The slate pencil urchin is known among researchers as Eucidaris tribuloides, and it is an uncommon sea urchin belonging to the family Cidaridae. Due to its unique molecular and morphological characteristics, it is considered one of the more fascinating varieties of sea urchin currently being studied by scientists. The creature is found mainly in the Atlantic Ocean, however, it is not limited to the coasts of the United States and Brazil, but can be found throughout the entire ocean. Its reproduction cycle is also worth mentioning, as the urchin is far more sensitive to seasonal changes than other members of the family Cidaridae.
Like other Eucidaris species, the slate pencil urchin features the same type of thick, blunt, cylindrical and radially arranged spines that have come to characterize pencil urchins. What truly makes this species unique, however, is its molecular and cellular traits, which scientists consider to be crucial for the study of the species’ evolution, as well as that of similar species. The pencil urchin possesses unique traits such as a larval skeleton that comes from a special cell lineage and its euechinoid embryonic development. Its cell lineages have helped scientists understand evolutionary biology at a much higher level.
This species of pencil urchin can be found on both sides of the Atlantic Ocean, from Gabon in the East to the coast of Brazil in the west. Cape Hatteras in North Carolina is one of the northernmost region where you are likely to find specimens of the species. Also, the Caribbean and the Gulf of Mexico, as well as the Azores, the Gulf of Guinea and the Ascension Islands are all teeming with slate pencil urchins. The slow-moving echinoid is a nocturnal creature that prefers anchoring itself into various rocks and crevices during the daytime and feeding on corals and sponges during the night. It stays close to rocky areas, never venturing too far from home.
Unlike other species, E. tribuloides is far more affected by both seasonal and lunar cycles. The shifts dictate and regulate the pencil urchin’s reproductive cycle, so that maximum gravidity is obtained during late summer and early autumn. However, depending on their placement, researchers have found that populations in Panama, for instance, tend to attain the same results during spring, summer and fall. In each case, the slate pencil urchin from the Caribbean reaches peak gravidity during the full moon.