The shape of the sea cucumber is an elongate cylinder with a mouth and anus on opposite sides. It has a worm like body that lays parallel to the ocean's floor. The external surface of the sea cucumber is very soft because it is an invertebrate (without a spine), it also has five rows of tube feet that are all along the length of their body. Around the mouth there can be more than ten ambulacral appendages, branched, oral tentacles, and ambulacral feet that can be on all sides.
The internal structure of sea cucumbers consists of an alimentary canal, which is a long tube that runs from the mouth of the sea cucumber at the forward end to the anus, which is at the posterior end of the sea cucumber. The posterior end of the sea cucumber is enlarged and becomes narrower towards the anterior end. There are two types of respiratory organs; they are the respiratory trees and the curvier's organ. These organs function as a pair to pump water through the system. The body wall of the cucumber consists of powerful longitudinal muscles running along the radii and transverse muscles in the inter-radii.
Sea Cucumber - Reproduction
Sea cucumbers tend to be having separate sexes. Spawning behavior tends to be seasonal. Many sea cucumbers on the Great Barrier Reef spawn during the mass spawning events seen in November. During spawning, sea cucumbers travel to the top of reef structures and release their gametes into the surrounding currents. A range of developmental modes is seen among sea cucumbers. Development via feeding larvae (Planktotrophy) or non-feeding larvae (lecithotrophy) occurs in a large number of species. In others, embryos and larvae may be brooded by the female. The feeding larva of sea cucumbers (when present) is very distinctive and is called an auricularia larva. It swims for about 10-40 days before settling on the bottom and metamorphosing into a baby sea cucumber.
Sea Cucumber - Distribution and Habitats
The sea cucumbers are found in most oceans and in all depths. Some move over the bottom of the sea, some swallow sand and or mud and others catch small organisms. Most of the sea cucumbers live near rocks, corals or seaweeds. Although most of the sea cucumbers live among the sea grasses some do live in the mud or in the sand.
Sea cucumbers have tough skins that probably lessen the risk of predation. However, they do face the problem of being eaten by large marine fish. Sea cucumbers, however, don’t just lie around and let this happen. They have a number of neat tricks. The first is that some sea cucumbers have the ability to throw up their entire digestive systems! They do this to distract the predator that generally focuses on the yummy bits thrown up with the stomach. The sea cucmber then crawls away and regrows its entire digestive tract over the next couple of months. Amazing huh! The second trick is that some other sea cucumbers have fine sticky threads that they are able to eject out their bottoms when trouble brews. These threads are called Cuverian Tubules and are as sticky as any glue you can buy in a shop. These threads are thrown out over the potential predator who gets them stuck all over it. This usually makes the potential predator desist from attacking the sea cucumber.
Sea Cucumber as Food
To prepare the sea cucumber after it is collected, the internal organs are removed, and dirt and sand are washed out of the cavity. It is then boiled in salty water and dried in the air to preserve it. When readied for use in making food, it is softened in warm water and then boiled.
According to analysis by principles of traditional Chinese medicine, the sea cucumber nourishes the blood and vital essence (jing), tonifies kidney qi (treats disorders of the kidney system, including reproductive organs), and moistens dryness (especially of the intestines). It has a salty quality and warming nature. Common uses include treating weakness, impotence, debility of the aged, constipation due to intestinal dryness, and frequent urination. Sea cucumber is traditionally served in the form of a soup.
From the nutritional viewpoint, sea cucumber is an ideal tonic food. It is higher in protein (at 55%) than most any other food except egg whites (at 99%), and it is lower in fat than most foods (less than 2%). For nourishing essence and blood in persons who suffer from emaciation, it is combined in soup with pork. For impotence, frequent urination, and other signs of kidney deficiency, sea cucumber is cooked with mutton. For yin and blood deficiency, especially manifesting as intestinal dryness, sea cucumber is combined with tremella (yiner, the silvery tree mushroom).
For modern applications, the dried or extracted sea cucumber is useful as a nutritional supplement, prepared in capsules or tablets. The fully dried material has a protein concentration as high as 83%. From the Western medical viewpoint, the reason sea cucumber is valuable is because it serves as a rich source of the polysaccharide condroiton sulfate, which is well-known for its ability to reduce arthritis pain: as little as 3 grams per day of the dried sea cucumber has been helpful in significantly reducing arthralgia. Its action is similar to that of glucosamine sulfate, which is useful for treating osteoarthritis. Sulfated polysaccharides also inhibit viruses; there is a Japanese patent for sea cucumber chondroitin sulfate for HIV therapy.
