Ceratosoma gracillimum

Semper in Bergh, 1876

Ceratosoma gracillimum
Photographed by: Jeffrey de Guzman

Kingdom:Animalia
Phylum:Mollusca
Class:Gastropoda
Subclass:Opisthobranchia
Order:Nudibranchia
Suborder:Doridina
Family:Chromodorididae
Species:Ceratosoma gracillimum

Comment from Richard Willan on photo #29323
Note the ‘smooth’ region behind the head and in front of the pre-branchial mantle extensions.

Comment from Richard Willan on photo #4230
Ceratosoma gracillimum definitely (note the smooth region between the rhinophores and lateral lobes).

Comment from Richard Willan on photo #3624
Ceratosoma gracillimum (foreground) and Pectenodoris trilineata (background, alongside the tail of the Ceratosoma)

Comment from Richard Willan on photo #2693
A good photo showing the smooth “neck’ region

Comment from Richard Willan on photo #2684
Both this species and Ceratosoma trilobatum have very great colour variation, so neither of them can be identified by colour alone. Fortunately the smooth ‘neck’ zone of Ceratosoma gracillimum (as against a continuous ridge in Ceratosoma trilobatum) is a consistently reliable way to distinguish between them.

Comment from Richard Willan on photo #2459
The feature you used to identify this species correctly is the complete absence of a mantle brim on the ‘neck’ region from behind the rhinophores to in front of the lateral processes. This completely smooth region is even more clearly shown in this other photo of Ceratosoma gracillimum.

Comment from Richard Willan on photo #2408
Comment from Dr. Richard C. Willan: Ceratosoma gracillimum is correct for the reason you have pointed out.

Comment from Nudi Pixel editor: Not sure if this one is Ceratosoma trilobatum as the line on the edge of the mantle is broken (which I think makes this species belongs to Ceratosoma gracillimum).

Comment from Richard Willan on photo #2067
This name is used because there seems to be a complete absence of a mantle brim (= sharp mantle margin) between the head and the lateral lobes, which is the diagnostic feature for Ceratosoma gracillimum. This certainly appears to be the case on the animal’s right side, but it cannot be checked on the left side because the rhinophore is blocking the view. However, given the locality, this might be just another colour form of Ceratosoma trilobatum.

Comment from Richard Willan on photo #1408
This individual has exceptionally large and flattened lateral mantle lobes. Note the way in which the posterior lobe (the ‘horn’) is recurved over the gills.

Locality:

 

Pictures of Ceratosoma gracillimum

Ceratosoma gracillimum from Anilao, PhilippinesIdentification reviewed by Richard Willan
Posted 8 years ago
Viewed 3890 times
Ceratosoma gracillimum from Bali, IndonesiaIdentification reviewed by Dave Behrens
Location: Bali, Indonesia
Posted 9 years ago
Viewed 5054 times
Ceratosoma gracillimum from Lembeh, Indonesia
Posted 9 years ago
Viewed 4047 times
Ceratosoma gracillimum from Lembeh, Indonesia
Posted 9 years ago
Viewed 3817 times
Ceratosoma gracillimum from Koh Rok, ThailandIdentification reviewed by Richard Willan
Posted 9 years ago
Viewed 4140 times
Ceratosoma gracillimum from Manado, Indonesia
Posted 9 years ago
Viewed 3592 times
Ceratosoma gracillimum from Lembeh, Indonesia
Posted 9 years ago
Viewed 3738 times
Ceratosoma gracillimum from Lembeh, Indonesia
Posted 9 years ago
Viewed 3795 times
Ceratosoma gracillimum from Lembeh, Indonesia
Posted 9 years ago
Viewed 3760 times
Ceratosoma gracillimum from Lembeh, Indonesia
Posted 9 years ago
Viewed 3682 times
Ceratosoma gracillimum from Pulau Hantu, SingaporeIdentification reviewed by Richard Willan
Posted 9 years ago
Viewed 5075 times
Ceratosoma gracillimum from Redang, MalaysiaIdentification reviewed by Richard Willan
Posted 9 years ago
Viewed 4404 times
 
 

Similar Species

Ceratosoma gracillimum can be distinguished externally by the complete absence of the mantle edge between the head and the well-developed lateral lobes on each side.

Ceratosoma trilobatum has the mantle edge, edged in purple, between the head and the lateral lobes. Both species have a similar range of colour variations, as does Ceratosoma tenue, but they differ from each other externally by the lack of a mantle edge in Ceratosoma gracillimum and the extra pair of small lateral lobes in Ceratosoma tenue.

Ceratosoma tenue from Lembeh, IndonesiaIdentification reviewed by Nathalie Yonow
(136 photos)
 
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