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Year 2 NSF > Small Mammals - Rodents > Flashcards

Small Mammals - Rodents Flashcards

1
Q

Describe the taxonomy of rodents and what are they classified by

A 
Taxonomy:
Kingdom - Animalia
Phylum - Chordata
Class - Mammalia
*Order: Rodentia*

Classified by having continuously growing incisors

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2
Q

What is the smallest and largest rodent?

A

Smallest - African pygmy mouse and Pygmy Jerboa 3g

Largest - Capybara 50-60 kg

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3
Q

How many orders is the rodents order divided?

A

5

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4
Q

List the rodent sub orders and give examples

A
  1. Myomorpha - mouse like: mice, rate, gerbils, hamsters
  2. Hystricomorpha - porcupine like: guinea pig, chinchilla
  3. Scuriomorpha - squirrel like (chipmunks)
  4. Castorimorpha - beavers, gophers, kangaroo mice, pocket mice, kangaroo rate
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5
Q

What should you never use when reducing crown length and why?

A

Nail clippers!!!!

  1. Can split the tooth along the length as teeth are brittle
  2. therefore they can easily fracture causing pain and discomfort
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6
Q

Why is it important to know the body weight and life expectancy

A

BW - drug dosage - often scales not designed to weight such small animals
LE - helps with prognosis and decision making e.g. end of life span therefore different treatment?

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7
Q

What are the important “pet suborders” and e.g

A

o Myomorpha - mouse like: mice, rats, gerbils, hamsters

o Hystricomorpha - porcupine like: guinea pig, chinchilla, degu (diff from all others so big debate)

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8
Q

Life expectancy

  1. mouse
  2. rat
  3. hamster
  4. gerbil
  5. guinea pig
  6. chinchilla
A
  1. 1-2.5 years
  2. 3 years
  3. 1.5-2 years
  4. 1.5-2 years
  5. 4-7 years
  6. 10-15 years
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9
Q

Bodyweight

  1. mouse
  2. rat
  3. hamster
  4. gerbil
  5. guinea pig
  6. chinchilla
A
  1. 20-40 g
  2. 400-800 g
  3. Syrian 100-200 g Russian 20-40 g
  4. 70-130 g
  5. 750-1000 g
  6. 400-500 g
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10
Q

Dentition Myomorpha

A 
I= 1/1
C = 0/0
PM = 0/0
M = 3/3
x 2 = 16
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11
Q

Dention Hystricomorpha

A 
I= 1/1
C = 0/0
PM = 1/1
M = 3/3
X2 = 20
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12
Q

Describe the incisors

A

Open rooted, continuously growing

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13
Q

Describe molars

A

Open rooted preM and M

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14
Q

Talk about the cheek teeth of Myomorphs and Hystricomorphs

A
  1. Myomorph = cheek teeth erupt continuously for short period of time, then STOP erupting. Very rare to get dental disease of molars and pre molars
  2. Hystricomorphs cheek teeth = continuously erupt so likely to have issues e.g. with overgrowth
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15
Q

Describe the mouth anatomy of rodents

A 
o	Large diastema (gap between incisors and cheek teeth)
o	Can GNAW without wearing molars or swallowing debris
o	Lower jaw moved forward 
o	Incisors opposed but molars apart
o	Cheeks drawn into diastema
o	Can CHEW
o	Lower incisors behind uppers
o	Molars opposed
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16
Q

What type of INCISOR teeth do rodents have?

A

Aradacular Eledont

Open rooted continually growing

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17
Q

Describe rodent Incisor teeth

Why don’t swallow when gnaw

A
  1. Chisel shaped incisors
  2. Lower incisors are about 3 X longer than upper (don’t mistake for overgrowth!)
  3. They can gnaw without swallowing debris as cheeks come together when bottom jaw forward
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18
Q

Why are rodent teeth chisel shaped?

A

o Hard enamel on one side (rostral)
o Softer dentine wears more quickly, resulting in chisel shape forming
o So as chew, back of tooth wears faster – sharp teeth

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19
Q

What type of molars do rodents have? and what deos it mean?

A
  1. hystricomorphs, the premolars and molars are ELODONT
    - means continue to erupt throughout life, dental disease common
  2. myomorphs the molars are ANELODONT
    - Means M overgrowth uncommon
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20
Q

What other animals have similar molars to hystricomorphs?

A

Horse and rabbit - continue to grow throughout life! therefore these animals are also prone to dental disease

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21
Q

Talk about the gastrointestinal system broadly

A
  1. Mono gastric
  2. Relatively large caecum
  3. Elongated colon
22
Q

Do rodents exhibit caecotrophy?

A

Most species do!

Reingesting faeces to enahnce the uptake of essential vitamins adn AA in hindgut

23
Q

Why do rodents have a relatively large caecum?

