herps: physiological ecology ( water and temperature )
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
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Herps: Physiological Ecology (Water and Temperature)
- Animals are 70-80% water - Solute concentrations and location - Q10 effect - Temperature and water linked
Hyla arenicolor
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Physiological Implications of the Environment
Increased temperature increased rate of chemical reactions
increased rate of metabolism
Q10 effects: Q10 = MR(t+10)
MRt
Q10 often = 2 to 3, depends on the two temps used
(Eckert 17-2)
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Pough e
t al.,
20
01
Snake Example
Pough e
t al.,
20
01
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Temperature and the Environment
(Eckert)
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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
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Water
Get water: 1. liquid water
Amphibians- liquid water via skin
Pough et al., 2001
Pough et al., 2001
2. preformed water 3. metabolic water
Rana pipiens
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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
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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)
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Water
Lose water: evaporation urine feces salt glands
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
Eleutherodactylus coqui Pough et al., 2001
Role of microhabitat
eyes
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Pough et al., 2001
Phyllomedusa
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More evap.
Less evap.
Pough et al., 2001
Chuckwalla
Monkey Tree FrogAnolis lizard
Alligator
Softshell Turtle
Bufo, Spadefoots, Rana
Water
(free water surface)
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Urine from kidney - ions (sodium, potassium, chloride, bicarbonate) - nitrogenous waste (byproduct of protein digestion):
Water
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
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Water
Dietary salts important (e.g., chuckwalla, desert
tortoise)
Salt gland - to excrete excess sodium and
potassium - conserve water, costs ATP
1. Lacrymal salt gland
sea turtles2. Lingual salt gland
crocodilians 3. Nasal salt gland
lizards
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Shoemaker et al., 1992
Resistance to Evaporation - Cutaneous properties - Boundary layer (greater in larger animals) - Humidity - Wind Speed - Temperature
Shoemaker et al., 1992
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Shoemaker et al., 1992
1 Humidity 2 Temperature
3 Body Size 4 Wind Speed
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Behavior vs. Physiology
Shoemaker et al., 1992
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Shoemaker et al., 1992
Non-arboreal
arboreal
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Shoemaker et al., 1992
Morphological and physiological differences
Dorsal skin
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Shoemaker et al., 1992
Cocoon Formation
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Shoemaker et al., 1992
AVT (arginine vasotocin) -from posterior pituitary -stimulates water uptake -stimulates reabsorption from kidney and bladder
Pelvic patch -vascularization
Amphibians rarely ‘drink’
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Shoemaker et al., 1992
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Shoemaker et al., 1992
Nervous and Hormonal Control of water balance
Urine production
Blood Pressure
Sodium excretion
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Shoemaker et al., 1992
Tolerance in salty water
Crab-eating frog
Larvae seem to excrete salt via gills (unique among amphibians in 930 mOsm NaCl)
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Water Balance
Gopherus agassizii example Urine as a water reserve (16 months without H20)
Pough et al., 2001
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Shoemaker et al., 1992
Larger animals have harder time getting enough O2 via skin
Gas exchange in lungless amphibians
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Shoemaker et al., 1992
Use lungs to meet increased O2 demands
Gas exchange in amphibians
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Temperature
Heat Gain (or loss)
Qabs = radiation absorbed by surface of animalM = 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)
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Temperature
Qabs = solar radiation absorbed by surface of animal
Pough et al., 2001
neutral
positive
negative
location - shade or sun posture - exposure
changes color - melanin in
melanophores of dermis
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Temperature
M = metabolic heat production chemical energy ‘lost’ as heat during metabolism
Pough et al., 2001
large species can use to be somewhat endothermic
- surface area to volume ratio - leatherback (Dermochelys coriacea) - pythons (female brooding clutch)
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Temperature
R = infrared radiation received/emitted surfaces emit and receive infrared (thermal) radiation
Callisaurus draconoides
smooth
matte
-not related to color, but texture instead matte - absorb and emit well
smooth - absorb and emit poorly
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Temperature
C = convection to surrounding fluid (air/water) - fluid movement takes heat away
lizard climb bush midday
Sauromalus ater Sceloporu
s occidental
is
- body size and boundary layer small - feel changes more quickly large - less influenced by convection
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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
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Thermoregulation
Temperature Set Point (often a narrow range) alter by season gravidity infection
Hypothalamus
Heliothermic vs. Thermoconformers Pough et al., 2001
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Body temperature & thermoregulation
