The Hatpin Urchin, scientifically known as Centrostephanus longispinus, is a fascinating species of sea urchin that can be found primarily in the Mediterranean Sea and the Atlantic Ocean. Known for their striking appearance and long, toxic spines, these urchins are a unique sight in the waters around Gozo. They are part of a diverse marine ecosystem, contributing to the underwater biodiversity that makes Gozo a popular diving destination
Identifying a Hatpin Urchin is easy due to its distinctive long spines, which can reach up to 30 centimeters in length. These spines are typically reddish-brown with tips that can be purple or pink. The central test, or body, of the urchin is small and surrounded by spines of varying lengths. The spines are mobile and used for locomotion. This urchin also has unique club-shaped spines on its lower surface.
Centrostephanus longispinus has a variety of characteristics that make it unique. The spines are not only for protection but also help in movement. The subspecies can have spines that are banded in purple on a pale green, buff, or whitish background. Juveniles often have reddish-brown spines on a pale background. Interestingly, this urchin has chromatophores, which are pigment-bearing structures sensitive to light, allowing it to change color from night-time black to daytime greyish brown.
The Hatpin Urchin prefers depths between 40 and 210 meters, avoiding direct sunlight by inhabiting hard substrates, cavities, and rock crevices. They are not typically found on living reefs, possibly due to the lack of macro-algae or the presence of predatory fish. In the Caribbean and Gulf of Mexico, they are often found on algae or broken coral substrates. These urchins are part of a species-rich community, feeding mainly on red algae and occasionally on small invertebrates or seagrass.
An interesting fact about Hatpin Urchins is their ability to change color based on light conditions. Their chromatophores enable them to shift from a night-time black to a greyish brown during the day. This adaptive feature helps them blend into their environment, providing camouflage from predators. Additionally, their long spines are not just for show—they are toxic and can deliver a painful sting if touched.
Care and attention is always advised when Diving in Gozo around any sea urchins. Hatpin Urchins are no different, but also nothing to worry about. These urchins are typically found at greater depths, such as 36 meters at Reqqa Point on Gozo’s north coast. The clear waters and rocky landscapes provide ideal conditions to observe these unique creatures in their natural habitat. Divers should exercise caution due to the toxic spines, but the sight of these impressive sea urchins is well worth the careful approach.
