Nudibranchs as a group are amazing animals. There are over 3,000 known species, with scientists estimating that there are another 3,000 or so nudibranch species yet to be discovered. The largest of these gastropod mollusks is the Hexabranchus Sanguineus, or Spanish Dancer. Whether you’ve had the pleasure of viewing Spanish Dancers as they swim through the water column, or if the colorful creatures are among those you have yet to check off your list, you’ll enjoy this intimate view into their lives.
Spanish Dancers: The Basics
The Spanish Dancer is a very large swimming nudibranch capable of attaining a length over forty centimeters, and record specimens have come in at over ninety centimeters. When you stop to consider that most nudibranchs are about the size of your finger, the creature’s size is even more astonishing. While most of these animals are bright red, there is a yellow variety which is occasionally encountered. As you may know, most nudibranchs propel themselves by simply crawling along; this variety is able to crawl and swim, making it more advanced than most of its relatives.
The way the Spanish Dancer appears varies depending on which mode of travel it is using. If you see the animal crawling along the reef, you’ll see that it takes on a long, slender appearance. This is because the parapodia or mantle edges are rolled up next to its body when it rests or sits on the bottom. When the creature unfurls its mantle to swim through the water column, you’ll see how it came by its name. Its brilliant red parapodia swirl and whirl in an exotic way that mimics the motions a flamenco dancer makes as she twirls hypnotically across a dance floor.
Even the egg ribbons Spanish Dancers lay have a beautiful appearance. Delicate, with multiple layers, the egg sacs look much like decorative rosettes; their bright red color leaves viewers with no doubt as to which creature the sacs belong to. The color serves a purpose though – besides attracting divers’ attention, it serves to alert other animals to the fact that it is highly toxic, just like the sponges and hydroids Spanish Dancers like to feed on.
Hexabranchus Sanguineus is named for its appearance. The first word in the animal’s name, “Hexabranchus” means “six gills.” The second word in its name, “Sanguineus” means “blood colored.” During the day, the Spanish Dancer’s color ranges from a vibrant pink hue to a rich, deep crimson. After the sun goes down, it often takes on a blotchy appearance, with colors of pink and red blending in with one another. It often displays white or cream-colored markings,. And it is usually trimmed in yellow or gold along its gills, mantle, and rhinophores (sometimes called tentacles.)
Don’t be surprised if you happen to see a tiny shrimp hitching a ride with a Spanish Dancer. The Imperial Shrimp, which grows to about ¾ inch long, and which is red and white like its host, sometimes lives within the Spanish Dancer’s gills, where it helps keep the nudibranch looking clean and feeling good. This is just one of the many commensal animals you might encounter while diving.
Spanish Dancers are distributed throughout the Red Sea nad the Tropical Indo-Pacific Ocean. You’re likely to encounter them at dive sites from Dahab to Hawaii, and from Bali to East Timor. If you’re diving in areas where the creatures are likely to be seen, you might be treated to a look at one of the greatest underwater performances anyone has ever had the pleasure of viewing.