Holothuria scabra, or the sandfish, is a species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 of sea cucumber

Sea cucumber

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. Sea cucumbers are found on the sea floor worldwide. There are a number of holothurian species and genera, many of which are targeted...

 in the family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 Holothuriidae

Holothuriidae

Holothuriidae is a family of sea cucumbers, a type of echinoderm.-Description:Members of the Holothuriidae family have thick fleshy bodies and several rows of tube feet which are used for moving around and for adhering to the surface. The body is often covered with blunt projections known as papillae...

. It was placed in the subgenus Metriatyla by Rowe in 1969 and is the type species

Type species

In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...

 of the subgenus. Sandfish are harvested and processed into "beche-de-mer"

Sea cucumber (food)

Sea cucumbers are marine animals of the class Holothuroidea used in fresh or dried form in various cuisines.The creature and the food product is commonly known as bêche-de-mer in French, trepang in Indonesian, namako in Japanese and in the Philippines it is called balatan...

 and eaten in China and other Pacific coastal communities.

Sea cucumbers are marine invertebrates and are closely related to sea urchin

Sea urchin

Sea urchins or urchins are small, spiny, globular animals which, with their close kin, such as sand dollars, constitute the class Echinoidea of the echinoderm phylum. They inhabit all oceans. Their shell, or "test", is round and spiny, typically from across. Common colors include black and dull...

s and starfish. All these groups tend to have radial symmetry and have a water vascular system that operates by hydrostatic pressure

Fluid statics

Fluid statics is the science of fluids at rest, and is a sub-field within fluid mechanics. The term usually refers to the mathematical treatment of the subject. It embraces the study of the conditions under which fluids are at rest in stable equilibrium...

, enabling them to move around by use of many suckers known as tube feet

Tube feet

Tube feet are the many small tubular projections found most famously on the oral face of a sea star's arms, but are characteristic of the water vascular system of the echinoderm phylum which also includes sea urchins, sand dollars and sea cucumbers and many other sea creatures.Tube feet function in...

. Sea cucumbers are usually leathery, gherkin-shaped animals with a cluster of feeding tentacles at one end surrounding the mouth.

Description

The sandfish is greyish-black on the upper side with dark-coloured wrinkles but paler on the underside. It grows up to four centimetres long, is broader than it is high and has a pliable skin. It is covered by calcareous spicule

Spicule

Spicules are tiny spike-like structures of diverse origin and function found in many organisms, such as the copulatory spicules of certain nematodes or the grains on the skin of some frogs.In sponges, spicules perform a structural function....

s in the form of tablets and buttons.

Distribution

This species is found in shallow water on soft sediments throughout the Indo-Pacific region.

Uses

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. Harvesting sandfish from the sea is known as trepanging

Trepanging

Trepanging is the Anglicisation of the act of collection or harvesting of sea cucumbers, known in Indonesian, as "trepang".The collector or fisher of trepang is coined a trepanger....

 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.

Hatchery rearing

Sandfish stocks are being increased in some areas by being bred in tanks at hatcheries. Spawning

Spawn (biology)

Spawn refers to the eggs and sperm released or deposited, usually into water, by aquatic animals. As a verb, spawn refers to the process of releasing the eggs and sperm, also called spawning...

 is induced by temperature shock and the fertilised eggs incubated for a day. The auricularian larvae that hatch from the eggs are fed on microalgae for nine days after which time they develop into doliolarian larvae. These are fed on diatom

Diatom

Diatoms are a major group of algae, and are one of the most common types of phytoplankton. Most diatoms are unicellular, although they can exist as colonies in the shape of filaments or ribbons , fans , zigzags , or stellate colonies . Diatoms are producers within the food chain...

s and after five days settle as pentactular larvae onto diatom-coated plates. Juveniles are grown on in tanks and may reach one to two centimetres in three months. They are then moved to larger ponds for a few months before being released into suitable habitats for ranching or restocking.