Small Mammal Anatomy 1

Small Mammal Anatomy 1

1. Thermoregulation

   • Cold adaptations
     • High activity - Shivering
     • Brown fat (more mitochon)
     • Peripheral Vasoconstriction
   • Heat Adaptations
     • Burrows
     • Water conservation
     • Peripheral Countercurrent System
       • Increase heat radiated at periphery
     • High surface to volume ratio
   • High metabolic rate
     • Susceptible to hypothermia and dehydration (think about anaesthesia)

2. Dentition

   • Rodent Dentition
     • Monophydont - 1 set of teeth
     • 16 teeth - 1-0-0-3/1-0-0-3
     • Incisors - aradicular
       • Can be yellow due to iron pigmentation
       • Need to be worn down (gnawing)
       • Fracture causes disproportionate increase in growth
     • Molars - Closed Roots - Enamel Folds + enamel free cusps
   • Rabbit Dentition
     • 2-0-3-3/1-0-2-3 28 teeth
     • 2nd incisor rudimentary (peg teeth) + premolars and molars are similar = cheek teeth
     • Diastema between incisors and premolars
     • Horizontal grooves in enamel of upper incisors suggests dental disease due to poor diet
     • Can only open jaw 30o angle + continual growth of all teeth (2mm/week
   • Ferret Dentition
     • Diphydont (2 sets of teeth)
       • Deciduous: 3(4)-1-3-0/3-1-3-0
       • Permenant: 3-1-3-1/3-1-3-2 (get around 7-10 weeks old)
     • Similar masticatory muscles and salivary glands to dog
   • Hamster Cheek Pouches
     • Distensible invaginations of lateral buccal endothelium
     • Extend to dorsocaudal scapula (nearly back of neck)
     • 4-8mm empty, 20mm full. Empty by massaging forelimbs and tongue

3. Digestion

   • Monogastric - Some have non-glandular areas. Vomiting difficult
     • Vomiting difficult due to angle of oesphagus into stomach
   • Simple small intestine
   • Caecum present
     • Larger in herbivorous species (rabbit, GPig)
     • Rabbit Hindgut: Caecum is 10x stomach capacity
       • 40% of GIT content with 3 gyral folds and thin walls acting as a fermentation vat
       • It is easy to cut into caecum as you make first incision as its against body wall + fragile
   • Ferret similar to other carnivores
   • Cecotrophy
     • Coprophagy - consumption of faeces
     • Consumption of caecal pellets (produced 8h post feeding
     • Essential for life - high fibre diet required for production of pellets. Low protein diet encourages consumption
     • High carb decreases consumption and allows bacterial overgrowth in caecum. Leading to efficient converstion of plant protein (70-80%)
     • Cecotrophs (pellets) form in caecum and proximal colon - high nutrient content and covered in mucus.
       • Highly undigestible fibre doesn't enter the caecum therefore passed out.
       • Cecotrophs are directly ingested from the anus

4. Taxonomy

   • Lagomorpha - Rabbit + Hare
   • Rodentia - Myomorpha - Rat + Mouse + Hamster
   • Rodentia - Caviomorpha - GPig + Chinchilla + Degu
   • Rodentia - Sciuromorpha - Squirrel + Chipmunk
   • Carnivora (Family Mustelidae) - Ferret + Weasel + Stoat + Otter + Badger