High Temperatures Flashcards
Burrowing: the Kangaroo Rat
Remains cool in burrow during day time
Respiratory moisture is condensed in nasal passages
Free water in seeds
Metabolic water derived from dry seeds
Urine concentrated by countercurrent exchange in extra long loop of henle
Feces dehydrated prior to defecation
Burrowing: the Antelope Ground Squirrel
Forages for short periods of time above ground during the day - retreats to burrow to cool down
Burrows during the night
Beetle (Onymacris rugatipennis)
High foraging in the morning
Stays in the shade in midday
Returns to foraging in the evening
Shovel Snouted Lizard (Desert Dweller)
Alternates by lifting feet off ground
rapidly cools feet by about 10 degrees
when temperatures are too high it shovels under the sand to cool
Golden-Wheel Spider
Burrows to escape predators and can escape predators by rolling away
Sidewinder Viper
side-winder movement allows minimal contact with hot sand
Aestivation
a period of physiological inactivity to avoid the hottest driest periods
eg the water-holding frog in Australia
o It aestivates in a chamber 1m below the surface
o This is a stable environment at a stable temperature
o Take down water with them
Evaporators
middle sized desert animals eg birds dogs small antelope
lose heat through sweat
birds don’t have sweat glands - bathe in water and let latent heat loss of evaporation to cool them down
Sweating is only really effective in mammals with short coats or those that are relatively hairless
Carotid Rete
Oxygen rich blood for the brain is supplied by the carotid artery.
This breaks up into a capillary network in the carotid rete where it runs adjacent to cool blood flowing from the nasal veins.
Blood in the nasal veins are cooled by evaporation from the moist nasal passages
Birds
Lose heat by gular fluttering
floor of the mouth and throat is vibrated rapidly
Endurers
Large mammals like oryx and camel
long appendages to lose heat
well developed carotid rete
short coat length, fat carried on the top of body
Dromedary camel
The hump contains fat and is simply used as a food store
It can withstand a loss up to 30% of its body water
It can drink rapidly – about 200 litres in a drinking bout of 3 minutes.
It can allow its body temperature to fluctuate widely: up to 41oC during day and down to 34oC at night
By acting as a heat store its body reduces evaporative water loss – adaptive hyperthermia
Desert Insects
high surface: volume ratio Impermeable integument and spiracles tolerate dehydration N waste: Uric acid (helps conserve water) Malphigian tubules Hypertonic urine (up to 10x hemolymph)
