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Adaptations for Diving in Mammals

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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  1. Adaptations for Diving in Mammals By Peter Zervas

  2. 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

  3. 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

  4. 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!

  5. Complications of Diving • Mobility in the water medium • Terrestrial appendages are not designed for locomotion in water

  6. 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

  7. 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

  8. Bradycardia • Part of “Mammalian Diving Reflex” • Heart rate slows • This leads to reduced consumption of O2 and plays a large role in prolonged diving

  9. 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)

  10. 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

  11. 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!!!!!!!!!!!!!!

  12. 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)

  13. Leptonychotes weddellii

  14. 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

  15. Leptonychotes weddellii • Spleen • Can store up to 24 liters of O2 • Spleen contracts during diving • Releases O2 – rich blood into blood stream!!

  16. Orcinus orca

  17. 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

  18. 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

  19. 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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