Goby on Soft Coral

It is sometimes thought that coral reefs are rocky edifices, but a coral reef is actual­ly composed of zillions of tiny coral polyps which have secreted hard skeletons to form the rigid mass of the coral reef. This rigid mass (a reef) is composed of calcium carbonate secreted by the coral polyps.

There are hard corals and soft corals. A hard coral polyp is a tiny little elongated animal which attaches its lower end to a solid surface of its own making and whose upper end has six or more little tentacles circling its mouth. The tentacles extend during feeding and ensnare plankton. Coral continually secretes around itself a hard skeleton of calcium car­bonate (chalk) to form a cup or hole in which the polyp can withdraw for protection when not feeding. With zillions of coral polyps secreting their protective chalk skeletons as a colony, a reef is slowly formed… and growing on this reef are more types of hard coral in all kinds of shapes, such as elkhorn coral, stagho­rn coral, rope coral, lettuce-leaf coral, fire coral (named for the sensation you feel if you touch it) and finger coral, to name just a few.

Soft coral is composed of soft delicate tissue and has a different type of “skeleton” struc­ture than hard coral. Soft coral manufactures calcium carbonate in the form of fibers or “spicule­s” within its tissue, and these spicules give soft coral its shape and structure. Except for black coral, all soft corals have eight tentacles and are referred to as octo­corals. Soft corals of the species Dendronephthya (this photograph) show striking colors of red, pink, orange, yellow, blue, or lavender in a translucent form. Soft corals are truly the lush “forests” of the coral reef.

Gobies and blennies are tiny fish only a few inches long with narrow bodies. They flit about actively on the reef and each fish is represented by hundreds of species. Gobies and blennies hide in holes and crevices in the reef and among intricate coral for protection. Like many small and vulnerable creatures of the reef, gobies seek to camouflage themselves against similarly colored backgrounds, such as this goby “hiding” on soft coral.