Tag Archives: nudibranch

Clinger crabs are members of wind drift community

Published February 3, 2018 in the
“Ocean Watch” column, Honolulu Star-Advertiser ©2018 Susan Scott

A pregnant clinger crab fits in the palm of a hand. ©2018 Susan Scott

When the wind is howling and the surf is busy salting everything in my house, I hit the beach. Those aren’t the best conditions for soaking up sun or playing in the water, but for us avid walkers it’s prime time for finding marine treasures.

Because I make mosaics from litter I find in albatross nests at Midway and on beaches in the Pacific, my gems are usually bits and pieces of colored plastic. Last week, though, my prize was alive. When I got home and dumped my junk in a colander for rinsing, there on a barnacle- and algae-encrusted toy truck clung an offshore crab.

This species of crab is a member of the wind drift community, a diverse bunch of animals that float on the surface eating anything they run into, including each other. They’re called wind drifters because they are indeed adrift, their direction and speed controlled entirely by current, wind and waves.

Common jelly-type critters floating offshore are Portuguese men-of-war (Physalia), by-the-wind sailors (Velella) and blue buttons (Porpita).

You might not expect snails to be members of this community, but two species are common: violet snails (Janthina) and snails-without-shells called nudibranchs (Glaucus).

Another unlikely offshore mariner is a little crab I call the clinger crab because it doesn’t have its own float system, as the others do, nor does it swim. Rather, the clinger crab spends its life hanging onto a piece of wood or debris. (I can’t find a common or scientific name for this little crab. If you have one, please write.)

Clinger crabs are about the size of a quarter and come in shades of blue or brown, depending on which object they’ve chosen to call home. This clinger was brown, a perfect match to the brown seaweed that grew on its floating toy.

You can tell a male crab from a female by the flap on the center of its underside. Narrow is male; females have wide flaps that hold their eggs.

When I examined my crab’s belly, I discovered, with some excitement, that I had a female with eggs. Hoping to raise some baby clingers, I rushed back to the ocean for a bucket of water, half filled my rescue tank and gave my pregnant crab her tiny truck, a pile of rocks to reach it and some frozen brine shrimp for energy.

A pregnant clinger crab fits in the palm of a hand. The eggs are the yellow mass under the flap. ©2018 Susan Scott

Alas, a tank being the utter opposite of her natural habitat, she did not survive. Even so, I was happy to have had a wind drift pet, even if just for a day.

During my beach walks I sometimes forget to bring a bag, and have to go trash-can diving for containers. Failing at both those things last week, I called Craig to come get me in the car, because I couldn’t walk home. After stuffing my pockets full of flotsam, I then filled my Crocs.

I have lived in Hawaii long enough that I sometimes think it’s too cold to go snorkeling. Never, ever, though, is it too cold for beachcombing.

Spanish dancer’s flare, eggs attract many devoted fans

Published July 8, 2013 in the “Ocean Watch” column, Honolulu Star-Advertiser ©2013 Susan Scott

A rose is a rose is a rose — except when it’s the egg cluster of a Spanish dancer.

My recent column about that nudibranch and its roselike eggs generated some inspired email. About the lovely red or pink “flower,” a reader wrote, “I have seen the same thing and it looked like someone cut chiffon rosettes off an old-fashioned dress and glued them to the reef. I couldn’t figure out what in the heck they were. Now I know! Thank you.”

And thank you, Steph­a­nie, for describing so elegantly one of the world’s prettiest clutches of eggs.

Biologists call these flower look-alikes egg ribbons, and they are fastened with remarkable strength to the reef. The nudibranch might attach the eggs with a special glue, or the adhesive quality might be in the stickiness of the gelatinous egg cases. No one knows.

Also remarkable is the concentration of poison in the eggs, which contain more recycled sponge toxin than the nudibranch that laid them. In one lab experiment, researchers ground up the red eggs and fed them to creatures that eat almost anything.The offering were rejected.

