 One such relationship is between "Branchiobdellida" and crayfish in which the "Branchiobdellida" acts as a bacterial gut cleaner for the crayfish species.Another example is the iron-oxide associated chemoautotrophic bacteria found crusted to the gills of "Rimicaris exoculata" shrimp that provide the shrimp with vital organic material for their survival while simultaneously supporting the bacteria with different organic material that the bacterial cannot produce itself.Groups of organisms, that is greater than a single pair of a host and parasite, can also form mutualistic ectosymbiotic interactions.