Homeostasis in
Herps
Herpetoculture
Pensacola Jr College
Homeostasis
w Maintenance of stable
internal conditions
w Two focal points of
homeostasis:
Water balance
Temperature balance
Water Balance in
Amphibians
w Skin allows ease of water
flow
Aquatic amphibians have
problem of hydration
Terrestrial amphibians have
problem of dehydration
Flow of water depends on
humidity of atmosphere
Water Balance in Amphibians
(contd)
w
Amphibian solutions:
Environmental selection
Avoidance behaviors (eg.
Burrowing)
Periods of inactivity
Nocturnal activity only
Kidney eliminate excess
water
Bladder water storage organ
Water Balance in
Reptiles
w Dry skin with low water permeability
No water absorbed
Small amounts of water lost
through skin
w Utilize microhabitat
selection and low water excretion to maintain water levels
Water Balance -
Excretion
w Protein metabolism results
in toxic ammonia production
w Ammonia requires lots of
water for excretion ΰ fishes, tadpoles,
crocodilians excrete directly
w Urea (moderate toxicity,
moderate water) ΰ adult amphibians, mammals
Water Balance
Excretion (contd)
w Uric acid (low toxicity, low
water to excrete) ΰ birds, most reptiles
Costs the most energy to
convert to uric acid
Reduces water loss
Reduces toxicity of
excrement in eggs
Temperature
Balance
w Activity Temperature Range =
the range of temperatures within which an amphibian or reptile can carry out
all of its activities (usually within a 4-10oC specific range)
w Regulation through:
Metabolism (endothermal)
Environment (ectothermal)
Endothermy
w Utilizing internal metabolic
or physiological processes to maintain temperature
w Rarely seen in herps a few
snakes use this to keep eggs warm, and marine iguanas use it in combination
with behavior for stable temp
Marine Iguana
Thermoregulation
Ectothermy
w Depend on external sources
of heat + behavior
w Heliotherms rely on
periodic basking to maintain temperature
w Thigmotherms derive heat
from their medium (air, water, soil)
Pathways of Heat
Exchange
w Radiation= flow of heat out
of object based on its temp
w Convection = heat exchange
based on air current flow
w Conduction= heat exchange
between body and substrate
w Evaporation= heat loss due
to water evaporation
w Metabolic heat production
Heat Exchange
Pathways
Eurythermy
w Cannot raise temperature
above that of environment
w Most amphibians
w Seek out shelter from
temperature extremes
w Nocturnal / diurnal
dependent on climate
w Utilize water evaporation
Dormancy
w When body is outside of
activity temperature range, herps become dormant
w Estivation = seek shelter
and reduce metabolism in heat
w Hibernation = Reduce
metabolism / den up in cold
Most non-tropics amphibians
Many non-tropics reptiles
Temperature
Tolerance Ranges