I. Ectotherms
II. ThermoregulationA. Temperature Regulation
B. Reptiles v. Amphibians
III. Controlling Body Temp.
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I. Ectotherms: all physiological processes are temperature dependent
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Temperature and Performance
• Effective escape
• Development
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II. Thermoregulation
• Temperature
• Ectothermy – limits options
• Metabolic heat –
• Temperature range
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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
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Ectotherm temp. profile -
Min. Max.
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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
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1. Adjusting convective heat exchange
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2. Body size affects thermoregulation
• Surface area • Heat gain/loss rate
decreases as body size increases
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Large leatherback turtles: inertial endothermsAble to retain metabolic heat in addition to generating heat from muscle activity
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B. Reptiles v. amphibians-
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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
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2) Impermeable skin – also challenging
• Panting,
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III. Controlling body temp (maintaining body temp. different from ambient temp.)
1) Behavior
2) Short term
3) Microhabitat selection
4) Water absorption & evaporative water loss to moderate temperatures
5) Heat production
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Cardiovascular control of heating/cooling
Circulatory adjustments
1) Higher heart rate during heating
2) Intracardiac shunt
3) Blood vessel dilation
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Acclimation, Recent History of Individual “Reset” Metabolism
(Eckert 17-3)
Seasonal or ontogenetic differences
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Thermoregulation
Cardiovascular control of heating and cooling
- Cardiac Shunts
- Peripheral Vasodilation
Pough et al., 2001
Pough et al., 2001
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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
Pough et al., 2001
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How do they work?
- RESPIRATION (gas exchange) - CARDIOVASCULAR SYSTEM - METABOLISM
novel systems, structures, behaviors, habitats...
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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...
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Respiration
- in AIR
- in WATER
Reptiles mostly air, Amphibs often both
1. Pulmonary - lungs
2. Non-Pulmonary - skin surface, gills, pharynx, cloaca
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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
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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 (non-pulmonary)
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Respiration (Pulmonary)
gills useless in air - so developed lungs...
Buccal Pumping (Positive-Pressure Ventilation) - ancestral tetrapod trait - amphibians use exclusively, reptiles
sometimes
e.g., Sauromalus ater inflate lungs for defense
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
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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)
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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)
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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!)
Respiration (Pulmonary)
Pough et al., 2001 Fig 6-6
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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)
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Turtles modified because of shell exhalation
- force viscera up against lungs inhalation
- increase vol. of visceral cavity so lungs expand
Respiration (Pulmonary)
inhale
inhale
exhale
exhale
Pough et al., 2001 Fig 6-7
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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
Respiration
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circulatory system heart, vessels, blood move O2 and CO2
Cardiovascular System
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)
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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
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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
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Anuran Heart conus arteriosus w/ spiral valve trabeculae (create channels) role of Tb and HR (in separation)
Cardiovascular System
Pough et al., 2001 Fig 6-8
Gets poor
Gets rich
rich in
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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
Cardiovascular System
RAA = right aortic arch LAA = left aortic arch PA = pulmonary artery
Muscular Ridge
Pough et al., 2001 Fig 6-9a
RA = right atrium LA = left atrium
rich
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Pough et al., 2001 Fig 6-9
Squamate Heart (and turtles) not “primitive”
RAA = right aortic arch LAA = left aortic arch PA = pulmonary artery
Muscular Ridge
CP = cavum pulmonale CV = cavum venosum CA = cavum arteriosum
IVC = intraventricular canal AVV = atrioventricular valve
1
22
1
3
4
4
55
6
77rich
rich
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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 (longer delay between valves opening)
Cardiovascular System
1. temperature regulation 2. breath holding (diving, turtle in shell, inflated lizards) 3. stabilize O2 content of blood when breathe intermittently
pulmonary then aortic
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Crocodylians (different!) 4-chambered heart - normally right to left shunt
e.g., at rest
Cardiovascular System
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
rich
right ventricular valve
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Shared Characteristics of Amphibians/Reptiles
• Ectothermy– Mammals, birds are endothermic.
