Red Coral

Associated Smithsonian Expert: Stephen D. Cairns, Ph.D.

Dr. Stephen Cairns studies deep-sea corals.

Credit: Smithsonian Institution

Dr. Stephen Cairns is a research zoologist and curator of corals in the Department of Invertebrate Zoology at the Smithsonian National Museum of Natural History. His research focuses on the diversity, distribution, and evolution of deep-water corals both fossil and living. Dr. Cairns was born and grew up in Louisiana and first became interested in corals when he lived for one year in Cuba as a child. In college (LSU) he studied biology and then pursued a master's and doctorate in biological oceanography at the University of Miami. Dr. Cairns has done fieldwork in the Galapagos, Hawaii, the Gulf of Mexico, the Mediterranean, the Philippines, and throughout Australia and New Zealand. At this point he has described about 450 new species of deep-sea corals.

Meet our associated expert

This image was obtained from the Smithsonian Institution. The image or its contents may be protected by international copyright laws.

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Basket star on Gorgonian coral
Courtesy of NURC/UNCW and NOAA/FGBNMS , public domain


About Gorgonians, Sea Fans, and Sea Feathers (Order Alcyonacea): Defense

Most alcyonacean corals do not make full-body, protective skeletons like the corals that build reefs. Their bodies are instead supported by separate skeletal pieces (sclerites) embedded in their flesh. While some Alcyonacea are called soft corals, the hard sclerites give their flesh a bumpy or spiky texture. Some grow in a globular, mushroom-like shape, but others (sea fans) have many, flattened branches that intertwine to form a lattice. The branching species get additional support from binding materials (such as proteins or calcium carbonate). This loose structure makes their bodies strong enough to grow as tall as several meters, while remaining flexible enough to sway in ocean currents. Many Alcyonacea release toxic chemicals, such as terpenes, that function in defense. Their often bright-colored bodies are a warning to predators that, between the toxins and the sclerites, they are not good to eat.

Tentacles of sea anemone (Ceriantheopsis americanus)
Courtesy of Greg McFall, Gray's Reef NMS, NOS, NOAA, public domain

About Anemones and Corals (Class Anthozoa): Feeding

Anthozoans (anemones and corals) have stem-like bodies that anchor to the ocean body or other surface. Tentacles radiate like petals around the top of the stem (anthozoa flower animals). Both their bodies and tentacles are hollow, opening into a mouth in the center of the flower. Anemones and corals capture food with their tentacles and push it into their mouths. While they mostly eat small, floating food (plankton), stingers (nematocytes) on their tentacles allow some anthozoans to consume larger prey (even fish or crabs) by stunning them first. Food travels from the mouth to the hollow space inside their bodies, where it is digested. Since they have only one opening, waste products are expelled back out their mouths. Some anthozoans benefit from a relationship with unicellular algae (mutualism). While the coral provides a safe place for the algae to live, the algae makes food by photosynthesizing.