Today we do not come to talk about a fish as we do most of the time. Today we find something known, but unknown at the same time. Its about sea ​​cucumber. It is an animal whose body is shaped like a worm and lives on the seabed of practically the whole world. Currently about 1400 species are known, so it is worth a thorough analysis.
Want to learn more about sea cucumbers? Read on. you will learn everything about him.
Key features
The sea cucumber belongs to the phylum of the echinoderms already the class HolothuroideaThe name sea cucumber comes from its strong resemblance to the vegetable, although it is an animal, not a plant.
What stands out the most about this echinoderm is the shape and texture of its skin. It treats a texture as if it were leather, but with a jelly-like appearance. At first glance it is an animal that could be mistaken for a slug.Depending on the species, their length can vary. However, the average is about 20 cm long. There are sea cucumbers that are less than a cm long or even larger.
The skin that makes the sea cucumber so special has the brown, olive green or black and has a leathery texture. This can vary slightly depending on the species. Its worm-like appearance allows it to adapt to the seabed without any problems.
We must remember that on the seabed the water pressure is much larger, so many species end up having a gelatinous texture that helps them survive in these environments. If not, let's remember the drop fish as one of the ugliest in the world only because of its texture that gives it that rare shape.
The sea cucumber has an outer wall of its body made of collagen that allows it to change its shape depending on the water pressure at any given time. Thanks to this ability, it can expand or contract its body at will. It is able to enter or exit the cracks of shelters where they hide from predators..
Beyond the external appearance, its anatomy shares features with other echinoderms: they have a internal pentaradial symmetry (the organs are organized in multiples of five) although externally they appear bilateral. Their internal skeleton is reduced to microscopic ossicles (sclerites) embedded in the dermis, which gives them that soft and flexible body. Around the pharynx they have a calcareous ring where the muscles that move the tentacles and contract the body are inserted.
The mouth is located at one end of the body and is surrounded by tentacles that can be simple, typed, pinnate o flattened, depending on the species, adapting to different types of food. At the other end is the cloaca (anus), which in addition to excreting, houses the respiratory trees, branched structures where gas exchange takes place: this is called cloacal respiration. Its water vascular system includes a internal madreporite (it opens into the coelom in most cases) from which channels run to the entire body, and the nervous system is organized into a ring and five main cords.
As for size, although many species are around 20-25 cm, there are tiny forms that do not exceed one centimeter and others that can reach lengths of several meters , the Synapta maculata. Its mobility is based on the tube feet (tubular legs with suction cups) arranged in radial bands; the lower ones are more specialized for locomotion and the dorsal ones perform sensory functions.
Habitat and area of ​​distribution
These animals use all the tube feet they have to be able to walk. spread over the largest possible territoryThese feet have sensory functions that help them recognize everything around them to see if they are in danger or not.
Like we have already said, can live in almost any marine environment, since they are spread almost throughout the planet. However, they can be found more frequently in shallow salty waters. It reaches its maximum population in areas close to coral reefs.
The home considered safe by these animals is located in the interstitial medium. Therefore, it's dangerous for them when the tide goes out and they have to move to deeper waters near ocean trenches. This is where they are safest.
Depending on the species we are analyzing, we can find benthic animals that are They are dedicated to digging up food in soft sediments or other sediments that can swim and are members of plankton. They do this by using the force of water currents.
To feel safe are placed in crevices or buried in soft substrates. This way they can hide from predators and not be seen by the light.
In addition, some holothurians have shown surprising behavior: certain deep-sea species, such as Enypniastes eximia, they can break away from the bottom and swim by wing-shaped folds. Others, such as Cucumaria frondosa, modulate their buoyancy absorbing water through their mouths and anuses to drift with currents when bottom conditions are unfavorable. These strategies increase their dispersal capacity and help them escape from overcrowded or low-salinity waters.
As for its distribution area, we find a very extensive area. It can be found throughout the Asian part of the Pacific Ocean with a large number of individuals. Its ability to spread across numerous ecosystems is due to its ability to adapt to different altitudes and temperatures.
Sea cucumber diet
This species of slug can feed on debris, algae or part of the plankton and waste materials found on the seabed. To feed, they collect all the superficial sediments that fall thanks to the use of their extended tentacles on the surface of the seabed.
To ingest food they use their tube-shaped feet to make a excavation process in the substrate. The tentacles in its mouth are covered with mucus, which helps it capture suspended food after digging.
Once the sediments have entered the mouth, they pass into the interior where they are taken to the small intestine for digestion. As expected, once it has processed food and obtained the nutrients it needs, it discards what it no longer needs in the form of mud and waste.
