Tag Archives: sea cucumber

Turbulent waters draw crowd of sea cucumbers

Published July 1, 2017 in the “Ocean Watch” column, Honolulu Star-Advertiser ©2017 Susan Scott

Sea cucumbers don’t use muscles to tighten and relax their body walls, so they expend little energy to stay anchored. ©2017 Susan Scott

Two weeks ago I picked up a flu bug that knocked me sideways. Aching muscles and violent coughing kept me down for days. Then one morning last week, I had enough. Sick or not, I had to get in the water.

The calm blue water off Lanikai felt soothing in the hot afternoon sun. Not feeling like swimming hard, I drifted over the sand in the shallows and, of course, discovered something marvelous.

The walls that some people have built in front of their beach houses cause the waves to reflect back and forth, creating swirls of bumpy water that stirs up the bottom. I don’t usually swim there because the surface is rough and the water cloudy with sand. But I’ve been missing out.

Black sea cucumbers have anchored their bodies under the rocky rubble there with their head ends poking out. And extended from the heads were the creatures’ feathery tentacles, happily vacuuming up the nutrients in the turbulent water.

I say happily because as I floated around the area, I found dozens of the creatures tucked under rocks and Hoovering away.

Sea cucumbers are easy to pass by because they usually look like plump, sand-covered sausages lying motionless on the ocean floor. But these leathery creatures can walk, some species moving slowly on sticky tube feet, and others inching along in waves, like worms.

When the water is too rough for the sea cucumber to keep its place, it crawls under or leans against a rock and molds itself there, using a remarkable feature in its body walls.

Sea cucumber skin contains microscopic bones shaped like anchors, buttons, tables and tripods. No one knows why the bones’ shapes are so varied, but each species has its own set. Researchers can identify one sea cucumber from another by studying its tiny skin bones.

At rest on the ocean floor, the sea cucumber’s little bones connect with one another with medium tension. But startle the animal, such as by picking it up, and the connections between the bones quickly tighten, turning the sea cucumber into a hard, solid mass.

The opposite occurs when the creature needs to squeeze into a small space. The tiny skin bones spread far apart, and their connections loosen, making the skin soft and flexible. Once the animal gets in the gap, the skin turns firm again, mooring the sea cucumber for as long as it wants to stay there.

Because sea cucumbers don’t use muscles to tighten and relax their body walls, the creatures use little energy to stay anchored.

Some practitioners of traditional Chinese medicine use sea cucumbers as a remedy for various illnesses, but I didn’t have to swallow any sea cucumber to get well. Just watching those animals clean up the ocean floor made me feel better than I had in days. Now that’s powerful medicine.

Some sea cucumber species use poison to stop predators

Published August 3, 2015 in the “Ocean Watch” column, Honolulu Star-Advertiser ©2015 Susan Scott

©2015 Susan Scott

©2015 Susan Scott

During my recent trip to Australia, I occasionally had Internet access to Hawaii news and learned that our sea cucumbers are in trouble because people have been harvesting them off Oahu and Maui. One headline in this newspaper said, “Sea cucumbers seem to need a friend right now.”

Well, little Hoovers of the sea, you’ve got a friend in me.

A more apt name for sea cucumbers would be sea sausages because they’re not veggies; they’re animals, hot dogs of the ocean that do a fine job of scrubbing the floor.

A ring of tentacles around sea cucumbers’ mouths sweeps the ocean bottom, picking up sand. The sea cucumber’s digestive system extracts bits of dead plants and animals from the grains and expels clean sand from its anus.

The sea cucumber has a busier anus than most animals — it also breathes through it. Inside the anus is a respiratory tree. Muscles around the branches circulate water to extract oxygen and release carbon dioxide. That’s why if you pick up a leathery sea cucumber, a stream of water often whooshes out of its anus.

The anus of some sea cucumber species provides shelter for several species of pearlfish, a narrow translucent fish that forages at night near its chosen host. Come dawn, the conspicuous pearlfish wiggles into its landlord’s anus and there rests, protected from daytime predators.

Not all sea cucumbers welcome pearlfish in their rectal chambers because the fish can get too cozy in there and start nibbling its host’s internal organs. Some sea cucumber species have a circle of five inward-pointing teeth around the anus, effective in keeping out potential parasitic squatters.

Hawaii hosts 50 or so species of sea cucumbers, half in shallow water, half in the deep sea. The diversity is large, ranging from firm and muscular to soft and squishy, and they grow from 1 inch to 3 feet long.

The squishy kind. ©2015 Susan Scott

The squishy kind. ©2015 Susan Scott

Because some fish eat the slow-moving sea cucumbers, they have evolved defenses you might expect to see only in sci-fi films. Some species shoot out sticky, toxic threads from their anuses to immobilize their enemies. Others produce a poison called holothurin that can kill fish and even people who eat them.

Another defense, called auto-evisceration, is what it sounds like. The creature ejects its internal organs, again through that all-purpose anus. This distracts the predator while the cucumber crawls into hiding. It takes a month or more for the organs to grow back.

A small species of sea cucumber. ©2015 Susan Scott

A small species of sea cucumber. ©2015 Susan Scott

A pearlfish barging into a sea cucumber’s anus doesn’t trigger the shooting of threads or the throwing up of organs. These defenses take place only when a threat occurs on the outside surface of the creature.

Some people like to eat several leathery species of sea cucumbers that live in Hawaii’s waters, but they aren’t abundant enough for limitless collecting. After the state discovered in June the commercial killing and selling of 3,000 to 4,000 individuals, the agency passed an emergency 120-day ban on taking any sea cucumbers in Hawaii’s waters. The agency is now working on long-term rules for the fishery that will keep the populations healthy.

Fortunately, our sea cucumbers have more friends that just me.

 

Sea Cucumbers

Sea Cucumbers at a remote French Polynesian Atoll. ©2015 Susan Scott

Marine biologist Susan Scott writes the newspaper column, “Ocean Watch”, for the Honolulu Star-Advertiser, www.staradvertiser.com

©2015 Susan Scott

For some sea cucumbers, back ends stave off enemies

Published August 26, 2013 in the “Ocean Watch” column, Honolulu Star-Advertiser ©2013 Susan Scott
Some sea cucumber species release sticky filaments from their tail ends when threatened. ©2013 Susan Scott

Some sea cucumber species release sticky filaments from their tail ends when threatened. ©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