Animal sea cucumber sea cucumber. Sea cucumber

International scientific name

Holothuroidea Blainville, 1834

Subclasses and units

Taxonomy
on Wikispecies

Images
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ITIS
NCBI
EOL

The modern fauna is represented by 1150 species, divided into 6 orders, which differ from each other in the shape of the tentacles and calcareous ring, as well as the presence of some internal organs. About 100 species are found in Russia. The oldest fossils of holothurians date from the Silurian period.

Holothurians are relatives of sea stars and urchins.

Biology

Unlike other echinoderms, holothurians lie “on their side” at the bottom, with the side bearing three rows of ambulacral legs ( trivium) is ventral, and the side with two rows of ambulacral legs ( bivium) dorsal. In deep-sea holothurians, the ambulacral legs can be greatly elongated and used as stilts. Some species move due to peristaltic contractions of the muscles of the body wall, pushing off from the ground with protruding calcareous bones.

Most sea cucumbers are black, brown or greenish in color. Body length varies from 3 cm to 1-2 meters, although one species ( Synapta maculata) reaches 5 m.

Lifestyle and nutrition

Holothurians are sedentary or crawling animals found in almost any part of the ocean - from coastal strip to deep-sea depressions; most abundant in tropical coral reef environments. Most species are bottom-dwelling, but there are also pelagic ones. They usually lie “on their side”, raising the front, oral end. Holothurians feed on plankton and organic debris extracted from bottom silt and sand, which is passed through the digestive canal. Other species filter food from bottom waters with tentacles covered with sticky mucus.

In case of severe irritation, the back part of the intestine is thrown out through the anus along with the water lungs, scaring off or distracting the attackers; Lost organs are quickly restored. In some species, Cuvier's tubules containing toxins are also released. Sea cucumbers are hunted by sea stars, gastropods, fish and crustaceans. Fish called fieraspheres ( Fierasfer), sometimes pea crabs ( Pinnotheres).

Reproduction and development

Life expectancy is from 5 to 10 years.

Economic importance

Some species of sea cucumbers, especially from the genera Stychopus And Cucumaria, are eaten as “trepangs”. In China and Southeast Asian countries they are considered a delicacy, served fresh or dried with fish and vegetables. Their fishing is most developed off the coast

Irina Kamshilina

Cooking for someone is much more pleasant than cooking for yourself))

Marine fauna is rich in various living organisms, many of which are used as food. One of them is the sea cucumber (holothurian), a class of which includes more than 1000 species. They vary in appearance (size, color, body length, etc.), and some are even used for cooking. Shellfish have a number of beneficial medicinal properties, and they even make medicines from sea cucumber extracts.

What is a sea cucumber

Such a representative of the fauna as the sea cucumber is a class of invertebrate animals, such as echinoderms. They are also called sea capsules and sea cucumbers. The sea cucumber looks like a large oblong worm or caterpillar. Depending on the species, the body of these mollusks can be smooth or rough (with short and long growths). The color of sea cucumbers is red, green, gray, brown and black. Their size varies from 0.5 cm to 5 m. Holothuria can be found both in deep depressions and in the coastal part of the ocean, and more often near coral reefs.

Lifestyle

The marine animal feeds on plankton or organic remains, which it extracts from the bottom sand and passes through digestive system. Some species of sea cucumbers have tentacles used to filter the food they detect. Mollusks lead a sedentary lifestyle, spending most of their time on one side, with their mouth opening raised. Animals crawl very slowly, sometimes contracting, sometimes stretching.

Types of sea cucumbers

Today, the class of holothurians includes about 1,150 species of animals, differing in size, weight, color, body structure, and habitat. Sea urchins and stars are the closest relatives of sea cucumbers. There are more than 100 species of such mollusks in Russia, but the most popular sea cucumbers are Far Eastern sea cucumber and cucumber, which are used in the preparation of tasty and healthy treats.

Useful properties of sea cucumbers

Representatives sea cucumbers have many beneficial properties thanks to dietary sterile meat, devoid of viruses and various diseases, but rich in iodine, calcium, phosphorus, amino acids, iron, copper, nickel, chlorine, vitamins B, C. The calorie content of shellfish is only 35 kcal per 100 g. Scientists note the following points of the therapeutic effect of sea cucumbers on the human body:

decrease in blood pressure;
stimulation of the heart muscle;
acceleration of tissue renewal;
normalization of metabolic processes;
relief from bradycardia, tachycardia;
treatment of arthritis, relief of joint pain;
strengthening the immune system;
improving the functioning of the nervous and cardiovascular systems.