Economical Uses and Biological Significance
Although about 200 species of sea cucumber have been recorded from Australian waters, only a few large tropical species were collected for processing as béche-de-mer. The process itself involved boiling the body in salt water, gutting it, smoking it and finally sun-drying it. The finished product is hard, dry and a fraction of the weight of the live animal. Although there is still considerable demand for béche-de-mer throughout much of Asia, there is very little commercial fishing for it in Australia today. The local industry wound down in the late 1940s largely because of lesser demand and poor prices.
There are a number of animals that live with sea cucumbers. Tiny polychaete worms that look almost identical to the skin of the sea cucumbers crawl across the skin and are probably responsible for cleaning the surface of the sea cucumber in return for getting a place to live. There are also some very strange relationships. There is a little fish that lives in the back end of sea cucumbers. Again, in return for being a cleaner, the fish gets a pace to live and something to eat.
The many varieties and species of Sea Cucumbers around the world are an essential part of the ecosystem of the ocean. They are both predators and prey to many different organisms. Their main food source is zooplankton (incredibly small drifting organisms in the sea,) they also provide food for certain Sea Stars. Because they are living animals, they are part of the ecosystem and will become a food source one way or another. As mentioned previously, the most fascinating characteristic of the sea cucumber is their ability to eviscerate their guts, thus providing food for their predators while still being able to survive themselves. The ability to provide food for other organisms labels the Sea Cucumber as a provider (of food) in their marine environment.
Chinese studies reveal that sea cucumbers also contain saponin glycosides. These compounds have a structure similar to the active constituents of ginseng, ganoderma, and other famous tonic herbs. Additional Chinese studies indicate anticancer properties of both the sea cucumber saponins and the polysaccharides.
Sea cucumbers are harmless. Unfortunately, they are good to eat and are considered a delicacy by many cultures. Did you know that a ton of dried sea cucumbers will fetch as much as a million dollars in some countries? This has lead to uncontrolled exploitation of sea cucumbers around the world. In some places they have almost completely disappeared. Several projects (e.g. Solomon Island) are currently underway to start growing sea cucumbers in aquaculture farms to try and reduce the fishing pressure on sea cucumbers. Sea cucumbers are seriously endangered in many parts of the world. As all other marine creatures, it is essential to protect both the Sea Cucumbers themselves, and their environment to ensure the continuing survival of diversity in the oceans.
Common Name: California Sea Cucumber
The Parastichopus Californicus can be identified by their prominent, stiff, conical papillae (cone-shaped spines). They also have tube feet on their ventral side. They are dark red or brown in color and have an approximate length of 40 cm (16 inches). They are found on the Northwest coastal waters from Alaska to Isal Cedros in Baja, California. They live in a sub tidal habitat, as well as feeding on detritus and small organisms. They are currently the only Sea Cucumber harvested in British Columbia, however only every three years to control population decline. They are eaten for their five muscle strips and body wall. One California Sea cucumber is shown below, this one is currently being kept at the Bamfield Marine Station and we have nick named him "Mike."
Common Name: Burrowing Sea Cucumber
This bright orange sea cucumber has ten branched tentacles and five rows of tube feet. They are 25 cm (10 inches) long and live along the western coast from Gulf of Alaska to Avila Beach in California. They live in rocky areas with lots of crevices to hide from their predators, particularly the Sea Star Solaster Stimpsonii. They live in the intertidal zone all the way out 24 m (80 ft) or so. Their branched tentacles are used to collect drifting food. The photograph below shows a Burrowing Sea Cucumber, along with sea grass, its favorite environment.
Common Name: White Sea Cucumber
These Sea Cucumbers cannot completely contract their tube feet. They have ten yellow or white-branched tentacles, eight long and two short. They are ten cm (four inches) in length and live both off the coast of Japan, as well as the Sacramento Reff, Baja, California. They like rocky places ranging from lower intertidal to 15m off shore. Their tentacles remain retracted during daylight hours. A White Sea cucumber is shown below, lying on a rocky surface.