POSTED: 1:30 a.m. HST, Dec 6, 2010
Newcomer to the islands Maria Regan e-mailed me several photos and this note: "I saw a bunch of small snake/eels (some orange or red) ... out on the Kaneohe Bay sandbar." Maria asked whether I could identify them for her, and I replied in technical terms: "The pink/red/orange things are sea cucumbers. They're OK to pick up and are really squishy and cool." (At least I knew they were sea cucumbers.)
Now that I'm home with my books and Internet, I can fill in a few more details about these colorful creatures.
The most widely used common name for this species is the conspicuous sea cucumber, but I also found it called the prickly and the sea worm sea cucumber. These wormlike sea creatures might look like pink party balloons, but they're active members of the reef's maintenance staff, vacuuming up organic matter that settles on the ocean floor.
I became acquainted with the 3-foot-long sea cucumbers years ago when I too was new to the islands and taking biology courses at UH. One of my professors took our class to Kaneohe Bay's Coconut Island, home of the Hawaii Institute of Marine Biology, and there I saw the weird, snaky things on the sand in about two feet of water. The teaching assistant told me they were harmless sea cucumbers. I could pick one up, but gently, she said.
Well, appearance isn't the only weird thing about this family. The skin of these cucumbers sticks to your fingers in an odd, Velcro-like way, and the water-filled tube that is the creature's body has no chambers. When you pick up this creature, therefore, the water falls to either side, and you're left holding what feels like a collapsed plastic bag with bulging ends. When you put it down, the animal recovers its cylindrical shape.
Hawaii hosts three species of serpentine sea cucumbers, a nickname for their family, Synaptidae. Because their body walls are thin and tear easily, it's best not to take the animal from the water, but rather slide a hand beneath its middle and gently lift. You'll see the body go flat and feel the creature's tiny hooks embedded in its skin.
These harmless hooks don't hurt human hands and detach easily when you pull away. The hooks help the animal hold its body in place as it eats.
Dead plant and animal particles, whether suspended in the water or sitting on the ocean floor, are food for these sea cucumbers (and the familiar firm-bodied kinds, too). The animals gather this nourishment with delicate tentacles at the mouth end of the body. In slow rhythm the tentacles unfurl, pick up food particles and furl, depositing the meal in the mouth.
Light-sensitive organs at the base of each tentacle sense shadows and movement, causing the sea cucumber to tuck in its tentacles and contract its body.
Conspicuous sea cucumbers are exactly that, ranging in color from bright orange to pink to white. Usually, you'll find them sprawled on sand or seaweed in three feet or less of water in either Kaneohe Bay or Pearl Harbor. The species is rare or absent everywhere else in Hawaii.
Conspicuous sea cucumbers have swellings along their bodies reminiscent of human colons. And speaking of which, sea cucumbers recycle particles from sewage spills, making them allies in helping manage our mistakes.
You can see excellent pictures of these pink/red/orange sea cucumbers on Hawaii biologists Keoki and Yuko Stender's website, www.marinelifephotography.com. Click on Invertebrates, then Sea Cucumbers, then Conspicuous Sea Cucumbers (Opheodesoma spectabilis).
They're squishy and cool.
Susan Scott can be reached at www.susanscott.net.