''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 Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only state ...

, the

Red Sea The Red Sea ( ar, البحر الأحمر - بحر القلزم, translit=Modern: al-Baḥr al-ʾAḥmar, Medieval: Baḥr al-Qulzum; or ; Coptic: ⲫⲓⲟⲙ ⲛ̀ϩⲁϩ ''Phiom Enhah'' or ⲫⲓⲟⲙ ⲛ̀ϣⲁⲣⲓ ''Phiom ǹšari''; ...

, and The Bahamas. They can reach in size.

Description

Collector urchins are dark in color, usually bluish-purple with white spines. The

pedicle Pedicle or pedicel may refer to: Human anatomy *Pedicle of vertebral arch, the segment between the transverse process and the vertebral body, and is often used as a radiographic marker and entry point in vertebroplasty and kyphoplasty procedures ...

s are also white, with a dark or black base. Individuals found at Green Island had orange-tipped spines. The spines of some specimens are wholly orange, while those of others are only orange-tipped or completely white. This color disappears when the individual dies or is taken out of the

ocean The ocean (also the sea or the world ocean) is the body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water. An ocean can also refer to any of the large bodies of water into which the wo ...

, and is difficult to preserve. Collector urchins reach in size. Debris tends to "collect" on these urchins, hence their name. Unlike some other sea urchins, collector urchins graze continually, day and night. They graze near the substrate, and their diet includes algae,

periphyton Periphyton is a complex mixture of algae, cyanobacteria, heterotrophic microbes, and detritus that is attached to submerged surfaces in most aquatic ecosystems. The related term Aufwuchs (German "surface growth" or "overgrowth") refers to the col ...

, and seagrass. Most collector urchins feed on seagrass fronds; this has an ecological impact varying with the season and abundance of the urchins. They feed voraciously between November and January; one study found they consumed up to or in excess of half of seagrass production. On an annual basis, however, the same study concluded that about 24% of seagrass production is consumed by the collector urchin. The seagrass species grazed are mainly '' Thalassodendron ciliatum'' and '' Syringodim isoetifolium'', but other algae may also be consumed. Collector urchins are prey for

puffer fish Tetraodontidae is a family of primarily marine and estuarine fish of the order Tetraodontiformes. The family includes many familiar species variously called pufferfish, puffers, balloonfish, blowfish, blowies, bubblefish, globefish, swellfish ...

, octopuses, and humans. T. gratilla collector.jpg, ''Tripneustes gratilla'' covering itself with rocks ( Réunion island). Tripneustes gratilla.jpg, ''idem''. T. gratilla podia.jpg, This urchin has long and obvious podia. T. gratilla face orale.jpg, Aboral side. File:Tripneustes gratilla Asia.jpg, More colored specimen in Asia. File:Tripneustes gratilla 10070605.jpg, Even more colored specimen from Polynesia.

Distribution and habitat

Collector urchins are found in the waters of the Indo-Pacific,

, the

, and

The Bahamas The Bahamas (), officially the Commonwealth of The Bahamas, is an island country within the Lucayan Archipelago of the West Indies in the North Atlantic. It takes up 97% of the Lucayan Archipelago's land area and is home to 88% of the ar ...

. They are distributed from

Mozambique Mozambique (), officially the Republic of Mozambique ( pt, Moçambique or , ; ny, Mozambiki; sw, Msumbiji; ts, Muzambhiki), is a country located in southeastern Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi ...

to the Red Sea, westward to Hawaii and

Clarion Island Isla Clarión, formerly called Santa Rosa, is the second largest, westernmost and most remote of Mexico's Revillagigedo Islands. The island is located west of Socorro Island and over from the Mexican mainland. It has an area of and three pr ...

, eastward to

Paumotu Tuamotuan, Paumotu or Paumotu (Tuamotuan: ' or ') is a Polynesian language spoken by 4,000 people in the Tuamotu archipelago, with an additional 2,000 speakers in Tahiti. The Tuamotu people today refer to their land as Tuamotu, while referring ...

, and as far south as Port Jackson. It also occurs at Shark Bay on the west coast of Australia and have been found in the waters of Governor's Harbor, Eleuthera Island, Bahamas. Mature collector urchins prefer open sea bottoms with some cover, but the young prefer rocky areas for concealment. Collector urchins inhabit depths of .

Relationship to humans

Collector urchins are economically important in some parts of the world. They are edible and sometimes exploited by humans; as a result, they have become less abundant. Over the past ten years, overexploitation has caused a sharp decline in the collector urchin population.

Removing invasive algae

Hawaii state aquatic biologists, working with divers from the Hawaii Division of Aquatic Resources placed 1,000 native collector urchins on a area of reef in Kaneohe Bay on January 29, 2011. The urchins were released to help control the invasive seaweed

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

'' Kappaphycus'', also known as "smothering seaweed," which has overrun local coral. Tripneustes gratilla stays on the reef and is an effective algae grazer. The urchins were bred at Anuenue Fisheries Research Center from about a million larvae. The larvae produced 25,000 specimens that reached at least in diameter in about five months. The delicate young had to be kept suspended in the water column for weeks after hatching. The project intends to release 10,000 to 25,000 urchins per month. Kaneohe Bay is the only barrier reef system in the United States. The alien seaweed was brought to Hawaii for commercial applications such as keeping ice chunks out of ice cream. It escaped when the industry failed. For years, the state used a marine vacuum pump to remove the algae, at one time removing . In 2009, the scientists gathered urchins from other parts of the state and released them at Kaneohe Bay. A year later, they found the urchins had successfully kept the seaweed down.

References

External links