Adaptations for Diving in Mammals

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.