Awesome, never heard of anything like that before. Is is possible that the Eel is just taking advantage of a grouper scaring fish into crevices? and that the signaling is something else that the scientists are associating with signaling? I'm not saying either way, as I wouldn't be extremely surprised if they were cooperating (as seen in cleaner fish). Just like to throw both sides out there since sometimes scientists tend to put things together that may not be fact based on what they want to see. Either way awesome video!