Herp Water Budgets

hydrophobic scalation

water repellent scales, useful for rain harvesting

herps that harvest rain via hydrophobic scalation

several vipers, some tortoises

method used by vipers to harvest rain

flatten out body to allow water to pool between coils, then drink the pooled water

method used by tortoises to harvest rain

eaves on their carapace drips water towards the mouth

hydrophilic scalation

water is absorbed between scales via capillary action, pulling water towards the mouth

herps that harvest rain via hydrophilic scalation

some Agamids (eg thorny devil), some Iguanids, Phrynosoma

arginine vasotocin (AVT)

hormone that increases skin permeability and water resorption from the bladder

pelvic patch

characteristic in anurans - thin and capillary rich, controls skin permeability through AVT

methods used by aquatic amphibians to retain/drink water

passively absorb water, produce dilute urine, reabsorb lost ions through skin and gills

salt tolerance in brackish water amphibians

internal osmolarity raised above saltwater, special enzyme that synthesizes urea

preformed water

water that comes from food

water losses from eating food

digestion increases metabolism (respiratory), urine, feces

metabolic water

product of carb, fat, and protein oxidation

organisms who use metabolic water

desert adapted mammals, less important in herps

stratum corneum in amphibians

single cell layer, very little keratin, highly permeable, major route of water loss

stratum corneum in reptiles

multiple layers of a lipid-keratin complex, not a major route of water loss

method used by treefrogs to prevent evaporation

produce a lipid layer

method used by desert frogs and Sirenids to prevent evaporation

produce a cocoon made of skin and mucus

respiratory water loss

air is moistened to protect water respiratory surfaces; exhaled water > inhaled water

effect of temperature on respiratory water loss

increases/intensifies

herps more affected by respiratory water loss

reptiles

herps more affected by evaporative water loss

amphibians

behavior displayed by reptiles to reduce respiratory water loss

seek shelter

nitrogenous waste

produced from protein catabolism

ammonia nitrogenous excretion

produced by amphibians

method of passing ammonia waste

from the bladder in dilute urine, or from skin and gills in urine (aquatic amphibs)

ammonia waste water and energy costs

costs water, saves energy

uric acid nitrogenous excretion

produced by reptiles

method of passing uric acid waste

through the cloaca along with feces (semisolid)

uric acid waste water and energy costs

costs energy, saves water

salt gland evolution

reinvented multiple times from multiple lineages

advantages of salt glands

more versatile in excretion (eg bicarbonate), 7x higher concentration of salts than urine (saves water)

salt gland function

sends ions to be excreted separately instead of being excreted via urine