Tubastrea aurea

f22 @ 1/60s, Nikonos II w 28mm and 1:3 extension tube, Oceanic 2000 flash with aluminum flash reflector

"Tubastrea," Wikipedia, the free encyclopedia. Tubastrea, also known as sun coral or sun polyps, is a genus of coral in the phylum Cnidaria. It is a cup coral in the family Dendrophylliidae.Sun corals belong to a group of corals known as large-polyp stony corals. This means that while they produce a hard skeleton, they do not build reefs. Different species have polyps in a variety of colors, including yellow, orange, and shades of black. Unlike most corals, Sun corals are not photosynthetic. Tubastrea do not host zooxanthellae,the symbiotic algae that provides energy to the coral via photosynthesis. Instead, they are heterotrophic, and extend long tentacles at night to catch passing zooplankton. Tubastrea is often found in deep waters, because they do not require sunlight for nourishment. They often colonize artificial surfaces, such as ship wrecks, for similar reasons.
Salt River Canyon, St. Croix, U.S. Virgin Islands