What is the origin of the name 'sea cucumber'?

The sea cucumber is called 'ナマコ' in Japanese, which is written as '海鼠' in kanji. Historically, this kanji combination was pronounced 'ko' and referred to dried sea cucumbers sold as a snack. During the Muromachi period, it became common to sell them fresh, and the name shifted to '生海鼠' ('nama-ko'), eventually shortening to 'ナマコ'.

Another theory suggests that 'ko' as a demonstrative pronoun for 'that', indicating the creature's unusual appearance, may have led to the name.

Why do sea cucumbers live there?

Sea cucumbers inhabit a wide range from shallow waters to the deep sea. Most crawl along the seabed, but some deep-sea species float freely. Despite their slow movements and vulnerability, sea cucumbers have few natural predators because they contain holothurin, a substance toxic to fish but harmless to humans.

What do sea cucumbers eat?

Sea cucumbers primarily feed on plankton, ingesting sand and mud in the process. An individual may consume about 30 kg of sediment in a year. During food shortages, they can metabolize their own tissues for energy, which isn't as painful for them due to their sedentary nature.

They are also more active in seeking food during winter because they tend to hibernate during summer. Depending on the species, they either lick up plankton or use their tentacles to capture it from the water.

How do sea cucumbers breathe?

Sea cucumbers have a respiratory organ called the 'respiratory tree', which branches extensively throughout their body. They can also breathe through their skin. Even if they lose their respiratory trees, they can still respire through their skin.

Is it true that sea cucumbers can expel their internal organs?

Yes, sea cucumbers can eject white thread-like organs from their anus when threatened, using an organ called the Cuvier's gland. Those without this gland may expel their internal organs as a defense mechanism. Despite the drastic defense, sea cucumbers can regenerate their organs in one to three months thanks to their high regenerative capabilities.

Can sea cucumbers really live after being cut in half?

Sea cucumbers have remarkable regenerative abilities, not limited to their internal organs. If cut in half, each part can regenerate into a new individual within three months. This biotic resilience is a key to their survival strategy. They typically live for about 5 to 10 years.

How are sea cucumbers born?

Sea cucumber spawning periods in Japan range from March to September, during which a single individual can produce up to 20 million eggs. Most young float freely in the ocean before settling on the seabed as they mature. In harsher environments like the Antarctic, some species develop inside their parent's body.

Are sea cucumbers used in medicine?

Yes, sea cucumbers are used in traditional Chinese medicine to treat a variety of ailments, including as a tonic and for treating skin diseases. They possess antifungal properties and are used in remedies for athlete's foot.