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Re: HELP DESPERATELY NEEDED



In article <1.5.4.16.19961120120338.31d700d6@netwalk.com>, Jeff
Poling <jpoling@dinosauria.com> writes
>At 09:02 AM 11/20/96 +1030, Gautam Majumdar wrote:
>>In article <v01540b06aeb53b50871e@[129.127.84.36]>, Jeff Poling
>><jpoling@dinosauria.com> wrote
>>
>>>   There is at least one ectothermic mammal, the naked mole rat, and two
>>>scaled mammals, the armadillo and rat (my ref. was published in 1987, so
>>>this may be out of date.  As of 1987, though, the scales were considered
>>>"reptilian", not conglomerated hairs like the scales of pangolins).
>>>
>>Is the naked mole rat  (Heterocephalus glaber) truely an ectotherm ?
>>Has it been shown that it acquires a significant amount of energy from the
>>environment ? Unless it does so (i.e., if it generates most of its energy
>>internally, irrespective of its body temperature) it is not a true ectotherm.
>
>   This is the 20,000,000,0000 dollar question.  According to the
>definitions I got out of Horner's _Digging Dinosaurs_ the term
>ecto/endotherm refers to temperature regulation.  NMR is ectothermic (its
>body temperature matches that of its environment) and is homeothermic (its
>body temperature stays within a small range; apparently maintaining it above
>ambient temperature is not required).  If Dr. Horner is in error, then so am
>I.  Unfortunately, that's all I can say on the subject, somebody with actual
>training in the science will have to take it from here.

I found the following definitions in The Concise Oxford Dictionary of
Ecology :

Ectotherm - an animal that maintains its body temperature within fairly
narrow limits by behavioural means such as basking or seeking
shade.

Endotherm - an animal that is able to maintain a body temperature that
varies only within narrow limits by means of internal mechanisms.

Homeotherm - an organism whose body temperature varies only
within narrow limits (this is irrespective of ectothermic or endothermic
process)

Poikilotherm (exotherm) - an organism whose body temperature
varies according to the temperature of its surroundings

According to these definitions NMR is a homeotherm in its natural
habitat but a poikilotherm in the laboratory. But it is still not clear to me
that it should be called an ectotherm since it does not use behavioural
means to maintain that temperature, except that it very rarely comes
out of the burrows. But that behaviour may have different reason.

>   I should point out, however, that there is another source of energy for
>the rats in their burrows:  food.

But that food has to be processed internally to generate heat - that is
endothermy.

What an unruly animal - does not want to fit into any nicely defined
categories :)

Gautam Majumdar                 gautam@majumdar.demon.co.uk