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Herps: Physiological Ecology ( Water and Temperature )

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  1. Herps: Physiological Ecology (Water and Temperature) Hyla arenicolor - Animals are 70-80% water - Solute concentrations and location - Q10 effect - Temperature and water linked

  2. Physiological Implications of the Environment Increased temperature increased rate of chemical reactions  increased rate of metabolism (Eckert 17-2) Q10 effects: Q10 = MR(t+10) MRt Q10 often = 2 to 3, depends on the two temps used

  3. Snake Example Pough et al., 2001 Pough et al., 2001

  4. Temperature and the Environment (Eckert)

  5. Herps: Physiological Ecology (Water and Temperature) Behavior and Physiology altered by... ~ Amphibs to regulate water balance ~ Reptiles to regulate body temperature Hyla arenicolor - Behavior - Microhabitat - Posture - Color - Heart Rate - Blood Flow

  6. Water Get water: 1. liquid water 2. preformed water 3. metabolic water Pough et al., 2001 Amphibians- liquid water via skin Pough et al., 2001 Rana pipiens

  7. Water Osmolality (mosM = ‘milliosmoles’) concentration of solutes (in plasma or urine) units are mmole solute/kg water 250 - 300 is about ‘normal’ Water moves from area of lower osmolality to area of higher osmolality e.g., -soil to toad (or vice versa) -plasma to cell (or vice versa) -frog to ocean

  8. Water - Amphibs in fresh water steep gradient into body (2 mosM -> 250 mosM) produce lots of dilute urine - Amphibs in salty water steep gradient out of body ( 500+ <- 250 mosM) therefore raise internal osmolality (urea, sodium, chloride in plasma) (amino acids in muscle cells) - Reptile skin relatively impermeable to water (lipids)

  9. Eleutherodactylus coqui Water Role of microhabitat Lose water: evaporation urine feces salt glands eyes Pough et al., 2001 Alter behavior and physiology to minimize water loss Water balance limits activity in time and space Amphibs lose most water via evaporation - cutaneous resistance 1 dried mucus 2 cocoon 3 wax

  10. Phyllomedusa Pough et al., 2001

  11. Water Chuckwalla Less evap. Monkey Tree Frog Anolis lizard Alligator Softshell Turtle More evap. Bufo, Spadefoots, Rana (free water surface) Pough et al., 2001

  12. Water Urine from kidney - ions (sodium, potassium, chloride, bicarbonate) - nitrogenous waste (byproduct of protein digestion): 1. ammonia - soluble but toxic 2. urea - very soluble and nontoxic - requires ATP and water 3. uric acid - insoluble - secreted as semisolid - conserve water - reptiles, waterproof frogs Phyllomedusa (Hylidae), Chiromantis (Rhacophoridae) - turtles and crocs can switch

  13. Water Salt gland - to excrete excess sodium and potassium - conserve water, costs ATP 1. Lacrymal salt gland sea turtles 2. Lingual salt gland crocodilians 3. Nasal salt gland lizards Dietary salts important (e.g., chuckwalla, desert tortoise)

  14. Shoemaker et al., 1992 Resistance to Evaporation - Cutaneous properties - Boundary layer (greater in larger animals) - Humidity - Wind Speed - Temperature Shoemaker et al., 1992

  15. 1 Humidity 2 Temperature Shoemaker et al., 1992 3 Body Size 4 Wind Speed

  16. Behavior vs. Physiology Shoemaker et al., 1992

  17. Non-arboreal Shoemaker et al., 1992 arboreal

  18. Dorsal skin Morphological and physiological differences Shoemaker et al., 1992

  19. Cocoon Formation Shoemaker et al., 1992

  20. Amphibians rarely ‘drink’ Shoemaker et al., 1992 Pelvic patch -vascularization AVT (arginine vasotocin) -from posterior pituitary -stimulates water uptake -stimulates reabsorption from kidney and bladder

  21. Shoemaker et al., 1992

  22. Blood Pressure Nervous and Hormonal Control of water balance Urine production Sodium excretion Shoemaker et al., 1992

  23. Tolerance in salty water Shoemaker et al., 1992 Crab-eating frog Larvae seem to excrete salt via gills (unique among amphibians in 930 mOsm NaCl)

  24. Water Balance Gopherus agassiziiexample Urine as a water reserve (16 months without H20) Pough et al., 2001

  25. Gas exchange in lungless amphibians Larger animals have harder time getting enough O2 via skin Shoemaker et al., 1992

  26. Gas exchange in amphibians Use lungs to meet increased O2 demands Shoemaker et al., 1992

  27. Temperature Heat Gain (or loss) Qabs = radiation absorbed by surface of animal M = metabolic heat production R = infrared radiation received/emitted C = convection to surrounding fluid (air/water) LE = condensation or evaporation G = conduction (direct contact with substrate)

  28. Temperature Qabs = solar radiation absorbed by surface of animal neutral positive location - shade or sun posture - exposure changes color - melanin in melanophores of dermis negative Pough et al., 2001

  29. Temperature M = metabolic heat production chemical energy ‘lost’ as heat during metabolism large species can use to be somewhat endothermic - surface area to volume ratio - leatherback (Dermochelys coriacea) - pythons (female brooding clutch) Pough et al., 2001

  30. Temperature R = infrared radiation received/emitted surfaces emit and receive infrared (thermal) radiation -not related to color, but texture instead matte - absorb and emit well smooth - absorb and emit poorly matte Callisaurus draconoides smooth

  31. Temperature C = convection to surrounding fluid (air/water) - fluid movement takes heat away lizard climb bush midday - body size and boundary layer small - feel changes more quickly large - less influenced by convection Sauromalus ater Sceloporus occidentalis

  32. Temperature LE = evaporation (or condensation) Evap. cooling not typically important for reptiles - some pant if overheated Amphibians - lots of evaporation G = conduction (direct contact with substrate) transfer between touching objects ventral surface on warm rocks aquatic herps typically same temperature as water

  33. Thermoregulation Temperature Set Point (often a narrow range) alter by season gravidity infection Hypothalamus Heliothermic vs. Thermoconformers Pough et al., 2001

  34. Body temperature & thermoregulation • Ectotherms • Thermoregulation • Temperature Regulation • Reptiles v. Amphibians • Controlling Body Temp.

  35. I. Ectotherms: all physiological processes are temperature dependent

  36. Temperature and Performance • Effective escape • Development

  37. II. Thermoregulation • Temperature • Ectothermy – limits options • Metabolic heat – • Temperature range

  38. Hypothalamus – temp. control • Set point temp. or set point range regulation control center • Sensor in hypothalamus integrates info about the temp. of the body, via blood flow

  39. Max. Min. Ectotherm temp. profile -

  40. A. Temperature Regulation • Heat gained = heat lost (steady state) • Heat energy gained • Qabs = radiation absorbed by the surface • M = metabolic heat production • R = infrared radiation received/emitted • C = Heat gained/lost by convection • LE = Heat gained by condensation or lost by evaporation • G = Heat gained/lost by conduction

  41. Body color can affect

  42. 1. Adjusting convective heat exchange

  43. 2. Body size affects thermoregulation • Surface area • Heat gain/loss rate decreases as body size increases

  44. Large leatherback turtles: inertial endotherms Able to retain metabolic heat in addition to generating heat from muscle activity

  45. B. Reptiles v. amphibians-

  46. 1) Permeable skin –big challenge • Evaporative cooling to balance effect of solar heating • Ventral surface next to wet substrate to replace water lost via evaporation • Selection of suitable microhabitat