Nudibranch protects itself by recycling toxins of others

Published in the Ocean Watch column,
Honolulu Star-Advertiser © Susan ScottJune 24, 2013

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.

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

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