When I posted about the lives of lovable native lampreys a couple weeks ago, commenter Allegra pointed me to some great videos of vegetarian lamprey in Vancouver's Morrison Creek. For the first couple seconds of watching, I honestly mistook the lamprey for water plants. And then they started building nests and spawning. Which plants don't tend to do.
This video shows a group of male and female lamprey building a nest by moving small stones with their sucker mouths. There's more videos of lamprey working together to build nests if you follow the link. Cool stuff! The group that put this together, the Morrison Creek Streamkeepers, also have a photo page that explains how to tell the difference between a girl lamprey and a boy lamprey–if I haven't burned you out on animal sex this week already.