Diadematoida Duncan 1889

A short note on these prickly pears of the sea. An article I found interesting Sea urchins off Jamaica’s north coast appear to be making a comeback, states an article in The Dallas Morning News. Furthermore, “scientists discovered many young corals, including hardy and reef-forming types, thriving along with the sea urchins.” The reefs have been struggling ever since a sea urchin species called Diadema antillarum died off dramatically in 1983 and 1984. Some species of sea urchins control the growth of seaweeds, which if left unchecked can devastate coral reefs. However, “new studies show that Diadema has sprung back, and corals may be doing the same,” the paper reports. Marine biologist Nancy Knowlton says that the recovery is “the best news to emerge from Caribbean reefs in decades.”

The Diadematoida are an order of sea urchins. They are distinguished from other sea urchins by the fact that their spines are hollow, or at best have an open mesh at the core, and by the presence of 10 buccal plates around the mouth. Their tests can be either solid or flexible.