Imagine you are on a night dive somewhere in the tropical Pacific. Suddenly, in the darkness above the reef, you spot what appears to be an animated vermillion dinner napkin convulsing wildly. Congratulations! You’ve found a Spanish dancer.
The Spanish Dancer
The Spanish dancer (Hexabranchus sanguineus, meaning “blood-colored six-gills”) is among the largest nudibranchs. It can grow as long as 24 inches (60 cm). By day it stays out of sight, tucked into crevices of the reef. It emerges at night to feed on sponges, some of which contain toxins that it can pass along to its eggs as a chemical defense.
Stretched flat, the Spanish dancer would be a large oval. It features a pair of rhinopores on one side and six gills, often bordered in white, on the other. Alone, the combo of its striking color (red, often speckled with white or yellow, or yellow, sometimes with red spots) and large size would create an underwater sensation. But this bombastic sea slug is not so flat and boring. When crawling along the sea floor, the edges of its mantle curl up like a scroll, lending it a Rococo flair. When disturbed, it “leaps” into the water column. There, its unfurls the scrolls and scissors its body like it’s doing an abs workout. The billowy mantle, wild movement, and frilly gills combine to make the inspiration for its common name obvious.
Where and how to find them
Spanish dancer habitat spans the tropical and sub-tropical Indo-Pacific, from the Red Sea to the Pacific shores of North and South America, and as far south as Australia. By diver accounts, there seems to be some geographic distribution to its coloring. Individuals in the Red Sea are almost invariably solid blood-red, whereas further east they tend to be more spotted/mottled and their color slightly more orange.
The hexabranchus sanguineus is most active at night, so a night dive is in order if you’d like to see one. You’ll find them at depths from three to 160 feet (1 to 50 m), usually near reefs with many daytime hiding places.
The highlight of spotting one would be to see an individual “dancing” in the water column. That said, if it’s crawling across the reef (before or after dancing), approach slowly and have a closer look. You might see its equally flamboyantly colored commensal partner, the emperor shrimp (Periclimenes imperator).
If you’re somewhere that divers have seen Spanish dancers recently, on your next daytime dive search the reef for a ribbon of its eggs. These resemble a large, bright-pink paper flower.
No matter how you see one, if you’re lucky enough to spot a Spanish Dancer, you’re in for a extraordinary performance.
Guest author Christina Koukkos is a New York-based freelance writer and editor. She covers scuba diving, responsible tourism, off-beat destinations, cultural travel and other topics. She’s a certified PADI dive instructor and MSDT as well as an amateur underwater (and topside) photographer. Learn more about her on her website, her blog, on Instagram or Twitter.