Orchitophrya stellarum is often associated with sea stars and other invertebrates, living on their outer surface and feeding on sloughed-off epidermal tissue.
In the Pacific Ocean, it may alternate between parasitising Evasterias troschelii and Pisaster ochraceus during the spring and summer and Leptasterias spp.
[3][4] In 2006, a mass die-off of the purple sea star (Pisaster ochraceus) occurred off the coast of British Columbia.
[5] In a study published in 2013, Ochitophrya stellarum, the parasitic ciliate, was discovered in 2007 in the tissues of blue crabs.
[6] The north Pacific sea star, Asterias amurensis, was first seen in Tasmania in 1986 and is spreading along the coasts of southern Australia.
Biological pest control of the starfish is being considered through the introduction of Orchitophrya stellarum, however its ability to regulate sea star populations is uncertain.