The soft "big guy" in the oceanSea cucumber belongs to the phylum Echinoderms, sea cucumber (holothuroidea), and sea urchin, starfish, sea lily is a distant relative, widely distributed in the temperate zone and tropical natural sea area of China. In the tropical natural sea area, the varieties of sea cucumber mainly include red-bellied sea cucumber, rough sea cucumber, ** sea cucumber, plum cucumber and so on. Tropical sea cucumber not only has many species, but also has large resources, which are mainly distributed in coastal areas such as Guangdong, Guangxi and Hainan in China, among which Xisha Islands, Nansha Islands and Hainan Island are the main production areas of tropical sea cucumbers in China.
When it comes to sea cucumbers, everyone seems to think of its deliciousness and efficacy. You're underestimating it!Sea cucumber is one of the longest-living animals in the world and is known as the "living fossil of the ocean". As early as 600 million years ago, sea cucumbers began to exist, and dinosaurs had to shout "big guy" when they saw it. Sea cucumbers have many "secrets" to survival, in addition to "doppelganger regeneration", distress "golden cicada shelling" and other skills, sea cucumbers will also hibernate in summer.
Sea cucumbers are notoriously afraid of heat, and when the surrounding water temperature rises above 20, they will hide under the reef in the deep sea and do not eat or move.
Three or four months. However, some tropical sea cucumbers have particularly unusual Xi, they are not as sensitive to heat as other sea cucumbers, but prefer "hibernation".
A red-bellied sea cucumber that hibernatesThe red-bellied sea cucumber (Holothuria edulis), "ginseng is as its name suggests", with a dark red "belly" and a purple-black "back", looks so deliberately that it looks like a burning charcoal fire, making people feel its "heat" as if they were there. However, scientific research has found that this big guy, who seems to be very "afraid of heat", does not sleep in summer, but hibernate in winter.
For example, the red-bellied sea cucumber "burned by charcoal" ** comes from the Internet.
Evidence 1: Decreased body weight
Bears are known to hibernate and their body weight decreases after hibernation, as is the case with tropical red-bellied sea cucumbers.
In the four seasons of spring (March), summer (June), autumn (September) and winter (December), the red-bellied sea cucumber (harvested from Sanya West Island in July 2019) was regularly dried with a towel, the wet mass was weighed, and the digestive tract tissue was sampled. The results showed that the wet weight of red-bellied sea cucumber increased in spring, summer and autumn, but decreased slightly in winter, and its growth was extremely slow. Stichopus japonicus is a typical summer hibernation animal, which is significantly "emaciated" in a summer state. And the red-bellied sea cucumber not only "grows fat" in summer, but also has a good "appetite" and eats vigorously, indicating that it will not sleep in summer. The changes in the relative wet mass of the digestive tract and the ratio of the length of the digestive tract to body length also showed that the low temperature in winter affected the feeding and state of the red bellied sea cucumber, and the intestinal tract of the cucumber changed in different seasons, but there was no serious atrophy and other degeneration. 
Changes in wet quality and digestive tract indexes of red-bellied sea cucumber in different seasons
Evidence 2: Morphological changes in digestive tract tissuesBy observing the morphological changes of the foregut of the digestive tract of the red-bellied sea cucumber, it was found that the apoptotic cavities were the least in summer, while the transverse folds of the intestinal wall structure of the digestive tract in winter showed more apoptotic cavities, and the intestinal wall cells showed severe apoptosis, and the columnar epithelium and serous layer became thinner. This change characteristic is similar to that of the summer hibernation of the sea cucumber, so it is preliminarily judged that the red-bellied sea cucumber has hibernation. 
Different seasons of red-bellied sea cucumber, digestive tract foregut transsection, HE stained sections, optical microscopy**.
Evidence 3: Changes in enzyme activity in the body
In addition to morphological changes, the activities of digestive enzymes and immune enzymes in the body of sea cucumber in the dormant state will also undergo significant changes, such as amylase, cellulase, superoxide dismutase (SOD), catalase (CAT), etc.
The study found that the digestive tract tissue of red-bellied sea cucumber had a high lysozyme activity in June, and showed a trend of "first rising and then decreasing" throughout the year, which further indicated that the red-bellied sea cucumber grew well in summer, and its digestive tract tissue secreted a large amount of lysozyme to digest the microorganisms brought in during feeding.
However, both pepsin and cellulase in its digestive tract tissues showed the highest activity in March, which may be due to the gradual resumption of feeding by sea cucumbers from hibernation in March. Amylase activity in the digestive tract has changed in line with the growth of the body, slowly increasing in the first 3 seasons and decreasing in winter due to the influence of ambient temperature (if you are interested in the change of immune enzyme indicators, please click "Read the original article" in the lower left). 
Changes in the activity of digestive enzymes in intestinal tissues of red-bellied sea cucumber in different seasons
Changes in immune enzyme activity in intestinal tissues of red-bellied sea cucumber in different seasons.
Epilogue.
In summary, the feeding of red-bellied sea cucumber was more vigorous in spring and summer, and the characteristics similar to that of summer hibernation of sea cucumber appeared in winter, such as decreased body weight, atrophy of digestive tract tissues, apoptosis and a large number of cavities, decreased thickness of transverse folds, and decreased density of columnar epithelium in intestinal wall structureMoreover, the activities of digestive enzymes and immune enzymes in the digestive tract were at low values in December, so it was judged that the red-bellied sea cucumber had hibernation.
Because sea cucumbers have the characteristics of summer hibernation or hibernation, there are them every year.
Three or four months in sleep, wild sea cucumber growth takes a very long time, some growth cycle in more than five years, this is one of the reasons for its high price, but also makes the sea cucumber justifiably become the first of the "eight treasures of ginseng wings". The next time you see a sea cucumber dish on the table, you may have to taste it with awe. Tan Chunming, Zhao Wang, Ma Zhenhua, Yu Gang*Seasonal changes of digestive tract indexes, histology and enzyme activities of red bellied sea cucumber[J].South China Fisheries Science, 2022, 18(5): 39-45
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Written by |Yang Jingru, Zhao Wang.
Edit |Zhang Liping.
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