The body is cylindrical, with a length of 11 ~ 21cm, and the extra-large body can reach 31cm. The color is usually dark black and full of prickles. Tentacles are wheel-shaped, 17 ~ 31, about 21. Touch and hand are well developed.

Most sea cucumbers have bone fragments, such as table, button, rod, perforated plate, pattern, wheel, anchor and cage. The number varies, an ugly sea cucumber has about 21 million bone pieces, while the sweet potato sometimes has no bone pieces at all; Stichopus japonicus with more bone pieces feels rough, while those with less bone pieces are smooth; Bone fragment is a kind of single caries endoskeleton, which is a smaller bone plate.

The unique organ of sea cucumber is the lime ring, which plays the role of supporting the pharynx, nerve ring and circular water pipe. Generally, it consists of 5 spokes and 5 intermediate spokes; The lime ring of some cladocera sea cucumbers is inlaid with many small pieces, and each spoke extends backwards in a fork shape. Generally, there are more than 111 lime rings without sufficient purpose.

The sea cucumber has a gonad, which is located on one side or both sides of the mesentery, and a main duct opens between the tentacles of the dorsal midline or later. The "coral mussels" sold in the seafood market are actually the edible parts left after these intestines are cleaned, and they are one of the materials when eating hot pot.

Extended information:

1. Living habits

When the water temperature reaches 21℃, Stichopus japonicus will move to the crevices of rocks in the deep sea or hide at the bottom of rocks, and it will not eat or move, and the whole body will shrink and harden like a thorn ball. Ordinary animals don't eat it. It is a summer when it sleeps, and it will not wake up until after autumn to resume its activities.

2. Growth and Reproduction

In order to ensure that the race will not be extinct, in the long-term evolution process of natural selection, sea cucumber has super reproductive ability. An adult sea cucumber over 4 years old can ovulate about 5 million pieces at a time during the spring breeding period. In this way, even if there is a survival rate of one in ten thousand, the continuation of the race can be guaranteed.

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