Holothuroidea | Sea Cucumber
LATIN NAME: Holothuroidea
COMMON NAME: Sea Cucumber
Species Profile
A sea cucumber is an echinoderm, closer to a sea urchin than to anything eaten with a shell, and it lies on the seabed on five rows of tube feet. The body is leathery and muscular, with a ring of tentacles around the mouth that it uses to shovel sediment, and the species sold as hai shen range from a hand’s length to half a metre. The dried product is dark, wrinkled and hard, and it looks nothing like the animal it came from.
The trade is built on about twenty species, of which the Japanese spiky cucumber and the sandfish are the most valuable. They are collected by hand, by diving or by wading at low tide, and the gut is removed and the body boiled and dried before sale. In Chinese cooking the dried body is rehydrated over several days and braised, and the texture rather than the flavour is the point.
Science & Biotechnology
The body wall is almost pure collagen, held in a mutable state that lets the animal stiffen or soften within seconds. That behaviour, called catch connective tissue, is controlled by the nervous system changing the bonds between collagen fibrils, and it is why a sea cucumber can pour itself through a narrow gap and then set hard. The same property is why the dried product rehydrates into a firm, gelatinous sheet.
The animal also contains saponins, called holothurins, which are toxic to fish and to many invertebrates and serve as a chemical defence. They are the reason the body wall must be boiled and soaked before eating, and the reason sea cucumbers are not eaten raw. A sulfated polysaccharide in the body wall, fucosylated chondroitin sulfate, has been studied as an anticoagulant, and it is structurally different from the heparin used in medicine.
Uses & Benefits
In Chinese food the dried body is a prestige ingredient, served braised with scallion and soy, or in a soup at banquets. It is valued for texture and for the belief that it strengthens the body, and it is one of the four sea delicacies alongside abalone, shark fin and fish maw.
In traditional medicine it is used as a tonic for the kidney and for weakness after illness, usually in a soup with chicken or with pork. There is no controlled trial to support these uses, and the marketing claims made for sea cucumber supplements run well ahead of the evidence. The collagen is nutritionally ordinary once digested; it is not a source of intact collagen for the skin.
Source & Harvest
Most of the trade is wild-caught, and that is the problem. Sea cucumbers are slow-growing and late to breed, and stocks near the main markets in China, Japan and Korea were fished down decades ago. Collection has moved to the Pacific islands, to East Africa and to Latin America, and in several places the fishery collapsed within a few years of opening.
Processing is done near the point of landing. The animal is slit, the gut and the respiratory tree removed, the body boiled in seawater, then smoked or sun-dried on racks until it is hard. Quality is judged by the thickness of the body wall and by how evenly it rehydrates, and a batch that has been dried too fast cracks along the back. Aquaculture now supplies a share of the market, mostly in China and Madagascar, but it depends on wild brood stock and on a supply of clean sediment.
Farming is possible but not simple. Hatcheries induce spawning by raising the water temperature, rear the larvae through several plankton-feeding stages, and settle the juveniles on plates of biofilm before moving them to ponds or to sea pens. The animals then graze on sediment and on added seaweed and fish waste, and they take two to four years to reach market size.
Sea ranching, where juveniles are released into a managed lagoon and harvested later, is the approach used in Madagascar and in parts of the Pacific. It works where the habitat is intact and where the community controls access. It fails where the released animals are collected by anyone who finds them, which is the usual outcome without a clear tenure arrangement.
Our Take
A slow-breeding animal under heavy fishing pressure, sold on texture and on claims that outrun the evidence. Buy from a supplier who can name the species and the fishery.
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