Ceratosoma tenue
Abraham, 1876

Suborder: DORIDINA
Family: Chromodorididae


Tropical Indo-West Pacific.


A,B. Baie de Koumac, Koumac Region, New Caledonia, 3 m, sandy mud, Caulerpa beds, October 1993, A, 63mm, B, 150mm long alive.
C. juvenile, 20mm long, Coffs Harbour region, northern New South Wales, Australia, December 1990. D. Cymodocea grass beds, Dar es Salaam, Tanzania, February 1974, 68mm long animal with dorsal horn bitten? off. PHOTOS: Bill Rudman.

The two common tropical species of Ceratosoma, C. tenue and C. trilobatum (Gray), are variable in colour, and as both can have very similar colour patterns, considerable confusion has occurred in the past over the identity of specimens. Ceratosoma tenue can be characterised by the three mantle lobes on each side of the body. There is a large anterior lobe on either side of the head and a large lobe on each side by the gills. Between these is a smaller lobe which is joined by a ridge to the gill lobe, but not the head lobe. The edge of the lobes and the ridge joining the posterior lobes is usually outlined with a broken purple line. There is usually no broken purple line between the head lobe and the posterior lobes. Colour variation is very similar to that of C. trilobatum. It does appear that the purple border to the mantle and foot in C. tenue is always a dotted line whereas in C. trilobatum it is usually an unbroken line. Although this species can grow to more than 120mm in length, it is relatively smaller and more elongate than C. trilobatum.

Most species of Ceratosoma have a long recurved dorsal 'horn' which acts as a defensive lure attracting potential predators to the part of the animal which contains most of the distasteful chemicals stored from their food. See Ceratosoma brevicaudatum for photos of its conspicuously marked 'tail', especially in juveniles. This colour 'target' probably also attracts potential predators to the most distasteful part of the animal. See photo below (D) of Ceratosoma tenue from Dar es Salaam, in which whole dorsal horn has been cut off, probably bitten off. although not visible in the photo the animal had a distinct white amputation scar.

•Rudman, W.B. (1984) The Chromodorididae (Opisthobranchia: Mollusca) of the Indo-West Pacific: a review of the genera. Zoological Journal of the Linnean Society 81: 115-273.
•Rudman, W.B. (1988b) The Chromodorididae (Opisthobranchia: Mollusca) of the Indo-West Pacific: the genus Ceratosoma J.E. Gray. Zoological Journal of the Linnean Society 93(2): 133-185.

Authorship details
Rudman, W.B., 1999 (September 29) Ceratosoma tenue Abraham, 1876. [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/ceratenu

Related messages

  1. Re: Ceratosoma tenue from Lembeh - with brittle-star
    From: Teresa Zuberb├╝hler, June 6, 2008
  2. Ceratosoma tenue from Lembeh - feeding?
    From: Kamal El Tawil, April 2, 2008
  3. Ceratosoma tenue from sthn Queensland
    From: Gary Cobb, October 12, 2007
  4. Ceratosoma tenue feeding [3]
    From: Bruce Wilkie, October 11, 2007
  5. Ceratosoma tenue feeding [2]
    From: Bruce Wilkie, October 11, 2007
  6. Ceratosoma tenue feeding [1]
    From: Bruce Wilkie, October 11, 2007
  7. Ceratosoma tenue feeding? from Lembeh
    From: Mike Krampf, July 17, 2007
  8. Ceratosoma tenue from Anilao, The Philippines
    From: Paul Osmond, April 10, 2007
  9. Ceratosoma tenue mating
    From: Bruce Wilkie, May 31, 2006
  10. Ceratosoma tenue with eggs from Buton Island
    From: Linda Ianniello, December 1, 2005
  11. Ceratosoma tenue laying eggs
    From: Mary Jane Adams, October 26, 2005
  12. Ceratosoma tenue from Sth Africa
    From: Riaan Marx, February 23, 2004
  13. Ceratosoma tenue from Sodwana, Sth Africa
    From: Charles Rowe, February 5, 2004
  14. Ceratosoma tenue with egg ribbon
    From: Danny Van Belle, June 5, 2003
  15. Ceratosoma tenue from Sth Korea
    From: Dong Bum Koh, May 30, 2003
  16. A Ceratosoma convention
    From: Danny Van Belle, May 28, 2003
  17. Ceratasoma tenue from North Sulawesi
    From: Marli Wakeling, October 12, 2002
  18. Variation: Ceratosoma tenue
    From: Valda Fraser, August 12, 2001
  19. Ceratosoma tenue from Southern Mozambique
    From: Ian Miller, December 19, 2000
  20. Mystery slug from Indonesia
    From: Marli Wakeling, October 29, 2000
  21. Ceratosoma tenue from South Africa
    From: Valda Fraser, November 5, 1999
  22. Re: Ceratosoma tenue from South Africa
    From: Valda Fraser , November 5, 1999

Show factsheet and all related messages