Holothuria scabra | |
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Echinodermata |
Class: | Holothuroidea |
Order: | Holothuriida |
Family: | Holothuriidae |
Genus: | Holothuria |
Species: | H. scabra |
Binomial name | |
Holothuria scabra | |
Synonyms | |
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Holothuria scabra, or sandfish, is a species of sea cucumber in the family Holothuriidae. It was placed in the subgenus Metriatyla by Rowe in 1969 and is the type species of the subgenus. [4] Sandfish are harvested and processed into "beche-de-mer" and eaten in China and other Pacific coastal communities.
Sea cucumbers are marine invertebrates and are closely related to sea urchins and starfish. All these groups tend to have radial symmetry and have a water vascular system that operates by hydrostatic pressure, enabling them to move around by use of many suckers known as tube feet. Sea cucumbers are usually leathery, gherkin-shaped animals with a cluster of feeding tentacles at one end surrounding the mouth.
The sandfish has the same basic anatomy as most other species of sea cucumber. Their bodies are elongated and cylindric, and relatively stubby. Their dorsal side can range in color from a grey-brown to black, with darkened wrinkles across the body and small black papillae from end to end. They are counter shaded with a lighter ventral side, which is relatively flat. They have a mouth located on the ventral surface at one end of the body, considered the front end. Like other sea cucumbers, they use feeding tentacles which protrude from the mouth. Sandfish have around 20 short tentacles. On the opposite end the anus is found on the dorsal side. [5] They can grow up to an average length of 22 cm with the largest reaching up to 40 cm, and reach maturity around 16 cm or 200 grams with some growing as much as 300 grams in one year. [5] [6] It is unknown how long they live undisturbed, but they can live to at least 10 years. [5]
Their gonads are found through a single genital orifice on their dorsal anterior end. Their digestive system is made up of a mouth, an esophagus, a stomach, an intestine, a cloaca, and an anus. They extend respiratory trees from their cloaca in order to breathe. Their body wall is thick, making up a total of 56% of their weight. [5] This body wall is filled with calcareous plates called spicules, and are used to ID species; the sandfish is identified by table and knobbed button shapes. [5] Like other sea cucumbers, they can eviscerate their internal organs if they undergo stress, and can regenerate their organs; in sandfish this takes about 2 months. [5]
The sandfish goes through 6 stages of growth before maturing into an adult. This starts when the adults spawn. After a day the fertilized eggs develop into a first planktonic phase, a gastrula, then after two days it becomes an auricularia, the feeding planktonic stage. Within the next 14 days the sandfish will enter a non-feeding doliolaria stage and a final planktonic pentactula stage, before becoming juveniles and settling into the sea grass meadows to mature. [5]
The species can be found in the Indo-Pacific region, from east Africa to the eastern Pacific. Some have been found in the Persian Gulf, Iran. [7] They are typically restricted to latitudes between 30° N to 30° S, due to it being a tropical species.
The sandfish inhabits shallow tropical waters, <20 m deep. They prefer seagrass meadows and muddy bottomed substrata with high nutrient levels due to their diet preference. They do have a tolerance for lowered salinity, down to 20 ppt, such as that found in brackish water. [5] Sandfish play a key role in the health of their habitat; like most sea cucumbers H. scabra are bioturbators and play a key role in reworking the sediment and ensuring that organic matter is evenly distributed for the ecosystem to function, and have a subsequent diet of detritus and other microorganisms. [8] [9] [10]
The sandfish exhibits some distinct behaviors. Their burrowing behavior varies as they mature, with younger sandfish responding to changes in light and coming out in darkness. Older sandfish are more sensitive to changes in temperature and will burrow to escape the cold. Sandfish are particular about sediment size and type, settling in fine sand and muddy substrates high in nutrients. [11] Like all sea cumbers, H. scabra exhibits defensive vomiting, where they expel their internal organs to distract predators while they escape. Male and females have distinct mating behaviors; when they spawn males erect their bodies and sway from side to side as they release sperm into the surrounding water. Shortly after, females will erect their bodies and send eggs into the water with the sperm in a short, forceful burst. [5] [12]
The sandfish has been eaten by man for over 1000 years. About twenty other species of sea cucumber are also consumed but the sandfish is the species most often used. In the 1990s it was being sold dried as beche-de-mer for up to US$100 per kilogram. [13] Harvesting sandfish from the sea is known as trepanging in Indonesia. In many areas the fisheries have declined over the years because of over fishing, so ranching, aquaculture and hatchery rearing are being attempted. [13]
