Subject: RE: blubber

Rui (rprieto@dop.uac.pt)
Tue, 7 Jul 1998 21:43:52 -0000

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Hi Susan,
Information about blubber would make a book as thick as  a Bowhead blubber
blanket itself. The first thing I advise you, is to search for "blubber"
with the WhaleNet searching engine
(http://whale.wheelock.edu:2834/cgi-bin/search.cgi/x-catalog:/whale.wheelock
.edu:2834/WhaleNet). You will get 60 hits, most of them from the ASK
archives, with a lot of relevant information about this matter.


Now let's just scratch the surface of this issue:


Cetaceans are warm blooded as any other mammal. Living in an environment
where the temperature is lower than 25:C (77:F) most of the time, and much
lower in some instances, they had to evolve adaptations to keep their inner
temperature well above that value (about 36-37:C - 97:F). But unlike most of
the mammals they can not rely on an insulating coat of fur, lost as an
adaptation to reduce the drag. For that reason they acquired a thick
insulating layer of fat (the blubber), which helps keeping the temperature
higher inside the body. In some species, like the bowhead whale, the blubber
may be as thick as 50 cm (19.7 in). This is not the only way of keeping the
warmth of the body. Other adaptations for that purpose include a relatively
small ratio between surface area and volume of the body (with a smaller area
exposed to the water, there is less heat loss), and reduced respiration
rates and higher metabolic rates. There are yet other adaptations as a
system known as counter-current consisting in a capillary network, which
allows a reduced heat loss, by the blood vessels.
The blubber serves not only as an insulating "blanket", but is also a
reserve of lipids, or in other words a kind of energy bank, which can be
used whenever energy requirements are higher than the food availability. For
that reason the thickness of the blubber can vary during the year, as well
as with age and sex.
But the blubber poses problems for the cetaceans as well. The oil obtained
from the melting of the blubber was one of the strongest reasons for the
whaling in the past, which led some species to the brink of extinction.
Pollutants pose other problem. Chlorinated hydrocarbons (DDT, PCBs,
Dieldrin) began to be used in the 40's and entered several food chains as
contaminants. These compounds are insoluble in water but are soluble in the
lipids, and are stored in tissues like blubber, persisting there for years.
For that reason the quantities of contaminants in the fat tissues can build
up. While in the fat these contaminants are harmless, but if the animal has
to use the a great amount of it's fat reserves, the pollutants become
metabolized and can cause poisoning situations.

Cheers,

Rui  :-+);




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Hi Susan,
Information about blubber would make a book as = thick=20 as  a Bowhead blubber blanket itself. The first thing I advise you, = is to=20 search for "blubber" with the WhaleNet=20 searching engine (http://whale.wheelock.edu:2834/cgi-bin/sea= rch.cgi/x-catalog:/whale.wheelock.edu:2834/WhaleNet).=20 You will get 60 hits, most of them from the ASK archives, with a lot of = relevant=20 information about this matter.


Now let's just scratch the = surface of=20 this issue:


Cetaceans are warm blooded = as any other=20 mammal. Living in an environment where the temperature is lower than = 25ºC=20 (77ºF) most of the time, and much lower in some instances, they had = to=20 evolve adaptations to keep their inner temperature well above that value = (about=20 36-37ºC - 97ºF). But unlike most of the mammals they can not = rely on=20 an insulating coat of fur, lost as an adaptation to reduce the drag. For = that=20 reason they acquired a thick insulating layer of fat (the blubber), = which helps=20 keeping the temperature higher inside the body. In some species, like = the=20 bowhead whale, the blubber may be as thick as 50 cm (19.7 in). This is = not the=20 only way of keeping the warmth of the body. Other adaptations for that = purpose=20 include a relatively small ratio between surface area and volume of the = body=20 (with a smaller area exposed to the water, there is less heat loss), and = reduced=20 respiration rates and higher metabolic rates. There are yet other = adaptations as=20 a system known as counter-current consisting in a capillary network, = which=20 allows a reduced heat loss, by the blood vessels.
The blubber serves = not only=20 as an insulating "blanket", but is also a reserve of lipids, = or in=20 other words a kind of energy bank, which can be used whenever energy=20 requirements are higher than the food availability. For that reason the=20 thickness of the blubber can vary during the year, as well as with age = and=20 sex.
But the blubber poses problems for the cetaceans as well. The = oil=20 obtained from the melting of the blubber was one of the strongest = reasons for=20 the whaling in the past, which led some species to the brink of = extinction.=20 Pollutants pose other problem. Chlorinated hydrocarbons (DDT, PCBs, = Dieldrin)=20 began to be used in the 40's and entered several food chains as = contaminants.=20 These compounds are insoluble in water but are soluble in the lipids, = and are=20 stored in tissues like blubber, persisting there for years. For that = reason the=20 quantities of contaminants in the fat tissues can build up. While in the = fat=20 these contaminants are harmless, but if the animal has to use the a = great amount=20 of it's fat reserves, the pollutants become metabolized and can cause = poisoning=20 situations.

Cheers, =

Rui  :-«)»

 

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