For this curious way of living we can say that its functionality in marine ecosystems is that of cleaning the substrates and enriching the soil with their depositions. A large number of these animals cause environmental conditions to change their physical and chemical characteristics.
Furthermore, by breaking down the food into such small sizes, help bacteria to serve as food for them.
His role as scavengers and bioturbators It is critical: by ingesting sediment rich in microalgae, bacteria and organic matter, they oxygenate the seabed and release nutrients such as nitrogen and phosphorus. It has been estimated that medium-sized individuals (e.g., Holothuria mexicana o Isostichopus badionotus) they can process more than 100 g of sediment per day, which on a population scale translates into tons removed and a significant healing effect on reefs. Where sea cucumbers are scarce, opportunistic algae increase and certain bacteria associated with coral diseases; on the contrary, their presence favors more stable bottoms and more diverse communities.
Reproduction
To finish with the information about the sea cucumber, let's talk about its reproduction. reproductive process of these animals is made externallyThat is, although some species are placental viviparous, the formation of the new individual generally takes place externally. This fertilization occurs with the expulsion of sperm and egg by the male and female.
Once the egg hatches, the larvae that come to light swim freely. It is in stage number three of their development that the tentacles grow. The reproduction period of the sea cucumber it is once a year, every two years. They are quite unpredictable when it comes to reproducing, so there is no certainty of when they will.
Expanding on this information: most species are dioecious (males and females separated) with a single branched gonad that releases eggs and sperm in water, where fertilization occurs. In several species, males emit pheromones that synchronize group spawning to increase the probability of gamete encounters. Planktonic larvae are given specific names: auricularia (first swimming phase), doliolaria (intermediate phase) and pentacle (stage that settles and develops feet), before becoming benthic juveniles. In some holothurians there are egg retention and protection on the female's body or under the tentacles, but there is no placenta as such; it is either parental care or external/semi-external incubation depending on the species. In addition, several species also reproduce asexually by fission, dividing into two halves that regenerate the missing parts.
Defenses, toxicity and predators
Sea cucumbers have developed defense mechanisms very effective. Many species expel Cuvier's tubes, sticky threads that immobilize or irritate potential predators. Others eviscerate part of their viscera through the sewer to distract the attacker, with the ability to regenerate them in a short time. Some may even self-select a damaged area of ​​the body to escape.
In their skin and viscera they can produce saponins (holothurins), chemical compounds that deter predators and, in high concentrations, are toxic to fish. In general, occasional contact with humans poses no risk, but they should not be eaten raw or mishandled. Against parasites, the production of a lectin with the ability to inhibit its development, demonstrating remarkable immunological sophistication for a brainless invertebrate.
Its predators These include fish such as wrasses and balistids, some starfish, crustaceans, and turtles, which tend to consume mostly juveniles. To reduce the risk, many species spend the day buried, leaving only their tentacles visible.
Ecological importance, human uses and conservation
From an ecological point of view, sea cucumbers are ecosystem engineers. Their bioturbation aerates the sediment, promotes oxygen penetration and nutrient circulation, and stabilizes the seabed, benefiting invertebrates such as worms, bivalves, and small crustaceans. They also keep the algal overgrowth and reduces potentially pathogenic bacterial communities, which helps coral health and reefs.
In the human sphere, its consumption is traditional in several cultures of the Indo-Pacific and other regions, where they are valued as food due to its high protein and low fat content, as well as its use in traditional medicine and cosmetics. This demand has driven specialized fisheries and the development of aquaculture to relieve pressure on wild populations.
However, intensive extraction and trade can lead to population declines, especially in high-value species. Sustainable management involves establishing seen during reproductive peaks, minimum sizes, quotas, licensing control and trade surveillance. Aquaculture and the repopulation can support recovery, always complemented by scientific monitoring. For consumers, learning about the origin and opting for certified products contributes to conservation.
A fascinating aspect is that sea cucumbers function as microhabitatsNumerous species of small crustaceans, fish, and worms live on their surface or even in their cloaca, forming symbiotic associations that increase local biodiversity. Understanding and protecting holothurians therefore means preserving ecological networks complexes that support life in the marine benthos.
Sea cucumbers, discreet and uncharismatic at first glance, gather extraordinary adaptations and play essential roles in ocean health. Understanding their biology, reproduction, and defenses allows us to better appreciate their ecological value and guide conservation measures. responsible management to ensure their long-term availability within more balanced and resilient marine ecosystems.