The sandfish has a high value in Asian markets where they are sold as beche-de-mer for food. This makes them a key species for aquaculture production, where the species flourishes; one of the only tropical holothurian species to do so. [14] They are also valuable in aquaculture for habitat restocking; juveniles are often grown in tanks and released into the wild with hopes of restocking the wild population and causing a spillover effect in protected areas. [15] Broodstock is the population of adults that will be used for reproduction. These are gathered from wild stocks and since the sandfish is found in environments close to the equator, they can spawn year round. Peak season for spawning though is typically during the dry seasons, August to November. [16] Approximately 30–45 adult sandfish are required to start a small batch of spawning individuals. [17] Spawning for H. scabra is closely related to the lunar cycle, and will occur in the afternoon to early evening. [16] Spawning can be induced using several methods: thermal stimulation involves increasing and decreasing water temperatures rapidly, dry treatment involves leaving the sandfish out of the water for 30–45 minutes before being returned to the tanks, and the food stimulant method involves providing a highly concentrated amount of algae to the water to overfeed the sandfish. Gonad extraction is also an option but requires the dissection of the animal. It is common in most aquaculture facilities to use a combination of the listed methods, in order to ensure spawning. [17] The sandfish larvae are closely monitored in order to ensure survival, as they are temperamental and require specific conditions for success. Once the larvae develop into juveniles they must be moved into growout tanks, at a density of 200-500 individuals per square meter to ensure that each one is receiving proper space to grow and the required nutrients. [18]
Due to its hardy nature, the sandfish is a good species for cocultures with other species. They are able to reuse waste material from other organisms and make nutrients usable. [19] The following species have been kept in tanks with H. scabra:
The worm pearlfish (Encheliophis vermicularis) is a parasite of this species and each parasitised Holothuria scabra will host a male and female pair of the fish which live inside its body. [24]
The sandfish is listed as an endangered with populations declining by the IUCN Red List. They face threats from over harvesting, but efforts are currently being taken around the Indo-Pacific including bans on the fishery and restocking via aquaculture efforts. [1]
Sea cucumbers are echinoderms from the class Holothuroidea. They are marine animals with a leathery skin and an elongated body containing a single, branched gonad. They are found on the sea floor worldwide. The number of known holothurian species worldwide is about 1,786, with the greatest number being in the Asia-Pacific region. Many of these are gathered for human consumption and some species are cultivated in aquaculture systems. The harvested product is variously referred to as trepang, namako, bêche-de-mer, or balate. Sea cucumbers serve a useful role in the marine ecosystem as they help recycle nutrients, breaking down detritus and other organic matter, after which bacteria can continue the decomposition process.
Sea cucumbers are marine animals of the class Holothuroidea. They can be used as food, in fresh or dried form, in various cuisines. In some cultural contexts the sea cucumber is thought to have medicinal value.
Holothuria atra, commonly known as the black sea cucumber or lollyfish, is a species of marine invertebrate in the family Holothuriidae. It was placed in the subgenus Halodeima by Pearson in 1914, making its full scientific name Holothuria (Halodeima) atra. It is the type species of the subgenus.
Holothuria mexicana, the donkey dung sea cucumber, is commonly found in the Caribbean and the Azores. It is a commercially important aspidochirote sea cucumber that can reach a total length of 50 cm (20 in).
Australostichopus is a genus of sea cucumbers in the family Stichopodidae. It is monotypic, being represented by the single species Australostichopus mollis, commonly known as the brown sea cucumber or Australasian sea cucumber. This species has stimulated interest for its fishery potential in the Southern Hemisphere, and for its capability to reduce waste produced by aquaculture. Despite its ecological role and abundance in New Zealand coastal waters, the scarcity of knowledge regarding A. mollis biology and ecology has hindered the development of a stable fishery industry. Importantly, A. mollis represents promising business potential within an important Asian market. Recently its potential as a functional food has been evaluated, highlighting the nutritious components
Sea cucumber stocks have been overexploited in the wild, resulting in incentives to grow them by aquaculture. Aquaculture means the sea cucumbers are farmed in contained areas where they can be cultured in a controlled manner. In China, sea cucumbers are cultured, along with prawns and some fish species, in integrated multi-trophic systems. In these systems, the sea cucumbers feed on the waste and feces from the other species. In this manner, what would otherwise be polluting byproducts from the culture of the other species become a valuable resource that is turned into a marketable product.
