Conservation and Ecology of Marine Reptiles

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Conservation and Ecology of Marine Reptiles MARE
494 Dr. Turner Summer 2007
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Diving Physiology
Among longest and deepest diving
vertebrates Spend 3-6 time at surface Central
features of dive ability efficient O2
transport tolerance for hypoxia maximum used of
limited O2 stores
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Diving Physiology
Physiological traits of breath-hold mode are
common reptilian traits Present in land-dwelling
ancestors However, several distinct
modifications to marine existence parallels with
marine mammals
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Dive Records
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Lung Structure Function
Few breaths (2-3s) at surface to empty refill
lungs breaths (time at surface) to increase
with duration of submergence time Tidal lung
volumes greater than terrestrial or aquatic
reptiles marine mammals have greater tidal
volumes than terrestrial
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Lung Structure Function
Similar structure to marine mammal
lungs Large-diameter airways are well enforced
cartilaginous bronchioles smooth muscle
with elastic fiber matrix Lack a
diaphragm Pelvic, gular, pectoral muscles
ventilate lungs
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Lung Structure Function
Phocid
Otariid
Odobenid
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Under Pressure
Tolerate ? in water pressure 1 atmosphere (atm)
for each 10m Leatherback gt 1000m
(100atm) Squeezes air-filled spaces Absorbing
gases at high pressure can be toxic damage from
bubbles Effect upon central nervous system
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In Fact Its a Gas
Sea turtles have the highest rates of O2
consumption and greatest aerobic scopes of any
reptile Can attain resting O2 consumption rates
similar to rates of mammals Greater area for gas
exchange (diffusion) than most reptiles lower
resistance
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Its a Gas Gas Gas
High pulmonary diffusion capacity advantage
during prolonged submergence when sea turtles
deplete lung, arterial, venous O2
stores Low-resistance lung support high
metabolic rates (maximum exercise) by maintaining
high saturation levels in arterial blood
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Its a Gas Gas Gas
High pulmonary diffusion capacity advantage
during prolonged submergence when sea turtles
deplete lung, arterial, venous O2
stores Low-resistance lung support high
metabolic rates (maximum exercise) by maintaining
high saturation levels in arterial blood
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Hope Floats
Regulate volume of air in lungs during shallow
dives for buoyancy control fine-scale shifting
among compartments Also thought to quickly
distribute blood warmed via heliothermy
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Oxygen Transport
Dive duration a function of total O2 store and
metabolic rate during the dive metabolic rate a
function of Size Activity Temperature Hor
monal status Dietary status O2 consumption
VO2
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STÖR
Diving birds mammals typically store O2 in
blood tissues Amphibians reptiles use lings
as major O2 stores Sea turtles may center
around shallow versus deep diving
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SHØP
Shallow divers (Cheloniids) depend upon lung as
the major O2 store Deep divers (Dermochelyids)
rely upon blood and tissue stores for O2
Hematocrit, hemoglobin, myoglobin
concentrations among highest in reptiles
similar to levels in marine mammals
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Total Body Oxygen Stores
Largest O2 stores in diving mammals Hemoglobin
O2 binding molecule of red blood cells can
deliver O2 where needed Myoglobin O2
binding molecule of muscle cells delivers O2
directly to muscles Hematocrit packed red
blood cell volume hemoglobin volume higher in
mammals with increased diving capacity
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Total Body Oxygen Stores
Resp Cardio Cellular All Equal Fewer
mitochondria
Cellular dominant More mitochondria
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Total Body Oxygen Stores
Respiratory properties of blood depends upon
whether O2 is primarily stores in tissues or in
the lung High hematocrit in leatherbacks
similar to marine mammals
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Total Body Oxygen Stores
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Total Body Oxygen Stores
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Dive Response
During dive, available O2 ? (hypoxia) and CO2 ?
(hypercapnia) Together create asphyxia Counterac
t with several adaptations Anaerobic diving
no O2 lactic acid H ions accumulate Bradycar
dia decline in heart rate Ischemia
preferential distribution of blood to O2
sensitive organs temperature metabolic rate
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Diving Adaptations
Cease breathing during diving events apneic
conditions conflicting conditions 1. O2 stores
? with ? activity (O2 demand) 2. CO2 lactate ?
in blood muscle During hypoxic events, muscle
activity is maintained anaerobically results in
? accumulation of lactate
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Low-Impact Aerobics
In the past 10-20 yrs research emphasis on
anaerobic dive physiology Recent on aerobic dive
limits and how animals stay within these
limits Know that aerobic diving is the only way
to facilitate multiple sequential dives over a
short period of time
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Aerobic Dive Limit
Longest dive that does not lead to an increase in
blood lactate concentration If dive within
ADL, can dive again immediately without recovery
period If dive exceeds ADL and accumulate
lactate surface recovery period is required to
burn-off (remove) lactic acid from the body
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Aerobic Dive Limit
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Total Body Oxygen Stores
Leatherback
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Anoxia
Vertebrate brain has an absolute dependence upon
O2 and dies within a few minutes without it
Ultimate determinant of dive endurance in
marine mammals Some FW sea turtles can survive
several hours of anoxia
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Anoxia
You have an absolutely unique genetic condition
known as Homer Simpson syndrome. Why, I could
wallop you all day with this surgical two-by-four
without ever knocking you down. But... I have
other appointments. Dr. Julius Hibbert
Unique mechanisms to protect brain Anoxic turtle
brain can maintain ATP levels ionic homeostasis
by severely reducing metabolic demands to a level
met by anaerobic glycolysis In FW turtles used
to survive hibernation
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Hibernation
In FW turtles used to survive hibernation in
frozen over hypoxic ponds In Sea
Turtles??? Torpid hibernating sea turtles may
survive 1-3 months (presumably without eating or
breathing) Know that cold can effect some
animals cold stunned coma
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Diving Pau
Huge gaps in knowledge (sounds familiar?) Possibl
y with newly developed sensors In order to
reduce deaths in fishing gear Maybe Sargassum
has an effect???