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 Five 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 Fur Whales Pinnipeds (fin-footed mammals)
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),
Williams et al. (2000). Sink or swim: Strategies for cost-efficient diving by marine mammals, Science, 288(5463),