Why We LOVE the Sea Cucumber

EUMCS Committee
Mar 4, 2021
3 min read

The Sea Cucumber; a humble creature. The bottom of the food chain. But take a closer look and a thing of beauty beholds. Digesting detritus and expelling nutrient-rich waste, the sea cucumber combs the sea floors, slowly revitalising the world’s oceans. Sea cucumbers play a vital role in fertilising and aerating ocean sediments, literally breathing life into coral reefs.

The Garlic bread sea cucumber (Holothuria scabra). Photo by Ria Tan (CC BY-SA 2.0)

Elegantly simple, the sea cucumber does not waste any effort on looks. In fact, it does not even have a face. Just a cylindrical blob with a hole at either end. Nor does it concern itself with the complexities of higher thought. Instead of a brain, a few neural tissues surround it's oral cavity. Free from distractions, the sea cucumber is fiercely productive and unrelentingly focussed; a quality that we as humans could only dream of as we look on from our busy, complicated lives. Sea cucumbers barely even stop for reproduction; instead simply releasing their sperm and eggs nonchalantly into the ocean currents in the vague hope that they might meet.

This pearlfish may look doomed, but its actually hiding inside the sea cucumber. This special relationship provides protection to the pearlfish, and causes no harm to the cucumber. SOURCE: BBC Earth

Unsurprisingly, the sea cucumber falls victim to the dinner plates of many creatures, from crustaceans, to turtles, to humans. It does have one fantastically alien trick up its sleeve whereby it can deter predators by shooting its sticky intestines out of its body, entangling its attacker. Even if the sea cucumber does get munched a bit, it is able to regenerate any missing body parts; a quality reminiscent of Arnold Swarzenegger's robotic nemesis in Terminator. Even more unthinkably weird, sea cucumbers breathe through their anus, where specialised respiratory "trees" extract oxygen molecules from the water.

Sea cucumbers can shoot their intestines from their body to deter predators.

The Red Box sea cucumber, proudly showing off it’s respiratory tree. Credit: Peter Southwood (CC BY-SA 3.0)

A delicacy in China, sea cucumbers are eaten on special occasions. They can be served dried, pickled or fried. Soaring demand has sadly resulted in the overfishing of sea cucumbers. In many areas, their depletion has resulted in murkier, more polluted waters. The melancholy of sea cucumber consumption is beautifully captured in this excerpt from Audrey C. Deng's poem,

Ode to the Sea Cucumber:

"The Sight of you

On display in Jars

Dried, Curdled Grey

and deprived of lubrication

Brings tears to my eyes...

...I dramatically cringe at your porcelain cradle.

It is terror accompanied by shiitake mushrooms."

"Sea cucumbers" by Juan Carlos Martín (CC BY 2.0)

"Sea cucumber" by Kent Wang (CC BY-SA 2.0).

Thankfully, the world is waking up to the very real threat of endangered sea-cucmber poaching. Just last year, the first ever sea cucumber conservation area was opened in the Indian Ocean to reduce smuggling into China. The reserve covers an area of 239 square kilometers - that’s roughly the size of the City of Edinburgh constituency.

A wonderfully varied animal, there are some 1,250 species of sea cucumber. They range from 0.75 inches to a somewhat terrifying 6.5 feet, and can be any colour from plain brown to striking fluorescent spots or rainbow stripes. Smooth or spiky, flat or round, the sea cucumber presents a rich bounty of discovery to the humble studier.

"Pineapple Sea Cucumber (Thelenota ananas)" by Richard Ling (CC BY-NC-ND 2.0).

Sea cucumbers are found in the coastal areas of nearly every country in the world. Despite this, sea cucumber are notoriously hard to study. Attempts to tag or dye sea cucumbers to track their movements in the wild are just slimed away through the bodies of the sea cucumbers. Growth is also tricky to measure, since sea cucumbers have the ability to eat themselves if they are starving, thereby becoming smaller. Ironically, this simple, common creature remains one of the most mysterious, illusive and beautiful beings in the ocean.