Do you still remember the stalk between the national football team and sea cucumbers?In the 2022 World Cup preliminaries, the national football team lost to the Vietnamese team, and then the team members said in an interview that they basically eat sea cucumbers every day, eat two sticks when they are tired, and usually eat one ......Losing the game said sea cucumber, sea cucumber is bitter: you lose, what does it matter to me?To say that sea cucumbers are indeed wronged. Sea cucumber has been a good nourishing product since ancient times, and is listed as the first of the "Eight Treasures of the Sea" because of its comprehensive nutritional value and unique medicinal value. The Ming Dynasty's "Five Miscellaneous Warriors" recorded: its sexual warmth is replenished, enough enemy ginseng, so it is called sea cucumber. Modern studies have shown that sea cucumber has high nutritional value and medicinal value, rich in amino acids, fatty acids, vitamins and polysaccharides, saponins, collagen and cerebroside esters and other active substances, with antioxidant, anti-tumor, anticoagulant and regulate immunity and other physiological effects. In the global consumption of sea cucumbers, tropical sea cucumbers dominate, accounting for more than eighty percent of their consumption. **Sea cucumber is a common tropical sea cucumber species in China, which has been artificially bred in 2013, but the high mortality rate from the development of planktonic larvae to the stage of attached seedlings is a common problem in tropical sea cucumber breeding, and the growth regulation mechanism behind it is still unclear. What are the characteristics of sea cucumbers, why do you want to breed them when breeding square snails, and what breakthroughs have been made in the artificial breeding of sea cucumbers?Let's find out. A tropical sea cucumber that "spouts white silk".**Sea cucumber (Holothuria leucoisplota) belongs to the phylum Echinoderms, sea cucumbers, sea cucumbers, sea cucumbers, sea cucumbers, sea cucumbers, also known as cucumbers, black cucumbers, red ginseng, etc., and has certain economic value. It is one of the most common sea cucumber species in the South China Sea, which has the characteristics of short growth cycle and high yield.
*Sea cucumbers are named for the jade-like color and texture of their legs. Although its name is soft and charming, its appearance is not good-looking. Its body is generally black or purplish-brown, cylindrical in shape, the posterior part is thicker than the anterior, and the individual is larger, and the ginseng can grow to more than 20 cm. Its mouth is ventral, and the ventral surface is scattered with a large number of milky protruding tube feet and irregular arrangement. The whole body looks furry.
** sea cucumber that is producing sperm.
*The Cuvignette of sea cucumber is very well developed. When threatened by predators, it will spew filamentous tubules from ** and stick around predators. These filamentous tubules are Cuviers, an organ of sea cucumber with a special smell and toxin, and a strong stickiness that allows it to avoid predation.
*Sea cucumber spits out Cuvi's device to defend against predators **From the Internet.
Sea cucumbers also have a life-saving stunt - draining internal organs. Compared with other sea cucumbers, sea cucumbers are more likely to remove internal organs. When the environment is uncomfortable or encounters predators and dangers, its body will contract violently, and then the entire internal organs will be spewed out to attract predators and take the opportunity to escape. The amazing thing is that without the internal organs, the ** sea cucumber will not die, and after a while it will grow new internal organs, this regenerative ability is really invincible!
Silent "seabed scavenger".In the marine coral reef ecosystem, sea cucumber is the "seabed scavenger", the silent guardian of the marine ecological environment, and plays an important role in the production of benthic communities and the process of ammonia salt cycle in coral reefs.
Sea cucumber lives on the seafloor and feeds mainly on marine microalgae, benthic detrital organic matter, etc., and since it has no chewing organs, it needs to swallow a lot of sand and broken shells to help digestion. The excrement of sea cucumber is mainly fine sand, but do not underestimate these excrements, it contains nutrients such as ammonia, nitrogen, calcium carbonate, etc., which is not only an important nutrient for coral reefs, but also helps the growth of coral bones, but also neutralizes the acidic substances in the seawater, making the environment more suitable for the survival of marine organisms. Where there are sea cucumbers, seagrass beds will also grow more luxuriantly.
