Holothuria scabra
Sandfish is the most harvested sea cucumber for beche-de-mer.
**Holothuria scabra**, better known as the sandfish, is a type of sea cucumber belonging to the family Holothuriidae. It serves as the type species for the subgenus *Metriatyla*, a classification established by Rowe in 1969. This sea cucumber is the most commonly harvested species for human consumption, typically dried into a product called beche-de-mer, which is eaten in China and various Pacific coastal communities.
**Anatomy and morphology** Sandfish share the basic body plan of most sea cucumbers. Their bodies are elongated, cylindrical, and somewhat stubby. The dorsal side ranges from grey-brown to black, marked by dark wrinkles and small black papillae running the length of the body. The ventral side is lighter, relatively flat, and countershaded. The mouth sits on the ventral surface at one end—considered the front—and is surrounded by about 20 short feeding tentacles. The anus is located on the dorsal side at the opposite end. Adults average 22 cm in length, with the largest reaching up to 40 cm. They reach maturity at about 16 cm or 200 grams, and some individuals can grow as much as 300 grams in a single year. Their lifespan is unknown, but they can live at least 10 years. The gonads exit through a single genital opening on the dorsal anterior end. The digestive system consists of a mouth, esophagus, stomach, intestine, cloaca, and anus. Respiratory trees extend from the cloaca for breathing. The thick body wall accounts for 56% of the animal’s weight and contains calcareous spicules—table-shaped and knobbed button forms—used to identify the species. Like other sea cucumbers, sandfish can eviscerate their internal organs under stress and regenerate them, a process that takes about two months.
**Life cycle** Sandfish pass through six growth stages before adulthood. After adults spawn, fertilized eggs develop into a gastrula within a day, then into an auricularia—a feeding planktonic stage—after two days. Over the next 14 days, they progress through a non-feeding doliolaria stage and a final planktonic pentactula stage before becoming juveniles that settle into seagrass meadows to mature.
**Ecology** *Distribution*: Sandfish are found across the Indo-Pacific, from east Africa to the eastern Pacific, including the Persian Gulf and Iran. They are a tropical species, typically restricted to latitudes between 30° N and 30° S.
Quick Facts
- Taxon
- Holothuria scabra
Facts from the source article.
Lore & Background
The sandfish has the same basic anatomy as most sea cucumbers: an elongated, cylindric, stubby body with a grey-brown to black dorsal side marked by darkened wrinkles and small black papillae, and a lighter, flat ventral side. Its mouth is on the ventral surface at the front end, surrounded by about 20 short feeding tentacles, while the anus is on the dorsal side. The body wall is thick, comprising 56% of its weight, and contains calcareous spicules—table and knobbed button shapes—used for species identification. Like other sea cucumbers, it can eviscerate its internal organs under stress and regenerate them over about two months.
The sandfish undergoes six growth stages: spawning, then after one day a gastrula, after two days an auricularia (feeding planktonic stage), within 14 days a non-feeding doliolaria and a pentactula, before settling as juveniles in seagrass meadows. It inhabits shallow tropical waters less than 20 meters deep, preferring seagrass meadows and muddy substrata with high nutrients, and tolerates salinity as low as 20 ppt. It is a bioturbator that reworks sediment and eats detritus and microorganisms. Younger sandfish burrow in response to light changes, emerging in darkness; older ones burrow to escape cold. Males and females exhibit distinct spawning behaviors: males erect and sway while releasing sperm, then females erect and forcefully expel eggs.
Reader's Guide
The sandfish has been eaten by humans for over 1000 years and is the species most often used among about twenty consumed sea cucumbers. In the 1990s, dried beche-de-mer sold for up to US$100 per kilogram. Harvesting, known as trepanging in Indonesia, has led to fishery declines due to overfishing, prompting ranching, aquaculture, and hatchery rearing. The species is listed as endangered by the IUCN Red List, with populations declining, but efforts such as fishery bans and restocking via aquaculture are underway across the Indo-Pacific.
In aquaculture, sandfish is one of the only tropical holothurian species that flourishes, valued for food and habitat restocking. Broodstock are gathered from wild stocks; spawning can occur year-round near the equator, with peak season from August to November. Spawning is induced by thermal stimulation, dry treatment (30–45 minutes out of water), food stimulant (concentrated algae), or gonad extraction, often combined. Larvae require careful monitoring, and juveniles are moved to growout tanks at 200–500 individuals per square meter. The species is also used in cocultures with black tiger prawn, red seaweed, and blue shrimp. The worm pearlfish (Encheliophis vermicularis) parasitizes it, with a male and female pair living inside its body.
Did You Know?
- They are identified by table and knobbed button shapes in their calcareous spicules.
- Spawning is closely related to the lunar cycle and occurs in the afternoon to early evening.
- The worm pearlfish (Encheliophis vermicularis) lives as a parasite inside Holothuria scabra as a male-female pair.
Frequently Asked Questions
What is Holothuria scabra?
Holothuria scabra, widely known as the sandfish, is a cylindrical sea cucumber in the family Holothuriidae. It also serves as the type species for the subgenus Metriatyla, a taxonomic grouping established by Rowe in 1969.
How big does a sandfish get and how fast does it grow?
Adults average around 22 cm in length, with a maximum of roughly 40 cm, and are considered mature at about 16 cm or 200 grams. A single sandfish can add up to 300 grams of body mass within one year.
Why is Holothuria scabra so heavily harvested?
It is the most commonly collected sea cucumber species for human consumption, typically dried and sold as beche-de-mer. This product is a valued delicacy in Chinese cuisine and across numerous Pacific coastal communities.
How long can a sandfish live?
Sandfish are long-lived invertebrates, surviving at least ten years in the wild. Their body wall makes up roughly 56 percent of total body weight, giving them a notably thick, stubby build.
What does a sandfish look like?
It has an elongated, cylindrical body that is somewhat stubby, sharing the general body plan seen in most sea cucumbers. The dorsal surface shows a range of coloration, and the overall form is well adapted to its sandy coastal habitat.
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