On Wed, 15 Dec 1999, Joao Pedro de Magalhaes wrote:
> > I had commented, that I thought the telomere theory applied mostly
> > to aging in dividing cells.
>
> That does not explain aging in postmitotic animals like Drosophila and
> C.elegans. Perhaps they age for a different reason than we do; which is
> something I'm becoming more convinced every day.
I agree. DNA damage (or poor repair), accumulation of garbage, or loss of ribosomal DNA, or a host of other things have to be invoked to explain aging in species with post-mitotic cells. One always has to be careful however that the cause-of-death isn't "aging" per se. In Drosophila, as in Elephants, the "wear-and-tear" theory seems to explain most of the causes of death. Drosophila lose their wings and mouth parts and Elephants lose their teeth. Michael Rose has commented that one of the reasons his flies live so long is that they have huge fat reserves. Their eating parts wear out and they survive on their remaining fat reserves. Starvation does not equal aging.
>
> Many non-aging species do appear to grow indefinately (lobsters, certain
> turtles, etc.). In fact, Bidder's hypothesis was that species with unlimited
> growth would not age (constant expansion or death, a bit transhuman once you
> think about it).
Hmmm, if you have a ref for Bidder, I'd appreciate it, this isn't ringing a bell in my brain. The problem as I see it is that if you grow indefinately, you eventually exceed the local food resources and die. So you have to be migratory or grow slowly. Strictly speaking, I don't think you need to "grow" indefinately if you can solve the problem of cleaning up junk and repairing damage in your cells. You do need to have increasing reproductive capacity so that the fraction of "longevity" genes in the reproductive population gets preserved. The "short-lived, faster-reproducing" variants of your species will win in the competition for resources unless you can out reproduce them.
> Although there are exceptions to this rule, the truth is
> that non-aging species' cells do undergo mitosis (one good exaple is the
> molting in lobsters).
Isn't this only the outer surface of the lobster though?
> My personal opinion is that, although telomeres are
> likely to have some relation to aging, the telomerase theory, despite
> elegant, is not the complete picture.
We agree on that point.
Thanks for the refs, I'll pull them on my next library jaunt.
Robert