).
Fractures of the tail vertebrae, and slipping of the tail skin can all occur with improper handling (A.). This usually involves picking up animals by the distal portion of the tail. Surgical amputation with cautery (silver nitrate cautery shown in B.) supportive post-surgical care may be necessary when large amounts of tissue are compromised. Such injuries may be prevented by handling animals by the base of the tail
Injection site • The loose skin of the neck is a site for subcutaneous injection
IM, IV injections • The muscles of the thigh are a site for intramuscular injections. Care must be taken to avoid the sciatic nerve, which lies parallel to the femur, it may be helpful for one person to restrain the gerbil while a second person pulls the leg out for injection. • After the gerbil is adequately sedated or anesthetized, intravenous injections can be made into the femoral, saphenous or tail veins.
IP Injections • Intraperitoneal injections are accomplished off midline in the caudal abdomen, after tilting the head of the gerbil down to displace internal organs forward.
Review • http://www.bva-awf.org.uk/resources/tutorials/BVA03-Gerbil/Gerbil.html
Chemical restraint • Chemical restraint can be accomplished with sodium pentobarbital, administered intraperitoneally at 60 mg/kg body weight. • A cocktail containing ketamine, xylazine and acepromazine can also be used at the following dosage: 0.6 ml/kg body weight, administered intramuscularly, or subcutaneously, of a mixture of 1.5 ml (150 mg) 100 mg/ml ketamine HCI, 1.5 ml (30 mg) of 20 mg/ml xylazine HCI and 0.5 ml (5 mg) of 10 mg/ml acepromazine • P#120
Chemical restraint • Inhalation anesthesia can be accomplished with Isoflurane
INFECTIOUS DISEASES • Tyzzer's disease The most commonly reported infectious disease in gerbils is Tyzzer's disease, an acute, often fatal, hepatoenteric disease. It is caused by Clostridium piliformi, an obligate intracellular, spore-forming, filamentous, argyrophilic rod. • The organism is transmitted by the fecal-oral route; spores survive in the environment for months or years. • Clinical signs include sudden death, perianal fecal staining, watery diarrhea, anorexia, lethargy and rough hair coat
Gross lesions • Gross lesions of Tyzzer's disease include hepatomegaly with yellow-white hepatic foci of necrosis, as seen here, typhlitis and enteritis with watery enteric contents.
Treatment • Treatment of Tyzzer's disease is often unsuccessful in gerbils, but oxytetracycline has been reported to reduce mortality in mice.
Nonspecific enteritis • Nonspecific enteritis in gerbils may result from bacterial infections, such as with Salmonella spp. Other possible causal agents include heavy protozoal infections and food deprivation • Signs of enteritis include perianal fecal staining (seen in photo), anorexia, depression and rough hair coat
Facial Dermatitis • In juvenile and adult gerbils, environmental stressors such as incompatible cagemates, high humidity, and overcrowding cause release of Harderian gland porphyrinsecretions around the external nares and eyes.
Nasal dermatitis Sore nose • Accumulation of the reddish-brown porphyrin pigment causes skin irritation and eventually leads to self-trauma, localized alopecia, and moist dermatitis with erythema, scabs, and ulceration
Sore nose Staphylococcussaprophyticus , Sxylosis , and Saureus may secondarily invade and exacerbate the dermatitis, spreading to the forepaws and ventral thorax and abdomen. Skin lesions are pruritic and frequent scratching may result in bleeding. The condition may be self-limiting with spontaneous recovery or, more often, progressive with bacterial infection
Treatment includes carefully cleaning the skin lesions and applying topical antibiotics (chloramphenicol 1% ophthalmic ointment, tid). Prevention requires careful control of environmental temperature and humidity or other sources of stress and providing sand baths or clay bedding.
Viral Diseases • No naturally-occurring viral diseases have been reported in gerbils.
Parasitism of the gerbil rarely causes clinical disease problems. Alopecia in aged or debilitated gerbils may be due to demodicosis (A.). Scrapes of affected areas may reveal hamster demodectic mange mites, Demodexaurati or Demodexcriceti(B.) .
Endoparasites of the gerbil may include mouse pinworms (Syphaciaobvelata) which can be found in the cecum and a small intestinal gerbil pinworm Dentostomellatranslucida(A.). Syphacia ova can be recovered on a cellophane tape test (see mouse parasitic diseases), while Dentostomella ova (B.) are identified by the fecal floatation test
Management-related conditions • Management-related problems include inadvertent starvation and water deprivation. The food may simply be too high to reach or inaccessible. The hopper may have openings that are too narrow, or the food may be too hard for weanlings to chew. Similarly, the water source may be too high to reach
Epilepsy • The gerbil displays spontaneous epileptiform seizures. These seizures may be precipitated by sudden stress, handling, or introduction to a novel environment. • Incidence of this syndrome is about 50% in natural populations. The condition appears to be inherited, and both seizure-resistant and seizure-sensitive strains have been developed by selective breeding. • Inbred animals can have up to 100% incidence
Epileptiform seizure • Seizure onset occurs at 2 to 3 months of age with seizure incidence and severity increasing with age until the animal reaches six months of age. • After a seizure, it may be several hours before seizure threshold is reached again
Treatment/ prevention • The seizures have no obvious adverse effects and do not require treatment. They should not be treated with diphenylhydantoin, as it can be fatal to gerbils. • Handling weanlings frequently is recommended to reduce the incidence of seizures later on.
Neoplasia • Older gerbils commonly develop a number of spontaneous neoplasms most commonly affecting the skin, adrenal gland, kidney, spleen, intestine and the female reproductive tract. The most frequently seen neoplasms include leiomyomas, subcutaneous fibrosarcomas, sebaceous gland adenomas and adenocarcinomas
Melanoma • Cutaneous tumors include squamous cell carcinomas and melanomas affecting the ear and feet. Masses may be surgically removed. The prognosis varies with the size, stage, and timing of surgical excision.
Tail barbering • Gerbils may barber each other, particularly if they are overcrowded. This results in subordinate animals having hair chewed off in a closely-shaven pattern, especially around the base of the tail.
Degloving tail wound • The tail of the gerbil is especially sensitive to degloving wounds. Gerbils must not be picked up by the tip of the tail. If the tail is degloved, it should be amputated at the level of the breakage