A
  1. Hystricomorph are herbivores
  2. Myomorphs are omnivores
  3. So a large caecum helps to utilise some bacterial digestion of plant material
24
Q

Can rodents vomit?

A

NOPE!

  1. Strong oesophageal sphincter (cardiac) and crural sling
  2. limiting ridge between oesophagus and cardia of stomach
  3. Diaphragmatic muscle is too “weak” to support emesis (vomiting)
25
Q

Interesting fact need to do before surgery

A
  1. Don’t need to starve as have a high metabollic rate and relatively fast gut transit time.
  2. poisons are good as once ingested are absorbed relatively quickly, and can’t vomit!
26
Q

Broadly describe the respiratory system

A
  1. Obligate nasal breathers
  2. Lungs: 4 lobes
    Left lung ahs a single lobe, right 4 (cranial, middle, caudal, intermediate
  3. but hamsters have an additional lobe caudal accessory (5 in total)
27
Q

Why are rodents obligate nasal breathers?

A
  1. due to high larynx and long epiglottis

2. means passage straight from trachea to nasal cavity, preventing mouth breathing in normal animal

28
Q

How is respiration optimised?

A

o Short airways and increased respiratory rates (breath in faster)
o More alveoli of thinner diameter (increased S.A for gas exchange)
o High chest wall compliance = increase vital capacity (take in more air in each breath), decrease residual lung capacity (when breath out, everything taken out)
o Optimised to expand lungs and efficiently expel air

29
Q

Oxygen dissociation curve - where are small animals vs larger?

A

Smaller animals move to right, harder for oxygen to bind but easy to release
Hb releases O2 more readily at tissue level

30
Q

How do rodents maintain thermoregulation cold

A

Behavioural
o Huddling, nest building, tunnelling underground where temp fluctuates less)
• Shivering
• Peripheral vasoconstriction (tails, ears, paws) keep heat in core
• Non-shivering thermogenesis
o Brown fat behind scapula, round neck and shoulders. Can persist for life

31
Q

What is heat adaption for rodents

A
  • Few sweat glands (minimal on feet)
  • Evaporation of saliva that is groomed over body (evaporative heat loss)
  • Arteriovenous shunts in ears, tails & feet
32
Q

Broadly describe Myomorph and hystricomorph reproductive strategies

A 
Myo
1. large litters
2. short gestation
3. Altricial young (blind deaf, no fur)
Hystrico
1. Smaller litters
2. long gestation
3. precocial young (ready to go with fur)
33
Q

What sort of ovualtors are rodetns?

A
  1. all are polyoestrus sponstaneous

2. apart from chinchillas whoa re poly oestrus seasonal - want young to be born at most optimal time

34
Q

Gestation of:

  1. mice
  2. rate
  3. hamsters
  4. gerbils
  5. guinea pigs
  6. chinchillas
A
  1. mice - 19-21 days
  2. rate - 21-23 days
  3. hamsters - 15-18 days
  4. gerbils - 23-26 days
  5. guinea pigs - 59-72 days
  6. chinchillas - 111 days
35
Q

Age of sexual maturity of rodents

A

mice, rate, hamsters, gerbils = 6-8 weeks
Guinea pig = 4-6 weeks
Chinchilla - 8 months

36
Q

Female rodent uterus

A

Bicornuate: guinea pig, ferret, dog, cat (single cervix, small body, long horns
Duplex: hamster, rat, mouse, chinchilla, rabbit (2 cervix)
If ever do a c section of a animal with duplate cervix you have to do 2 incisions, one on either horn as can’t milk offspring from one side to other

37
Q

Why type of penis do male rodents have?

What can they do with testes?

A

Os penis like dog

2. they have an open inguinal canal so can retract testes back into abdomen

38
Q

What is interesting about chinchilla testes?

A
  1. testes are often inguinal unlike others that descend into scrotal sac following puberty
39
Q

Name the accessory sex glands of the male rodents

A 
o	Seminal vesicles
o	Prostate
o	Coagulating gland
o	Bulbourethral gland
o	Preputial gland
o	Mucous plug into vaginal to help with intromission
40
Q

How do you sex rodents and what do you need to know when doing so?

A
  1. know that is is pretty stress inducing
  2. Ano genital distance - longer in males than females
  3. mice and rats - only females have nips
    Gerbils and hamsters both sexes have nips, but more obvious ones in females
    Guineapig both have obvious nips!
  4. male gerbil has a much larger ventral scent gland (bald path on abdomen)
  5. Male hamsters - lump
  6. Male guinea pig (boars) looks like I and penis can be everted using gentle pressure
  7. Female looks like a y
  8. Chinchilla dont mistake clitoris for penis!
41
Q

What are the 4 distinct periods of female reproductive cycle

A

o Proestrus
o Oestrus
o Metoestrus
o Dioestrus

42
Q

What is the copulatory plug?

