If you frequent Chinese restaurants (and doesn’t everyone?) you may be familiar with sea cucumbers as food.
And if you have never tasted this delicacy – fear not, it is probably there somewhere on the menu.
Sea cucumbers, also known as bêche-de-mer or trepang (in the processed form), were one of the treasures sought after by early traders.
Along with sandalwood, mother-of-pearls, and other goodies, these strange and slightly scary animals provided a source of income and a reason to sail vast distances.
But the demand remained low until the emergence of a Southeast Asian middle class that craved status symbols and traditional medicine.
Sandalwood and pearl shells are now grown commercially and there has been progress in farming sea cucumbers, but the bulk of the market still comes from village communities in the Indo-Pacific.
At first blush this is a very attractive cottage industry.
The crop is free and easy to catch – after all sea cucumbers don’t swim away.
The problem is over-harvesting.
And with over-harvesting the darker side of the industry emerges.
Fishers change to scuba to collect the animals.
Filling scuba tanks and taking dive courses is a hassle, so sometimes fishers buy hookah sets and here is where the problem arises.
Hookah uses a surface-based compressor that pumps air down to the diver.
No longer limited by the one tank of air and without necessary training, divers stay down until they are too cold to continue.
Not only do the sea cucumber stocks become depleted but more tragically, divers often become afflicted with “bends” that can lead to paralysis and death.
Fiji has a terrible record with regard to this.
The Fiji Times reported in April of 2013, that “over the past eight years, 18 villagers from Naviti died from the use of UBAs (Underwater Breathing Apparatus) while more than 12 developed partial paralysis.”
Fiji banned the export of sea cucumbers in 2017 but recently lifted it.
Now, only certain species can be taken only from July 1 to August 30.
Whether even this limited season is sustainable has yet to be determined.
So, what the heck do you do with a sea cucumber once you’ve caught it?
You cut it open down the midline, remove the internal organs, wedge a couple of short sticks into the opening and then smoke the thing for hours.
The result is a dry, smoked, leathery product that is now almost immune to bacterial decay.
Then you pack it up and send it off to Asian suppliers where it makes its way onto world markets.
So that’s the commercial and social side of sea cucumbers.
But they are much more than just another food item from the ocean.
Sea cucumbers are echinoderms, those alien-looking creatures that include the sea stars, sea urchins and feather stars.
One of the things that make echinoderms so alien-looking is their pentamerous symmetry.
Put simply, most animals are bilaterally symmetrical.
Cut them down the middle and the two halves are mirror images of each other.
But the echinoderms have a five-fold symmetry, there are five different ways in which you can bisect them and produce mirror images.
Sea cucumbers appear to be bilaterally symmetrical, but they aren’t.
Think of a sea urchin, take away the spines, elongate it and turn it on its side and you have a sea cucumber.
Most of the other echinoderms have a hard calcium carbonate endoskeleton but in the sea cucumber this is reduced to a bunch of spicules in the body wall.
Biologists use these spicules, which are unique to each species, as a way of identifying them.
Most sea cucumbers crawl along the seafloor using hundreds of tiny tube feet while ingesting sand.
Sand does not sound very nutritious, but millions of micro-organisms and pieces of decaying organic matter are found in and around the sand grains.
So, these biological vacuum cleaners play a major role in marine ecosystems.
Some sea cucumbers are even found in very deep waters.
Not all species evince a vacuum cleaner lifestyle.
Others project feeding tentacles into the water and catch drifting food particles.
On the face of it, sea cucumbers are a easy prey.
But that isn’t the case.
Many species can produce a substance called holothurin, which is toxic to fish and some species produce special defensive tissues called cuvierian tubules which they can expel.
These are extraordinarily sticky and release holothurin while sticking to the mouth of their predator.
Other species can eject their entire internal organs which distract the predator while the sea cucumber (or what is left of it) makes a slow get away.
The organs will regenerate within a few weeks.
I have long been fascinated with sea cucumbers.
As a kid in Korotogo a friend and I would use them as water pistols to squirt each other.
And if we got Cuvierian tubules in the other’s hair that was even better.
Our Mums did not appreciate having to cut the sticky mass out.
A few years ago, while diving in Taveuni, I encountered a baked potato.
Now one doesn’t normally encounter a baked potato underwater, so I immediately suspected my friend Allan Gortan of planting it for me to
find.
I decided to take it back to the dive boat to confront him with it.
But when I went to remove it from under the coral ledge it wouldn’t come out (more on this shortly).
So, I pulled harder and when I had it in my hands, I suddenly realized it wasn’t a baked potato but a sea cucumber I had never seen before.
As I examined it, I realized there were five projections in its anus.
A closer look revealed what looked like teeth.
“Teeth in its anus!” I thought.
“No way.”
But they were. I later discovered that this genus, Ictinopyga, often has anal teeth.
But why?
Well, there is a fish called the pearl fish which lives inside some sea cucumbers.
It has a long, thin, pointed tail which it inserts into the cloaca of its unwilling host and wriggles in backwards.
Not only does it live inside the sea cucumber, but it also feeds on the sea cucumber’s gonads and other organs.
Perhaps these anal teeth are there to prevent this happening?
As for not being able to pull the animal out from under the coral ledge – that’s another twist on an already amazing story.
Most echinoderms possess mutable collagenous tissues (MCT).
These can change from soft to hard under the influence of the nervous system (and I’m surprised Marvel comics hasn’t hitched onto this).
I could not pull the baked potato sea cucumber (still unidentified by the way) out of the crevice initially because it changed the soft tissues into hard the instant it felt my fingers.
And once I realized it was not a joke perpetrated by Allan, the baked potato sea cucumber was put back under his ledge with a hell of a story to tell his buddies (or her …).
Have a happy week, keep smiling.