Using sea cucumber as food

It is not difficult to prepare sea cucumber; the main thing is to carry out a number of activities to pre-prepare the mollusk. First, it is washed thoroughly until the black powder completely disappears. Next, the carcass is soaked in water, which is changed several times, and then boiled for at least 3 hours. The Japanese prefer to eat the delicious sea cucumber meat raw, since it preserves more useful substances.

Many different delicious snacks are prepared from sea cucumber; it is fried, boiled, dried, and canned shellfish are made. Shellfish meat is used as the main component of some soups and cutlets. Experienced chefs argue that sea cucumbers must be cooked with other products that have a pronounced aroma and absorb unpleasant odors. Egg pod meat should not be eaten by pregnant or lactating women, children, allergy sufferers, or people with hyperthyroidism.

Sea Cucumber Recipes

Sea pod as a food product is often used in Asian cuisine. Used to prepare seafood different ways heat treatment. You can buy shellfish at large grocery stores and turn them into a dish rich in useful vitamins and microelements. If you don't know how to cook sea cucumber, use detailed tutorials with photos that will teach you how to properly clean, prepare and cook sea cucumber.

Sea cucumber scraper

Time: 1 hour 15 minutes.
Number of servings: 8 persons.
Calorie content of the dish: 154 kcal per 100 g.
Difficulty: easy.

One of the dishes of Old Russian cuisine that has been forgotten is skoblyanka. It was prepared from potatoes, mushrooms and vegetables, but in the Far East the mushrooms were replaced with sea cucumber meat. This shellfish contains much more vitamins and microminerals than fish, so the beneficial properties of the scraper are very great. If you purchased fresh sea cucumber, you must first gut it, wash it, then boil it twice for half an hour in water. Then change the water again and cook the shellfish for about 2 hours.

Ingredients:

sea cucumber – 6 pcs.;
pork – 0.5 kg;
onions – 3 pcs.;
carrots, tomatoes - 1 pc.;
vegetable oil – 50 ml;
tomato paste – 1 tbsp. l.;
garlic – 2 cloves;
greens – 0.5 bunch;
salt, pepper - to taste.

Cooking method:

Cut the seafood into strips, fry in a cauldron for about 15 minutes, then add pork, chopped in the same way.
While the seafood and meat are fried, chop the onion into half rings and the carrots into thin strips. Add to meat and seafood. Simmer for 10 minutes.
Chop the tomato into small cubes, add to the cauldron, add salt and pepper, and stir.
Pour in ½ tbsp. water, simmer over low heat under the lid for 15 minutes.
Squeeze the garlic, chop and add the herbs, stir, remove from heat.

Sea cucumber with honey

Time: 16 days.
Number of servings: 200 persons.
Calorie content of the dish: 496 kcal per 100 g.
Purpose: medicine.
Difficulty: easy.

Sea cucumber with honey is used as an alternative medicine used for the treatment and prevention of various diseases. The tincture recipe appeared in China, and is famous for the following properties: eliminating inflammation, stimulating tissue regeneration, slowing down the development of cancerous tumors, improving the functioning of the endocrine system, restoring vision, removing waste, toxins, removing cholesterol plaques, etc. Take the finished extract, 1 tsp. . half an hour before meals twice a day for a month.

Ingredients:

dried sea cucumber – 100 g;
alcohol (40%) – 1 l;
honey – 1 kg.

Cooking method:

Fill the dried seafood with water so that the liquid completely covers the product, leave for a day, and then grind it (you can put it through a meat grinder).
Mix crushed sea cucumbers with alcohol, leave to infuse for 15 days in a dark, dry, cool place, shaking occasionally.
Combine the prepared tincture with honey and stir thoroughly.

Sea cucumber with rice

Time: 1.5 hours.
Number of servings: 6 persons.
Calorie content of the dish: 171 kcal per 100 g.
Purpose: for breakfast, lunch, dinner.
Difficulty: easy.

Housewives who are looking for options on how to cook sea cucumber should try a recipe with rice and soy sauce. The dish turns out not only tasty, but also satisfying. It is better to peel the tomatoes listed in the product list by first dousing them with boiling water and making an incision in the area of the stalk. In addition to curry spices, you can add others at your discretion.

Ingredients:

sea cucumber – 300 g;
rice – 0.5 kg;
tomatoes – 2 pcs.;
onions – 2 pcs.;
garlic – 3-4 cloves;
curry – 1 pinch;
soy sauce – 1 tbsp. l.

Cooking method:

If the shellfish are raw, boil them in 2 waters, then chop them randomly and fry until cooked.

