Rodents Flashcards
What characteristic is rodent classification based on?
Continuously growing incisor teeth
How are rodents classified?
Order = Rodentia Suborders = myomorphs (mouse-like), hystricomorphs (porcupine- like), scuriomorphs (squirrel-like), castorimorphs (beavers ect.), anomaluromorphs (scaly-tailed squirrels)
What is the dental formula of a myomorph?
I 1/1 C 0/0 P 0/0 M 3/3 = 16
What is the dental formula of a hystricomorph?
I 1/1 C 0/0 P 1/1 M 3/3 = 20
What is the lower:upper incisor crown ratio of myomorphs?
3:1
Describe the growth of myomorph molars
Anelodont = NOT continually growing/ erupting
Describe the growth of hystricomorph molars
Elodont = continually growing
What kind of GI tracts do rodents have?
mono-gastric
Describe the stomach of rodents
glandular part of the stomach is separated from forestomach by ridge
Why can’t rodents vomit?
limiting ridge b/w oesophagus + cardia of stomach, strong oesophageal sphincter, diaphragmatic muscle too weak
What is the advantage of caecotrophy?
Enhances the uptake of essential vitamins/ amino acids
What anatomical structures make rodents obligate nasal breathers?
high larynx, elongated soft palette
Describe the lungs of rodents
- L lung = 1 lobe
- R lung = cranial, caudal, middle, accessory
How are rodents respiratory systems adapted for high O2 requirements?
- short airways + increased rr
- more alveoli + thinner diameter
- high chest wall compliance
Explain the shift of the haemoglobin curve in rodents
Curve shifted to R- haemoglobin offloads O2 more readily @ tissues
Describe what thermogenesis mechanisms rodents have?
- Behavioural (huddling/ tunnelling)
- Shivering
- Peripheral vasoconstriction
- Brown fat behind scapula/ neck
What heat loss mechanisms do rodents have?
- Sweat glands (minimal)
- Saliva
- Arteriovenous shunts in ears/ feet/ tail
Compare the reproductive strategies of myomorphs + hystricomorphs
- Myomorph = large litter, short gestation, altricial young
- Hystricomorph = small litter, long gestation, precocial young
What type of reproductive tract does a guinea pig have?
bicornate (1 cervix, 2 horns)
What type of reproductive tract do rat, mice, hamsters have?
Duplex (cervix associated w/ each horn)
What is the most reliable method of sexing rodents?
ano-genital distance- longer in males than females
Name the method used to determine the stage of oestrus?
Cytology of vaginal secretions
What is the ‘Copulatory Plug’?
congealed sperm, mucus + accessory ejaculatory fluid that hardens within cervix for 8-12hrs- makes making more successful
