Slatepencil urchin

Eucidaris tribuloides

ORDER Cidariida

FAMILY Cidaridae

TAXONOMY

Eucidaris tribuloides Lamarck, 1816.

OTHER COMMON NAMES English: Mine urchin, club urchin.

PHYSICAL CHARACTERISTICS

Size can reach 3.1 in (8 cm) in diameter, but with spines up to 5.1 in (13 cm). Coloration variable, from brown, red-brown to sometimes mottled brown-red with grayish white spine. Spines vary in color because of the attachment of encrusting organisms, particularly algae such as coralline. Solid brown cylindrical spines attached to a globular test.

DISTRIBUTION

Commonly found in less than 165 ft (50 m) of water, although can occur to a depth of 2,265 ft (800 m). Inhabits the coastal waters of North Carolina to Brazil.

HABITAT

Hides among sea grass beds such as turtle grass and in rocky crevices amongst coral, under rocks, and coral rubble. Usually found in lagoon areas. Spine length related to habitat. In high wave-exposed areas, spines are usually short.

BEHAVIOR

Forages for food at night. In coral reef habitats, spines used to defend against predators and as a mechanism to wedge itself in a crevice. In sea grass beds, it does not cover itself with algae and detritus as camouflage, as do other urchins. Instead, it allows encrusting organisms to settle and grow on spines; a very slow-moving urchin.

FEEDING ECOLOGY AND DIET

Omnivorous, feeding on algae and small invertebrates like sea squirts, sponges, bryozoans, algae, gastropods, and bivalves. Although E. tribuloides has not been shown to be destructive to corals, a close relative that shares similar feeding habits, E. galapagensis, is destructive.

REPRODUCTIVE BIOLOGY

Sexual reproduction; eggs and sperm are shed into the water column where fertilized eggs develop into free-living and transparent larvae with reddish eyespots before metamorphosing into juveniles and settling on the seabed. Spawning period linked to day-length and lunar cycle, but actual event varies geographically.

Pencil Sea Urchins Anatomy

CONSERVATION STATUS Not listed by the IUCN.

SIGNIFICANCE TO HUMANS None known. ♦

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