Gymnodoris inariensis Hamatani & Osumi, 2004

Description

A very small Gymnodoris species, up to 5 mm in body length, limaciform with a circular cross section. The mantle margin does not project over the foot, the dorsal surface is smooth, and branchial gills are completely absent. The body is generally blackish with densely scattered minute dark brownish-black spots. The rhinophores are very small, retractile, and situated close together; in the holotype they are elongated and triangular, tapering toward the tips, while in some specimens they are clavate with rounded tips. They are colorless and translucent, sometimes yellowish or slightly orange, and tinged orange when preserved. Rhinophoral sheaths are absent, and only three weak folds are present bilaterally. Eyes are buried deeply beneath the cutaneous layer just behind the rhinophore bases. Oral tentacles were not observed. The anal opening lies on the midline of the posterior dorsal surface; the genital orifice is on the right side, slightly posterior to the head. The sole is translucent white.

Distribution

Kagoshima Bay, southern Japan. Found on muddy sand substrates near a river mouth at depths of 5-20 m.

Etymology

From the original description (Hamatani & Osumi, 2004):

The specific epithet, inariensis, refers to the type locality of this new species.

The name derives from the mouth of the Inari river in Kagoshima Bay, where the type material was collected.

Notes

Resembles G. nigricolor Baba, 1960 in body color, but is clearly distinguished by its much smaller size, complete absence of branchial gills, and different radular morphology. Superficially recalls Limapontia and Veyssierea in lacking dorsal gills, but Limapontia has no true rhinophores, and Veyssierea has finger-shaped rhinophores without folds. The radula shows the typical features of Gymnodoris: central tooth absent, first lateral tooth large and hamate, outer laterals pyriform and decreasing in size outward, all without denticles.

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References

• Gymnodoris inariensis n. sp.クロヒメキヌハダウミウシ(新種・新称), Hamatani I. & Osumi D. (2004 ["2003"]) A new gill-less species of Gymnodoris Stimpson, 1855 (Opisthobranchia: Nudibranchia) from Kagoshima Bay, southern Japan. Venus 62(3-4)
• Gymnodoris sp. 42 ?, Terrence Gosliner, Ángel Valdés and David Behrens. (2018). Nudibranch and Sea Slug Identification Indo-Pacific 2nd Edition. New World Pubns Inc.