OddFile: Mosquitofish Think Size Matters

Does size matter? Let’s ask female mosquitofish…

That’s what some researchers did in “Females prefer to associate with males with longer intromittent organs in mosquitofish“:

Sexual selection is a major force behind the rapid evolution of male genital morphology among species. Most within-species studies have focused on sexual selection on male genital traits owing to events during or after copulation that increase a male’s share of paternity. Very little attention has been given to whether genitalia are visual signals that cause males to vary in their attractiveness to females and are therefore under pre-copulatory sexual selection. Here we show that, on average, female eastern mosquitofish Gambusia holbrooki spent more time in association with males who received only a slight reduction in the length of the intromittent organ (‘gonopodium’) than males that received a greater reduction. This preference was, however, only expressed when females chose between two large males; for small males, there was no effect of genital size on female association time.

This study really sucked for the mosquitofish: The reduction was done by a surgery I would not much want to watch (though, you can see the results at right). But I guess if your species is named “mosquitofish,” you’re never gonna get to pretend to be much of a big man anyway.

HT: Deric Bownds’ MindBlog

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