| Diadematacia Temporal range: | |
|---|---|
 | |
| Echinothrix diadema | |
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Echinodermata |
| Class: | Echinoidea |
| Infraclass: | Acroechinoidea |
| Superorder: | Diadematacia |
| Orders | |
The Diadematacia are a superorder of sea urchins. Unlike most other sea urchins, they generally have hollow spines. The tubercles on their tests are perforated, and most species possess gills.
An echinoderm is any member of the phylum Echinodermata. The adults are recognisable by their radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the sea lilies or "stone lilies". Adult echinoderms are found on the sea bed at every ocean depth, from the intertidal zone to the abyssal zone. The phylum contains about 7,000 living species, making it the second-largest grouping of deuterostomes, after the chordates. Echinoderms are the largest entirely marine phylum. The first definitive echinoderms appeared near the start of the Cambrian.
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 5,000 meters. The spherical, hard shells (tests) of sea urchins are round and covered in spines. Most urchin spines range in length from 3 to 10 cm, with outliers such as the black sea urchin possessing spines as long as 30 cm (12 in). Sea urchins move slowly, crawling with tube feet, and also propel themselves with their spines. Although algae are the primary diet, sea urchins also eat slow-moving (sessile) animals. Predators that eat sea urchins include a wide variety of fish, starfish, crabs, marine mammals, and humans.
Sand dollars are species of flat, burrowing sea urchins belonging to the order Clypeasteroida. Some species within the order, not quite as flat, are known as sea biscuits. Sand dollars can also be called "sand cakes" or "cake urchins".
Roe or hard roe is the fully ripe internal egg masses in the ovaries, or the released external egg masses, of fish and certain marine animals such as shrimp, scallop, sea urchins and squid. As a seafood, roe is used both as a cooked ingredient in many dishes, and as a raw ingredient for delicacies such as caviar.
A pedicellaria is a small wrench- or claw-shaped appendage with movable jaws, called valves, commonly found on echinoderms, particularly in sea stars and sea urchins. Each pedicellaria is an effector organ with its own set of muscles, neuropils, and sensory receptors and is therefore capable of reflex responses to the environment. Pedicellariae are poorly understood but in some taxa, they are thought to keep the body surface clear of algae, encrusting organisms, and other debris in conjunction with the ciliated epidermis present in all echinoderms.
Kelp forests are underwater areas with a high density of kelp, which covers a large part of the world's coastlines. Smaller areas of anchored kelp are called kelp beds. They are recognized as one of the most productive and dynamic ecosystems on Earth. Although algal kelp forest combined with coral reefs only cover 0.1% of Earth's total surface, they account for 0.9% of global primary productivity. Kelp forests occur worldwide throughout temperate and polar coastal oceans. In 2007, kelp forests were also discovered in tropical waters near Ecuador.
Tube feet 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 brittle stars, and have only a feeding function in feather stars. They are part of the water vascular system.
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.
Algae eater or algivore is a common name for any bottom-dwelling or filter-feeding aquatic animal species that specialize in feeding on algae and phytoplanktons. Algae eaters are important for the fishkeeping hobby and many are commonly kept by aquarium hobbyists to improve water quality. They are also important primary consumers that relay the biomass and energy from photosynthetic autotrophes up into the food web, as well as protecting the aquatic ecosystem against algae blooms.
In biology, a test is the hard shell of some spherical marine animals and protists, notably sea urchins and microorganisms such as testate foraminiferans, radiolarians, and testate amoebae. The term is also applied to the covering of scale insects. The related Latin term testa is used for the hard seed coat of plant seeds.
Strongylocentrotus purpuratus, the purple sea urchin, lives along the eastern edge of the Pacific Ocean extending from Ensenada, Mexico, to British Columbia, Canada. This sea urchin species is deep purple in color, and lives in lower inter-tidal and nearshore sub-tidal communities. Its eggs are orange when secreted in water. January, February, and March function as the typical active reproductive months for the species. Sexual maturity is reached around two years. It normally grows to a diameter of about 10 cm (4 inches) and may live as long as 70 years.
The heart urchins or Spatangoida are an order of sea urchins.
Echinozoa is a subphylum of free-living echinoderms in which the body is or originally was a modified globe with meridional symmetry. Echinozoans lack arms, brachioles, or other appendages, and do not at any time exhibit pinnate structure. Their two extant classes are the sea urchins and the sea cucumbers.
Tripneustes gratilla, the collector urchin, is a species of sea urchin. Collector urchins are found at depths of 2 to 30 metres in the waters of the Indo-Pacific, Hawaii, the Red Sea, and The Bahamas. They can reach 10 to 15 centimetres in size.
Tripneustes ventricosus, commonly called the West Indian sea egg or white sea urchin, is a species of sea urchin. It is common in the Caribbean Sea, the Bahamas and Florida and may be found at depths of less than 10 metres (33 ft).
Cidaridae is a family of sea urchins in the order Cidaroida.
Toxopneustes pileolus, commonly known as the flower urchin, is a widespread and commonly encountered species of sea urchin from the Indo-West Pacific. It is considered highly dangerous, as it is capable of delivering extremely painful and medically significant stings when touched. It inhabits coral reefs, seagrass beds, and rocky or sandy environments at depths of up to 90 m (295 ft). It feeds on algae, bryozoans, and organic detritus.
Paracentrotus lividus is a species of sea urchin in the family Parechinidae commonly known as the purple sea urchin. It is the type species of the genus and occurs in the Mediterranean Sea and eastern Atlantic Ocean.
The Great Southern Reef is a system of interconnected reefs that spans the southern coast of continental Australia and Tasmania and extends as far north as Brisbane to the east and Kalbarri to the west. It covers 71,000 km2 (27,000 sq mi) of ocean and straddles five states, running along the coast for 8,000 km (5,000 mi).
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