SEA CUCUMBER SPECIES
More than a thousand species of sea cucumbers exist around the world. They vary in size from two centimeters to two meters. In some places they are quite plentiful, making up 90 percent of the biomass found there. Wikipedia says there are over 1,700 species; Encyclopedia Britannica says there are 1,200. Other sources say less. The discrepancies might be attributed to how different groups of sea cucumbers and sea-cucumber-like animals are classified.
Sea cucumbers belong to the class Holothuroidea, which are part of the phylum of echinoderms, which includes starfish and sea urchins. The sea cucumber orders are 1) Apodida, 2) Arthrochirotida, 3) Seilacher, 4) Dendrochirotida Elasipodida 5) Holothuriida, 6) Molpadida, 7), Persiculida, 8) Synallactida, Each order has two to twelve families listed under it.
Holothurian (sea cucumber) classification is complex and their paleontological phylogeny relies on a limited number of well-preserved specimens. The modern taxonomy is based first of all on the presence or the shape of certain soft parts (podia, lungs, tentacles, peripharingal crown) to determine the main orders, and secondarily on the microscopic examination of ossicles to determine the genus and the species Commercially exploitable species are mainly in the order Aspidochirotida. [Source: Wikipedia]
Black sea cucumbers are one of the few poisonous species of sea cucumber. When their skin is rubbed, they release a toxic red fluid. When threatened, they do not eject Cuvierian tubules in the way that some sea cucumbers do; instead they extrudes white, thread-like secretion from their anus called Cuvierian tubules. They are found in the Kii Peninsula of Japan and in the Indian and Pacific Ocean. Sea Apples are also toxic (See Below).
Websites and Resources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Fishbase fishbase.se; Encyclopedia of Life eol.org; Smithsonian Oceans Portal ocean.si.edu/ocean-life-ecosystems ; Monterey Bay Aquarium montereybayaquarium.org ; MarineBio marinebio.org/oceans/creatures; Websites and Resources on Coral Reefs: Coral Reef Information System (NOAA) coris.noaa.gov ; International Coral Reef Initiative icriforum.org ; Coral Reef Alliance coral.org ; Global Coral reef Alliance globalcoral.org ; Global Coral Reef Monitoring Network gcrmn.net
Colorful Sea Apples and Glowing Sea Cucumbers
Glowing sea cucumbers (Pannychia moseleyi) are deep sea sea cucumber that flashes spirals of blue light when threatened. The bright bands swirl along its body and may ward off would-be predators. These creatures are about 20 centimeters (8 inches) long and feed on detritus, organic material, bacteria, and plankton. They live in Pacific Ocean at depths from 30 to 2,300 meters (100 to 7,500 feet). [Source: Monterey Bay Aquarium]
Sea apples are common name for what are regarded as the most colorful sea cucumbers. Somewhat round in shape and native to the Pacific and Indian Oceans, they belong to the genus Pseudocolochirus and are filter feeders with tentacles, ovate bodies, and tube-like feet. As is the case with most other sea cucumber they can release their internal organs into the water when threatened or stressed. In addition, they can release a toxic saponin called holothurin into the water as a defense mechanism. Sea apples are listed as 'Vulnerable' on the International Union for Conservation of Nature (IUCN) Red List. Many are harvested for the aquarium trade. Ironically, they do not make good aquarium specimens as they are often toxic to their tank mates.[Source: Wikipedia]
Sea apples are generally 10 to 20 centimeters long. They have five rows of long ,slender tube feet that are bright yellow. The two rows on the upper side of the body are usually less distinct. The body is usually red on the upperside, and transitions to light purple and white on the underside. The mouth is ringed with blue. The feeding tentacles are red. Their branched tips may be purple, yellow or white. During low tide, these sea cucumber retract their colourful feeding tentacles. Their anus is surrounded by five tiny teeth-like structures that are bright yellow. When relaxed, their normal shape is short and sausage-like like most other sea cucumbers. When threatened or stressed, they may inflate itself into a large round balls. [Source: Wild Singapore]
Sandfish and Teatfish — Commonly-Eaten Sea Cucumbers
Sandfish (Holothuria scabra) is a species of sea cucumber. It is raised on aquaculture farms and are harvested and processed into "beche-de-mer" and eaten in China and other Pacific coastal communities. The sandfish has been eaten by humans for over 1000 years. About twenty other species of sea cucumber are also consumed but the sandfish is the species most often used. In the 1990s it was being sold dried as beche-de-mer for up to US$100 per kilogram. Harvesting sandfish from the sea is known as trepanging in Indonesia. In many areas the fisheries have declined over the years because of over fishing. Breeding and raising sandfish is done in the Philippines.
The black teatfish (Scientific name: Holothuria nobilis) is a species of sea cucumber that occurs in coral reef habitats in the Indian Ocean, and is most commonly found in reef flats and outer reef slopes with a preference for hard substrates. Teatfish are non-migratory and relatively sedentary, with slow growth rates and longevity estimated at several decades. [Source: NOAA]
Large numbers of sea cucumbers are traded internationally each year, and the black teatfish is one of the most highly valued sea cucumber species in the Indo-Pacific region. It is sold dried and processed as “beche-de-mer” primarily to luxury food markets in Hong Kong, Singapore, Taiwan, China, Korea and Malaysia. For preparation, sea cucumbers are first gutted and their body walls are dried. They are usually made into a soup
The Convention on International Trade in Endangered Species (CITES) places the black teatfish in Appendix II, which lists species not necessarily threatened with extinction now but may become so unless trade is closely throughout Its range. In many places where sea cucumbers are legally harvested, all fishermen must possess special licenses; some coastal areas are closed to sea cucumbers harvesting and are restricted to certain times of the year in order to protect the species.
Largest, Heaviest and Smallest Sea Cucumbers
The largest sea cucumber ever documented was a snake sea cucumber that was three meters (10 feet) long. These creatures have long and slender bodies and, as their name suggests, look like snakes. Many sea cucumbers move around by using their tiny tube feet but this species moves in undulating, wavelike motions due to its body length. Snake sea cucumbers live in shallow waters of the Indo-Pacific Ocean on reefs, sandy bottoms and sea grass beds at depths up to 20 meters (66 feet). Snake sea cucumbers come in a variety of colors and patterns — ranging from brown to yellowish, with wide darker-colored stripes or patches. These sea cucumbers are also sediment feeders that use their tentacles to sift through the sand for food. [Source: Bubbly Diver]
The tiger’s tail sea cucumber is the largest sea cucumber species in the western Atlantic Ocean. It can grow to about two meters (6.6 feet) m) long. Its name cames from its long tail-like shape and body-covering white stripes. This species lives in coral reefs in the Caribbean Sea, the Gulf of Mexico and the tropical western Atlantic Ocean at depths from three to 30 meters (9.8 to 98 feet). This sea cucumber’s markings camouflage it so well it was described until in 1980.
The king sea cucumber (Thelenota anax, family Stichopodidae) is one of the heaviest known sea cucumbers, weighing up five kilograms. Their average length is about 69 centimeters. The long, longest recorded one was was 89 centimeters long. One of its two sex organs is 50 centimeters long. Its hard to do an accurate weighing of a sea cucumber because of its weight its largely determined by how much water the animal is retaining at the time it is being weighed. [Source: Wikipedia]
The smallest sea cucumber is the Thyonina bijui. It only grows to a size of about two centimeters (0.8 inches). just 0.8 in (2 cm). It lives in the Indian Ocean and a barrel-shaped body and reddish brown color. They get around using the numerous tube on their bottom side.
Warty Sea Cucumbers
Warty sea cucumbers (Scientific name: Parastichopus parvimensis) are native to the eastern Pacific Ocean. They are found along the west coast of North America from Monterey Bay, California to Baja California, Mexico. They are most abundant south of Point Conception, California. They are typically found at depths of zero to 30 meters (98 feet) in rocky and sandy bottom environments beyond the low intertidal zone. The largest specimens are found in the subtidal zone on sandy bottoms and rock surfaces where there is abundant food (mainly particulate material from under the kelp canopy and granular sediments). Their lifespan in the wild is typically five to 10 years. [Source: Allison Knight, Animal Diversity Web (ADW) /=]
Warty sea cucumbers are detritivores (mainly eat decomposed plants and/or animals), using oral tentacles and tube feet covered with adhesive mucus to collect debris and sediment. This is passed to the mouth, located within the center of the tentacles, where it is swallowed. After digestion, the remaining non-organic material is eliminated in long fecal castings. Wart sea cucumbers are also prey for a number of fish, gastropods, crustaceans and sea stars. Young ones and larvae are vulnerable to predation by fish and other animals; it is thought that this is why juveniles are typically only found under rocks.
Like other sea cucumbers, warty sea cucumbers help the ecosystem by creating habitat and fostering biodegradation. They recycle nutrients and clean the benthic (ocean-bottom) environment when they collect and eat detritus and rework benthic sediments, oxygenating the top layers and making them more suitable for burrowing animals. Their feeding activity prevents the buildup of organic decaying material and possibly pathogenic organisms in the sediment environment. Additionally, their eggs, larvae, and juveniles provide food for filter feeders and other species of echinoderms,
Humans consume a variety of sea cucumber species, including warty sea cucumbers. They are harvested by almost exclusively divers and shipped to Asian markets in China, Hong Kong, Taiwan, and South Korea; they are sold for food consumption and folk medicine uses. Although there is evidence that warty sea cucumbers are over-exploited, and overharvested wart sea cucumbers have not been evaluated for the International Union for Conservation of Nature (IUCN) Red List. They have no special status according to the Convention on the International Trade in Endangered Species (CITES).
Warty Sea Cucumber Characteristics and Behavior
Warty sea cucumbers reach lengths of 40 centimeters (15.75 inches). Body weight is difficult to estimate because sea cucumbers have the ability to take on sea water and eviscerate some of their internal organs, which can dramatically increase or decrease their mass. As a rule, their wight is greatest in the winter months due to increased feeding and gonad maturation. [Source: Allison Knight, Animal Diversity Web (ADW) /=]
Warty sea cucumbers are brown or orange and have wart-like black-tipped papillae on their bottom side — the source of their common name. Both sexes are roughly equal in size and look similar. According to Animal Diversity Web: The mouth and anus are on opposite ends of their cylindrical bodies. Their soft body walls and lack of a skeleton enable these animals to expand and contract significantly. They possess tube feet which help them to gather food as well as move across the ocean floor. Water is pumped in and out of sea cucumber's anus into two specialized breathing apparati known as respiratory trees or water lungs. The base of each tree is connected to the cloaca and oxygenated water is drawn in through this sphincter, with deoxygenated water then being expelled. /=\
Warty sea cucumbers are diurnal (active during the daytime), nocturnal (active at night), crepuscular (active at dawn and dusk), motile (move around as opposed to being stationary) and migratory (make seasonal movements between regions, such as between breeding and wintering grounds). They travel across the sea floor, ingesting sediment. They do not appear to maintain a home range beyond remaining in areas where food is available. Sea cucumbers neither establish nor defend territories. From August through November, warty sea cucumbers migrate to deeper waters, nearly disappearing from the shallow waters where they are normally found. They engage an annual evisceration cycle to expel sediment built up in their systems from feeding on detritus. Over a four week period, typically sometime between August and October, these animals expel their viscera and gonads then begin to regenerate them for the next year. /=\
Warty Sea Cucumber Mating, Reproduction and Development
Warty sea cucumbers are oviparous (young are hatched from eggs) and iteroparous (offspring are produced in groups such as litters multiple times in successive annual or seasonal cycles). They engage in external reproduction in which sperm from the male fertilizes the female’s egg outside her body and employ broadcast (group) spawning, the main mode of reproduction in the sea. It involves the release of both eggs and sperm into the water and contact between sperm and egg and fertilization occur externally. [Source: Allison Knight, Animal Diversity Web (ADW) /=]
Warty sea cucumbers breed once a year. The breeding season is typically in the early summer (May/June). Near Santa Catalina Island, spawning occurs in May and June but in Baja, California spawning can begin as early as February. They are polygynandrous (promiscuous), with both males and females having multiple partners. Because warty sea cucumbers broadcast spawn and larvae develop independently in the water column as plankton, there is no parental investment . /=\
Their life cycle is characterized by metamorphosis — a process of development in which individuals change in shape or structure as they grow. According to Animal Diversity Web: Five stages of gonad development have been identified in this species: Undifferentiated/in repose, gametogenesis, ripe, spawing and post-spawning (similar to other sea cucumber species). Size at sexual maturity of warty sea cucumbers has been recorded at anywhere between 40 grams to 120 grams. Gonads begin developing each year around January. Breeding season is typically from May to June and is likely triggered by changes in water temperature or phytoplankton blooms. Gonads are reabsorbed beginning in September. /=\