A
  • Found following copulation in most female rodent species
  • Thought to be congealed sperm, mucus and accessory ejaculatory fluids, which harden within the cervix
  • Remains in place for 8-12 hours
  • Often found on cage floor rather than in vagina! – hard waxy
  • Thought to seal vagina and make it more likely for mating to be successful
43
Q

• High surface area to body weight means susceptible to

A

o Dehydration
o Hypothermia
o Hypoglycaemia
o Have to consider when doing any procedure on them

44
Q

• Fast metabolism

A

o Increased O2 consumption and increased food intake

o Husbandry very important

45
Q

• Constantly growing molars in GP’s and chinchillas

  • Larynx high in oropharynx
  • Coprophagy is normal
A

o Susceptible to dental disease
– obligate nose breathers
– vitamin recycling

46
Q

Individual species features of rat

A

Naturally nocturnal
Yellow incisors due to iron pigment – normal
Prominent harderian gland
o Red brown gland fills large part of orbit and lies behind the globe
o Increased secretion when stressed or unwell
o Looks like blood but NO!
Venupuncture sites – take <1% bodyweight
o Lateral tail vein
o Lateral saphenous
o Ventral tail artery
No gall bladder
Urethral orifice separates from vulva
Extensive mammary tissue from axilla to groin in females
o 6 pairs of mammary glands
o Prone to tumour formation
o Mammary fibroadenoma – benign, can remove and be successful
o Mammary adenocarcinoma – malignant

47
Q

Individual species features of chinchilla

A

• Naturally nocturnal, but can adapt to diurnal lifestyle
o Need 12hr:12hr light dark periods
o If cycle differs such, often get problems
• Very dense fur – 50-60 hairs from each follicle
o Tolerant of cold (but not wet) and sensitive to heat
o Will ‘drop’ coat if stressed, careful handling required (fur slip) as a vet handle carefully
o Dust baths help maintain coat condition
• Long gestation period (111 days)
o Young precocial  fully formed and ready to go
• Blood sampling
o Cranial vena cava and lateral saphenous

48
Q

Interesting species facts about Guinea pig

A

• Absolute requirement for vitamin C
o 10mg/kg/day (3 times this so 30mg/kg/day if pregnant)
o Scurvy can develop within 4 days of decreased intake
• Males have prominent caudal sebaceous gland
• Pubic symphysis dilates to allow parturition, important to breed females before age of 7-8 months to prevent fusion and subsequent dystocia. If want to breed older animal with no litter prior warn for dystocia
• Blood sampling
o No tail so
o Cranial vena cava
o Jugular
o Femoral or lateral saphenous vein
• Thymus is cervical
o Often used in laboratory science
• Young – precocial! Pregnant for 63-65, like dogs

49
Q

Interesting species facts about Gerbils

A

• Form monogamous pairs
o Dad helps with raising young
o Post mating vaginal plug deep and not easily seen
• Both sexes have large ventral midline sebaceous gland
o Larger in males
o Not a tumour, however, is a site for tumour formation
• Drink very little (4ml/100g/day), are desert species and have excellent urine concentrating abilities. Popular pets as not too smelly
• Avoid handling by tail – can slough, skin can just fall off
• Absolute requirement for vitamin C
o 10mg/kg/day (30mg/kg/day if pregnant)
o Scurvy can develop within 4 days of decreased intake
• Males have prominent caudal sebaceous gland
• Pubic symphysis dilates to allow parturition, important to breed females before age of 7-8 months to prevent fusion and subsequent dystocia

50
Q

Interesting species facts about Hamsters:

A

Bilateral cheek pouches which can extend caudally as far as the shoulder blades - primary function storage adn transport food
o Often site of impaction – you will need to go in and clear out
o Lined with oral mucosa
o Immunologically privileged site
o can inflate - keep afloat
• Stomach is compartmentalised into
o Forestomach (like ruminants)
o Glandular stomach
• Sensitive to antibiotics due to bacterial population
o Disruption of normal gut flora
• Females have separate vaginal and urethral openings
• Bilateral vaginal pouches internally making vaginal cytology hard to interpret
o Vaginal plug deep and difficult to see
o See post mating vaginal discharge
• Shortest gestation of all eutherians
o 15-18 days (Syrian)
• Flank glands – androgen responsive. Litke ventral scent gland in gerbal, similar appearance
o More obvious in males than females
o Often mistaken for tumours
• Blood sampling tricky
o No tail vein!
o Use jugular, cephalic, cranial vena cava
• Will enter state of hibernation
o If temperature drops below 5C
• Nocturnal but very active during hours of darkness can travel around 5 miles in one night!
• High water consumption
o Up t0 20ml a day in some large adults

Year 2 NSF (10 decks)

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