''Lytechinus williamsi'', the jewel urchin, is a sea urchin in the

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Toxopneustidae Toxopneustidae is a family of globular sea urchins in the class Echinoidea. Characteristics All Camarodonts have imperforate tubercles and compound ambulacral plates. In addition, the Toxopneustids are characterised by the peristome, or open ...

. It occurs on shallow reefs off the coasts of Panama, Belize, the Florida Keys and Jamaica.

Description

The jewel urchin grows to a diameter of about and has spines up to long. Many of them are shorter than this and provide a dense covering. The

test Test(s), testing, or TEST may refer to: * Test (assessment), an educational assessment intended to measure the respondents' knowledge or other abilities Arts and entertainment * ''Test'' (2013 film), an American film * ''Test'' (2014 film), ...

is usually a pale brown colour with a red or dark brown stripe along the joints of the main inter

ambulacra Ambulacrum is an architectural word that denotes an atrium, courtyard, or parvise in front of a basilica or church that is surrounded by arcades or colonnades, or trees, and which often contains a fountain A fountain, from the Latin "f ...

l plates. The spines are either deep green or white and have a ridge running along one side of each, a fact that distinguishes this species from the very similar ''

Lytechinus variegatus ''Lytechinus variegatus'', commonly called the green sea urchin or the variegated sea urchin, is a species of sea urchin that can be found in the warm waters of the western Atlantic Ocean and Caribbean Sea. Subspecies There are four subspec ...

''. In between the spines are large purple tweezer shaped structures called

pedicellaria A pedicellaria (plural: pedicellariae) is a small wrench- or claw-shaped appendage with movable jaws, called valves, commonly found on echinoderms (phylum Echinodermata), particularly in sea stars (class Asteroidea) and sea urchins (class Echi ...

e which are also distinctive, ''L. variegatus'' having white pedicellariae.

Distribution and habitat

The jewel urchin is the commonest sea urchin on some coral reefs in the Caribbean Sea but it seems to be restricted to the coasts of Panama, Belize, the Florida Keys and Jamaica at depths between . It is found in crevices in rocks and coral reefs and on the surfaces of other organisms such as table corals, '' Acropora spp.'', and lettuce corals in the family

Agariciidae The Agariciidae are a family of reef-building stony corals. This family includes cactus corals, plate corals, and lettuce corals. Members of the family include symbiotic algae called zooxanthellae in their tissues which help provide their energ ...

. It does not feed on these corals.

Biology

The jewel urchin does not protect itself from the sun by covering its upper surface with bits of seagrass and shell but instead, tends to hide in cracks during the day and emerge to feed at night. Like other sea urchins, the diet is mainly algae which are scraped off the surface of rocks or chewed by the rasping mouthparts situated on the oral (under) surface of the animal. In Panama the jewel urchin's spawning period occurs annually in the rainy season. It occurs over an extended period and does not seem to be linked with phases of the moon as is the case in some other species of sea urchin.

References

{{Taxonbar, from=Q3203465 Animals described in 1968 Lytechinus Fauna of the Atlantic Ocean