Long-Spined Sea Urchin – Diadema antillarum
The Long-Spined Sea Urchin, also known as the Lime Urchin, Black Sea Urchin or Grabaskey’s Bane, is a species in the class of the Sea Urchins and thus belongs to the phylum of the Echinodermata. Diadema antillarum was first described in 1845 by Philippi.
The body of the Long-Spined Sea Urchin is shaped like a hemisphere. Its particularly long spines are striking.
The colour is dark violet to black, sometimes also white to greyish spines can be seen.
The body of Diadema antillarum reaches a maximum diameter of 10cm and the spines are up to 20cm long, in some large individuals even up to 30cm.
Habitat and Distribution
Diadema antillarum lives on rocky ground. It is widely spread in depths of down to 10m, but it can befound down to several hundred meters.
When diving in the Canaries you can observe it very often, so there is hardly a dive without it. Especially in the case of night dives, one can see how many individuals are around the reefs.
Its distribution area extends over the tropical and subtropical zones of the Atlantic. In the western Atlantic Diadema antillarum is found mainly in the Gulf of Mexico and the Caribbean Sea.
In the eastern Atlantic you can find the Long-Spined Sea Urchin around Madeira, the Canary Islands, Cape Verde to the Gulf of Guinea and the islands of Annobón.
Diadema antillarum is nocturnal. While it is hiding in columns, holes, and overhangs during the day, it goes out to look for food at night. It feeds mainly on algae, which it grazes within a radius of about one meter to its hiding place. In the Caribbean, this protects the coral reefs from being overgrown. In the Canary Islands, however, many rocky reefs are left blank, thus robbing the habitat of other species. In addition, there are invertebrates, young corals, zoanthids , Cnidaria and zooplankton on its menu.
The reproduction of Diadema antillarum takes place in the summer time. It was observed that many individuals gather. There is no reproduction between couples. Instead sperm and oocytes are released into the open water once a month, where fertilization takes place.
The age of the Long-Spined Sea Urchin depends on the food supply and the water temperature. While animals grow faster in warmer areas and thus age faster, specimens are usually getting older in colder water. The average age is 6 years. The life expectancy varies from 4 to 8 years.
Providing protection to other species
Although the Long-Spined Sea Urchin is a threat to the balance of the ecosystems in the Canary Islands, there are also species which it benefits. For example, the sea urchin partner shrimp Tuleariocaris neglecta lives on its spines. In addition, one often finds Arrow Crabs, which are hidden between its spines, as well as protection-seeking juvenile fishes.
Sea Urchin Plague on the Canaries
In the Canary Islands you will find many reefs that have been eaten completely blank by the Long-Spined Sea Urchin. This is mainly due to the fact that its natural enemies become less, whether due to overfishing or changes in living conditions. Normally, Diadema antillarum is chased by Spotfin Burrfish, Grey and Ocean Triggerfish, various Sea Breams, the Spiny Starfish, the Blue Spiny Starfish and the Atlantic Triton Trumpet. However, there is currently not enough individuals to keep the amount of Long-Spined Sea Urchins under control.
The large-scale lack of algae growth robs other species of the habitat, the food base, hiding places and breeding grounds.
What to do when being stung?
If one was careless, it is not the end of the world. The Long-Spined Sea Urchin is poisonous, but this does not pose a threat to humans!
The spines of Diadema antillarum are porous and when you try to remove them, they probably break off. The wound should be disinfected and rubbed with vinegar as this dissolves the lime. You will have to live with some pain and hopefully remebmer to take more care next time.