Ceratosoma trilobatum (Gray, 1827)

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This species has been observed on Mayotte and Madagascar Islands

Order : Nudibranchia
Suborder : Euctenidiacea
Superfamily : Doridoidea
Family : Chromodorididae
Distribution : Tropical Indo-West Pacific
Maximal size : 150 mm
Abundance :

Species characteristics :

It has a hard, almost rigid body with a long tapering foot and highly branched gills set between the three rounded triangular lobes of the mantle, one to each side and one arching over the gill, posteriorly

The mantle is usually blotchy red with bright yellow spots

The purple border to the mantle and foot is usually an unbroken line


ceratosoma trilobatum
Showing species characteristics...

Photo Alain-Benoît Rassat
Madagascar, Nosy bé, banc corail noir, 25 m, 18 July 2013, size : 150 mm

See more about : Sightening and mating periods

Remarks :

Identification confirmed by Nathalie Yonow
    Synonymous (according worms) :
          - Ceratosoma berghi, Rochebrune, 1895                   - Ceratosoma lixi, Rochebrune, 1894
          - Ceratosoma caledonicum, Fisher, 1876                 - Doris trifida, J. E. Gray, 1850
          - Ceratosoma corallinum, Odhner, 1917                   - Doris trilobata , J. E. Gray, 1827
          - Ceratosoma cornigerum, Adams & Reeve, 1850     - Polycera cornigera, Adams & Reeve in Adams, 1848
          - Ceratosoma gibbosum, Rochebrune, 1894

Bibliographic data :

There is a distinct ridge around all the mantle edge
    The lamellate rhinophores are tall. They are usually brown with yellow flecks on the lamellae and a blue apex
    The numerous long bushy gills form a circle around the anus. They are translucent white with red streaks up both axes
    The colour pattern is complicated and very variable :
            - The mantle purple border can be unbroken or broken. In some specimen there is a continuous purple line which breaks up at the “neck” between the "cephalic expension" around the head and the "lateral expansion" in front of the gills
            - In some specimens, the "horn" is spotted with larger red spots on both sides
            - Body red with yellow, orange or reddish spots. In some specimens, each ring is situated on a lighter, sometimes white background area. Some specimens haven't any spots...
            - The background colour can vary from orange-red to brown
            - Sometimes there is a violet edge around the gills and rhinophore pockets
    It has 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.
    In species of Ceratosoma the oral tube is brightly coloured rather than colourless as in species of Chromodoris.
    It feeds on a bluish sponge colony, a dysideid sponge, perhaps a species of Euryspongia
    We have is indirect evidence of the feeding sponge from chemists (Mollo, 2005) who have found molecules characteristic of dysideid sponges in the mantle glands of C. trilobatum.
    The egg mass is orange.
    This species has 1 dorsal lobe and 1 lateral mantle lobe on each side (= 3 lobes) which makes it C. trilobatum (tri = 3; lobatum = lobes).
    The two common tropical species of Ceratosoma , C. tenue and C. trilobatum, 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.
        But these two similar species have some differences.


Ceratosoma trilobatum

Ceratosoma tenue

Mantle lobes

It is characterised by having only one large lateral lobe on each side of the body, just anterior to the gills

It is characterised by the three mantle lobes on each side of the body

Purple border

The purple border to the mantle and foot is usually an unbroken line

The purple border to the mantle and foot is always a dotted line

Gills and rhinophores pockets

The gills and rhinophores pockets bear purple around its margin

The gills and rhinophores pockets do not bear purple around its margin

References :

Bill Rudman Seaslug site : Sea Slug Forum : Ceratosoma trilobatum
   Nudipixel Ceratosoma trilobatum

Publications :

Gray, J.E. 1827. Mollusca, pl. 3. In : E. Smedley (Ed.). Encyclopaedia Metropolitana; or, Universal dictionary of knowledge. London
    Mollo, E., Gavagnin, M., Carbone, M., Guo, Y.-W., and Cimino, G. (2005) Chemical studies on Indopacific Ceratosoma nudibranchs illuminate the protective role of the dorsal horn. Chemoecology 15: 31-36
    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
    Rudman, W.B. (1991) Purpose in Pattern: The evolution of colour in chromodorid nudibranchs. Journal of Molluscan Studies, 57 (T.E.Thompson Memorial Issue) : 5-21

Other photos of Ceratosoma trilobatum :

Fabrice Schubert

Mayotte, "Mhila", 15 m, 21 March 2010, size : 15 mm

It is a juvenile (15 mm) form with some interesting characteristics :
            - A pale mantle coloration (a)
            - A broken purple border on the mantle (b) and the foot (c)
            - Some red spots (d) on the "horn"
            - Yellow-orange rhinophores (e) with very pale blue ( almost white) apex (f)

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