Marine Vertebrates: Lecture 12

Diving, Part 2

Part 2: Diving Physiology• Diving depth records

Humans, free diving• ♀, Mandy Cruickshank: 78 m

• ♂, Martin Stepanek: 102 m

Leatherback turtle = 1200 m

Emperor penguin = 500 m California sea lion = 250 m N. elephant seal = 1000 m Weddell seal = 700 m Sperm Whale = 2500 m

What are the key problems of pressure for vertebrate divers?

• Decompression sickness (“the bends”)

• Nitrogen narcosis

• Barotrauma (air space squeeze)

• High pressure neurological syndrome

• [Oxygen toxicity, free-radical formation]

• Effects on buoyancy

Decompression sickness, a.k.a. “the bends”

• What causes decompression sickness?

Henry’s Law: • The amount of gas

entering a solution is proportional to its partial pressure

The problem is on the ascent: Why?

Decompression sickness, a.k.a. “the bends”

• What are the effects (human divers)?

Symptoms depend upon location of bubbles• In skin: rashes or even bubbled appearance

of skin

• In joints: Extreme pain

• In central nervous system: Weakness, paralysis, dizziness loss of consciousness

Long term effects: Deterioration of tissue. WHY?

Decompression sickness, a.k.a. “the bends”

• What protects marine mammals from it? DISCUSSION!

Three distinct mechanisms (including one specific to Weddell seal)

• Is there evidence that some marine mammals experience the “the bends”?

Bone lesions of sperm whales… (Controversial)

Barotrauma• Middle ear squeeze

How does one “equalize” middle ear pressure? Special adaptations of marine vertebrates?

Barotrauma

• Lung Humans

• Lungs collapse to “residual volume” at 30 m

Marine mammals• DISCUSSION!

Deep-diving turtles• Lungs: Similar to marine mammal

adaptation

• Flexible plastron

Barotrauma

• Sinuses: air pockets in bones of skull and face

Humans can equalize sinus spaces via nasal passages• Sometimes

problematic• Rate of

descent/ascent critical

Marine mammals?

High pressure neurological syndrome

• Caused by increased excitability of neurons

• Marine mammals deal with by: apparently utilizing negative

feedback circuits to mitigate this effect.

Weddell seals? (DISCUSSION!)

Buoyancy!

•Next time,with focus on…

•Will also cover special sensory systems