Dermatobranchus gonatophorus van Hasselt, 1824

Description

Reaches about 120 mm in length. Ground colour milky white to yellowish white, rarely bluish grey. Fine yellow longitudinal ridges run along the dorsum. Dark blotches mark the dorsum, and the ridges crossing these blotches turn black. The mantle margin is undulating and bordered by a yellow to orange line. The rhinophores are white at the base with a black longitudinal stripe in front, and the lamellate portion is black.

Distribution

Indian Ocean and western Pacific. Records include South Africa, the Red Sea, Malaysia, Thailand, Indonesia and Japan. The type locality is Anyer Bay (Anjer-baai), west Java, Sunda Strait, Indonesia.

Etymology

The specific epithet gonatophorus is from the Greek gónu ("knee" or "angle") and -phoros ("bearing"), meaning "angle-bearing". Van Hasselt's diagnosis describes oblique transverse grooves "ab utroque latere in lineam dorsalem medianam antrorsum recto angulo confluentibus" — converging from both sides into the dorsal midline at a forward-pointing right angle, forming the diagnostic V-shaped pattern.

Remarks

Originally described by van Hasselt (Bulletin des Sciences Naturelles et de Géologie, vol. 1: 243, 1824) as the third of three congeners erected with the genus Dermatobranchus, alongside the type species D. striatus and D. pustulosus. Van Hasselt characterised the species as "rara" (rare).

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References

• Dermatobranchus gonatophorus, Hasselt J.C. van (1824). Extrait d'une lettre du Dr. J.C. Van Hasselt, à M. C.J. Temminck, sur les mollusques de Java (traduit du Algemeene Konst- en Letterbode 1824 par H. Boie). Bulletin des Sciences Naturelles et de Géologie (Férussac), Tome 1: 237-247.
• Dermatobranchus gonatophorus, Terrence Gosliner, Ángel Valdés and David Behrens. (2015). Nudibranch and Sea Slug Identification Indo-Pacific. New World Pubns Inc.
• フトウネオトメウミウシ（新称）, 中野理枝. (2018). 日本のウミウシ. 文一総合出版.