Mioglobin is the primary oxygen carrier in the muscles and its values have been recorded as being much higher for the marine mammals.
This study shows an oxygen (O2) concentration of 20 ml/kg in humans and 3 X higher for some marine mammals
Is the blood volume really relevant? As we can see here test shows that blood volume is correlated with the dive time
Retia Mirabilia” is a group of blood vessels at the sternum level (tissues with contorted spirals of mainly arteries but also veins) functioning as a blood reservoir to increase O2 stores for the dive. The sperm whale (the deepest mammal) has the most developed Retia Mirabilia The blood irrigation of the brain is not done by the carotids but directly by retia mirabilia.
During effort/dive for humans, as well as marine mammals, the spleen, by contracting, releases fresh blood with oxygenated red blood cells. The advantage for the marine mammals comes from the size of their spleen which is bigger than for the terrestrial mammals.
For the marine mammals (pinnipeds), aorta increases at the immediate exit from the heart by 30-40% and ramificates for all grate vessels (bronchiocephalic, left common carotid and left subclavian arteries) and decreases in diameter by 50% after this.
In addition of having higher blood values, the marine mammals also have higher concentration of red cells (hematocrit) and consequently higher haemoglobin levels
Seal blood consists of 60% haemoglobin vs. 35 to 40% in humans. (Julien Baudoin Gregory Zottos - Les limites physiologiques de l&apos;apnée,.)
The seals aren&apos;t fazed at all by low levels of oxygen that would cause humans to black out.
With this we are closing the chapter on “energetic resources” The level of effort has an effect on the O2 consumption for both terrestrial and marine mammals but the loading time is different. The effort and O2 loading is: simultaneously for terrestrial mammals temporally delayed for the marine mammals (the effects comes post dive during the recovery period ).
Man rely mainly on lungs to store oxygen but for the marine mammals, the percentage of O2 contained in the lungs is minimal. This, together with the collapsible airway system makes the exhale dive an obvious choice for the deep diving marine mammals This is reducing the risk of DCS & Narcoses. How? With collapsible lungs, air goes in the superior airways where it’s no more in contact with the blood; this avoids gas exchanges and implicitly the N2 problems.
We do stretching exercises
This allows progressive collapse of lung structures at pressure with initial collapse of the alveoli, followed by small and then large airways. This pattern works in reverse during ascent and the lungs are able to re-inflate in a progressive manner.
At 37 °C, body temperature of the animal on surface, spermaceti lipids are liquefied. When diving, the cachalot inhale cold water through the left nostril, and circulates it to cool down his spermaceti; the temperature going down crystallises the spermaceti (lipids): the density increases, its volume reduces and brings negative floatability. To come up, the sperm whale is heating the spermaceti with an influx of warm blood; the process is reversing bringing positive buoyancy this time.
This way, the cachalot is diving with a minimum of energy expenditure and this body density control system also explains the fact that sperm whales when diving deep they come up almost in the same place (like on a « no limit » dive on the vertical line).
However, a 2004 study on sperm whales showed that, they are also prone to accidents of decompression. The whales do suffer osteonecrosis and bone deformities
We use to know the set of physiological adaptation to dive under the name of “dive reflex” and this is also what the scientific community was using up to the point when voluntary bradicardia has been discovered – since then, the terminology changed to “dive response”
the prove are the continuous dives with only few minutes recovery. If glycogen stores would be depleted it would be not possible to continue diving at the same pace.
In human forensics, one of the element that confirm a diagnosis of drowning is based on the research of diatoms in the body of the victim. The unicellular algae are composed of silica plates present in all waters. With the breathing reflex at the end of the apnea (eventually after black-out) they enter the lungs, pass the alveolar-capillary barrier and go into the circulation & organs.
1) the alveoli are highly vascularised to promote rapid uptake of oxygen. 2) marine mammals have extensive elastic tissue in the lungs. These fibres recoil during expiration to rapidly and near completely empty the lungs
Freedivers are not the only ones doing shallow worm-up dives to prepare for the deep dives:
ppt: Physiological adaptations to freediving in marine mammals
PHYSIOLOGICAL ADAPTATIONS TO FREEDIVING
IN MARINE MAMMALS
Freedive Dahab, AIDA Instructor Course, September 2009
- The dolphin is often recognised as a symbol of Freediving (e.g. Apnea
- Swimming techniques and materials (e.g. the monofin) are inspired from
what we tend to see as a model – the marine mammals, the perfect
Together with the fascination for the marine mammals comes also some
Why are they diving better than us? Do they have the same physiological limitations
Do they use different diving techniques?
more O2 in the muscles
higher blood volume
Splenic O2 stores
aerobic system more O2 in the blood
more red cells
more O2 in the brain more globins
1. More energetic
Lactic acid delayed
2. Better adaptation to
Flexible chest walls
variable body density
3. Better dive
4. Better breath hold
5. Better O2 recovery
More oxygen stored in the muscles:
Terrestrial mammals: 1g mioglobin / 100g muscle
Marine mammals: 3-7g mioglobin / 100g muscles
Splenic O2 stores
The seals & sea lions spleen is 4.5% of their body weight and 3 times heavier than
terrestrial mammals of same size
For the Weddell seal, the spleen gives 60 % increase in haemoglobin concentration
in the first 10 min of the dive.
