Gastropteron bicornutum
Baba & Tokioka, 1965
Order: CEPHALASPIDEA
Superfamily: PHILINOIDEA
Family: Gastropteridae
DISTRIBUTION
Japan, Papua New Guinea [nth coast], Nth Queensland.
PHOTO
Ose-zaki, west coast of Izu Peninsula, Japan
Depth: 10m, Length: 12mm, 25 April 2001. Photo: Hisako Yamada
This species was described from a number of preserved animals and brief colour notes. I think this is probably the first published colour illustration of the species. In Baba & Tokioka's description of this species they give some brief colour notes from the collector:
" ... yellowish white shaded in places .. with sepia black .. and the whole surfaces of the cepahilc shield, dorsal hump and parapodia are evenly covered by orange-yellow pigment spots."
The other distinctive feature of this species are the two dorsal posterior processes from which the species gets its name. In an earlier message I suggest the photo in Okutani (2000) - Marine Mollusks in Japan, which is labelled G. bicornutum, is a misidentified specimen Siphopteron nigromarginatum [p. 749].
Reference:
• Baba, K. & Tokioka, T. (1965) Two more new species of Gastropteron from Japan, with further notes on G. flavum T. & B. (Gastropoda : Opisthobranchia). Publications of the Seto Marine Biological Laboratory, 12(5): 363-377, Text-figs 1-8, Pl.25.
• Baba, K. (1970) List of the Gastropteridae and Runcinidae from Japan. Collecting and Breeding, 32(2): 46-48
• Gosliner, T.M. (1989) Revision of the Gastropteridae (Opisthobranchia: Cephalaspidea) with descriptions of a new genus and six new species. The Veliger, 32(4): 333-381. (Figs 1-32)
Rudman, W.B., 2002 (February 12) Gastropteron bicornutum Baba & Tokioka, 1965. [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/gastbico
Related messages
Gastropteron bicornutum from Koumac
January 16, 2004
From: Bill Rudman
Here is a record of Gastropteron bicornutum from Koumac in northern New Caledonia.
• Chenal de la Passe de Koumac, N of Ilot Kendac, 20°38.8'S, 164°15.6'E, New Caledonia. 32-37m, 8 Oct. 1993. 6mm live length 1 specimen, AM C200414
The animal was translucent with scattered spots of yellow, brown and white. It agrees with G. bicornutum in colour and radular morphology [see separate message], but lacks the second papilla on posterior visceral hump which gives this species it name. I can only assume that the papillae has either been lost through damage or is absent trhough some developmental mistake. This is the first record of the species from New Caledonia and with other recent records on the Forum suggests it has a wide distribution at least in the tropical and subtropical western Pacific
Best wishes
Bill Rudman
Gastropteron bicornutum from Sydney
January 16, 2004
From: Bill Rudman
To accompany my record of Gastropteron bicornutum from New Caledonia, here is a reocrd of an animal from the temperate waters of Sydney, Australia.
• Long Reef, Collaroy, Sydney, New South Wales, Australia. 20 January 1992. Coolected from algal washings, low tide. AM C172761
The body is translucent with clear and dark regions. In the clear regions there are small yellow & opaline green spots (yellow predominate) and scattered larger dark brown diffuse spots. In dark regions the dark brown spots all tend to coalesce. In the translucent regions are larger yellow spots and some greeny blue patches.
Down the midline of the visceral hump there are 4 rounded but raised tubercles, 2 of which have white tips. There is a very distinctive large floppy papilla off the edge of the mantle flap. I presume this is the upper of the two papillae normally found in this species. As with the animal from New Caledonia, this specimen had only one of the two posterior papillae considered characteristic of this species
Best wishes
Bill Rudman
Radula of Gastropteron bicornutum from Koumac
January 16, 2004
From: Bill Rudman
Here are some scanning electron photographs of the radula of the specimen of Gastropteron bicornutum from Koumac in northern New Caledonia, which I reported in a separate message.
• Chenal de la Passe de Koumac, N of Ilot Kendac, 20°38.8'S, 164°15.6'E, New Caledonia. 32-37m, 8 Oct. 1993. 6mm live length 1 specimen, AM C200414
PHOTOS:
• Upper right - whole radular ribbon. Note change in denticulation of innermost teeth from old teeth [at top of photo] to new teeth [at bottom]. Scale = 200 microns.
