By Susan Milius
Female fish living in a cave still prefer a mate with a nice, big body, even though it’s too dark to see him.
In plenty of species, females choose large males, so that preference in the Atlantic molly (Poecilia mexicana) comes as no surprise.
What interested Martin Plath of Hamburg University in Germany and his colleagues was what happens when mollies adapt to life in a pitch-black cave.
The researchers collected Atlantic mollies from water in a cave, at the cave entrance, and in a portion of the river outside of the cave. Researchers raised offspring of these fish for lab tests.