Hey does anyone know what this is under my rock? It opens slightly like a clam and shuts when I touch it . Looks like it has a neck coming off it with 2 tentacles sticking out .
Super cute whatever it is. I doubt it will cause any problems, I bought a big rock with zoas from live aquaria, turned out the zoas were on an oyster (or some other bivalve).
I am guessing a bit due to the difficult picture, but if the part that closes is a hole in the neck you mentioned, then it might be a tunicate. They are leathery in texture and do retract some when they are touched. If you get a clearer picture and confirm the body shape and behavior, you might have your ID.
The first picture taken the whole area I circled opens slightly. Second picture looks very similar to one on a empty snail shell. Tried my best with the pictures .
That might be two different animals. First one is a clearer picture and looks like a oyster.
Second picture, if the circled area is the opening part... I am not sure what it is. Interesting!