Orange Cup Coral - Balanophyllia elegans
Most common coral (scleractinian) in southern California. A common solitary coral, occurring in the same range as the brown cup coral Paracyathus stearnsii. Generally orange, with orange tentacles bearing wart-like clusters of stinging cells. Though commonly called orange cup coral, yellow color morphs also exist. Cups up to 25 mm (1 inch) in diameter, and 25 mm (1 inch) high. Found from British Columbia to central Baja California. Found on or under shaded rocks, on sides of surge channels, and under ledges, from low intertidal zone to 200 meters (1968 feet).
The orange cup coral polyp can almost completely retract into its stony skeleton. Food is primarily caught by the tentacles, but the mouth may open widely, permitting the stinging cells in the gastrovascular cavity to trap food. Its tentacles evert specialized stinging cells (spirocysts), producing tangles of sticky tubules to capture prey or attach the coral to the bottom, or both. Sexes are separate, with eggs fertilized and developing in the female's gastrovascular cavity, releasing worm-like orange larvae in spring and summer, or year-round but mainly in winter (depending on which source you read!). A filamentous blue-green photosynthetic bacterium/alga (cyanobacteria/cyanophyte) can occur in the skeletal matrix of the orange cup coral, producing a purple-red coloration seen in the tissue-free skeleton.
Brown Cup Coral - Paracyathus stearnsii
A common solitary coral in California, occurring in the same range as the orange cup coral Balanophyllia elegans. Color ranges from light brown to a deep purple/brown, with almost clear long tentacles. Tends to occur singly rather than in groups like the orange cup coral Balanophyllia elegans. Cups up to 38 mm (1.5 inches) in diameter, and 32 mm (1.25 inches) high. Found from British Columbia to Cedros Island, Baja California. Found on lower sides of rocky reefs, from 30 to 200 feet depth.