Transcript Anaerobic diving

Conservation and
Ecology of Marine
Reptiles
MARE 494
Dr. Turner
Summer 2007
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
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
Dive Records
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
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
Lung Structure & Function
Phocid
Otariid
Odobenid
Under Pressure
Tolerate ↑ in water pressure
1 atmosphere (atm) for each 10m
Leatherback > 1000m (100atm)
Squeezes air-filled spaces
Absorbing gases at high pressure can be
toxic – damage from bubbles
Effect upon central nervous system
In Fact It’s 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
It’s 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
It’s 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
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
Oxygen Transport
Dive duration a function of total O2 store and
metabolic rate during the dive
metabolic rate a function of:
Size
Activity
Temperature
Hormonal status
Dietary status
O2 consumption – VO2
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
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
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
Total Body Oxygen Stores
Resp – Cardio – Cellular = All Equal
Fewer mitochondria
Cellular dominant
More mitochondria
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
Total Body Oxygen Stores
Total Body Oxygen Stores
Dive Response
During dive, available O2 ↓ (hypoxia) and
CO2 ↑ (hypercapnia)
Together create asphyxia
Counteract with several adaptations:
Anaerobic diving – no O2; lactic acid &
H+ ions accumulate
Bradycardia – decline in heart rate
Ischemia – preferential distribution of
blood to O2 sensitive organs;
temperature & metabolic rate
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
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
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
Aerobic Dive Limit
Total Body Oxygen Stores
Leatherback
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
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
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
Diving Pau
Huge gaps in knowledge (sounds familiar?)
Possibly with newly developed sensors…
In order to reduce deaths in fishing gear…
Maybe Sargassum has an effect???