Hatpin Urchin, Centrostephanus longispinus
The Hatpin Urchin (Centrostephanus longispinus) is a species of sea urchin belonging to the family Diadematidae. There are two subspecies, Centrostephanus l. longispinus, found in the eastern Atlantic and Mediterranean Sea and Centrostephanus I. rubricingulus, found in the western Atlantic.
In the year 1940, Mortenson believed that C. longispinus and C. rubricingulus were closely related species but that they could be distinguished due to the fact that C. longispinus has smaller and fewer secondary interambulacral tubercles. In 1975, Fell re-examined the genus but was not able to find sufficient distinction to justify separating them into two species. He proposed that C. rubricingulus should be considered a subspecies of C. longispinus. He couldn’t reliably distinguish the pair from C. besnardi except by the location from which they had been gathered. Additionally, he was unable to distinguish between the juveniles of C. coronatus and the juveniles of the other species.
C. longispinus has a small central test and spines up to 12 inches long. These are toxic and have the ability to cause a painful sting. The spines vary in length and are mobile and used for movement. There are numerous of club-shaped spines on the oral, meaning lower, surface, a trait that this species shares with C. besnardi and C. coronatus but not other members of the genus. These spines are a reddish brown and are tipped with a purple or pink pigment. The subspecies C. l. longispinus has spines that are banded in purple on a pale green, beige or whitish background. Juvenile C. I. rubricingulus have reddish brown colored spines on a pale background while the adults have either spines that are banded in brown on a pale brown or uniformly dark colored spines. It’s been shown that C. longispinus has chromatophores that are sensitive to the light. By changing their shape, these modify the color of the animal which is changed from a night time black to a day time grayish brown.
C. longispinus can be found on the continental shelf on either side of the Atlantic Ocean. Its range stretches from the Mediterranean Sea and North African coast to the Caribbean Sea and the Gulf of Mexico. The depth range is between 130 and 690 feet. Off of Florida this urchin is typically found on algae or on broken coral substrates, especially the rubble remains of dead ivory bush coral. It creates a portion of a species-rich community which includes other sea urchins, mollusks, crabs, polychaete worms, and encrusting organisms. These sea urchins aren’t usually found on living reefs, perhaps because there is rarely macro-algae growing there or because predatory fish hiding amongst the coral heads consume the juvenile sea urchins.
Assessment of the contents of this urchin’s stomach have shown that C. longispinus mainly feeds on several species of red algae. During the times of the year when this isn’t available, it most likely consumes small invertebrate prey. In the laboratory they will feed on the sea grass Thalassia testudinum and may assault the starfish Narcissia trigonaria if it is hungry enough.
Image Caption: Hatpin Urchin, Centrostephanus longispinus. Credit: Guido Picchetti/Wikipedia (CC BY-SA 3.0)