Holothuria is an unusual animal that visually resembles a plant. This animal belongs to the class of invertebrates, the type of echinoderm. These “sea sausages”, which is exactly what they look like, have many names - sea cucumber, sea cucumber, sea ginseng.

Class Holothuria unites many species, namely 1150. Each species differs from other representatives of this class in a number of characteristics. Therefore everything holothurian species were combined into 6 types. The criteria that were taken into account during separation were the following: anatomical, external and genetic features. So, let's get acquainted with the types of sea cucumbers:

1. Legless holothurians do not have ambulacral legs. Unlike their other relatives, they perfectly tolerate desalination of water, which has affected their habitat. A large number of legless ones can be found in the mangrove swamps of the Ras Mohamed Nature Reserve.

2. Side-footed holothurians are equipped with ambulacral legs on the sides. They prefer life at great depths.

3. Barrel-shaped holothurians. The shape of their body is spindle-shaped. Such type of holothurian adapted to life in the soil.

4. Tree-tentacled holothurians are the most common. The most primitive sea cucumbers belong to this type.

5. Thyroid-tentacles have short tentacles that do not hide inside the body.

6. Dactylochirotids unite sea cucumbers that have from 8 to 30 tentacles.

Holothuria maritime, due to its diversity and ability to adapt to any living conditions, is found in almost all seas. The only exceptions are the Caspian and Baltic Sea.

The ocean spaces are also perfect for their living. Largest accumulation holothurian sea cucumber in tropical and subtropical waters. These cucumbers can settle both in shallow water and in deep-sea depressions. Their main refuge is coral reefs and rocky soils overgrown with vegetation.

The body of these underwater inhabitants is oblong, which is probably why they are called sea cucumbers. The skin is rough and wrinkled. All muscles are quite developed. At one end of the body there is a mouth, and at the other an anus. There are tentacles around the mouth.

With their help, sea ginseng captures food and sends it into the mouth. They swallow food completely, since they have no teeth. Nature did not endow these monsters with a brain, but nervous system represents only a few nerves connected in a bundle.

Holothuria sea cucumber

Distinctive feature sea cucumber sea ginseng is their hydraulic system. The water lungs of these extraordinary animals open in front of the anus into the cloaca, which is completely unusual for other living organisms.

The color of these animals is quite bright. They come in black, red, blue and green. Skin color depends on where holothurian lives. Their color most often harmoniously combines with color scheme underwater landscape. The sizes of such “underwater worms” have no clear boundaries. They can be from 5 mm to 5 m.

Character and lifestyle of sea cucumbers

Lifestyle of sea cucumbers- inactive. They are in no hurry and crawl slower than turtles. They move along the seabed on their sides, since this is where their legs are located.

Pictured is sea cucumber sea ginseng

You can see such an unusual way of transportation at photo of sea cucumber. During such walks, they use their tentacles to capture edible particles of organic matter from the bottom.

They feel great at great depths. So, at a depth of 8 km, sea ginseng considers itself a full-fledged owner, and this is not accidental. They make up 90% of all bottom dwellers at great depths.

But even these “bottom masters” have their enemies. Holothurians have to defend themselves from starfish, crustaceans and some species. For protection, sea cucumbers use “ special weapon" In case of danger, they can shrink and throw their internal organs into the water.

As a rule, these are the intestines and genitals. Thus, the enemy is lost or feasts on this “dropped ballast”, and in the meantime the front part of the cucumber escapes from the battlefield. All missing body parts are restored in 1.5-5 weeks and the sea cucumber continues to live as before.

Some species defend themselves slightly differently. During skirmishes with the enemy, they produce toxic enzymes that are deadly poison for many fish.

This substance is not dangerous for people, the main thing is that it does not get into your eyes. People have adapted to use this substance for their own purposes: for fishing and scaring.

In addition to enemies, sea ginseng also has friends. About 27 species of the carp family use sea cucumbers as a home. They live inside these unusual animals, using them as shelter in case of danger.

Sometimes these "cucumber fish" eat reproductive and respiratory organs sea cucumbers, but due to its restorative ability, this does not cause much harm to the “hosts”.

Holothuria edible not only underwater inhabitants, but also people believe. Sea cucumbers are used to prepare delicacies, as well as in pharmacology. They are tasteless, but very healthy.

An interesting fact is that once you get the sea cucumber to the surface, you must sprinkle it with salt so that it becomes hard. Otherwise, upon contact with air, the mollusk will soften and resemble jelly.

Holothurian nutrition

Sea cucumbers are considered the orderlies of the ocean and seas. They feed remnants of the dead animals. Their mouth end is always raised in order to catch food with the help of tentacles.

