Marine Vertebrates: Lecture 12

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Marine Vertebrates Lecture 12

• Diving, Part 2

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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

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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

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Decompression sickness, a.k.a. the bends

• What causes decompression sickness?
• Henrys Law
• The amount of gas entering a solution is
  proportional to its partial pressure
• The problem is on the ascent Why?

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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?

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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)

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Barotrauma

• Middle ear squeeze
• How does one equalize middle ear pressure?
• Special adaptations of marine vertebrates?

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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

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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?

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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!)

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Buoyancy!

• Next time,with focus on
• Will also cover special sensory systems