The Primnoa polyps are crowded onto the branches of the skeleton where they feed by filtering particles out of the water flowing past. Unlike reef-forming tropical corals, deep sea coral polyps do not form symbiotic associations with photosynthetic microorganisms. This specimen was collected off southern Nova Scotia. This specimen of Primnoa resedaeformis was hauled up on a longline by fishermen working in the region of the northern peak of Georges Bank. It is amazing that it was not ripped from the rock as it came up.
Most corals require a hard substrate on which to establish.
Coral polyps are sometimes lost from parts of the secreted skeleton. In this case, the bare skeleton has been secondarily colonized by large barnacles. Many other species find the bare branches of dead corals to be excellent substrates for colonization, and recolonization by coral polyps can also occur. This species sometimes grows on the same skeleton as Primnoa resedaeformis. Whether they compete for space aggressively, or co-exist is unclear.