The number of tentacles varies among different species. Their maximum number is 30 pieces, and they are all in constant search of food. The holothurian licks each of the tentacles in turn.

Some species feed on algae, others on organic debris and small animals. They are like vacuum cleaners, collecting food mixed with silt and sand from the bottom. The intestines of these animals are adapted to select only nutrients, and send everything unnecessary back outside.

Reproduction and lifespan of holothurians

Holothurians have 2 methods of reproduction: sexual and asexual. During sexual reproduction, the female releases eggs into the water. Here, outside, fertilization of the eggs occurs.

After a while, larvae will emerge from the eggs. In their development, these babies go through 3 stages: dipleurula, auricularia and doliolaria. In the first month of their life, the larvae feed exclusively on unicellular algae.

The second option for reproduction is self-reproduction. In this case, holothurians, like plants, are divided into several parts. Over time, new individuals grow from these parts. These extraordinary creatures can live from 5 to 10 years.

Sea cucumber

Holothurians, sea capsules, sea cucumbers ( Holothuroidea), a class of invertebrate animals such as echinoderms. Species eaten as food are collectively known as "trepang".

The modern fauna is represented by 1,150 species, divided into 6 orders, which differ from each other in the shape of the tentacles and calcareous ring, as well as the presence of some internal organs. The oldest fossils of holothurians date from the Silurian period.

Biology

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Synonyms:

See what “Sea Cucumber” is in other dictionaries:

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Sea capsules or sea cucumbers are animals whose body contracts strongly at the slightest touch, after which it, in many forms, becomes similar to an old egg capsule or fresh cucumber. About 900 species are known.... ... Biological encyclopedia

Trepang, sea cucumber Dictionary of Russian synonyms. holothurian noun, number of synonyms: 4 echinoderms (12) ... Dictionary of synonyms

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Holothurians- Holothuria. Holothurians (sea cucumbers), a class of animals of the echinoderm type. The body is usually worm-shaped, from a few mm to 2 m. About 1100 species, found throughout the seas and oceans. Bottom, crawling forms. Many people, when irritated, are able to throw out... Illustrated Encyclopedic Dictionary

Sea cucumbers are echinoderms from the class Holothuroidea (Holothurians). These are marine animals with a leathery shell and an elongated body containing one branched gonad. Sea cucumbers live on the seabed. The number of sea cucumber species worldwide is about 1,717, with greatest number is located in the Asia-Pacific region. Many are harvested for human consumption, and some species are farmed in aquaculture systems. The harvested product is called differently - sea cucumber, bêche-de-mer or balat. Sea cucumbers play an important role in the marine ecosystem as they help recycle nutrients, break down detritus and other organic matter so bacteria can continue the breakdown process. Like all echinoderms, just below the skin sea cucumbers have an endoskeleton, calcified structures that are usually reduced to isolated microscopic ossicles (or sclerieta) connected connective tissue. In some species, they can sometimes be enlarged into flattened plates, forming a protective covering. In pelagic species such as Pelagothuria natatrix (order Elasipodida, family Pelagothuriidae), the skeleton and calcium ring are absent. Sea cucumbers are so named because of their resemblance to cucumber fruit.

Review

Most sea cucumbers, as their name suggests, have a soft and cylindrical body, more or less elongated, rounded and sometimes fuller in the limbs and usually without hard appendages. Their shape ranges from almost spherical in the sea apples (genus Pseudocolochirus) to serpentine in Apodida, or the classic sausage shape, while others are caterpillar-like. “The mouth is surrounded by tentacles that can be retracted into the animal.” Holothurians are usually from 10 to 30 centimeters in length, however, species measuring a few millimeters in size (Rhabdomolgus ruber) and up to more than 3 meters in length (Synapta maculate) are found. Largest American look Holothuria floridana, which lives in abundance just below low water mark on the reefs of Florida, has a well volume of more than 500 cubic centimeters and a length of 25-30 cm. Most of them have five rows of tube feet, except the species Apodida, which moves by crawling; the legs may be smooth or with fleshy appendages (for example, Thelenota ananas). The legs on the dorsal surface usually do not serve for movement and turn into papillae. A rounded mouth opens at one end, usually surrounded by a crown of tentacles, which can be very complex in some species (and they are actually modified legs); anus - retrodorsal. Holothurians do not look like other echinoderms at first glance, due to their tubular body, without a visible skeleton or rigid appendages. In addition, the fivefold symmetry, classic for echinoderms, although structurally preserved, is here doubled through bilateral symmetry, which makes them similar to chordates. However, central symmetry still observed in some species through five "radii" that extend from the mouth to the anus (just like sea urchins), to which tube feet are attached. Thus, these animals do not have any "front" or "dorsal" face, like starfish and other echinoderms, but the animal stands on one of its sides, and this face is called trivium (with three rows of tube feet), and the dorsal face called bivium. A remarkable feature of these animals is the “trapping” collagen that forms their body wall. It can be loosened and tightened at will, and if an animal wants to squeeze through a small gap, it can significantly compress its body. To keep itself safe in these cracks and cracks, the sea cucumber uses all of its collagen fibers to harden its body again. The most common way to separate subclasses is by the appearance of their oral tentacles. The order Apodida has a thin and elongated body, without tube feet, and up to 25 simple or feathery oral tentacles. Aspidochirotida are the most common sea cucumbers with a strong body and 10-30 leaf-shaped or shield-shaped oral tentacles. Dendrochirotida are biofilter feeders with plump bodies and 8-30 branched oral tentacles (which can be extremely long and complex).

