New research shows that male sea lampreys (that's a sea lamprey mouth pictured above) entice females into reproduction with the help of a special bump of tissue. No, not that. Get your mind out of the gutter. The lamprey's "rope tissue" is fascinating, writes Science Codex, because it's made of heat-generating fat cells similar to the kind found on mammals that maintain their own internal body temps — something the lamprey can't do.

Image: Sea Lamprey Mouth, a Creative Commons Attribution (2.0) image from usfwspacific's photostream