UPPER RIGHT, LOWER LEFT: North point of Île Nou, Nouméa, New Caledonia, intertidal: 10 October 1988, AM C156617.
LOWER RIGHT: Pointe de Pandop, Koumac, New Caledonia, 20°35.2'S, 164°16.6'E, 2 m, hard substrate, 18 October 1993, 3 specimens (13, 20 & 24mm long alive), AM C200509.
PHOTOS: Bill Rudman.
Very characteristic colour pattern, with a dark, almost black, background, fine white longitudinal lines and the foot, head and rhinophores edged with bright orange. In some specimens the parapodia can also be bordered with bright orange and in some specimens elongate white or bright blue spots are present along the outside of the parapodia just down from the edge.Thuridilla bayeri is clearly a synonym and so is T. ratna.
Described by Risbec as having 8 rows of white streaks down the parapodia, which are bordered with orange. He also describes a whitish T-shaped mark on the head between the rhinophores. Gosliner (1995) discusses the synonymy of T. bayeri and T. ratna but considers that the original description of Risbec's Elysia gracilis is insufficient to allow an accurate identification. My photographs from New Caledonia clearly fit Risbec's description and painting, which I have reproduced below. Gosliner considers that the 10 denticles on the radular teeth in Risbec's description shows that E. gracilis is distinct from T. bayeri with 10-15 denticles. Considering the optical equipment available to Risbec to view these tiny teeth, I don't think this difference can be considered significant. I have retained the Thuridilla bayeri page as a cross-reference, but I feel that it is a synonym of T. gracilis.
• Risbec, J. (1928) Contribution a l'etude des nudibranches Neo-Caledoniens. Faune de Colonies Francaises: Paris. 1-328.
• Gosliner, T.M. (1995) The genus Thuridilla (Opisthobranchia: Elysiidae) from the tropical Indo-Pacific, with a revision of ther phylogeny and systematics of the Elysiidae. Proceedings of the California Academy of Sciences, 49(1): 1-54.
Rudman, W.B., 2000 (August 12) Thuridilla gracilis (Risbec, 1928). [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/thurgrac
Thuridilla gracilis from S. E. Queensland
From: David Mullins, May 14, 2010
Re: The foot of Thuridilla bayeri
From: John Fraser, May 14, 2010
Thuridilla gracilis from Lembeh, Indonesia.
From: Brian Mayes, March 4, 2009
Thuridilla bayeri ? from Bangka Island, Indonesia
From: Francois Zylberman, October 13, 2008
Re: The foot of Thuridilla bayeri
From: Clay Carlson, December 3, 2007
The foot of Thuridilla bayeri
From: Clay Carlson, November 30, 2007
Possible colour variant of Thuridilla gracilis
From: Heidi Hösel, October 16, 2007
Thuridilla gracilis from West Papua
From: Wendy Atkinson, June 5, 2007
Mating Thuridilla gracilis from nthn Mariana Islands
From: Yuji Fujie, January 30, 2007
Sea grass hitch hiker
From: Charles Raabe, July 4, 2006
Thuridilla gracilis from Thailand
From: Nararongpon Sittithaweepat, September 29, 2005
Thuridilla from Mombasa, Kenya
From: Valérie Besnard, May 18, 2005
Thuridilla gracilis from Singapore
From: Lim Han Peng, April 28, 2005
Thuridilla bayeri? found in tank
From: Marc, February 14, 2004
Thuridilla from the Philippines
From: Erwin Koehler, February 11, 2002
Thuridilla bayeri ? from the Seychelles
From: Erwin Koehler, June 18, 2001
Re: Thuridilla gracilis from the Solomon Ids
From: Kathe R. Jensen, June 16, 2001
Thuridilla gracilis from the Solomon Ids
From: Bruce Potter, June 15, 2001
Thuridilla gracilis from Coral Sea
From: Des Paroz, October 29, 2000
Thuridilla bayeri & T. gracilis
From: C. Carlson & P.J. Hoff, September 28, 2000
Thuridilla from coral rock
From: Andrew Trevor-Jones, September 24, 2000
Thuridilla gracilis from Great Barrier Reef
From: Stuart Hutchison, August 12, 2000