Anatomy

Sea cucumbers are generally between 10 and 30 cm in length, although the smallest known species is only 3 mm in length, and the largest can reach three meters. The body can be almost spherical or worm-like, without legs, like many other echinoderms, such as the starfish. The anterior end of the animal, containing the mouth, corresponds to the oral pole of other echinoderms (which, in most cases, is the lower part), and the posterior end, containing the anus, corresponds to the dorsal pole. Thus, compared to other echinoderms, sea cucumbers can be said to lie on one side.

Body structure

The body of the holothurian is approximately cylindrical. It is radially symmetrical along the longitudinal axis and has weak bilateral symmetry transversely with the dorsal and ventral surface. Like other echinozoans, holothurians have five ambulacra separated by five ambulacral grooves, the mesambulacrum. The ambulacral grooves contain four rows of legs, but these are smaller or absent in some holothurians, especially on the dorsal surface. Two dorsal ambulacra make up the bivium, and three ventral ones make up the trivium. At the anterior end, the mouth is surrounded by a ring of tentacles that usually retract into the mouth. These are modified tube feet that can be simple, branched or tree-like. These are known as the proboscis, and at the back there is an inner ring of large calcium bones. Attached to them are five strips of muscles that run longitudinally along the ambulacra inside. There are also circular muscles, the contraction of which causes the animal to lengthen and the trunk to expand. In front of the bones lie further muscles, the contraction of which causes the trunk to retract. The body wall is composed of epidermis and dermis and contains smaller calcified ossicles, the types of which are characteristics that help identify different types. Inside the body wall is a secondary cavity divided by three longitudinal mesenteries that surround and support the internal organs.

Digestive system

Behind the mouth is the pharynx, surrounded by a ring of ten calcified plates. In most sea cucumbers, this is the only important part of the skeleton, and it forms the attachment point for the muscles that can retract the tentacles into the body for safety, as for the major muscles of the body wall. Many species have an esophagus and stomach, but some have pharynxes that open directly into the intestines. The intestine is usually long and coiled, and passes three times through the body to the cloacular chamber or directly into the anus.

Nervous system

Sea cucumbers do not have a true brain. A ring of nerve tissue surrounds the oral cavity and directs nerves to the tentacles and pharynx. The animal, however, is quite capable of functioning and moving if the nerve ring is surgically removed, suggesting that the ring does not play a central role in neural coordination. In addition, five major nerves run from the nerve ring along the length of the body under each of the ambulacral regions. Most sea cucumbers do not have distinct sensory organs, although they do have various nerve endings scattered throughout the skin, giving the animal a sense of touch and sensitivity to the presence of light. However, there are a few exceptions; Members of the order Apodida are known to have statocysts, while some species possess small eyespots near the bases of their tentacles.

Respiratory system

Sea cucumbers extract oxygen from the water in a pair of "respiratory trees" that branch into a cloaca just inside the anus, so they "breathe" by drawing water in through the anus and then expelling it. The trees consist of a number of narrow tubes branching from a common duct and are located on either side of digestive tract. Gas exchange occurs through the thin walls of the tubules, into and out of the fluid of the main body cavity. Together with the intestines, the respiratory trees also act as excretory organs, with nitrogenous wastes being distributed along the walls of the tubules in the form of ammonia and phagocytic coelomocytes depositing the waste as particulates.