Using the function of sea cucumber "scavenger", people will polyculture ** sea cucumber to improve the substrate and polyculture seaweed to improve water quality when cultivating babylonia areolata, which significantly improves the survival rate.
*Schematic diagram of sea cucumber promoting ammonia nitrogen cycling in benthic environment Editorial Department However, tropical sea cucumbers generally grow slowly and take a long time to mature sexually, which determines that the replenishment cycle of new individuals in their populations is longer. In recent years, overfishing has led to the destruction of sea cucumber population resources, the purification of coral reef ecosystems and the impaired function of material cycling, which in turn has led to the aggravation of the degradation of coral reef ecosystem functions. In particular, after years of disorderly fishing, sea cucumber resources have been depleted, posing a serious threat to the homeostasis of coral reef ecosystem functions in the South China Sea.
Therefore, large-scale bottom-sowing of ** sea cucumber seedlings in the seabed area will contribute to the restoration of eutrophication tidal flats and benthic ecological environment. In the construction of modern marine ranches, sea cucumbers have great potential for bottom sowing and breeding.
* Sea cucumber bottom seeding culture and cage culture**New exploration of artificial breeding of sea cucumbersAt present, only the northern imitation of the stinging cucumber (Apostichopus spp.) in China) has achieved large-scale breeding, although a variety of tropical sea cucumbers have achieved artificial breeding success, such as rough sea cucumber (h.).scabra), *sea cucumber, red-bellied sea cucumber (h.).edulis) and so on, but the key problems have not been solved in large-scale farming. Recently, researcher Huang Wen of the Guangdong Academy of Agricultural Sciences and his research team have explored and made a breakthrough in the large-scale cultivation technology of sea cucumbers.
1) Compared with the traditional induced labor stimulation method of yin dry stimulation, the labor induction efficiency of sea cucumber was significantly improved, and the egg production of each female ginseng could be increased by up to 10 times.
2) The embryonic development and seedling development process of **sea cucumber were followed up and observed, and a complete digestive tract appeared 3 36 h after fertilization, and the larvae first grew larger and developed to the late stage of big-eared larvae, and then developed to the stage of the larvae of the bottle, and the volume became the smallest, and began to sink to the bottom from the planktonic state, and then began to grow five-tentacles, and after entering the five-tentacle larval stage, the larvae of sea cucumber fed and exercised through the tentacles. The highest mortality rate occurred from the late stage of big-eared larvae to the stage of larvae, indicating that the development process was the most important factor affecting the survival rate of sea cucumbers.
*Early and middle stage of sea cucumber**Developmental stage (3) Large-scale cultivation technology of non-live algae bait was explored, and the ratio of non-live algae bait was figured out, that is, the ratio of chlorella powder, yeast powder and sea mud was 2:1:2. It avoids the pollution and breeding of pests and diseases in live algae, and the deterioration of water quality caused by live algae decay.
4) The automatic agitation of the air chamber is added, which saves the labor cost of manual agitation during the floating period and adhesion period, and greatly facilitates the large-scale cultivation.
Unravel the molecular mechanism of sea cucumber breeding
Critical reproductive challenges
In recent years, researchers have actively explored the breeding, breeding management and specific environmental factors of sea cucumber broodstock and larvae, and breakthroughs have been made in the research on feed, salinity, temperature, pH, etc., but the key breeding problems still hinder the large-scale development of sea cucumber. The study found that the mortality rate in the larval stage was as high as 54%, which was highest during the development of sea cucumber and throughout the growth process. In the larval stage, sea cucumbers mainly feed on planktonic organic matter such as marine algae, and in the later stage of larvae, they are bottle-shaped larvae, and they mainly feed on shallow sedimentary materials after attachment. Thus, these two very different lifestyles may involve two very different sets of gene regulatory networks.
*Sea cucumber seedlings at the attachment stage and their breeding environment.
Molecular mechanisms of attachment periods
In order to solve the above problems, based on full-length transcriptome sequencing technology, high-throughput sequencing analysis of sea cucumber larvae (microtia larvae, middle ear larvae, macrotia larvae and bottle-shaped larvae) at four different developmental stages was carried out using Illumina sequencing platform, revealing the following molecular mechanism information.
