Transcript Gerbils Biology anatomy and more

Mongolian Gerbil
Meriones unguiculatus
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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
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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 semierect 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
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The Mongolian gerbil, Meriones
unguiculatus, 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
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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
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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
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The adrenal glands (arrow) are large for
their body weight.
Breeding and
reproduction
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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
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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..
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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 71 0 days and their
eyes will open at 2-3
weeks.
Maturation/ life cycle
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Gerbils are ready to be weaned at 2030 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
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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
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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
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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 58 grams of pelleted rodent
ration per day.
Water
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Captive gerbils
need a water
supply - either a
water bottle or an
automatic watering
device
USES IN RESEARCH
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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
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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
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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
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The loose skin of the neck is a site for
subcutaneous injection
IM, IV injections
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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
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Intraperitoneal
injections are
accomplished off
midline in the caudal
abdomen, after tilting
the head of the gerbil
down to displace
internal organs
forward.
Review
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http://www.bva-awf.org.uk/resources/tutorials/BVA03Gerbil/Gerbil.html
Chemical restraint
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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
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Inhalation anesthesia can be
accomplished with Isoflurane
INFECTIOUS DISEASES
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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 fecaloral 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
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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
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Treatment of Tyzzer's disease is often
unsuccessful in gerbils, but
oxytetracycline has been reported to
reduce mortality in mice.
Nonspecific enteritis
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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
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In juvenile and adult gerbils, environmental
stressors such as incompatible cagemates, high
humidity, and overcrowding cause release of
Harderian gland porphyrin secretions around the
external nares and eyes.
Nasal dermatitis
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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
Sore nose
Staphylococcus saprophyticus , S xylosis , and S aureus 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
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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
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No naturally-occurring viral diseases
have been reported in gerbils.
Parasites
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, Demodex
aurati or Demodex criceti (B.) .
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Endoparasites of the gerbil may include mouse
pinworms (Syphacia obvelata) which can be found
in the cecum and a small intestinal gerbil pinworm
Dentostomella translucida (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
MISCELLANEOUS
DISEASES
Management-related
conditions
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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
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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
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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
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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
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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
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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
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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
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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
Hey buddy, don’t look now but your tail slipped !
A slipped tail- ouch!
Questions??