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