Holothuria tubulosa, the cotton-spinner or tubular sea cucumber, is a species of sea cucumber in the family Holothuriidae. It is the type species of the genus Holothuria and is placed in the subgenus Holothuria, making its full name Holothuria (Holothuria) tubulosa.
Bohadschia marmorata, commonly known as the brown sandfish or chalky cucumber, is a species of sea cucumber in the family Holothuriidae. It lives on the seabed in shallow waters in the Indo-Pacific region.
Holothuria spinifera, the brown sandfish, is a species of sea cucumber in the family Holothuriidae. It is placed in the subgenus Theelothuria, making its full name Holothuria (Theelothuria) spinifera. In India it is known as cheena attai or raja attai. It lives in tropical regions of the west Indo-Pacific Ocean at depths ranging from 32 to 60 metres. It is fished commercially to produce beche-de-mer.
Holothuria parvula, the golden sea cucumber, is a species of echinoderm in the class Holothuroidea. It was first described by Emil Selenka in 1867 and has since been placed in the subgenus Platyperona, making its full scientific name Holothuria (Platyperona) parvula. It is found in shallow areas of the Caribbean Sea and Gulf of Mexico and is unusual among sea cucumbers in that it can reproduce by breaking in half.
Holothuria edulis, commonly known as the edible sea cucumber or the pink and black sea cucumber, is a species of echinoderm in the family Holothuriidae. It was placed in the subgenus Halodeima by Pearson in 1914, making its full scientific name Holothuria (Halodeima) edulis. It is found in shallow water in the tropical Indo-Pacific Ocean.
Actinopyga caerulea, the blue sea cucumber, is a species of sea cucumber in the family Holothuriidae. Named for its unique blue coloration, this species can be found along the continental shelf of the tropical Western Indo-Pacific region, at depths between 12 and 45 m. It is a commercially important species, and is harvested for food along its range.
Actinopyga lecanora, commonly known as the white-bottomed sea cucumber or stonefish, is a species of sea cucumber in the family Holothuriidae. It is native to the tropical Western Indo-Pacific region and is harvested for food.
Holothuria grisea, the gray sea cucumber, is a mid-sized coastal species of sea cucumber found in shallow tropical waters of the Atlantic Ocean from Florida to Southern Brazil and West Africa. They have a variety in color and can range from red to more yellowish with brown markings. They are also a food source for local and international markets with the majority of harvesting taking place in Brazil. This species is currently not over-fished and is not endangered or threatened.
Actinopyga varians, the Pacific white-spotted sea cucumber or Hawaiian sea cucumber, is a species of sea cucumber in the family Holothuriidae. It is found in the Pacific Ocean near Hawaii and also in the Indo-Pacific Ocean.
Holothuria pervicax is a species of sea cucumber in the genus Holothuria. It is commonly called the stubborn sea cucumber due to its inability to be kept alive in captivity. It is commonly found buried beneath rocks on reefs in warm waters.
Holothuria stellati, also known as the Brown sea cucumber,is a species of sea cucumber in the family Holothuriidae. First described by Delle Chiaje in 1824. There are two accepted subspecies, Holothuria stellatidakarensis and Holothuria stellati mammata, though there is still debate on whether or not they are separate species.
Holothuria (Cystipus) cubana is a species of sea cucumber in the family Holothuriidae. This species was first described by Ludwig in 1875.
Holothuria (Microthele) whitmaei, commonly known as the black teatfish, is a species of sea cucumber in the family Holothuriidae. The sea cucumber is distributed in the western Indian and Pacific oceans, with specimens being found off of Tanzania, New Caledonia and the Philippines. They are usually found in groups of 5-25 individuals.
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