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Herps: Physiological Ecology (Water and Temperature) Hyla arenicolor - Animals are 70-80% water Solute concentrations and location Q10 effect Temperature and water linked Physiological Implications of the Environment Increased temperature increased rate of chemical reactions increased rate of metabolism Q10 effects: Q10 = MR(t+10) (Eckert 17-2) MRt Q10 often = 2 to 3, depends on the two temps used Pough et al., 2001 Pough et al., 2001 Snake Example Temperature and the Environment (Eckert) 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 Water Get water: 1. liquid water 2. preformed water 3. metabolic water Pough et al., 2001 Amphibiansliquid water via skin Pough et al., 2001 Rana pipiens 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 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) Role of microhabitat Water Lose water: evaporation urine feces salt glands eyes Eleutherodactylus coqui 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 Phyllomedusa Pough et al., 2001 Water Chuckwalla Less evap. Monkey Tree Frog Anolis lizard Alligator Softshell Turtle Bufo, Spadefoots, Rana More evap. Pough et al., 2001 (free water surface) 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 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) Shoemaker et al., 1992 Resistance to Evaporation - Cutaneous properties - Boundary layer (greater in larger animals) - Humidity - Wind Speed - Temperature Shoemaker et al., 1992 1 Humidity 2 Temperature Shoemaker et al., 1992 3 Body Size 4 Wind Speed Behavior vs. Physiology Shoemaker et al., 1992 Non-arboreal Shoemaker et al., 1992 arboreal Dorsal skin Morphological and physiological differences Shoemaker et al., 1992 Cocoon Formation Shoemaker et al., 1992 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 Shoemaker et al., 1992 Blood Pressure Urine production Sodium excretion Shoemaker et al., 1992 Nervous and Hormonal Control of water balance 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) Water Balance Gopherus agassizii example Urine as a water reserve (16 months without H20) Pough et al., 2001 Gas exchange in lungless amphibians Larger animals have harder time getting enough O2 via skin Shoemaker et al., 1992 Gas exchange in amphibians Use lungs to meet increased O2 demands Shoemaker et al., 1992 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) Temperature Qabs = solar radiation absorbed by surface of animal location - shade or sun posture - exposure changes color - melanin in melanophores of dermis Pough et al., 2001 neutral positive negative 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 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 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 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 Thermoregulation Temperature Set Point (often a narrow range) alter by season gravidity infection Hypothalamus Heliothermic vs. Thermoconformers Pough et al., 2001 Body temperature & thermoregulation I. II. Ectotherms Thermoregulation A. B. Temperature Regulation Reptiles v. Amphibians III. Controlling Body Temp. I. Ectotherms: all physiological processes are temperature dependent Temperature and Performance • Effective escape • Development II. Thermoregulation • • • • Temperature Ectothermy – limits options Metabolic heat – Temperature range 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 Min. Ectotherm temp. profile - Max. 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 Body color can affect 1. Adjusting convective heat exchange 2. Body size affects thermoregulation • Surface area • Heat gain/loss rate decreases as body size increases Large leatherback turtles: inertial endotherms Able to retain metabolic heat in addition to generating heat from muscle activity B. Reptiles v. amphibians- 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 2) Impermeable skin – also challenging • Panting, III. Controlling body temp (maintaining body temp. different from ambient temp.) 1) 2) 3) 4) Behavior Short term Microhabitat selection Water absorption & evaporative water loss to moderate temperatures 5) Heat production Cardiovascular control of heating/cooling Circulatory adjustments 1) Higher heart rate during heating 2) Intracardiac shunt 3) Blood vessel dilation Acclimation, Recent History of Individual “Reset” Metabolism (Eckert 17-3) Seasonal or ontogenetic differences Thermoregulation Cardiovascular control of heating and cooling Pough et al., 2001 - Cardiac Shunts - Peripheral Vasodilation Pough et al., 2001 Pough et al., 2001 Thermoregulation Freezing - ice crystal formation alter osmolality physical destruction 1. Freeze Resistance supercool prevent ice crystals (Sceloporus jarrovii) (Chrysemys picta) 2. Freeze Tolerance (Rana sylvatica ) glucose or glycerol as antifreeze in cells How do they work? - RESPIRATION (gas exchange) - CARDIOVASCULAR SYSTEM - METABOLISM novel systems, structures, behaviors, habitats... Respiration - Bring in Oxygen (and get it to the tissues) - Get rid of Carbon Dioxide (and control blood pH) Gas Exchange - into solution - water balance... Respiration - in AIR - in WATER Reptiles mostly air, Amphibs often both 1. Pulmonary - lungs 2. Non-Pulmonary - skin surface, gills, pharynx, cloaca Respiration (non-pulmonary) Amphibians - gas exchange/water balance - buccal region Plethodontids: skin + buccal - skin folds, highly vascularized water needs to be moving e.g., Hellbender, Lake Titicaca frog - Male Hairy Frog (Trichobatrachus robustus) breeding season gets skin filaments - why? Cryptobranchus Respiration (non-pulmonary) Reptiles - drier skin - lipid layers to retard water loss - less cutaneous gas exchange -BUT, some aquatics… Hydrophiinae (sea snakes) cutaneous respiration Chelonia many with gas exchange at pharynx or cloaca e.g., Pleurodiran Rheodytes leukops (Australia) - bursae from cloaca lined with villi - pump water in and out bursae 80x/min Hydrophis melanocephalus Respiration (Pulmonary) gills useless in air - so developed lungs... Buccal Pumping (Positive-Pressure Ventilation) - ancestral tetrapod trait - amphibians use exclusively, reptiles sometimes How it works… 1. Close glottis, open nostrils, lower buccal floor - air into mouth 2. Open glottis valves, nostrils still open, buccal floor low - air out of lungs, passes over new air, leaves nostrils 3. Glottis still open, close nostrils, raise buccal floor - positive pressure pushes air into lungs Repeat e.g., Sauromalus ater inflate lungs for defense Respiration (Pulmonary) Aspiration (Negative-Pressure Ventilation) - reptiles use to breathe - expand thoracic cavity, creating vacuum Lepidosaurs (lizards, snakes, tuataras) inhalation - internal and external intercostals contract relaxation - lungs inflated, glottis closed exhalation - hypaxial contraction (~ventral) Some species can’t breathe and locomote others use gular to force air into lungs e.g., Varanidae Respiration (Pulmonary) LUNGS - vary from simple sacs to complex Amphibs: generally simple more complex in frog than salamander (more surface area too) Reptiles: paired ancestrally reduction or loss in elongate forms e.g., snakes with reduced left lung lung complexity correlated with activity in lizards turtles and crocodylians with multi-chambered lungs Respiration (Pulmonary) Snakes right lung with two parts 1. vascular anterior and chambered, lots of blood vessels 2. saccular posterior, no chambers regulates airflow buoyancy in marine groups (~ to cloaca!) Pough et al., 2001 Fig 6-6 Respiration (Pulmonary) Crocodylians liver as plunger to compress and expand lungs instead of trunk musculature liver and lung linked by connective tissue exhalation liver pulled anteriorly by abdominal muscles inhalation liver pulled posteriorly by diaphragmaticus muscles that attach to pelvis Respiration (Pulmonary) Turtles modified because of shell exhalation - force viscera up against lungs inhalation - increase vol. of visceral cavity so lungs expand exhale inhale Pough et al., 2001 Fig 6-7 inhale exhale Respiration EGGS crocs and many turtles - calcified shell - pores in calcium crystalline structure lepidosaurs and some turtles - flexible fibrous shell - diffusion of gases through fiber gaps Cardiovascular System circulatory system heart, vessels, blood move O2 and CO2 gills simple: 1. Blood goes to gills 2. O2-rich blood goes to tissues 3. O2-poor blood goes to heart 4. Blood gets pumped back to gills lungs more complex because get 2 circuits in parallel: 1. Pulmonary circuit (lower pressure) 2. Systemic circuit (higher pressure) Cardiovascular System Herps (except crocs) with 3 chambers (= one ventricle) - no ventricular septum - BUT separate rich and poor blood - AND alter pressure in systemic and pulmonary Cardiovascular System Amphibians only vertebrates where O2 poor blood to skin (as well as to lungs) adults with paired pulmocutaneous arteries divide into two branches 1. Pulmonary 2. Cutaneous (to flanks and dorsum) skin provides 20-90% O2 uptake 30-100% CO2 release Cardiovascular System Gets rich Anuran Heart conus arteriosus w/ spiral valve trabeculae (create channels) role of Tb and HR (in separation) Gets poor rich in Pough et al., 2001 Fig 6-8 Cardiovascular System RAA = right aortic arch LAA = left aortic arch PA = pulmonary artery Squamate Heart (and turtles) (no conus arteriosus, no spiral valve) 2 systemic arches and one pulmonary artery from single ventricle BUT, single ventricle functions as THREE 3-chambered heart anatomically 5-chambered heart functionally rich Pough et al., 2001 Fig 6-9a Muscular Ridge RA = right atrium LA = left atrium Squamate Heart (and turtles) not “primitive” IVC = intraventricular canal AVV = atrioventricular valve RAA = right aortic arch LAA = left aortic arch PA = pulmonary artery rich 11 2 2 rich 7 3 7 4 5 6 5 4 Muscular Ridge CP = cavum pulmonale CV = cavum venosum CA = cavum arteriosum Pough et al., 2001 Fig 6-9 Cardiovascular System Cardiac Shunts R to L O2 poor to systemic via aortic arches (short delay between valves opening) L to R O2 rich to pulmonary artery pulmonary then aortic (longer delay between valves opening) 1. temperature regulation 2. breath holding (diving, turtle in shell, inflated lizards) 3. stabilize O2 content of blood when breathe intermittently Cardiovascular System Crocodylians (different!) 4-chambered heart - normally right to left shunt e.g., at rest rich Pough et al., 2001 Fig 6-10 (shown in use) BUT have foramen of panizza allows blood from left ventricle to get to the left aorta when left ventricular pressure is high (thereby closing right ventricular valve) e.g., when diving right ventricular valve METABOLISM Shared Characteristics of Amphibians/Reptiles • Ectothermy – Mammals, birds are endothermic. • Body temp is maintained at most efficient level for maximum performance. • Body size, shape Herps are Ectothermic Pough et al., 2001 - source of body heat is sun, rather than metabolism - still regulate body temperature (Tb) rather precisely Herps are Ectothermic lizard uses 3% of energy of similar-sized mammal: 1. ~1/10 the metabolic requirements at a given Tb 2. Let Tb decrease at night 3. Overall lower activity than mammals Implications for production vs. maintenance Pough et al., 2001 Ectothermic Amphibians, Reptiles • Control body temp within narrow limits during active periods. – Warms up from direct sunlight (basking), sitting on warm substrate – Cools in shade Thermoregulation of desert iguana Night: 20oC Day: up to 42oC Advantages of Ectothermy • Uses less energy to maintain same body temp as squirrel of same size. • Drop in body temp at night conserves energy even more. • Less active than endotherm; even less use of energy. • Requires less food. Metabolic Rates of Ectotherms/Endotherms Mass-specific energy use: MR of endotherms is 7-10x that of ectotherms. Effect of Body Temp on Activities of Ectotherms Disadvantages of ecto? Escape? Vulnerability at night? Activities in winter? Impact of Ectothermy and Endothermy on Ecosystem • Study of Hubbard Brook experimental forest in NH: – Salamanders consumed food worth 46,000kJ/hectare – Birds consumed 209,000kJ/hectare. – Conversion efficiency of salamanders is 60%; birds < 2%. Sal. provide much more energy to food chain