I have been wondering about how deep sea animals survive under such high
pressure; more specifically how they behave. I already know the basics about
swim bladders and how only deep sea subs like Jason can reach that far down,
but nothing in detail. Thanks for all your help.
Marine mammals can dive to great depths without suffering from the adverse
pressure of the ³bends: because they have a greater ability to transport
oxygen across lung membranes, have a higher percentage of oxygen in their
blood, and a high carbon-dioxide tolerance. During deep dives these animals
reduce their heart rate (bradycardia) and peripheral blood flow and
circulation to all areas except the heart and brain.
Cetaceans can exhale as much as 88% of its lung air with a single breathe
(humans approx. 12%). They also collapse their lungs at about 100m which
prevents the absorption of nitrogen into the blood, thereby preventing the
bends. Oxygen use is reduced and heat loss inhibited. They regain the
ability to dive by maximizing cardiovascular and respiratory activity at the
surface by varying breathing techniques.
These adaptations to the respiratory system have allowed deep diving in
mammals. They do not suffer apnea or asphyxia from lack of oxygen, and they
avoid decompression sickness despite the retention of air within the
While recovering from a dive, cetaceans (whales, dolphins, and porpoises)
and pinnipeds (seals, sea lions, and walruses) breathe by exhaling and
inhaling very rapidly at the surface. Neither animal dives on residual lung
volume. To restrict nitrogen absorption these animals can transfer alveolar
air into cartilage-supported airways. Diving mammals probably have
reinforced bronchioles for shunting of pulmonary gas away from the
respiratory capillaries at depth.
1. Harrison, R.J., Functional Anatomy of Marine Mammals, Academic Press:
2. Leatherwood, S., Reeves, R., Whales and Dolphins (The Sierra Club
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