Subject: Diving

Lindsay J Porter (h9390327@hkucc.hku.hk)
Sat, 4 Apr 1998 20:28:06 +0800 (HKT)

>Hello!
>I am a student at Ume=E5 university in Sweden. I want to ask about whales=
 and
>diving.What happens in the body when a whale dives? How can it take the
>difference in pressure? How does the mouscles get enough oxygen when the
>whale dives? Where can I find some material or where can find the anwers?
>
>Please send your answer to gunvor.gunnarsson@swipnet.se

Hallo,
The best reference I have for diving physiology is in A.R. Martins
Encyclopedia of Whales (Portnland House 1990) and it is from this text that
the following brief summary is derived.

The ability to function underwater without 'topping up' oxygen levels is an
ability  common to all diving species (including birds and seals) although
the physiological mechanisms to cope with such oxygen deficit may vary from
species to species. =20

TO OBTAIN OXYGEN
All cetacean species inhale prior to diving although the air which actually
remains in the lungs plays only a minor role in oxygen uptake (as lung
collapses at 100m besides the volume of air in the lungs is exhausted very
quickly).  Instead, oxygen is stored in the muscle and blood.  Cetaceans
have a relatively large volume of  blood which is high in haemoglobin
(increasing its oxygen carrying capacity).  The muscle is high in the
protein myoglobin (which attracts oxygen from blood), which is what gives
cetacean muscle its characteristic dark colour.  It is believed that 50 per
cent of the bodies oxygen capacity is stored in the muscle.  Cetaceans also
have teh abilty to preferentially direct blood to the essential organs
(brain, muscles) at the cost of others (lungs).  Additionally, cetaceans
have the ability to considerabley slow their heart rate (bradycardia) - and
can utilise an anaerobic metabolism, whereby muscles suffer an oxygen
deficit which is 'paid back' on the first breathes taken at the surface.=20

COMPRESSION=20
At 100m the lung collapses, a feature which has an advantage in that the
remaining air - mainly nitrogen - in the lung is forced into the relatively
rigid trachea in which  minimal gaseous transfer with the tisuue occurs
therefore minimising the risk of decompression sickness (the bends).
Additionally, the cappilary network to the brain (retia mirabilia) is
thought to be able to filter out gas bubbles formed during deep dives
therefore preventing air embolisms. =20
=20
The lungs are able to collapse and the rib cage remains undamaged as it is
flexible with many 'floating ribs' (not attached to breast bone or spine).

Of whales, the deepest depth recorded is=20
3000m (on occasion) for sperm whales, although  normally measured at around
500-1000m.
Baleen whales usually measured at 100m. =20

All the diving information known for most whales, however, is still limited
and the individual mechanisms used by different species and even different
populations of the same species is still to be researched.

I hope this brief summary helps answer your questions=20
best wishes=20
Lindsay J Porter=20


email h9390327@hkucc.hku.hk
Dolphin Research Group
The Swire Institute of Marine Science
The University of Hong Kong
Cape d'Aguilar
Hong Kong
website: http://www.webdivers.co.uk/dolphin/index.html