than birds. – Small salamanders eat small prey that is not available to larger endotherms. Ectothermic Metabolism Pough et al., 2001 Metabolism Energy (ATP = adenosine triphosphate) Activity... ATP, then Phosphocreatine (30 sec) then need to synthesize ATP: 1. Oxidative/Aerobic 1 CHO -> 35 ATP (+ CO2 and H20) efficient but slow (sustained) 2. Glycolytic/Anaerobic 1 CHO -> 3 ATP (+ lactic acid) rapid but inefficient (burst) Oxidative vs. Glycolytic Metabolism How measure: 1. Oxidative metabolism - oxygen consumption 2. Glycolysis - lactic acid production Muscles (or parts thereof) specialized to be either oxidative or glycolytic - Anuran calling (males) muscles hypertrophy in breeding season - Locomotion example... Muscle Fiber-Types Twitch Speed (SPRINTING) Oxidative Capacity (ENDURANCE) 1. FG = Fast Glycolytic 2. FOG = Fast-Oxidative Glycolytic 3. SO = Slow Oxidative Histochemistry Iliofibularis muscle More sustained contractions Greater force production IF Dorsal view of lizard hindlimb Iliofibularis Muscle (IF) cross-section with darker oxidative core that appears red in fresh tissue Histochemistry IF Cross Section of Hindlimb at Mid-Thigh Femur Aerobic Capacity Fast Twitch (~Glycolytic) Histochemistry Myosin ATPase Succinic Dehydrogenase (SDH) Iliofibularis Muscle (IF) Fiber-Type Histochemistry mATPase SDH (fast-twitch) (oxidative) FOG (fast-twitch oxidative glycolytic; dark mATPase and dark SDH) SO FG (slow-oxidative; light mATPase, dark SDH) (fast-twitch glycolytic; dark mATPase, light SDH) 11 Species of Phrynosomatinae Sceloporus Group -- Uta stansburiana Sceloporus magister Sceloporus undulatus Sceloporus virgatus Uma notata Sand Callisaurus draconoides Cophosaurus texanus Holbrookia maculata Phrynosoma cornutum Phrynosoma modestum Horned Phrynosoma mcallii Iliofibularis FG and FOG compositions vary among phrynosomatine subclades; composition of SO fibers does not vary ANCOVA conventional P < 0.001 phylogenetic P < 0.005 80 Slow Oxidative (SO) % Slow-Oxidative Glycolytic (FG) % % Fast Fast-Glycolytic 80 70 60 50 40 30 20 70 50 40 30 20 10 0 0 10 Body Mass (g) 100 Sand Lizards Horned Lizards 60 10 1 Scelop. Group 1 10 Body Mass (g) 100 Speed predictors across lizard taxa r2 = 0.899 p < 0.0001 Metabolism Locomotion in Herps - good burst performance Pough et al., 2001 - poor endurance Fig 6-15 (Varanidae, Teiidae exceptions) - often intermittent increases total distance before fatigue - snake modes have different costs concertina>lateral>sidewinding Metabolism Glycolytic metabolism - [lactate] can increase 20x (~ = fatigue) - egg-laying - territorial defense - locomotion (80% sprint ATP) - prey swallowing - first 30 sec of activity compared to mammals, herps have ~10x lower aerobic capacity BUT, herps achieve equivalent burst capacity and, better able to reconvert lactate to glycogen Pough et al., 2001 Fig 6-13 Metabolism Metabolic Rates 1. Standard postabsorptive, inactive, inactive part of day 2. Resting postabsorptive, inactive, active part of day usually 10% greater than standard 3. Maximum e.g. maximum aerobic speed beyond that speed need to use glycolysis (intermittent) Metabolism ~max - resting - standard Pough et al., 2001 Fig 6-11 Metabolism Anuran Vocalizations - male calling is hardest work he does - same amount of noise energy as bird 10x larger - VO2 25x that of resting rates (higher than jumping) - anatomical and biochemical specializations trunk muscles hypertrophy % body mass corr. with calling effort highly oxidative mitochondria, capillaries, oxidative enzymes - lipid if call a lot, glycogen if don’t call as much - reserve depletion, weight loss, few nights then recuperate Pough et al., 2001 Fig 6-18 Mating success correlated with - call rate - chorus tenure Metabolism Egg Development - TSD for some reptiles - embryos metabolize yolk 1. Maintenance and growth 2. Fat storage (temperature and moisture determine allocation) - in general, wetter egg means larger hatchling because more yolk is metabolized - larger hatchlings likely have higher fitness (~faster locomotion) Turtle Hatchlings Pough et al., 2001