Another Honolulu
reader, physician and photographer Russell Gilbert, wondered how the nudibranch
eggs held together, so he took a close-up picture. You can see the individual
eggs (and Russell’s other excellent underwater photos) here.

“After taking this shot,” he wrote, “I realized how the eggs were structured — embedded in sheets in some kind of gel-like material.”

He’s right. Multiple eggs are enclosed in rigid, protective mucus capsules, which stick to each other to form the spiraled ribbon.

Once hatched, free-swimming larvae drift in the plankton, eating tiny plants. When a baby dancer is ready to settle down, it alights on its food, one of several species of sponges.

Depending on which sponge species they’re eating, Spanish dancers are red, pink or orange, sometimes mixed with yellow or white.

Most nudies only crawl, but Spanish dancers get their common name from their ability to swim in midwater, flexing their bodies energetically, their soft edges flaring like the skirts of a flamenco dancer. Most people who see this flamboyant dance become lifetime fans and protectors of Spanish dancers.

Nudibranchs in general are not long-lived, some for only a month. The life span of dancers is about a year.

Occasionally, they beach. A San Francisco reader wondered by email whether returning a grounded one to the water revives them or if the creatures were trying to die.

I don’t know, but since nudibranchs have no eyes, my guess is that groundings are accidents occurring when the creatures get too near the shore break.

At the shoreline I once found a live Spanish dancer larger than my hand and waded, fully clothed, to place the creature on the ocean floor. I don’t know whether the orange beauty survived, but it was worth getting wet to give it a chance.

Spanish dancers and their eggs inspire most everyone who sees them. Maybe Elton John’s tiny dancer was a nudibranch, and Gertrude Stein’s rose its eggs.

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

Nudibranch protects itself by recycling toxins of others

The egg mass, top, looks like a rose. Their red color comes from the red sponges the Spanish dancer eats. ©2013 Susan Scott

From my Kailua neighbor Marya, who swims with mask and snorkel every morning before work, came this email:

“I saw something that everyone says is impossible … a beautiful dark pink rose, seemingly growing out of the coral. Ridiculous, I thought to myself, must be a plastic rose. So I went down and touched it gingerly, and sure enough, it was soft and felt like a petal. It wasn’t plastic, definitely. It wasn’t like a big rose, but more like the inside two or three layers of a rose. It was so lovely. Could there be such a thing?”

Yes. Marya’s reef rose is the egg mass of the spectacular nudibranch (noody-brank) called the Spanish dancer.

Nudibranchs, also known as sea slugs or nudies, are snails without shells. But lacking a shell doesn’t mean nudibranchs are lackluster. An author of a book I have on Hawaii’s nudibranchs (sorry, out of print) writes that nudibranchs “are among the most beautiful and fascinating animals that live in the ocean.”


Spanish dancer. Their red color comes from the red sponges the Spanish dancer eats. ©2013 Susan Scott

I agree. And fortunately for us, nudibranchs live mostly in shallow water and are therefore visible to snorkelers, divers and tide pool walkers.

The stunning patterns and colors that most nudibranchs display carry a message: I am poisonous. Don’t eat me.

Nudies don’t make their own poisons, but instead swallow them, gobbling up toxic species, such as sponges, hydroids and Portuguese men-of-war, and recycling those creatures’ poisons for their own protection.

The Spanish dancer and its roselike egg mass are red because the species eats red sponges.

All nudibranchs are hermaphrodites that carry both eggs and sperm. The animals never fertilize themselves, but mate with their own kind sometimes in end-to-end chains. Afterward the creatures lay egg masses in spirals that look like delicate flowers, each species having its own color and shape.

Most nudibranchs are garden slug size or smaller. At 15 inches long the exquisite Spanish dancer is the largest nudibranch the world. It’s found in tropical waters around the world, including Hawaii.

So finding a rose on the reef, Marya, is not only entirely possible, but means that Spanish dancers are doing well off Windward Oahu. It’s also a wonderful way to start the day. Thanks for writing.


Another image of a Spanish Dancer Egg Mass. ©2013 Susan Scott

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

©2013 Susan Scott