Leucochloridium perturbatum in a Succinea putrison.
https://media.giphy.com/media/ZZqz2QNCBPIxI0Boog/source.mov via GIPHY I found, and photografed a parasite worm, Leucochloridium perturbatum, in a snail in shell (Succinea putrison). Then I made a movie, and at the end a gif.