The coenosarc (living tissue) of the host coral sometimes grows over the surface of the barnacle.

[3] Observations of a number of these barnacles growing on the black coral Antipathes atlantica and all orienting themselves in one direction against the water current, with their cirri forming a cup-like shape, indicate that the barnacles were actively engaged in intercepting and feeding on plankton.

[4] The living tissue of black corals such as Plumapathes pennacea may grow over the surface of this barnacle.

[2] Black corals are mostly deep water animals; specimens (including fan-shaped and bottlebrush-shaped species) from the Gulf of Mexico, collected and recorded with remotely operated vehicles at depths ranging from 68 to 124 m (223 to 407 ft), revealed O. gracilis growing on six different species.

Other animals sharing the black coral habitat included squat lobsters (Uroptychus sp.