What are these freshwater bugs?

UPDATE: My brother, Karl Koenig found some info, and I looked too. Someone even answered on youtube, and we all agree, they are leaches! During my research, I was surprised to read that they are still being sold for medicinal purposes. I put them back with the worms in their aquarium so if they wanna make more, I’m sure the fish will love them as much as the brown worms.

[original post] They came with live freshwater brown worms for feeding aquarium fish. Just to look at them without bright light behind them, the ‘fingers’ or whatever that is on the inside of their bodies are not visible. They cling tightly to whatever they’re climbing, including my finger ^.^)
I thought at first they were snail poo, as when they are threatened, they roll into a round ball. Sorry about the music, I thought i listened and clicked cancel, but don’t care enough to upload again. [using the ‘free’ music on youtube’s site, also gives them permission to show ads on your video, but the ‘x’ works to close the ad.