How sea cucumber (Apostichopus japonicus) reproduces and how it differs from other sea cucumbers

Apostichopus japonicus grows in deep-sea areas free of pollution. Because of natural environmental factors and the influence of tides, its harvest is seasonal to a certain extent, and sea cucumbers that have not grown for enough years are generally not harvested. This is also why Apostichopus japonicus has thick, plump flesh, a good chewy texture, a large amount of accumulated active substances in its body, and high nutritional value. So how does Apostichopus japonicus reproduce? Where is the difference from other sea cucumbers?

1. How does Apostichopus japonicus reproduce?

(1) Hatching

(1) Hatching in hatching tanks

The density for hatching in hatching tanks is generally 100 per milliliter to 200 per milliliter. During hatching, the hatching water is stirred at regular intervals or aerated to keep the eggs suspended. Once the eggs develop to the blastula stage, they are moved to rearing ponds at a density of 0.5 per milliliter to continue cultivation.

(2) Hatching in rearing ponds

Fertilized eggs are moved into rearing ponds at a density of 1 per milliliter to 2 per milliliter. Because the eggs have relatively low density, they can usually be hatched in still water.

(2) Artificial insemination

(1) Spawning and insemination in spawning boxes

Spawning boxes are mostly made from 0.1-liter to 0.5-liter plastic or fiberglass tanks. Before spawning, the tanks are first filled with seawater at the same temperature as the water in the broodstock holding pond or stimulation pond. Generally two spawning boxes are prepared, one for female sea cucumbers to release eggs and the other for male sea cucumbers to release sperm. When broodstock show signs of spawning or sperm release, they are promptly transferred into the spawning boxes; be careful to handle them gently so as not to affect the number of eggs spawned. Because the eggs of Apostichopus japonicus are sinking eggs, the water in the box must be continuously stirred or lightly aerated during spawning to prevent the eggs from being affected in their development due to lack of oxygen. At the same time as spawning, semen should also be added promptly, and it is best to use mixed semen from multiple male sea cucumbers. The density of eggs in the spawning box is generally controlled within 200 per milliliter to 500 per milliliter. Once this density is exceeded, the eggs should promptly be transferred to hatching ponds or rearing ponds for hatching and cultivation. This method allows artificial control of the amount of semen added, avoids polyspermy, and can greatly reduce the deformity rate of larvae.

(2) Spawning and insemination in ponds

This method lets the broodstock spawn and release sperm directly in the holding pond or rearing pond, and then the eggs are moved into a hatching pond or hatched in the original pond. Generally, males release before females, so the males are allowed to release in the pond for a while first, so that a certain sperm density in the pond induces the females to spawn. After females begin to spawn, the males are removed from the pond, allowing the females to spawn and be fertilized in the pond. Because the amount of sperm is difficult to control with this method, it is prone to excessive semen and thus an excessively high deformity rate.

2. Where is the difference between Apostichopus japonicus and other sea cucumbers?

1. Apostichopus japonicus: sea cucumbers with fleshy spines on their backs are called Apostichopus japonicus.

2. Sea cucumber: this includes both spiny sea cucumbers and smooth sea cucumbers; smooth sea cucumbers are those without fleshy spines.

So sea cucumber is only a general term, and everyone should distinguish this clearly: Apostichopus japonicus can also be called a sea cucumber, and smooth sea cucumbers can also be called sea cucumbers. Farmed sea cucumbers can also be called sea cucumbers.