Spanish dancer
A large, colorful sea slug that swims like a dancer.
The Spanish dancer, scientific name *Hexabranchus sanguineus* (literally meaning "blood-colored six-gills"), is a dorid nudibranch, a very large and colorful sea slug, a marine gastropod mollusk in the family Hexabranchidae. Its common name comes from its particular defense: when disturbed, it unfolds its mantle edges and swims through contractions and undulations of the body, resembling a flamenco dancer's skirt. This species commonly reaches a length of 25 centimeters, though some specimens in the Red Sea have been reported up to 40 centimeters. All members of the genus *Hexabranchus* possess soft, flattened bodies with a pair of retractable rhinophores at the front and six independently contractile gills at the rear. A pair of oral tentacles is formed by a fine, flexible membrane bearing large digital lobes. When crawling normally, the edges of the mantle curl upward, creating a peripheral blister. The Spanish dancer inhabits rocky and coral reefs rich in sponges, sheltering in crevices from one to 50 meters deep. It is reported from the Red Sea, the Western Indian Ocean, French Polynesia, and the Western Pacific, with distinct color morphs in each region that cannot be differentiated by morphology or DNA barcodes. Active only at night, it hides from light during the day. Like all nudibranchs, it is hermaphroditic, producing large, spiral-shaped egg ribbons that range in color from bright red to pink. It feeds on sponges from the family Halichondriidae, deriving potent chemical defenses from its prey. These defensive compounds, passed into the egg ribbons via macrolides, protect the otherwise defenseless eggs. The emperor shrimp (*Periclimenes imperator*) is a commensal species commonly found living on the Spanish dancer. Notably, a thorough molecular and morphological study published in 2023 revealed that the name *H. sanguineus* had been applied to at least five distinct species, making the genus’s taxonomy controversial.
- scientific_name
- Hexabranchus sanguineus
- common_name
- Spanish dancer
- maximum_length
- 25 cm (up to 40 cm in the Red Sea)
- habitat
- Rocky and coral reefs with sponges, 1 to 50 meters deep
- distribution
- Red Sea, Western Indian Ocean, French Polynesia, Western Pacific
- known_for
- Swimming defense resembling a Spanish dancer's skirt
Quick Facts
- Taxon
- Hexabranchus sanguineus
Facts from the source article.
Lore & Background
The Spanish dancer is a large dorid nudibranch commonly growing up to 25 cm, with some reports to 40 cm in the Red Sea. All Hexabranchus species have soft, flattened bodies, with a pair of retractable rhinophores on the anterior dorsal portion and six contractile gills inserted independently in the posterior part. The pair of oral tentacles are constituted by a fine flexible membrane provided with large digital lobes. When crawling normally, the edges of its mantle are curled upwards creating a peripheral blister; if disturbed, it unfolds its edges and can swim through contractions and undulations of the body to move away from the disturbing element.
Reader's Guide
The Spanish dancer is significant as a striking example of a nudibranch that uses active swimming as a defense mechanism, earning its common name from the flamenco-like motion. It is reported from the Red Sea, Western Indian Ocean, French Polynesia, and the Western Pacific, with different color morphs in each region that are not differentiated by morphology or DNA barcodes. A thorough molecular and morphological study published in 2023 showed that the name H. sanguineus was being used for at least five distinct species, highlighting ongoing taxonomic uncertainty. The species consumes sponges from the family Halichondriidae, deriving potent chemical defenses that it passes into its egg ribbons via macrolides. These egg ribbons, ranging in color from bright red to pink, are spiral-shaped and relatively large. The emperor shrimp, Periclimenes imperator, is a commensal shrimp commonly found living on Hexabranchus sanguineus. The Spanish dancer hides in crevices during daytime and emerges late at night.
Did You Know?
- The Spanish dancer's scientific name, Hexabranchus sanguineus, literally means 'blood-colored six-gills'.
- A 2023 molecular and morphological study showed that the name H. sanguineus was being used for at least five distinct species.
- The Spanish dancer consumes sponges from the family Halichondriidae and derives a potent chemical defense from them.
- The emperor shrimp, Periclimenes imperator, is a commensal shrimp commonly found living on Hexabranchus sanguineus.
Frequently Asked Questions
What is the Spanish dancer?
The Spanish dancer is a large, vividly colored dorid nudibranch (sea slug) whose scientific name is Hexabranchus sanguineus, a marine gastropod in the family Hexabranchidae. It lives in warm tropical seas and is one of the most visually striking nudibranchs you can encounter on a dive.
Why is it called the Spanish dancer?
When the slug feels threatened it flares out the edges of its mantle and undulates its whole body to swim away, producing a flowing, skirt-like ripple. That dramatic escape motion is said to resemble a flamenco dancer spinning a wide dress, which is where the common name comes from.
How big can the Spanish dancer grow?
In most of its range the slug reaches roughly 25 cm in length. In the Red Sea, individuals have been recorded at up to about 40 cm, making it one of the largest dorid nudibranchs.
Where can I find the Spanish dancer in the wild?
It favors rocky and coral reef habitats that are rich in sponges, typically at depths between 1 and 50 meters. Its distribution spans the Red Sea, the Western Indian Ocean, French Polynesia, and the Western Pacific.
Is the Spanish dancer dangerous to scuba divers?
No, the slug is not venomous or aggressive toward humans. Its only real defense is to spread its mantle and swim off in that characteristic undulating motion when you get too close, so it poses no threat to divers.
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