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Adaptations for Diving in Mammals. By Peter Zervas. Complications of Diving. Inability to extract oxygen from underwater environment This is a fancy way of saying that an animal with lungs cannot “breathe” water. Complications of Diving.

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Adaptations for Diving in Mammals

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Adaptations for Diving in Mammals

By Peter Zervas


Complications of Diving

  • Inability to extract oxygen from underwater environment

    • This is a fancy way of saying that an animal with lungs cannot “breathe” water


Complications of Diving

  • Low supply of O2 to organs intolerant of low levels of O2

    • Organs requiring high concentration of O2

      • Brain

      • Heart

      • Adrenal glands


Complications of Diving

  • Pressurization of gasses due to increasing hydrostatic pressure

    • Hydrostatic pressure increases with increasing depth

      • At only 10 m, hydrostatic pressure is twice that of atmospheric pressure at sea level!


Complications of Diving

  • Mobility in the water medium

    • Terrestrial appendages are not designed for locomotion in water


Complications of Diving

  • Loss of heat

    • Most ocean water is cold (relative to air temp)

      • Since mammals are homeothermic, excesive heat loss is a problem


General Adaptations

  • Seven general adaptations for diving

    1.) Bradycardia

    2.) Arterial Constriction/Blood Shunting

    3.) High Concentration of Myoglobin in muscles

    4.) Insulation

    5.) Hydrodynamics


Bradycardia

  • Part of “Mammalian Diving Reflex”

    • Heart rate slows

    • This leads to reduced consumption of O2 and plays a large role in prolonged diving


Arterial Constriction/Blood Shunting

  • Again, triggered by diving reflex

    • Arteries constrict near heart to limit blood flow to extremities

    • Send less blood to:

      • Viscera

      • Muscles

  • Leaves more blood for

    • Heart

    • Brain

    • Adrenal gland

  • Leads to more efficient use of O2

    • (Bron et al. 1966)


Higher Concentration of Myoglobin in the Muscles

  • Myoglobin – primary oxygen-carrying pigment of mammalian muscles

    • In Weddell seal (Leptonychotes weddellii)

      • 25% of total oxygen during diving is stored in myoglobin

      • Only 12% in humans


Insulation

  • Blubber

    • Whales

      • Up to 2 inches thick over entire body

    • Pinnipeds (fin-footed mammals)

      • Up to 1/3 of entire weight

  • Fur

    • Phocid seals (true seals)

      • 18,000 hairs/cm2

  • Otariid seals (sea lions)

    • 57,000 hairs/cm2!!!!!!!!!!!!!!


Hydrodynamics

  • Energetic costs to mammalian swimming estimated 2-23 times more expensive than in fish

    • Leads to:

      • Streamlining

      • Swimming “gait”

        • Period of continuous stroking

        • Followed by prolonged period of gliding to max depth

          • (Williams et al. 2000)


Leptonychotes weddellii


Leptonychotes weddellii

  • Weddell Seal

    • Storage of O2

      • 5% of O2 in lungs and 75% in bloodstream

      • Humans hold 36% in lungs and 51% in circulating blood

    • Blood volume

      • Almost twice the amount of blood per kilo of body weight compared to humans


Leptonychotes weddellii

  • Spleen

    • Can store up to 24 liters of O2

      • Spleen contracts during diving

        • Releases O2 – rich blood into blood stream!!


Orcinus orca


Orcinus orca

  • Collapsible lungs

    • During diving, lungs collapse

      • Force air out of lungs and into trachea and nasal cavities

      • Trachea and nasal cavities do not abosrb N as well as the lungs


Orcinus orca

  • Why is this advantageous?

    • A condition known by divers as “the bends” occurs when divers come to the surface after a dive

    • The rapid decompression of N (which is nearly 70% of air) causes bubbles in capillaries

    • If there is no air the lungs to absorb during diving, there will be no N to cause these bubbles when returning to the surface


Works Cited

  • Bron, K. M. et al. (1966). Arterial constrictor response in a diving mammal. Science, 152(3721),540-543.

  • Williams et al. (2000). Sink or swim: Strategies for cost-efficient diving by marine mammals, Science, 288(5463),133-136.


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