Transcript Lecture 3 Water balance, Respiration and cardio

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