Another question on feeding

"Dr Engelbert Buxbaum" wrote in message
...
NetMax wrote:

"Dr Engelbert Buxbaum" wrote in message
...
Remember that fish are cold-blooded and
don't need to spend a lot of energy on maintaining their body
temperature like us mammals do.

A technicality I've been corrected on in the past is that fish are not
classified as cold-blooded, but as poikilothermic ectotherms (which I
presume to mean that they do have some ability to regulate their
temperature, so are not true 'cold-bloods'). My point is only
educational
trivia, and not critiquing of course.


The expression "cold-blooded" is outdated because technically incorrect:
their blood is not generally cold, but follows the temperature of their
environment (ecto = outside). So if the water is warm, the fish
(including its blood) will be too. That is what those foreign terms
(derived from Greek) refer too. Mammals and birds are different, they
actively regulate their temperature and keep it at a constant value,
independent of the environment.

However justified these phrases may be in a scientific paper I find that
in a discussion with lay-persons the old expressions cold- and
warm-blooded are good enough.


Agreed, however these trips into the technical arenas are IMO entertaining
too. In regards to 'cold-blooded', my reference was not the wordage, but
because I thought that tropical fish have some ability to heat their blood,
while true cold-blooded creatures cannot. After several days of the water
temperature being different from usual, their blood then adjusts to the new
ambient. This buffers their internal organs from the effects of spending
several hours at different depths (and temperatures) while foraging.
However when I looked again, I couldn't find the scientific data to support
this, so I might be mistaken.
--
www.NetMax.tk

NetMax wrote:


Agreed, however these trips into the technical arenas are IMO entertaining
too.

Definetly ;-)

In regards to 'cold-blooded', my reference was not the wordage, but
because I thought that tropical fish have some ability to heat their blood,
while true cold-blooded creatures cannot. After several days of the water
temperature being different from usual, their blood then adjusts to the new
ambient. This buffers their internal organs from the effects of spending
several hours at different depths (and temperatures) while foraging.
However when I looked again, I couldn't find the scientific data to support
this, so I might be mistaken.

Never heard of that story either. Something like that happens in insects
when they "pump" with their wings on a cold morning, so that the waste
heat warms them up enough for flying. But in aquatic organisms the high
heat conductivity of water would probably make that inefficient.

Very large cold-blooded animals can keep an elevated body temperature
simply because the increased volume/surface ratio, the metabolic heat in
the body can no longer be radiated to the environment completely
(gigantothermia). This is discussed for certain carnivorous dinos, to
explain their apparent agility. But it is certainly not important for
our charges ;-)