Re: Ectothermy?

["Mickey P. Rowe" <mrowe@indiana.edu>]

TomHopp@aol.com wrote:

>     Seriously though, lets keep an eye on the molecular
> systematists.  As Mickey Rowe pointed out, an analysis of
> "uncoupling protein" genes will probably give a good time-estimate
> for the origin of heat generating metabolism.

Actually that's not quite what I wrote.  I suggested that people
should look into uncoupling proteins (UCPs) to see how their presence
and function is distributed amongst extant animals.  The proteins
themselves most probably pre-date the existence of thermoregulation by
millions of years since it's likely that there are benefits to moving
protons around irrespective of anything having anything to do with
thermoregulation.  What I was suggesting was that variations in UCP
sequence and function across mammals and birds could falsify the
notion that (at least this aspect of) thermoregulation evolved only
once.  That is, if UCPs are not used in birds the same way they are
used in mammals then it would be more than prudent to conclude (or
continue to accept as the case may be) that birds and mammals acquired
their metabolic statuses independently.

Anyhoo, Chris Lavers <chris.lavers@nottingham.ac.uk> asked about the
UCPs:

] There has been talk on the list of uncoupling proteins, their role
] in generating heat and the molecular systematics thereof. Does
] anyone have any references? Any help would be much appreciated.

I don't know a whole lot about UCPs (it's my impression that not much
is known about them period), so don't take my word for it.  However, I
don't think anybody has looked at all at their systematics.  Anyhoo, I
recommend you search a bit yourself -- it's pretty easy to do without
getting out of your chair.  Point your web browser at:

http://www.ncbi.nlm.nih.gov/PubMed/

to get to the U.S. National Library of Medicine.  Not too long ago
they made searching Medline free.

I just punched in "uncoupling proteins" and pulled up 2624 references
(though it looks like they don't all discuss UCPs).  As I expected, a
search on "UCP bird" pulled up no relevant references (presuming you
can judge a paper by its title) whereas "ucp mammal" pulled up 788
references (I'll leave it as an exercise for the reader to judge how
many might be relevant to this conversation).

I mentioned the subject here before (and I'm harping on it again now)
because I think the field is pretty wide open on this issue.  Though,
I might add that Tom (Holtz) has been exceptionally (for others; it's
the norm for him) patient in all this.  You'd likely have a good deal
of difficulty finding funding for the sort of project I'm thinking
about since I suspect most of the reviewers you'd find would already
think the evidence for independent origins of endothermy in birds and
mammals is pretty convincing.  I hope Tom will disagree if he thinks
otherwise.

--
Mickey Rowe     (mrowe@indiana.edu)