The black sea nettle provides the Pacific butterfish with food and protection. The silvery butterfish feeds on the plankton gathered by the jelly, and when danger approaches, the butterfish actually hides inside the jelly's bell.
The black sea nettle is a mysterious creature; during most years its whereabouts are unknown. Scientists just recently named this jelly in 1997, although pictures of the species were taken as early as 1926. Much about its behavior, distribution and life cycle remain a puzzle.