• Body temp is maintained at most efficient level for maximum performance.
• Body size, shape
METABOLISM
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Herps are Ectothermic
- source of body heat is sun, rather than metabolism - still regulate body temperature (Tb) rather precisely
Pou
gh
et
al., 2
00
1
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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
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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
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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.
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Metabolic Rates of Ectotherms/Endotherms
Mass-specific energy use: MR of endotherms is 7-10x that of ectotherms.
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Effect of Body Temp on Activities of Ectotherms
Disadvantages of ecto?Escape?Vulnerability at night?Activities in winter?
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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.
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Ectothermic Metabolism
Pough et al., 2001
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Energy (ATP = adenosine triphosphate)
Metabolism
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
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Metabolism
Muscles (or parts thereof) specialized to be either oxidative or glycolytic - Anuran calling (males)
muscles hypertrophy in breeding season - Locomotion example...
How measure: 1. Oxidative metabolism - oxygen consumption 2. Glycolysis - lactic acid production
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Twitch Speed (SPRINTING) Oxidative Capacity (ENDURANCE)
1. FG = Fast Glycolytic 2. FOG = Fast-Oxidative Glycolytic 3. SO = Slow Oxidative
Muscle Fiber-Types
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Iliofibularis muscle
Iliofibularis Muscle (IF) cross-section with darker oxidative core that appears red in fresh tissue
Dorsal view of lizard hindlimb
IF
Histochemistry
More sustained contractions
Greater force production
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Femur
Cross Section of Hindlimb at
Mid-Thigh
Histochemistry
IF
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Iliofibularis Muscle (IF)
Succinic Dehydrogenase
(SDH)
His
toch
emis
try
Myosin ATPase
Fast Twitch (~Glycolytic)
Aerobic Capacity
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mATPase (fast-twitch)
SDH (oxidative)
SO (slow-oxidative; light mATPase,
dark SDH)
FG
(fast-twitch glycolytic; dark
mATPase, light SDH)
FOG
(fast-twitch oxidative
glycolytic; dark mATPase and
dark SDH)
Fiber-Type Histochemistry
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- -
Uta stansburiana
Sceloporus magister
Sceloporus undulatus
Sceloporus virgatus
Uma notata
Callisaurus draconoides
Cophosaurus texanus
Holbrookia maculata
Phrynosoma cornutum
Phrynosoma modestum
Phrynosoma mcallii
Sceloporus
Group
Sand
Horned
11 Species of Phrynosomatinae
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0
10
20
30
40
50
60
70
80
1 10 100
Body Mass (g)
% F
as
t-G
lyc
oly
tic
0
10
20
30
40
50
60
70
80
1 10 100
Body Mass (g)
% S
low
-Ox
ida
tiv
e
Iliofibularis FG and FOG compositions vary among phrynosomatine subclades; composition of SO fibers does not vary
Scelop. Group Sand Lizards Horned Lizards
% F
ast
Gly
coly
tic
(FG
)
% S
low
Oxi
dat
ive
(SO
)
ANCOVA conventional P < 0.001 phylogenetic P < 0.005
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Speed predictors across lizard taxa
r2 = 0.899 p < 0.0001
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Metabolism
Locomotion in Herps - good burst performance - poor endurance
(Varanidae, Teiidae exceptions)
- often intermittent increases total distance before fatigue
- snake modes have different costs concertina>lateral>sidewinding
Pough et al., 2001 Fig 6-15
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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
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Metabolism
1. Standard postabsorptive, inactive, inactive part
of day
Metabolic Rates
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)
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Metabolism
Pough et al., 2001 Fig 6-11
- standard
- resting
~max
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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
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Pough et al., 2001 Fig 6-18
Mating success correlated with - call rate - chorus tenure
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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)
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Turtle Hatchlings
Pough et al., 2001