The small fish pictured here, a Gambusia mosquitofish, may well be the
most studied organism in the country. Much this research is headed by
one of the most talented young evolutionary biologists in the U.S.,
Brain Langerhans (see his Bahamas photo gallery here).
Brian is studying every aspect of the ecology and evolutionary biology
of this fish, everything from what they eat, their body shape, their fin
colors, their predators, and, most interestingly, their fish “penises”. This
structure, actually a modified anal fin (i.e., the fin on the bottom side
of the fishes body, see above) is termed a “gonopodium”. It acts very
much like a penis – it is used to internally fertilize female mosquitofishes.
It actually is rather complex structure – see some high resolution
photographs at the bottom of this page.
In an elaborate series of experiments, Brian documented that females
actually prefer males with larger gonopodia (here is the scientific paper).
The problem is that a larger gonopodium makes the male fish a slower
swimmer, and thus more easily captured by predators. What results
is an evolutionary trade-off between attracting mates and avoiding predators.
This research in The Bahamas was featured in numerous international media
outlets, for example:
Look for a lot more posts to come on the ecology and evolution of
mosquitofish. One of the main current projects on Abaco is looking at how
blocking wetlands, e.g., this isolated wetland on Great Cistern, may affect
mosquitofish biology. Lots more to come…