Spanish 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.[3]

For the sea cucumber also known as the Spanish dancer, see Enypniastes.
For the 1923 silent movie, see The Spanish Dancer.

Spanish dancer
90 cm long specimen of the Spanish dancer, at night in Bali
Scientific classification
Kingdom:
Animalia
Phylum:
Mollusca
Class:
Gastropoda
(unranked):
clade Heterobranchia
clade Euthyneura
clade Nudipleura
clade Nudibranchia
clade Euctenidiacea
clade Doridacea
Superfamily:
Polyceroidea
Family:
Hexabranchidae
Genus:
Hexabranchus
Species:
H. sanguineus
Binomial name
Hexabranchus sanguineus
(Ruppell & Leuckart, 1828)[1]
Synonyms[2]
  • Doris lacera Cuvier, 1804 (nomen oblitum)
  • Doris sanguinea Rüppell & Leuckart, 1828-1830 (nomen protectum)
  • Hexabranchus praetextus Ehrenberg, 1828
  • Doris flammulata Quoy & Gaimard, 1832
  • Doris marginata Quoy & Gaimard, 1832
  • Doris cardinalis Gould, 1852
  • Doris sandwichiensis Souleyet, 1852
  • Hexabranchus pulchellus Pease, 1860
  • Hexabranchus suezensis Abraham, 1876
  • Hexabranchus pellucidulus Abraham, 1876
  • Hexabranchus aneiteumensis Abraham, 1877
  • Hexabranchus mauritiensis Abraham, 1877
  • Hexabranchus orbicularis Abraham, 1877
  • Hexabranchus anaiteus Bergh, 1878
  • Albania formosa Collingwood, 1881
  • Doris imperialis Kent, 1897
  • Hexabranchus digitatus Eliot, 1903
  • Hexabranchus plicatus Hägg, 1903
  • Hexabranchus aureomarginatus Ostergaard, 1955
  • Hexabranchus tinkeri Ostergaard, 1955

Description
A Spanish dancer swimming, its anterior end on the right

The Spanish dancer is a large dorid nudibranch which can grow up to a maximum length of 90 cm.[4] However, the commonly observed size is between 20 and 30 cm long.[5] Its body coloration is generally orange-red speckled with multiple small white dots but it also can be uniformly bright red or yellow with red scattered spots. Its body is soft and flattened, the anterior dorsal portion has a pair of retractable rhinophores and the posterior part has six contractile gills inserted independently in the body. The pair of oral tentacles are constituted by a fin flexible membrane provided with large digital lobes.

In a normal situation when the animal is crawling, the edges of its mantle are curled upwards creating a peripheral blister. If the animal is disturbed, it unfolds its edges and can swim through contractions and undulations of the body to move away from the disturbing element. Its common name, Spanish dancer, comes from this particular defense.

Juveniles are rather whitish to yellowish with multiple purplish points and orange rhinophores and gills.

  • The egg ribbon of Hexabranchus sanguineus in the northwest Hawaiian Islands
  • Spanish dancer in daylight, Dahab
  • Spanish dancer, a posterior view showing the gill rosette
  • Encountered at night on the North coast of East Timor

Distribution and habitat

The Spanish dancer is widespread throughout the tropical and subtropical waters of the Indo-Pacific area from the eastern coasts of Africa, Red Sea included, to Hawaii and from south Japan to Australia.[4][5]

It likes rocky and coral reefs with many sponges and shelters from 1 to 50 meters deep.[4]

Biology

During daytime, the Spanish dancer hides away from the light in the crevices of its natural habitat to only come out late at night. It feeds on various species of sponge. Like all nudibranchs, it is hermaphrodite and its bright red to pink egg ribbon has a spiral shape related to the size of the animal so relatively large. The latter is coveted by some other species of nudibranch as Favorinus tsuruganus or Favorinus japonicus.[4] The Emperor shrimp, Periclimenes imperator, is a commensal shrimp that is commonly found living on Hexabranchus sanguineus.

gollark: Yes. Factorials can be extended to real numbers in many ways.
gollark: Don't worry, I rebound π as that gamma constant.
gollark: Lyricly doesn't know that I really made #π.
gollark: Those do nothing, you realise.
gollark: I wrote all of them! Even the antimemetic ones!

References
  1. Rudman, W.B., 1999 (March 31) Hexabranchus sanguineus (Ruppell & Leuckart, 1828). [In] Sea Slug Forum. Australian Museum, Sydney.
  2. Valdés Á. (2002). "How many species of Hexabranchus (Opisthobranchia : Dorididae) are there?". Molluscan Research 22(3): 289-301. doi:10.1071/MR02012, PDF.
  3. http://www.seaslugforum.net/hexasang.htm Seaslug forum
  4. DELUNEL Anthony, WARREN Lindsay, COROLLA Jean-Pierre, MITEL Cédric, in : DORIS, 17/7/2014 : Hexabranchus sanguineus (Rüppell et Leuckart, 1830), http://doris.ffessm.fr/fiche2.asp?fiche_numero=411
  5. http://www.seaslugforum.net/find/hexasang
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