RE: NANFA-L--Mollies - old and new topics

Peter Unmack (peter.lists at)
Sun, 6 Mar 2005 15:27:09 -0600 (CST)

On Sun, 6 Mar 2005, Hoover, Jan J ERDC-EL-MS wrote:

> Also : Mar 2005 issue of Natural History has a blurb about the Amazon
> molly, p. 18. It summarizes a recent paper (Aspbury and Gabor, 2004.
> Proc Nat Acad Sci. 101: 5970-73)

101: 15970-15973 to be precise. :-)

> addressing the question "why should a male sailfin molly waste sperm on
> a sexual parasite like a parthenogenic Amazon molly?" Results indicate
> that "female sailfins are drawn to males that score with a female molly
> of any species." Also - it appears that males save energy by producing
> less sperm when around the Amazons.

Just some nit picky comments, but I am always a little suspicious of this
type of stuff (yes, I am biased). Interestingly, they give the sperm
counts for day 0, but then only the statistical results for the other
comparisons (although they kind of show it in the figure). I like to see
some numbers rather than just a p-value. They also don't seem to have run
any controls either (i.e., measuring sperm counts again from the males
kept by themselves), although I doubt this would have changed. Also, why
would males make less sperm when shown a heterospecific female rather than
a conspecific male (all of the males were kept together away from females
before the measurements were taken)? That doesn't make much sense in
light of their explanations. It would also be interesting to know what
would have happened if they were offered both species together-in-the same
time. Also, it would be extremely hard to quantify, but what would have
happened should they have been able to actually mate? Maybe if the males
were able to mate with the Amazon mollies they would have increased their
sperm production? I am being a bit nit picky here though, I'll freely
admit. :-) Another point is sperm is not a very costly item to produce.
Most animals (and people) will gladly get rid of it any chance they get!
Probably not because they want to make babies, but because it feels good.
Natures great con as they say. Seems to have worked pretty good so far,
or most of us probably wouldn't be here now.

Peter Unmack
Canadian River, Oklahoma
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