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Re: Bakker lecture



Jason Head (head@lust.isem.smu.edu) wrote:

>        I remember reading somewhere that all amphibians are pretty much
> disappearing (water permeable integument + acid rain = dead amphibs').

The actual story is a bit more complicated than that.  As Darren
pointed out, the golden toad (of central america, not south) has
apparently disappeared.  However, red-eyed tree frogs (which inhabit
the same forests) appear to be doing as well as ever.  There's a group
in Oregon that's trying to claim that the increased UV radiation
filtering through the atmosphere as a result of the decrease in
stratospheric ozone is responsible for amphibian deaths.  Supposedly
amphibians that lay their eggs in sheltered locations, or amphibians
that produce a lot of an enzyme called photolyase are not disappearing
(or at least not disappearing as quickly).  Photolyase recognizes and
repairs DNA that's been damaged by UV irradiation.  The lack of good
data about how much UV radiation strikes the Earth's surface (let
alone how the amount has changed over the past decade) is a real
sticking point, though, and the matter is hotly debated.

In any case, a lot of frogs and salamanders do seem to be having a bit
of a crisis right now.  And as a cautionary note:  we're having a lot
of trouble determining the cause(s) of extinctions that we're
watching.  That might make you want to think hard before deciding that
you know for sure why the dinosaurs became extinct.  (and you all
thought I was letting this drift off topic ;-)

-- 
Mickey Rowe     (rowe@lepomis.psych.upenn.edu)