''Tripneustes ventricosus'', commonly called the West Indian sea egg or white sea urchin, is a species of

sea urchin Sea urchins () are spiny, globular echinoderms in the class Echinoidea. About 950 species of sea urchin live on the seabed of every ocean and inhabit every depth zone from the intertidal seashore down to . The spherical, hard shells (tests) of ...

. It is common in the

Caribbean Sea The Caribbean Sea ( es, Mar Caribe; french: Mer des Caraïbes; ht, Lanmè Karayib; jam, Kiaribiyan Sii; nl, Caraïbische Zee; pap, Laman Karibe) is a sea of the Atlantic Ocean in the tropics of the Western Hemisphere. It is bounded by Mexico ...

, the

Bahamas The Bahamas (), officially the Commonwealth of The Bahamas, is an island country within the Lucayan Archipelago of the West Indies in the Atlantic Ocean, North Atlantic. It takes up 97% of the Lucayan Archipelago's land area and is home to ...

and

Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and to ...

and may be found at depths of less than .

Description

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), ...

of the West Indian sea egg is dark in color, usually black, dark purple or reddish brown, with white spines long. The test can reach in diameter. It is often covered with pieces of

seagrass Seagrasses are the only flowering plants which grow in marine environments. There are about 60 species of fully marine seagrasses which belong to four families (Posidoniaceae, Zosteraceae, Hydrocharitaceae and Cymodoceaceae), all in the orde ...

, fragments of shell and other debris in a manner similar to the closely related ''

Tripneustes gratilla ''Tripneustes gratilla'', the collector urchin, is a species of sea urchin. Collector urchins are found at depths of in the waters of the Indo-Pacific, Hawaii, the Red Sea, and The Bahamas. They can reach in size. Description Collector urch ...

''.Humann, Paul, ''Reef Creature Identification'', Edited by Ned Deloach. New World Publications, Inc., 1992, p. 292-293. These decorations are held in place by

tube feet Tube feet (technically podia) are small active tubular projections on the oral face of an echinoderm, whether the arms of a starfish, or the undersides of sea urchins, sand dollars and sea cucumbers; they are more discreet though present on britt ...

among the spines and are believed to provide protection from the intense sunlight that penetrates the shallow water.

Distribution and habitat

The West Indian sea egg is found in shallow parts of the western Atlantic Ocean, the Caribbean Sea and Gulf of Mexico. Its range extends from Bermuda, the Carolinas and Florida to Belize, Venezuela and Brazil and also includes the west coast of Africa and Ascension Island. It seldom occurs in water deeper than . It is found in

seagrass meadow A seagrass meadow or seagrass bed is an underwater ecosystem formed by seagrasses. Seagrasses are marine (saltwater) plants found in shallow coastal waters and in the brackish waters of estuaries. Seagrasses are flowering plants with stems and ...

s, in rubble areas and on shallow rocky reefs. Young sea urchins conceal themselves in crevices and under rocks during the day but larger individuals stay out in the open.

Biology

The West Indian sea egg feeds on algae but tends to avoid the

crustose Crustose is a habit of some types of algae and lichens in which the organism grows tightly appressed to a substrate, forming a biological layer. ''Crustose'' adheres very closely to the substrates at all points. ''Crustose'' is found on rocks ...

, highly calcified

coralline algae Coralline algae are red algae in the order Corallinales. They are characterized by a thallus that is hard because of calcareous deposits contained within the cell walls. The colors of these algae are most typically pink, or some other shade of re ...

. Ripe gonads were found in urchins at any time of year but breeding probably takes place mostly in the summer. Male and female urchins liberate

gamete A gamete (; , ultimately ) is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. In species that produce t ...

s into the sea where fertilisation takes place. The eggs soon hatch into larvae which are

plankton Plankton are the diverse collection of organisms found in Hydrosphere, water (or atmosphere, air) that are unable to propel themselves against a Ocean current, current (or wind). The individual organisms constituting plankton are called plankt ...

ic. These develop through a number of larval stages over the course of about one month before settling on the seabed and undergoing

metamorphosis Metamorphosis is a biological process by which an animal physically develops including birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. Some inse ...

into juveniles. Young urchin recruits in Barbados are thought to have originated off the coast of South America. Various bottom feeding fish feed on the young sea urchins. In Jamaica, the

queen triggerfish ''Balistes vetula'', the queen triggerfish or old wife, is a reef dwelling triggerfish found in the Atlantic Ocean. It is occasionally caught as a gamefish, and sometimes kept in very large marine aquaria. Etymology This fish is called ''coc ...

, (''Balistes vetula''), is the main

predator Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...

. During their first year, young urchins increased their diameter by about a month. Growth slowed thereafter and halted completely after maturity was reached while the gonads were ripening. After liberation of the gametes, growth restarted.

Uses

The gonads of the West Indian sea egg are traditionally consumed in the West Indies and there is an important fishery in Barbados. Urchins are collected by skin diving and it used to be possible to collect a thousand in a few hours. In order to conserve stocks, a closed period was introduced during the breeding season (May to August) during which no sea urchins were allowed to be taken. Despite this, sea urchin numbers have declined during the late twentieth century and they are now uncommon and the fishery non-viable. The cause of this population collapse is thought to be overfishing, though pollution and disease may have played a part. The sea urchins have become rare in the most easily fished locations and are still common in more remote places. Attempts are being made to raise urchin larvae in the laboratory and restock depleted areas.

References

External links

* {{Taxonbar, from=Q2054392 Toxopneustidae Animals described in 1816 Articles containing video clips Fauna of the Caribbean