''Tripneustes gratilla'', the collector 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 ...

. Collector urchins are found at depths of in the waters of the

Indo-Pacific The Indo-Pacific is a vast biogeographic region of Earth. In a narrow sense, sometimes known as the Indo-West Pacific or Indo-Pacific Asia, it comprises the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the ...

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 stat ...

, 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''; T ...

, 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 Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...

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 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 ...

. 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 ''Thalassodendron ciliatum'', the sickle-leaved cymodocea, is a species of plant in the ''Thalassodendron'' genus of seagrasses in the family Cymodoceaceae. Distribution ''Thalassodendron ciliatum'' has a wide distribution throughout the Indo-Pa ...

'' 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, swellfis ...

octopus An octopus ( : octopuses or octopodes, see below for variants) is a soft-bodied, eight- limbed mollusc of the order Octopoda (, ). The order consists of some 300 species and is grouped within the class Cephalopoda with squids, cuttle ...

es, and humans. T. gratilla collector.jpg, ''Tripneustes gratilla'' covering itself with rocks (

Réunion Réunion (; french: La Réunion, ; previously ''Île Bourbon''; rcf, label= Reunionese Creole, La Rényon) is an island in the Indian Ocean that is an overseas department and region of France. It is located approximately east of the island ...

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

, 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 Atlantic Ocean, North Atlantic. It takes up 97% of the Lucayan Archipelago's land area and is home to ...

. 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 Port Jackson, consisting of the waters of Sydney Harbour, Middle Harbour, North Harbour and the Lane Cove and Parramatta Rivers, is the ria or natural harbour of Sydney, New South Wales, Australia. The harbour is an inlet of the Tasman Sea (p ...

. It also occurs at

Shark Bay Shark Bay (Malgana: ''Gathaagudu'', "two waters") is a World Heritage Site in the Gascoyne region of Western Australia. The http://www.environment.gov.au/heritage/places/world/shark-bay area is located approximately north of Perth, on the ...

on the west coast of

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

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 Overexploitation, also called overharvesting, refers to harvesting a renewable resource to the point of diminishing returns. Continued overexploitation can lead to the destruction of the resource, as it will be unable to replenish. The term app ...

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 Kāneohe () is a census-designated place (CDP) included in the City and County of Honolulu and located in Hawaii state District of Koolaupoko on the island of Oahu. In the Hawaiian language, ''kāne ohe'' means "bamboo man". According to an a ...

on January 29, 2011. The urchins were released to help control the invasive

seaweed Seaweed, or macroalgae, refers to thousands of species of macroscopic, multicellular, marine algae. The term includes some types of '' Rhodophyta'' (red), ''Phaeophyta'' (brown) and ''Chlorophyta'' (green) macroalgae. Seaweed species such as ...

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

Kappaphycus ''Kappaphycus'' is a genus of red algae. Species are distributed in the waters of East Africa, Indonesia, Malaysia, Hainan Island, the Philippines, and Micronesia.Guiry, M. D. In: Guiry, M. D. & G. M. Guiry. 2013''Kappaphycus''.AlgaeBase. Nationa ...

'', also known as "smothering seaweed," which has overrun local

coral Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and sec ...

. 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 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 ...

. 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 A water column is a conceptual column of water from the surface of a sea, river or lake to the bottom sediment.Munson, B.H., Axler, R., Hagley C., Host G., Merrick G., Richards C. (2004).Glossary. ''Water on the Web''. University of Minnesota-D ...

for weeks after hatching. The project intends to release 10,000 to 25,000 urchins per month. Kaneohe Bay is the only

barrier reef A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in groups. Co ...

system in the United States. The alien seaweed was brought to Hawaii for commercial applications such as keeping ice chunks out of

ice cream Ice cream is a sweetened frozen food typically eaten as a snack or dessert. It may be made from milk or cream and is flavoured with a sweetener, either sugar or an alternative, and a spice, such as cocoa or vanilla, or with fruit such as str ...

. 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