Goniobranchus geminus

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Goniobranchus geminus
Chromodoris geminus.jpg
Scientific classification
Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
(unranked): clade Heterobranchia
clade Euthyneura
clade Nudipleura
clade Nudibranchia
Superfamily: Doridoidea
Family: Chromodorididae
Genus: Goniobranchus
Species: G. geminus
Binomial name
Goniobranchus geminus
(Rudman, 1987à[1]

Chromodoris geminus Rudman, 1987 (basionym)

Goniobranchus geminus, also known as the gem sea slug[3] or twin sea slug[by whom?], is a species of very colourful sea slug, a dorid nudibranch, a marine gastropod mollusc in the family Chromodorididae.[2]

Taxonomic history[edit]

Until 2012 this species was known as Chromodoris geminus but was moved to the genus Goniobranchus as a result of a molecular (DNA) study.[4]


The gem sea slug can reach a maximum size of 5 cm in length.[5] it has four distinctive coloured lines around the mantle edge. Starting from a thin white outer line, then a light grayish line, followed by another white line and finally a bright golden yellow line. The background coloration from the back is light brown to yellowish speckled with mauve ocelli circled with a white margin. The foot, clearer and with a white margin, also has ocelli. The rhinophores are yellow or purple and laminated, gills are white outlined with beige.

Distribution and habitat[edit]

This sea slug lives in the Indian Ocean from Kenya to Sri Lanka and in the Red Sea and has a predilection for the external slopes of coral reefs.[5]

Similar species[edit]


  1. ^ Rudman W. B. (1987). "The Chromodorididae (Opisthobranchia: Mollusca) of the Indo-West Pacific: Chromodoris epicuria, C. aureopurpurea, C. annulata, C. coi and Risbecia tryoni colour groups". Zoological Journal of the Linnean Society 90: 305-407. doi:10.1111/j.1096-3642.1987.tb01357.x
  2. ^ a b Bouchet, P. (2012). Goniobranchus geminus. Accessed through: World Register of Marine Species on 2012-05-03
  3. ^ King, Dennis; Fraser, Valda (2014). The Reef Guide: fishes, corals, nudibranchs and other invertebrates (of the) East and South Coasts of Southern Africa. Cape Town: Struik Nature. p. 316. ISBN 9781775840183. 
  4. ^ Johnson R.F. & Gosliner T.M. (2012) Traditional taxonomic groupings mask evolutionary history: A molecular phylogeny and new classification of the chromodorid nudibranchs. PLoS ONE 7(4): e33479.
  5. ^ a b Rudman, W.B., 1999 (January 22) Chromodoris geminus Rudman, 1987. [In] Sea Slug Forum. Australian Museum, Sydney.

Further reading[edit]

  • Debelius, H. & Kuiter, R.H. (2007) Nudibranchs of the world. ConchBooks, Frankfurt, 360 pp. ISBN 978-3-939767-06-0 page(s): 164 [
  • Gosliner, T.M., Behrens, D.W. & Valdés, Á. (2008) Indo-Pacific Nudibranchs and seaslugs. A field guide to the world's most diverse fauna. Sea Challengers Natural History Books, Washington, 426 pp. page(s): 220