• Lower Left - outer teeth on right side. Scale = 50 microns.
• Lower Right - Deveoping innermost teeth showing aberrant denticulation. Scale = 50 microns. Photos: Alison Miller.
The radular formula was 18(+2) x 3-4.1.0.1.4-3
In the mount the outermost of the 4 lateral teeth was often missing, probably lost in prepartion of the mount. The denticulation along the edge of the large innermost lateral teeth appears to be aberrant. In the oldest teeth [uppermost rows in upper right photo] there are a series of small denticles along the whole of the cutting edge of the tooth, while in the younger teeth [lower rows in upper most photo] the teeth are irregularly shaped and restricted to the inner end of the tooth. Both Baba & Tokioka (1965) and Gosliner (1989) describe small denticles right along the cutting edge.
Best wishes
Bill Rudman
Gastropteron bicornutum from Lizard Is
January 9, 2004
From: Nils Anthes
Dear Bill,
Here is another picture of Gastropteron bicornutum. We found it 1 January 2004 at 4m depth on sandy bottom at Lizard Island (QLD, Australia). Body length was about 7mm.
Best wishes
Nils
anthes@uni-muenster.de
Anthes, N., 2004 (Jan 9) Gastropteron bicornutum from Lizard Is. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/11840Thanks Nils,
I think this is probably a new record from Australia
Best wishes
Bill Rudman
On Gastropteron bicornutum
February 14, 2002
From: Bill Rudman
In an recent message I mention that a photo in Okutani (2000) - Marine Mollusks in Japan, which is labelled G. bicornutum is a misidentified specimen of Siphopteron nigromarginatum.
I have just noticed that there are two photos in the book which are labelled as G. bicornutum.
• On page 749 there is an unnumbered colour plate with a photo of Siphopteron nigromarginatum incorrectly identified as G. bicornutum.
• On page 754, in Plate 375, fig. 2 there is a photo of a correctly identified specimen of G. bicornutum.
Bill Rudman.
Rudman, W.B., 2002 (Feb 14) On Gastropteron bicornutum. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/6247Gastropteron bicornutum? from Izu Peninsula, Japan
February 13, 2002
From: Haruo Kinoshita
Hello,
Miss Hisako Yamada who is my friend sent an e-mail me with some sea-slug pictures that were found and taken at Izu Peninsula. She is thinking this is one of the Gastropteridae, especially similar to Gastropteron bicornutum. And she also said this is not rare on there. Can you please identify this for her?
Date : 25-Apr-2001
Location : Ose-zaki on the west of Izu Peninsula, Japan
Depth : 10m
Length : 12mm
Water temperature: 14c
Photo: Hisako Yamada
Regards,
Haruo Kinoshita
kinoh@vesta.ocn.ne.jp
Kinoshita, H., 2002 (Feb 13) Gastropteron bicornutum? from Izu Peninsula, Japan. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/6155Dear Haruo,
Please thank Miss Hisako Yamada for this excellent photo. I agree that it is almost certainly Gastropteron bicornutum. This species was described from a number of preserved animals and to my knowledge only brief colour notes have ever been published. So this is probably the first published colour illustration of the species.
In Baba & Tokioka's description of this species they give some brief colour notes from the collector:
" ... yellowish white shaded in places .. with sepia black .. and the whole surfaces of the cepahilc shield, dorsal hump and parapodia are evenly covered by orange-yellow pigment spots."
The other distinctive feature of this species are the two dorsal posterior processes from which the species gets its name. In an earlier message I suggest the photo in Okutani (2000) - Marine Mollusks in Japan, which is labelled G. bicornutum, is a misidentified specimen Siphopteron nigromarginatum.
• Baba, K. & Tokioka, T. (1965) Two more new species of Gastropteron from Japan, with further notes on G. flavum T. & B. (Gastropoda : Opisthobranchia). Publications of the Seto Marine Biological Laboratory, 12(5): 363-377, Text-figs 1-8, Pl.25.
This is another interesting find from Japan,
Best wishes,
Bill Rudman
