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

Hoover, Jan J ERDC-EL-MS (
Sun, 6 Mar 2005 14:35:24 -0600

Follow-up to an old thread:
Got a copy of the thesis by Steven Sheinbaum, University of South Florida,
who was studying life histories of sailfin mollies in the Tampa Bay Area in
the 1970s. It is a very nice field study of three populations - one in
freshwater (Hillsborough River), one in fluctuating salinities, one in
brackish water. In general, estuarine populations had greater percentages of
males, bigger heavier adults of both genders, bigger fish-in-maturity, and
bigger brood sizes. Differences between fresh- and brackish-water populations
were attributed to a combination of temperature effects (estuaries were
warmer) and predation (River was believed to have higher densities of
predatory fish and birds). Thesis does not include results of the experiment
in which Steven reared fish from one population-in-different salinities to
see if salt was responsible for these effects.

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) 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.

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