1) The number of differentially expressed genes in adjacent periods decreased and slowed down. This indicates that the reaction in the body of the sea cucumber caused by development has changed from the initial unstable state to the transition to the neostable state, and reached a new equilibrium in the stage of bottle-shaped larvae. (2) During the transition from big-eared larvae to bottle-shaped larvae, the enrichment frequency of cell adhesion classes increased significantly, and its biological function was to bring cells with the same surface characteristics together to form tissues and organs through cell recognition and adhesion, which is likely to be the key function of the growth of larvae from the planktonic stage to the attachment stage of specific organs. (3) The KEGG annotation showed that the functional genes of the larvae of 4 different developmental stages of **sea cucumber involved 8 signaling pathways closely related to **development, such as cell cycle, WNT, PI3K-AKT, pentose phosphate, insulin signal transduction, protein digestion and absorption, cholesterol metabolism, and MAPK signaling pathway. (4) The enrichment analysis of KEGG annotation pathway in adjacent periods showed that the annotation was mostly related to the metabolic processes of nerve and muscle development. This indicates that during the attachment and development period, many transcription factors that control the expression pathways of nerves, muscles and other tissues are likely to be the key factors affecting the normal development of organisms, such as actin cytoskeletal regulation, ECM-receptor interaction, calcium and other signaling pathways. (5) In this process, the gene and pathway regulatory network mainly controls the life activities such as apoptosis, proliferation and differentiation of larvae, and the color of the larvae will gradually deepen and the body size will gradually become smaller. Eventually, big-eared larvae become bottle-shaped larvae after these procedures are performed normally. This massive operating mechanism is one of the most complex and extremely important steps, which is probably the main reason for its high mortality rate.
5 Research Prospects
*Although the quality of sea cucumber is not as good as the imitation sea cucumber in the north of China, the plum cucumber (Thelenota ananas) in the south, etc., it grows faster, and can be used as a model species of tropical sea cucumber in a wider range of applications and popularization, so that ordinary people have the ability to consume, and its development prospects are considerable.
At present, the first-class sea cucumber has not yet been artificially cultivated on a large scale, and the research on the molecular mechanism and regulatory mechanism of its systematic growth and development is still blank. Exploring the molecular mechanism of the growth and development of sea cucumber is a very wide field of research, and the exploration of the internal mechanism of related growth genes and pathways will help to reveal the law of growth and development of sea cucumber, lay the foundation for the subsequent research on large-scale breeding technology, and also provide reference for the artificial breeding of other tropical sea cucumbers.
References:
1]conand c, byrne m. a review of recent developments in the world sea cucumber fisheries[j]. oceanogr liter rev, 1995, 42(7): 570.[2]huang w, huo d, yu z h, et al. spawning, larval development and juvenile growth of the tropical sea cucumber holothuria leucospilota[j]. aquaculture, 2018, 488: 22-29.[3]carpenter k and niem v. fao species identification guide for fishery purposes. the living marine resources of the western central pacific. volume 2. cephalopods, crustaceans, holothurians and sharks[m]. rome: fao, 1998: 687-1396.[4]chen x y, huang m w, peng k, et al. artificial spawning, hatchery and culture of the tropical sea cucumber (holothuria leucospilota) using non-living food[j]. aquaculture, 2023: 739762.Related Articles:
Xiaopeng Wu, Minwei Huang*, Xiaoying Chen, Kai Peng, Jichen Zhao, Ping Zhong, Fengkun Liu, Yehui Zhang, Wen Huang*Transcriptome analysis of sea cucumber in attachment stage[J].South China Fisheries Science, 2023,19(6): 84-96
Written by Wu Xiaopeng.
Edited by Ai HongIf you want to know more exciting content, come and pay attention to Southern Aquatic Science.
Method 1: WeChat inputSouthern Aquatic Sciences, pay attention to the WeChat of this journal***
Method 2: Log in to the official website: