40 Fun Facts About Sea Cucumbers

Sea cucumbers pump seawater in and out through the anus to carry out which vital function?

Breathing is done by two branching respiratory trees just inside the anus, which draw oxygen from each gulp of seawater before it is squirted back out.

Which organ does every sea cucumber live its whole life without?

A brain is absent: the nerves form a ring around the mouth, and a sea cucumber can still move about after that ring has been surgically removed.

Some sea cucumbers scare off a crab by ejecting which parts of themselves, which later grow back?

Internal organs such as the gut are thrown out through the anus or a rupture near the mouth, a defence called evisceration. The animal lives off its reserves until replacements grow.

Which farm animal names Scotoplanes, the sea cucumbers that walk the deep seabed on stilt-like legs?

Pigs give Scotoplanes the common name sea pigs, and the animals roam the abyssal plain in groups that early collectors counted in the hundreds.

Which slender, see-through fish is known for living inside the anus of a sea cucumber?

Pearlfish shelter in the cloaca of a sea cucumber, and a few parasitic species go further and eat the host's gonads from the inside.

Some reef sea cucumbers defend themselves by firing what from the anus at an attacking crab or fish?

Sticky threads called Cuvierian tubules swell to as much as 20 times their length in seawater and glue an attacker fast in under ten seconds while the sea cucumber crawls away.

A sea cucumber can pour itself through a narrow crack by loosening which protein in its body wall?

Collagen fibres in the body wall can be unhooked until the animal all but liquefies, then locked together again so it sits firm inside its hiding place.

Enypniastes eximia, a swimming sea cucumber filmed off East Antarctica, goes by which unflattering nickname?

Headless chicken monster is the popular name for this deep-sea swimmer, which uses webbed fins to rise as much as 1,000 metres above the seabed between meals.

Actinopyga sea cucumbers keep lodgers out of the anus with a ring of which hard structures?

Teeth ring the anus of Actinopyga species, blocking the small fish, crabs and worms that set up home inside the bodies of other sea cucumbers.

Sea cucumbers belong to which animal phylum, along with starfish, brittle stars and sand dollars?

Echinoderms share a five-part body plan, and in a sea cucumber it survives as five bands that run the length of the body from mouth to anus.

Campaigns against which soup ingredient made sea cucumber a popular replacement on Chinese menus?

Shark fin lost favour after campaigns against the soup, and sea cucumber, long served in Chinese soups and stews, stepped into its place.

Sea cucumbers drove the first recorded trade between Asia and the Indigenous peoples of which continent?

Australia's Arnhem Land coast drew fishing fleets from Makassar, in what is now Indonesia, which gathered sea cucumbers there to supply the markets of southern China.

Sea cucumbers, called namako in Japan, have inspired thousands of poems in which verse form?

Haiku about namako run into the thousands, and a single English-language book translates almost 1,000 of them.

Which Greek philosopher's 'holothurion' gave sea cucumbers their scientific class name, Holothuroidea?

Aristotle listed the holothurion among sea creatures that seemed to lack sensation, alongside sponges, though nobody can be sure the animal he meant was a sea cucumber.

Holothurin, the toxin a stressed sea cucumber releases, behaves much like which household product?

Soap is the closest match: holothurin is a saponin, a surfactant that ruptures red blood cells and can kill other animals nearby.

Scientists first mistook Pelagothuria natatrix, the only sea cucumber that never visits the seabed, for which animal?

A jellyfish is what a 2011 NOAA expedition thought it had photographed. The animal drifts beneath an umbrella-like veil and was only identified three years later.

Which fruit names the sea cucumber that crowds rock walls in New Zealand's Fiordland by the thousand?

Strawberry sea cucumbers pack together at up to 1,000 animals per square metre, which is why one stretch of Fiordland is known as the strawberry fields.

One sea cucumber can swallow more than 45 kilograms a year of which material, cleaning the seabed as it feeds?

Sediment goes in at one end and comes out finer and purer at the other, once the animal has digested the organic scraps mixed into it.

Many sea cucumbers have flattened, disc-shaped cells in their body fluid that carry which oxygen-binding pigment?

Hemoglobin in those cells turns both the blood and the body-cavity fluid red in many species, a pigment only a handful of their brittle star relatives share.

Which country set up the world's first conservation reserve for sea cucumbers, in its Lakshadweep islands?

India protects sea cucumbers under the same wildlife schedule as tigers and lions, and the Lakshadweep reserve was created to curb smuggling to black markets abroad.

Dried sea cucumber is traded under which French name, a reshaping of the Portuguese bicho do mar?

Bêche-de-mer comes from the Portuguese bicho do mar, and the Pacific Community's long-running scientific bulletin on sea cucumbers takes the name for its title.

Which Indonesian word for sea cucumber gave English its name for gathering the animals by hand from small boats?

Trepang gave English the verb trepanging, and the dried catch has to be boiled and soaked for days before it is soft enough to cook.

Which animals, the only other living class in their subphylum, are sea cucumbers' closest relatives?

Sea urchins and sea cucumbers both lack arms and share a body plan based on a globe, stretched into a tube in one and armoured with spines in the other.

When the water grows too warm, some temperate sea cucumbers stop feeding and enter which state of dormancy?

Aestivation shrinks the animal as well as slowing it: the gut wastes away and it loses weight, then rebuilds itself once the sea cools.

The skeleton of most sea cucumbers is reduced to microscopic ossicles in the skin, made of which mineral?

Calcium carbonate ossicles come in shapes such as tables and buttons that differ between species, so biologists can name a sea cucumber from a scrap of skin under a microscope.

Round, colourful Pseudocolochirus sea cucumbers, sought after for marine aquariums, are named after which fruit?

Apples lend their name to these sea apples, which can poison a whole tank with their toxin and swell to nearly twice their size by gulping seawater.

The deep-sea sea cucumber Psychropotes longicauda, with its upright tail-like lobe, is nicknamed the 'gummy' what?

Squirrel is the comparison that stuck, because the animal looks like a squirrel-shaped gummy sweet. Its eggs, 4.4 mm across, are the largest of any animal in its phylum.

Holothuria scabra, a tropical sea cucumber widely farmed for food, goes by which misleading common name?

Sandfish burrow into the seabed, and the older animals, which are more sensitive to temperature, dig in to escape the cold.

Which name did 18th-century English give to sea cucumbers before it passed to a group of molluscs?

Sea slugs was the name the Oxford English Dictionary records for sea cucumbers in the 1700s, before it passed to the nudibranchs and their kin.

Compared with a starfish, whose mouth faces the seabed, a sea cucumber spends its life in which position?

Lying on its side is the normal posture: the mouth is at one end and the anus at the other, so three of its five rows of feet face down and do the walking.

Sea cucumbers extend their tentacles and tube feet using pressure from which network of fluid-filled canals?

Water vascular system canals are a hallmark of the whole phylum, but a sea cucumber's opens into its own body cavity rather than to the sea outside.

The sea cucumber Rynkatorpa pawsoni is unusual for living in partnership with which deep-sea fish?

Anglerfish are its partners, which makes this species a rare exception among sea cucumbers, nearly all of which scavenge debris on the seabed.

The Turkish name for the sea cucumber, deniz patlıcanı, swaps the cucumber for which other vegetable?

Eggplant, or aubergine, is the Turkish pick, while the Japanese name namako is written with characters that can be read as sea mice.

Tonna galea, a hunter that shrugs off sea cucumber toxins and swallows its prey whole, is what kind of animal?

A snail, and a very large one: the giant tun paralyses a sea cucumber and then envelops it, and sea cucumbers make up most of its diet.

What is the first free-swimming larval stage of a sea cucumber called, a tiny form ringed by a band of cilia?

Auricularia larvae appear about three days after the eggs are fertilised, then turn into a barrel-shaped doliolaria before the first tentacles grow.

The oldest known sea cucumber fossils, more than 450 million years old, date from which geological period?

Ordovician seas held the earliest known sea cucumbers, but well-preserved fossils are rare, so much of the group's early history is still uncertain.

The Japanese delicacy konowata is made by salting and fermenting which part of a sea cucumber?

Intestines are squeezed clean of sand, rinsed in seawater and mixed with salt to make konowata, which is counted among Japan's chinmi, or rare tastes.

Most sea cucumbers lack eyes, yet nerve endings in the skin let them sense touch and what else?

Light registers through the skin itself, although a few species go one better and carry small eyespots near the base of the tentacles.

In Japan's Kojiki, the goddess Ame-no-Uzume answered the sea cucumber's silence by doing what to its mouth?

Cut it with a dagger, which the Kojiki gives as the reason the animal's mouth is slit; the same goddess is better known for luring the sun goddess Amaterasu out of her cave.

Sea cucumbers go by the name loli in the Indigenous language of which US state?

Hawaii's word loli joins a long list of local names for the animal, from balatan in Tagalog to minch' i mari in Sicilian.