Published August 26, 2013 in the “Ocean Watch” column, Honolulu Star-Advertiser ©2013 Susan Scott
Moorea, French Polynesia » I’ve been playing with sea cucumbers.
The way they lie around on the ocean floor, sea cucumbers resemble the vegetables they are named after, and are about as active.
But don’t let that sedentary appearance fool you. These animals spend their lives vacuuming the ocean floor, helping keep the water clear and the reefs clean.
They also defend themselves as only a sea cucumber can, by shooting a weapon from their anus.
At the mouth end of all sea cucumbers are 10 to 30 sticky tentacles that the creature either stretches over the ocean bottom or holds up in the water. When organic particles stick to the tentacles, the sea cucumber pops them, one at a time, into its mouth. As the animal pulls the tentacle out, it wipes off the food.
But the sea cucumber’s anus is equally busy. The creature breathes through it.
To take a breath, the anus dilates and fills with sea water. Closing and contracting the anal sphincter forces the inhaled water into two respiratory trees, the sea cucumber’s version of lungs. It takes six to 10 openings and closings of the anus to fill the trees with oxygen-rich water, each contraction taking about a minute.
The water exits, though, in one big whoosh. When you lift a sea cucumber above the surface, it exhales, releasing one long stream of water from the respiratory trees out the anus.
That’s not all it releases. When irritated or attacked by a predator, some sea cucumber species eject super sticky tubes from the anus like silly string from a can.
The blue-white filaments entangle an attacking crab or lobster in a mass of adhesive threads.While the helpless predator struggles, the sea cucumber crawls away on tiny tube feet, soon regrowing its tacky tubules for the next time it needs them.
Since I learned about this unusual sea cucumber defense years ago, I have picked up countless of these animals to inspect them. Not all species have this weapon, and nothing ever happened.
Tahiti’s reefs, however, are loaded with big, fat, paisley-patterned sea cucumbers that are loaded with sticky string.
The unlucky predator that messes with one of these creatures dies a slow and snarly death. A curious, camera-bearing snorkeler, however, gets a good picture, but also gets her fingers stuck together for the rest of the swim.
The strings delivered no pain, but they sure were a pain to get off my skin.
I’m grateful to the couple of cukes that satisfied my curiosity, and hope rearming themselves doesn’t take too long. Now that I’ve experienced the wrath of a sea cucumber, I will leave them to vacuum in peace.
Marine biologist Susan Scott writes the newspaper column, “Ocean
Watch”, for the Honolulu Star-Advertiser, www.staradvertiser.com
©2013 Susan Scott