''Echinometra viridis'', the reef urchin, is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

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 ...

in the

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

Echinometridae. It is found on reefs in very shallow parts of the western Atlantic Ocean and the Caribbean Sea.

Description

The reef urchin has an elliptical reddish brown

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), ...

(shell) covered with medium length spines. These are greenish in colour with paler bases and darker, often violet, tips. This urchin grows to a diameter of with the longest spines being . It looks very similar to the rock-boring urchin ''

Echinometra lucunter ''Echinometra lucunter'', the rock boring urchin, is a species of sea urchin in the family Echinometridae. It is found in very shallow parts of the western Atlantic Ocean and the Caribbean Sea. Description ''Echinometra lucunter'' has an elli ...

'', but the dark tips and the greater length of the spines are distinctive.

Distribution

The reef urchin is found on reefs 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 ...

from southern

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 ...

Venezuela Venezuela (; ), officially the Bolivarian Republic of Venezuela ( es, link=no, República Bolivariana de Venezuela), is a country on the northern coast of South America, consisting of a continental landmass and many islands and islets in th ...

at depths down to about . It is not as common as the rock-boring urchin and seems to be absent from the

West Indies The West Indies is a subregion of North America, surrounded by the North Atlantic Ocean and the Caribbean Sea that includes 13 independent island countries and 18 dependencies and other territories in three major archipelagos: the Greater A ...

to the east of the

Virgin Islands The Virgin Islands ( es, Islas Vírgenes) are an archipelago in the Caribbean Sea. They are geologically and biogeographically the easternmost part of the Greater Antilles, the northern islands belonging to the Puerto Rico Trench and St. Croix ...

Biology

The reef urchin conceals itself in crevices or under boulders. It emerges at night to feed by grazing on algae with its five teeth, part of the Aristotle's lantern organ that surrounds its mouth. It is not believed to bore holes, but its grazing still causes

bioerosion Bioerosion describes the breakdown of hard ocean substrates – and less often terrestrial substrates – by living organisms. Marine bioerosion can be caused by mollusks, polychaete worms, phoronids, sponges, crustaceans, echinoids, and ...

in reefs. In Panama, breeding takes place during the period April to December. It does not seem to be correlated with the phases of the moon as in some other sea urchin species. Fertilisation is external and the echinopluteus

larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. The ...

e 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. When these settle, they undergo a rapid

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 juvenile sea urchins. Researchers have studied the likely effect on the reef urchin of a rise in the

carbon dioxide Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...

levels which are likely to increase

ocean acidification Ocean acidification is the reduction in the pH value of the Earth’s ocean. Between 1751 and 2021, the average pH value of the ocean surface has decreased from approximately 8.25 to 8.14. The root cause of ocean acidification is carbon dioxid ...

by the end of the 21st century. It was found that the urchins would be negatively impacted because of decreased calcification, lowering their ability to build their

tests 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), ...

, especially during winter and in the more northerly parts of their range.

Ecology

The reef urchin is an important grazer on fleshy algae in the Caribbean area. Its abundance is reduced by predation by fish, especially the jolthead porgy (''

Calamus bajonado The jolthead porgy (''Calamus bajonado'') is an ocean-going species of fish in the family Sparidae. In Bermuda, it is known as the blue bone porgy, in the United States, it is also known by the Spanish name ''bojanado'', in Jamaica, it is one of ...

''), the queen triggerfish (''

Balistes vetula ''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 ...

''), the ocean triggerfish (''

Canthidermis sufflamen ''Canthidermis '' is a genus of triggerfishes commonly known as Ocean triggerfishes. Species There are currently 3 recognized species in this genus:Matsuura, K. (2014): Taxonomy and systematics of tetraodontiform fishes: a review focusing prima ...

'') and the hogfish ('' Lachnolaimus maximus''). Because of this predation, the reef urchin avoids open reef flats and in these locations there is an overgrowth of fleshy algae. It is unable to take over the algal controlling role of the black sea urchin (''

Diadema antillarum ''Diadema antillarum'', also known as the lime urchin, black sea urchin, or the long-spined sea urchin, is a species of sea urchin in the family Diadematidae. This sea urchin is characterized by its exceptionally long black spines. It is the ...

'') which is subject to great fluctuations in population.

References

{{Taxonbar, from=Q937376 Echinometridae Animals described in 1863 Taxa named by Alexander Agassiz