For humans, the increase in haemoglobin is around 3%
The Aortic bulb
The aortic bulb
the bulb has a capacity for storage of the
stroke work of more than two normal heart
beats and a volume of more than three times
normal stroke volume.
functions through energy and volume storage
actions and through uncoupling actions to
maintain arterial pressures and stroke volume at
near predive levels during a dive
It is common to all pinnipeds but the size of
the bulb is bigger for the deep diving species
More red cells/haemoglobin
Humans have 20ml/kg
Shallow diving mammals
14-17g haemoglobin / 100 ml blood
Deep diving mammals 21-25g haemoglobin / 100 ml blood
Higher concentration of globins
Some species have evolved the capacity to protect their brains
from conditions of low oxygen.
They are protected by elevated levels of complex oxygen-
carrying proteins--called globins--, in the cerebral cortex.
Weddell seals, animals that dive and hunt under the Antarctic
sea ice hold their breath for as long as 90 minutes, and remain
active and mentally alert the whole time.
More glycogen stored in the muscles
“the heart of harp seals has enlarged stores of glycogen” which means
that cardiac tissues have a bigger anaerobic capacity
Delayed effects of the Lactic Acid
The lactic acid is blocked by the vasoconstriction
Flexible chest walls
The chest can squeeze to let the lungs virtually airless
Cartilaginous rings reinforcing the
Shallow diving mammals have partially calcified rings prohibiting
Deep diving mammals have low calcification of trachea rings
which can bent without breaking at depth.
Sphincter muscles in the smaller
Marine mammals have very muscular bronchioles able to close the air
Control of body floatability (density)
The dugong uses the
sphincter muscles of
the bronchioles to
compress the density
of air in the lungs and
without expelling air or
Spermaceti is an organ regulating the corporal density of the sperm whale,
with similar benefits as the BCD of a scuba diver
The spermaceti weights a few tones and is positioned in the head of the animal
– ideal positioning for a “variable weight” dive
The collapsible airway system is probably the most important
adaptation to pressure and it’s main advantage is the fact that it allows
to avoid the N2 build-up and the related problems (DCS & narcoses).
Heart rate of marine mammals can go bellow 5% of predive period vs. 70% for
The heart rate at the start of the dive is correlated with the duration of the dive
they prepare for a dive of a certain time (if they go for a longer dive they
start with a lower heart rate).
Metabolic inhibition with reduction in
They adjust swimming speeds and metabolic rates to sustain all dives aerobically
peripheral vasoconstriction, like for humans
No diaphragmatic contractions
The inspiratory reflex in marine mammals is diminished, allowing them
to remain under water until the total exhaustion of available oxygen
Measurements on exhaled gases after deep diving showed values of :
- 10% CO2 (man would black-out at 6%)
- and less than 2% O2.
Further evidence is provided by the analysis of intratissualires diatoms.
No diatom has ever been found in the bodies of marine mammals found
dead in fishing nets, suggesting that they die not drowned, but
More effective recovery
marine mammals remove almost 90% of the O2 available in each breath in
comparison with humans which are only able to remove 20% .
The Phocids exhale at the initiation of the dive - they have a collapsible
Otariids inhale before the dive and their airway system does not completely
Exhale on descent
Throughout its descent, the seal let escape from his rib cage, the air
pushed by the pressure.
Exhale on ascent
Antarctic fur seals dive with full lungs and exhale on the last part of
Beaked whales are feeding close to 2000m deep and it looks
like even they need to prepare for such a dive.
Beaked whales have been observed doing a succession of
shallow dives (without eating behaviour, 90 min) and just
after going for the deep dives (with eating behaviour )
The four digits feeding depths of the sperm whales are
exposing them DCS and they naturally follow a
decompression protocol: slow ascent and "deco stop" before
• From a physiological perspective, the specific adaptations of the
cardio-vascular & respiratory system makes the marine mammals
better freedivers than humans
• however, this is not necessarily the most relevant perspective for
• Diving for cultural reasons instead of physical necessities makes us
more sensitive to the cultural perspective and here the better
freediver may be the one who enjoys it more and makes the most
out of it to enhance his life experience