Diadema
Diadema is a genus of sea urchins in the family Diadematidae. These urchins are characterized by their long, slender spines that can be quite sharp, and they are found in a variety of tropical and subtropical marine environments around the world.
Common Names
Species of Diadema are commonly known as "long-spined sea urchins" due to their distinctive spines.
Characteristics
Diadema sea urchins are easily recognized by their long, slender spines, which can be up to 10 cm long. The spines are often black or dark brown, but can also be reddish, purple, or even green in some species. The body of the urchin, known as the test, is usually covered in short, dense spines that are much smaller than the primary spines. These urchins are also notable for their small, delicate pedicellariae, which are small, pincer-like structures that help protect them from predators.
Environments
Diadema sea urchins are found in a variety of marine habitats, including coral reefs, seagrass beds, and rocky shores. They are typically found in shallow waters, but can also be found in deeper waters. Some species prefer specific types of environments, while others are more adaptable.
Species
There are over 20 recognized species within the genus Diadema, some of the most common include:
- Diadema antillarum (West Atlantic Long-Spined Sea Urchin)
- Diadema setosum (Indo-Pacific Long-Spined Sea Urchin)
- Diadema savignyi (Red Sea Long-Spined Sea Urchin)
Ecological Role
Diadema sea urchins play an important role in maintaining the health of coral reefs. They are herbivores, feeding primarily on algae, which helps to prevent the overgrowth of algae and maintain the balance of the reef ecosystem. They are also an important food source for some marine animals, including fish and sea turtles.
Conservation
Many Diadema species are facing threats from habitat loss, pollution, and overfishing. In the 1980s, a mass die-off of Diadema antillarum severely impacted Caribbean coral reefs, highlighting the vulnerability of these species. Conservation efforts are underway to protect these important species and the ecosystems they inhabit.