Circulatory systems

Like all echinoderms, sea cucumbers have both an ambulacral system, which provides hydraulic pressure to the tentacles and tube feet that allow them to move, and a hemal system. The latter is more complex than that of other echinoderms, and consists of well-developed vessels, as well as open sinuses. The central gemmal ring surrounds the pharynx adjacent to the annular canal of the ambulacral system and sends additional vessels along the radial canals beneath the ambulacral areas. In larger species, additional vessels flow above and below the intestines and are connected by more than a hundred small muscular ampoules that act like miniature hearts, pumping blood around the hemal system. Additional vessels surround the water lungs, although they connect them only indirectly, through the coelomic fluid. In fact, the blood itself is essentially identical to the coelomic fluid that directly bathes the organs and also fills the ambulacral system. Phagocytic coelomocytes, somewhat similar in function to the leukocytes of vertebrates, are formed within the hemal vessels and travel throughout the body cavity, as well as to both circulatory systems. An additional form of coelomocyte, not found in other echinoderms, has a flattened discoid shape and contains hemoglobin. As a result, in many (though not all) species, the blood and coelomic fluid are colored red. High concentrations of vanadium were found in the blood of sea cucumbers, but researchers were unable to reproduce these results.

Motor organs

Like all echinoderms, sea cucumbers have pentaradial symmetry. However, due to their body position, they have secondarily developed some degree of bilateral symmetry. For example, since one side of the body is usually pressed against a surface and the other is not, there is usually a difference between the two surfaces (except in Apodida species). Like sea urchins, most sea cucumbers have five striped ambulacral regions running the length of the body from the mouth to the anus. The three ambulacral areas on the lower surface have numerous tube feet, often with suckers, which allow the animal to crawl; they are called trivium. Two areas on the upper surface have underdeveloped or vestigial tube feet, and some species have no tube feet at all; this face is called the bivium. In some species, the ambulacral regions can no longer be distinguished, with the tube feet extending over a much wider area of the body. Species of Apodida have no tube feet or ambulacral regions at all and move by muscular contractions of the body, like worms, however, they typically have five ray lines running along their body. Even sea cucumbers, which do not have the usual tube feet, have feet around the mouth. They are modified into contractile tentacles much larger than tube feet for locomotion. Depending on the species, sea cucumbers have between ten and thirty of these tentacles, and they can have a wide variety of shapes depending on the animal's diet and other factors. Many sea cucumbers have papillae, conical fleshy projections of the body wall with sensory tube feet at the tops. They can even develop into long antenna-like structures, especially in the abyssal genus Scotoplanes.

Endoskeleton

Echinoderms typically have an internal skeleton composed of plates of calcium carbonate. However, in most sea cucumbers these plates have shrunk to microscopic bones under the skin. A few genera, such as Sphaerothuria, retain relatively large plates.

Life history and behavior

Habitat

Sea cucumbers in large quantities found in the deep sea, where they often make up the majority of animal biomass. At depths greater than 8.9 km, sea cucumbers make up 90% of the total macrofauna. Sea cucumbers form large schools that move across the deep ocean, hunting for food. The body of some deep-sea holothurians, such as Enypniastes eximia, Peniagone leander and Paelopatides confundens, consists of tough gelatinous tissue with unique properties that allows the animals to control their buoyancy, allowing them to either live on the ocean floor, actively swim, or move to new places. Holothurians appear to be the best-adapted echinoderms to extreme depths and are still very common at depths greater than 5000 m. Several species in the family Elpidiidae ("porpoises") can live at depths greater than 9500 m, and some species of the genus Myriotrochus (in particular, Myriotrochus bruuni) live at depths of up to 10,687 meters. In shallower waters, sea cucumbers can form dense populations. The New Zealand strawberry sea cucumber (Squamocnus brevidentis) lives on rocky cliffs along the southern coast of the South Island, where its populations sometimes reach densities of 1000 animals per square meter. For this reason, one such area in Fiordland is called the "strawberry fields".

Movement

Some abyssal species in the abyssal order Elasipodida have evolved to "benthopelagic" behavior: their body is almost as dense as the water around them, so that they can make long (up to 1000 m) jumps before slowly sinking to the ocean floor. Most of them have specific swimming appendages, such as an umbrella (for example, Enypniastes) or a long projection on the body (Psychropotes). Only one species is known to be a true, completely pelagic species that never approaches the bottom - Pelagothuria natatrix.

