Mosquitofish With More Predators Have Larger Genitals (PHOTOS)

Male Bahamas mosquitofish (Gambusia hubbsi) that live in predator-heavy waters have larger genitalia and more aggressive mating techniques than their peers that live in safer "neighborhoods."

The researchers found the fish that lived in regions where they faced a pressing predatory threat had longer gonopodium tips, which transfer sperm, than members of the same species living in areas with less of a threat, a North Carolina State University press release reported.

These gonopodium tips are usually only one millimeter long, so the difference is miniscule, but researchers were able to identify a pattern of size linked to where the fish lived.