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A typical sea anemone is a sessile polyp attached at the base to the surface beneath it by an adhesive foot, called a basal or pedal disc, with a column-shaped body topped by an oral disc. Most are from 1 to 5 cm (0.4 to 2.0 in) in diameter and 1.5 to 10 cm (0.6 to 3.9 in) in length, but they are inflatable and vary greatly in dimensions.
Diadema antillarum, also known as the lime urchin, black sea urchin, or the long-spined sea urchin, [2] is a species of sea urchin in the family Diadematidae. This sea urchin is characterized by its exceptionally long black spines. It is the most abundant and important herbivore on the coral reefs of the western Atlantic and Caribbean basin.
The coast of Southern California is known as a source of high quality uni, with divers picking sea urchin from kelp beds in depths as deep as 24 m/80 ft. [85] As of 2013, the state was limiting the practice to 300 sea urchin diver licenses. [85]
The anemone feeds on sea urchins, small fish, and crabs, but detached mussels seem to be the main food source. [5] [7] There are rare instances where the giant green anemone has consumed seabirds. [9] It is not known whether the birds were alive or dead when engulfed by the anemone.
If the sea urchin comes into contact with the tentacles of the sea anemone, it may be unable to tear itself free, however, if it is swathed in seaweed fragments or concealed among the seaweed fronds, the sea anemone's tentacles may adhere to the algal material, enabling the sea urchin to make good its escape. [5]
Like many creatures living in the midnight zone, the sea anemone produces its own light. This is in the form of a bioluminescent mucus that it emits. The glow helps to attract prey which notices ...
In 1983, for example, the mass mortality of the tropical sea urchin Diadema antillarum in the Caribbean caused a change from a coral-dominated reef system to an alga-dominated one. [103] Sea urchins are among the main herbivores on reefs and there is usually a fine balance between the urchins and the kelp and other algae on which they graze.
For marine scientists, it was deja vu: Another die-off swept through the region in the 1980s and slashed sea urchin populations by around 98%. Last year, sea urchins in the Caribbean started ...