Diet

Holothurians are typically scavengers, feeding on debris in the benthic zone of the ocean. Exceptions include some pelagic cucumbers and the species Rynkatorpa pawsoni, which have a symbiotic relationship with deep-sea monkfish. The diet of most sea cucumbers consists of plankton and decaying organic matter, discovered in the sea. Some sea cucumbers catch food that flows near their exposed tentacles. They also sift through sediment using their tentacles. Other species may burrow through the lower mud or sand until they are completely underground. They then extend their feeding tentacles, ready to escape at any sign of danger. In the South Pacific, sea cucumbers can occur at densities of 40 individuals per square meter. These populations can process 19 kilograms of sediment per square meter per year. The shape of the tentacles is usually adapted to the diet and size of the particles consumed: biofilters generally have complex tree-like tentacles designed to maximize the surface area available for filtration, while substrate-feeding species most often require finger-like tentacles for sorting nutritious material; detrital species that live in fine sand or mud most often require shorter, "toothed" tentacles shaped like scoops. One individual can ingest more than 45 kg of sediment per year. The outstanding digestive abilities of sea cucumbers allow them to reject finer, cleaner and more uniform sediment. Therefore, sea cucumbers play an important role in the biological treatment of the seabed (bioturbation, scavenging, substrate homogenization, etc.).

Communication

Sea cucumbers communicate with each other by transmitting hormonal signals through the water. The main purpose of communication is reproduction; otherwise, individuals tend to ignore each other. Sea cucumbers do not exhibit territorialism. Some species, including abyssal species such as porpoises (Scotoplanes globosa), can live in groups.

Reproduction

Most sea cucumbers reproduce by releasing sperm and eggs into the ocean water. Depending on conditions, a single organism can produce thousands of gametes. Sea cucumbers are generally dioecious, with separate male and female organisms, but some species are protandrous. The reproductive system consists of a single gonad, consisting of a cluster of tubules flowing into a single canal that opens on the upper surface of the animal, next to the tentacles. At least 30 species, including Pseudocnella insolens, fertilize their eggs internally and then pick up the fertilized zygote with one of their tentacles. The egg is then inserted into a bursa on the adult's body, where the fetus develops and eventually hatches from the bursa. Several species are known to breed in body cavities and give birth through a small tear in the body wall, near the anus.

Development

In all other species, the egg develops into a larva, which is free-swimming, usually after about three days of development. The first stage of larval development is known as auricularia (the larva is about 1 mm long). Such a larva swims with the help of a long strip of cilia wrapped around its body, and somewhat resembles a bipinnaria (larva starfish). As the larva grows, it develops into a doliolaria with a barrel-shaped body and three to five individual rings of cilia. "Pentacular" is the third larval stage of the sea cucumber, in which the tentacles appear. The tentacles are usually the first features of the adult to appear before the normal tube legs.

Symbiosis and commensalism

Predators and defense mechanisms

Marine predators often refuse to eat sea cucumbers due to the toxins they contain (particularly holothurin) and their impressive defense mechanisms. However, they remain prey for some highly specialized predators that are unaffected by their toxins, such as the large clams Tonna galea and Tonna perdix, which paralyze the sea cucumbers using a powerful venom before swallowing them completely. Some other, less specialized and opportunistic predators may also prey on sea cucumbers if they cannot find more suitable food, such as certain types of fish (triggerfish, puffer fish) and crustaceans (crabs, lobsters, hermit crabs). Some species of coral sea cucumbers in the order Aspidochirotida can defend themselves by expelling their sticky Cuvier tubes (extensions of aquatic lungs that float freely in the coelom) to entangle potential predators. When sea cucumbers are startled, they may expel some tubes through a tear in the cloaca wall in an autonomous process known as emptying. Replacement tubes grow within one and a half to five weeks, depending on the type. The release of these tubes can also be accompanied by the release of a toxic chemical known as holothurin, which has properties similar to soap. This chemical can kill animals in the surrounding area and is another method of protecting sea cucumbers.

Aestivation

If the water temperature gets too high, some types of sea cucumber from seas with moderate temperature may hibernate during the summer. While they are in this state of rest, they stop feeding, their intestines atrophy, their metabolism slows, and they lose weight. The body returns to its normal state when conditions improve.

Phylogeny and classification

Holothurians do not have a skeleton like other echinoderms and their classification is more complex, with their paleontological phylogeny relying on a number of well-preserved specimens. Modern taxonomy is based primarily on the presence or shape of certain soft parts (legs, lungs, tentacles) to determine the major orders and, secondly, on microscopic examination of the ossicles to determine the genus and species. Modern genetic methods have greatly contributed to the development of the classification of these animals. Taxonomic classification, in accordance with the World Register of Marine Species:

Squad Apodida (Brandt, 1835)

Family Chiridotidae (Östergren, 1898)

Family Myriotrochidae (Théel, 1877)

Family Synaptidae (Burmeister, 1837)

Squad Aspidochirotida (Grube, 1840)

Family Holothuriidae (Burmeister, 1837)

Family Mesothuriidae (Smirnov, 2012)