After fertilization, the embryo hatches into a free-swimming gastrula within 64 hours. By approximately 14 days post-fertiliztion, the gastrula develops into an auricularia larvae, which ingests phytoplankton. The final larval stage of this sea cucumber is the doliolaria (barrel shaped, non-feeding larvae with ciliary band/s). After approximately 27 days these doliolaria larvae settle onto rocks and algae, metamorphosing into pentacula juveniles. Juveniles grow to 3.5 centimeters in length within one year and are strictly found under rocks, never on them. /=\
Chocolate Chip Sea Cucumber
Chocolate chip sea cucumber (Scientific name: Isostichopus badionotus) are primarily found along the northern Pacific coast of South America and around the Galapagos Islands. Also known as three-rowed sea cucumbers, because their three distinct rows of podia on their bottom side, they have also been observed along the northeastern coast of Venezuela. Like most echinoderms, "bottom-feeding" animals that prefer shallow water. The favor substrates in the calm waters of channels and coves, shielded by high cover. [Source: Celia Rangel, Animal Diversity Web (ADW)]
Chocolate chip sea cucumbers are shaped like other sea cucumbers and have radial symmetry (symmetry around a central axis). They range in length from two .02 to 2 meters (0.07 to 6.56 feet and have an average length to 10 to 30 centimeters (four inches to one foot. They lack spines, typical of most echinoderms, and . also lacks any true appendages other than its tube feet. According to Animal Diversity Web: The animal is mostly solid in color, however, the side of its body that it uses to move along the sea floor is slightly lighter in pigment. Calcareous deposits are embedded in the epidermal layer of this animal. Having definite anterior and posterior ends, the sea cucumber has a large mouth surrounded by bushy tentacles with thick bases that divide into numerous tiny branches. A dark pigmented peristomial membrane surrounds a circular lip.
Chocolate chip sea cucumbers are largely solitary creatures that spend most of their lives feeding. They are deposit-feeders, literally eating deposited material or sediments off of the ocean floor. Using their tentacles, they push large scoops of sediments into their mouth. Because sediments are typically low in nutrients, the sea cucumbers ingest enormous amounts of sediment per day to ensure they get enough nourishment. It is estimated that each Chocolate chip sea cucumber ingests between 1 and 2.3 tons of sediment per year. Despite this chocolate chip sea cucumbers are considered selective feeders, pursuing particular blends of sediment that are high in organic material.
Chocolate chip sea cucumbers employ broadcast (group) spawning, the main mode of reproduction in the sea. It involves the release of both eggs and sperm into the water and contact between sperm and egg and fertilization occur externally. Females have an oviduct and males have a vas deferens. In temperate climates, eggs are laid in late winter and early spring. Sperm reach the eggs by way of the water. The fertilized eggs develop into free-swimming pelagic larvae. Chocolate chip sea cucumber have the unique ability to divide themselves into two.
U-Shaped and S-Shaped Sea Cucumbers
Trachythyone elongata and Paraleptopentacta elongata are a species of sea cucumber in the family Cucumariidae found in the northeastern Atlantic Ocean and parts of the Mediterranean Sea. These slender, greyish-brown sea cucumbers have U-shaped, or sometimes S-shaped bodies, reaching a maximum length of about 10 centimeters (4 inches). [Source: Wikipedia]
U-shaped sea cucumbers can be found in the sand and mud from sea level to 110 meters (365 feet) in the water. They dwell burrows in the sediment, with the two extremities projecting. Their The dorsal surface is covered with darker brown or grey, conical projections. In small specimens, the ventral surface bears five longitudinal rows of tube feet, and in larger specimens, it bears five double rows. The body wall is featureless except minutel ossicles and is very elastic and leathery in texture. Their mouth is surrounded by a ring of simple branched tentacles that are usually retractable when they catch their prey. They have a water vascular system that includes a water ring around a proximal pharnyx with 5 radial canals that run the length of the body wall.. (Carson 1955) [Source: Ashlea Rives, Animal Diversity Web (ADW)]
According to Animal Diversity Web: Movement is very slow and is like that of an earthworm crawling along the ocean floor. When they are attacked by predators, mainly sea stars, they respond violently by arching back and forth in defense. This is one of the only times that they move faster than a crawl. These sea cucumbers eat almost anything they can get their tentacles on but favor plankton and other small microscopic organisms. They ingest food like earthworms, taking in sand and mud along with the plankton and pass it through their bodies Some species of sea cucumbers have annual periods of dormancy where they eat nothing. During these periods their internal organs atrophy and are flused out. After new internal organ are then regenerated when they are ready to eat again, about 6 weeks later.
Image Sources: Wikimedia Commons, NOAA
Text Sources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.
Last Updated May 2023