Sea cucumbers are found worldwide, and are commonly seen on Singapore shores. They appear in many different colours and sizes, and belong to a remarkable group called the Echinoderms that includes sea stars and sea urchins.
One of the most highly sought after seafood products in the market, the dried body of the sea cucumber is prized for their medicinal properties and are often touted as an aphrodisiac.
Though some know how to cook them, most just know how to eat them; how much do YOU know about their lives in the ocean?
1. Sea cucumbers (despite the name) are not fruits- they are animals
The name sea cucumber comes from their resemblance to the popular fruit due to their ‘worm-shaped’ bodies. The biological name for sea cucumbers is holothurians.
2. Sea cucumber bodies are arranged in a circular fashion
Sea cucumbers are radially symmetrical. This means that identical body parts are arranged around a central point. They have a top and a bottom, but no left or right side.
They have a mouth on one end and they excrete waste from the other. Interestingly, this is not how they begin their lives- when they are young they can be divided into two halves!
3. Sea cucumbers have thousands of tiny ‘feet’
The movement of a sea cucumber is controlled by a system that pushes water through canals into thousands of tiny tube feet. A single sea cucumber can possess more than 2,000 tube feet!
4. Sea cucumbers tube feet are sticky
Sea cucumbers attach themselves to the seafloor by secreting a sticky substance through their feet. They can also release a chemical that breaks this bond when they want to move.
5. Sea cucumbers provide a great hiding place
The anus of a sea cucumber is extremely popular with certain species of Pearlfish, which hide there for protection from predators and use the sea cucumber’s waste as a source of food.
6. Sea cucumbers communicate by sending hormones
Sea cucumbers can communicate by sending hormone signals to each other through the water. The animals release both eggs and sperm into the water and fertilisation occurs when they meet.
7. Sea cucumbers can change sex
There is no way of telling a male or female sea cucumber from the outside. Sea cucumbers are usually either male or female, but some species can also change sex during their lifetime.
8. Sea cucumbers have no brain as we know it
Instead sea cucumbers have a network of nerves that receive information from the skin. Interestingly, their tube feet have cells that allow them to sense light and possibly vision.
9. Sea cucumbers fight by shooting out their guts
Many species of sea cucumber can deliberately expel their internal organs as a form of self-defence. The animal can rid itself of its entire digestive system, along with respiratory organs and gonads. All parts are eventually re-formed.
10. Sea cucumbers are scavengers
Like earthworms they are scavengers, moving along the seafloor and feeding on tiny particles of algae or microscopic animals that they collect with their tube feet. The particles they grind down to smaller pieces are further broken down by bacteria, and become part of the ocean’s nutrient cycle. Some sea cucumbers have been found to process more than 130 kg of sediment per year!
Why are sea cucumbers important?
Sea cucumbers provide an important contribution to economies and help provide livelihoods to many coastal communities. As they are one of the more economically important seafood exports in many countries, it is not surprising to find that populations of wild sea cucumbers have decline significantly under intense fishing pressure.
As a result, there are over 377 species of sea cucumbers on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species, of which 7 are classified as ‘Endangered’, and 8 are classified as ‘Vulnerable to extinction’.
However, there is a new glimmer of hope as positive steps are now being taken to develop environmentally sustainable fishing practices for the commercially important species. This will ensure a safe environment for sea cucumbers to grow, and in turn provide a healthy livelihood for fishermen, and a good supply for everyone!
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