Close up of Balanophyllia. Photo by Dr.A.Svoboda

The orange cup coral is one of the few true corals. It is found from Oregon to Southern California and also in British Columbia.. It is found in low intertidal zones and at Race Rocks it is very abundant, often associated with the brooding anemone and encrusting tubeworms of the 8-10 metre level. It is usually found on and under shaded rocks, on the sides of surge channels and under ledges.

Its physical characteristics include the following: It has a stony, cuplike, calcareous, external skeleton. It has polyps coloured bright orange to yellow. Balanophyllia elegans transparent tentacles bearing wart-like batteries of nematocysts are present in the marginal portion of their discs. The polyps nearly completely retract into the skeleton. The orange cup coral feeds on living and dead animal matter using its tentacles.

Food is caught primarily in the tentacles, but in addition the mouth may open widely, permitting their mesenteries with their nematocyst-laden margins to trap food. Studies done on the orange cup coral and a few similar organisms showed that the tentacles have organelles called spirocysts which resemble nematocysts and evert to produce tangles of sticky tubules. These spirocysts may be important in capturing prey or in attaching coelenterates to the substratum or both. The orange cup coral reproduces by releasing eggs into the parents gastrovascular cavity, where they are fertilized and undergo development to the planula stage before release to the ocean. These then settle on a rock substrate and metamorphose into tiny polyps, which then secrete a skeleton.

References

Kozloff, E.N. 1996 Marine invertebrates of the Pacific Northwest.

Morris, Abbott, Haderlie 1980, Intertidal Invertebrates of California.