Precious coral

Corallium rubrum and several related species of marine coral. The distinguishing characteristic of precious corals is their durable and intensely colored red or pink skeleton, which is used for making jewelry.

Distribution

Mediterranean Sea.

Habitat

Red corals grow on rocky seabottom with low sedimentation, typically in dark environments—either in the depths or in dark caverns or crevices. The original species, C. rubrum (formerly Gorgonia nobilis), is found mainly in the Mediterranean Sea. It grows at depths from 10 to 300 meters below sea level, although the shallower of these habitats have been largely depleted by harvesting. In the underwater caves of Alghero, Sardinia (the "Coral Riviera") it grows at depth from 4 to 35 meters. The same species is also found at Atlantic sites near the Strait of Gibraltar, at the Cape Verde Islands and off the coast of Southern Portugal. Other Corallium species are native to the western Pacific, notably around Japan (Corallium japonicum) and Taiwan; these occur at depths of 350 to 1500 meters below sea level in areas with strong currents.

Anatomy

In common with other Alcyonacea, red corals have the shape of small leafless bushes and grow up to a meter in height. Their valuable skeleton is composed of intermeshed spicules of hard calcium carbonate, colored in shades of red by carotenoid pigments. In living specimens, the skeletal branches are overlaid with soft bright red integument, from which numerous retractable white polyps protrude. The polyps exhibit octameric radial symmetry.