Family Stichopodidae (Haeckel, 1896)

Family Synallactidae (Ludwig, 1894)

Squad Dendrochirotida (Grube, 1840)

Family Cucumariidae (Ludwig, 1894)

Family Cucumellidae (Thandar and Arumugam, 2011)

Family Heterothyonidae (Pawson, 1970)

Family Paracucumidae (Pawson and Fell, 1965)

Family Phyllophoridae (Östergren, 1907)

Family Placothuriidae (Pawson & Fell, 1965)

Family Psolidae (Burmeister, 1837)

Family Rhopalodinidae (Théel, 1886)

Family Sclerodactylidae (Panning, 1949)

Family Vaneyellidae (Pawson and Fell, 1965)

Family Ypsilothuriidae (Heding, 1942)

Squad Elasipodida (Théel, 1882)

Family Deimatidae (Théel, 1882)

Family Elpidiidae (Théel, 1882)

Family Laetmogonidae (Ekman, 1926)

Family Pelagothuriidae (Ludwig, 1893)

Family Psychropotidae (Théel, 1882)

Squad Molpadida (Haeckel, 1896)

Family Caudinidae (Heding, 1931)

Family Eupyrgidae (Semper, 1867)

Family Gephyrothuriidae (Koehler & Vaney, 1905)

Family Molpadiidae (Müller, 1850)

Holothurians: use in cooking and medicine

To supply market demand in Southern China, Makassar sea cucumber fishermen trade with indigenous Australians from Arnhem Land. This is the first recorded example of trade between the inhabitants of the Australian continent and their Asian neighbors. There are many commercially important species of sea cucumber that are harvested and dried for export for use in Chinese cuisine. Some of the most commonly found types in markets include:

Holothuria nobilis

Thelenota pineapples

Actinopyga echinites

Actinopyga palauensis

Holothuria scabra

Holothuria fuscogilva

Actinopyga mauritian

Stichius japonicus

Apostichopus californicus

Acaudina molpadioides

Isostichopus fuscus

Sea cucumber as a food product

Sea cucumbers are marine animals of the class Holothuroidea. They are used in fresh or dried form in various cuisines around the world. In some cultural contexts, sea cucumber is believed to have medicinal value. The animal and food product itself is usually called bêche-de-mer in French, from the Portuguese "bicho do mar" (literally " sea worm"), trepang (or tripang) in Indonesian, namako in Japanese, balatan in Tagalog, and loli in Hawaiian Islands. In Malay, sea cucumber is known as gamat. In most cultures in Eastern and Southeast Asia, sea cucumbers are considered a delicacy. Sea cucumber is used in a number of dishes. Common ingredients used in sea cucumber dishes include wax melon, dried scallop, kai-lan, shiitake, and bok choy.

Culinary use

Fresh and dried forms of sea cucumber are used in cooking, although preparation is difficult due to the fact that it is completely tasteless. The Suiyuan shidan, a Qing Dynasty Chinese guide to gastronomy, states: “As an ingredient, sea cucumbers have little taste, are full of sand and have a strong fishy smell. For these reasons, they are difficult to cook tasty.” Much of preparing a sea cucumber for consumption involves peeling and boiling it, then simmering it in meat broths and extracts to flavor each sea cucumber. According to Chinese popular belief, sea cucumber has a positive effect on male sexual health and is an aphrodisiac, as it physically resembles a phallus and uses defense mechanism, similar to ejaculation, because in case of danger it freezes and pushes a stream of water towards the aggressor. Sea cucumber is also believed to protect against tendinitis and arthritis.

Commercial fee

IN recent years, the sea cucumber industry in Alaska has increased due to increased exports of sea cucumber skin and muscle to China. In China, sea cucumbers are sold commercially in artificial ponds. These ponds can reach an area of 400 hectares and satisfy most of the local demand. Wild sea cucumbers are collected by divers and these wild Alaskan sea cucumbers have higher nutritional value and larger size than farmed Chinese sea cucumbers. Larger sizes and taller nutritional value have allowed Alaskan fisheries to continue to compete for market share despite increased cultivation of local, Chinese sea cucumber. One of Australia's oldest fisheries is the collection of sea cucumbers by divers from around the Coral Sea ( Pacific Ocean, off the coasts of Australia, New Guinea and New Caledonia) in far North Queensland, Torres Strait and Western Australia. In the late 1800s, 400 divers were deployed to collect sea cucumbers in Cooktown, Queensland. Overharvesting of sea cucumbers in the Great Barrier Reef threatens their population. Their popularity as a delicacy in Asian countries poses a serious threat to the order Aspidochirotida.