Siphopteron nigromarginatum Gosliner, 1989
- Location
- Aka toudaimoto, Kannoura, Kouchi, Japan
- Date
- 2020/04/12
- Length
- 5mm
- Depth
- 20.0m
- Water temperature
- 17.0℃
Description
A small cephalaspidean reaching 3–4 mm in length in the type series. The ground color is pale yellowish white to lemon yellow, sometimes with scattered orange mottling on the head shield and visceral hump. An opaque white patch lies at the base of the head shield, just anterior to the visceral hump. Black pigment adorns the apex of the siphon, the tip of the siphonal crest, the parapodial margins, and the flagellum and its base — these black margins are diagnostic. The flagellum is bifurcate in the holotype but uniramous in the remaining type material. The parapodia are widest anteriorly, never overlap, and leave most of the visceral hump exposed. The gill consists of 3–4 simply plicate lamellae. Radular formula 17–18 × 3.1.0.1.3; the inner lateral teeth bear a strong inner limb, an expanded outer lobe, a large triangular masticatory denticle (formed by fusion of smaller denticles), and 5–18 small irregular denticles on the inner side. The penial bulb carries four rows of chitinous spines (6, 10, 15, 15 from posterior to anterior in one specimen).Distribution
Type locality: SE side of Pig Island, Madang, Papua New Guinea, 10 m depth. Originally known only from the Madang region; subsequent records extend the range across the western Pacific, including Palau, the Philippines, Guam, and Japan.Etymology
Verbatim from the original description (Gosliner, 1989, p.346):The epithet nigromarginatum refers to the black pigment that ornaments the siphonal and parapodial margins of this species.
Remarks
Described as a new species in Gosliner, T.M. 1989 The Veliger 32(4):333-381. The author noted in the Discussion that S. nigromarginatum is most similar in external appearance to S. citrinum, and that specimens from Papua New Guinea were originally thought conspecific with the latter. Several consistent differences distinguish the two: "Specimens of S. nigromarginatum always have black pigment on the margins of the parapodia and along the apical margin of the siphon. Siphopteron citrinum lacks black parapodial margins and black pigment is restricted to the apex of the siphonal crest, but is absent from the apical margins of the siphon" (p.348). Internally, the penial bulb of S. nigromarginatum bears distinct rows of chitinous spines, whereas spines are entirely absent in S. citrinum; the inner lateral teeth bear more denticles than in S. citrinum; and the central nervous system also differs in the appression of the left pleural, subintestinal and visceral ganglia. Siphopteron brunneomarginatum (Carlson & Hoff, 1974) differs in having a wider brown-black marginal band and parapodia that touch or overlap.References
- Siphopteron nigromarginatum Gosliner, sp. nov., 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.
- オレンジウミコチョウ, 小野篤司. (1999). ウミウシガイドブック. TBSブリタニカ.
- クロフチウミコチョウ（新称）, 小野篤司. (2004). 沖縄のウミウシ. ラトルズ.
- クロフチウミコチョウ, 中野理枝. (2004). 本州のウミウシ. ラトルズ.
- クロフチウミコチョウ, 中野理枝. (2018). 日本のウミウシ. 文一総合出版.
- Siphopteron nigromarginatum, Terrence Gosliner, Ángel Valdés and David Behrens. (2018). Nudibranch and Sea Slug Identification Indo-Pacific 2nd Edition. New World Pubns Inc.
Featured in this book
Terrence Gosliner, Ángel Valdés and David Behrens. (2018). Nudibranch and Sea Slug Identification Indo-Pacific 2nd Edition. New World Pubns Inc.
New World Publications
This species, Siphopteron nigromarginatum, is included in the book.
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Tag:
Same Genus Nudibranchs
Similar Colors Nudibranchs
Academic Database
Sea slug observation data is available in international marine biodiversity databases.