Size DOES Matter...

...If you happen to be a fish, apparently it IS an issue of some import.

--ryan


Fish Genital Size Matters for Sexual Attraction, Natural Selection
By Qingqing Ho
May 15, 2005, 11:04

New Haven, Conn. May 14 - For certain fish species to survive, the male genitalia should be large enough to attract the females, and small enough to escape predators, stated a study presented in the proceedings of the National Academy of Sciences.

The study was to find the female sexual preference and male swimming performance in two species of mosquitofish -Western and Bahamas mosquitofish.

In the study, researchers analyzed the gonopodia (modified fin) in the mosquitofish that transfer sperm to females. Mosquitofish can not retract their gonopodia and they swing them during courtship.

Researchers concluded that the females preferred to spend time watching videos of males displaying digitally enlarged gonopodia rather than those with average-size gonopodia. This indicates that a larger gonopodium is the female sexual preference.

However, larger gonopodia make the males more susceptible to predation, because the males with larger gonopodia swim slower.

"Our results suggest that both mating selection, favoring larger genitalia, and natural selection, favoring reduced size, may direct evolution and diversification of genitals," said Layman, co-author of the study.

The study was conducted by Craig A. Layman in Yale University, and colleagues Brian Langerhans at Washington University and Thomas J. Dewitt at Texas A&M University.

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