Holothuria scabra

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. Sandfish share the basic body plan of most sea cucumbers.

Anatomy and morphology

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. Sandfish pass through six growth stages before adulthood.

Life cycle

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.