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[Killietalk] low temp egg incubation and gender ratios
I found Keith's posting quite interesting. I wonder if anyone has compared
the gender ("sex") ratios produced
when eggs of the same species (preferably the same pair of the same species)
were incubated at low vs high
temperatures?
In Kyrptolebias (formerly Rivulus) marmoratus, a hermaphroditic species, most
of the time, from most stocks,
eggs incubated above 20 - 21 C (around 68 - 70 F) but below 26 C (roughly 79
F) develop fairly uniformly into
hermaphrodites. However, those incubated through a critical developmental
stage at 18 C (around 64.4 F),
which is below the temperature at which adults usually lay eggs, develop into
males at very high frequency
(near 100%). I have repeated this observation, first made by the late R.W.
Harrington, several times. It is very
dramatic, essentially a "threshold effect." (Note: There are other ways of
making males in this species as well,
but that's another story).
I have often wondered if incubation temperatures could have a similar effect
on non-hermaphroditic
("gonochoristic") species. I realize that a shift between males and
hermaphrodites is not the same thing as a
shift between conventional males and females. After all, hermaphrodites
already possess the ability to
differentiate into both genders at the same time, so males can be interpreted
as simply the loss of the female
component at low temperature. Nonetheless, it is not especially far-fetched
to suspect that there might be a
similar effect in other species. If anyone has any data on this issue, I
would be hapy to hear from him/her.
"For the strength of the Wolf is the Pack, and the strength of the Pack is the Wolf..." Rudyard Kipling
"Not all who wander are lost..." J.R. Tolkien
"Truth, she lives in a distant land, of snow, and ice... and burning sand..." Stephen Crane
"Life is short, dance naked and wiggle your ass!" Big Daddy Catfish
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