Vellicolla okamotoi (Habe, 1952)

Description

A small shelled cephalaspidean with a shell length of about 6–7 mm. The shell is rather slender and ovate-cylindrical, a shape echoed by the Japanese name tokkuri-tamago-gai ("sake-flask egg shell"). As in other haminoeids the soft body is pale and semitranslucent, with a well-developed cephalic shield and lateral parapodial flaps that almost cover the shell in life.

Distribution

Type locality is Kyushu, Japan. In Japan it has been recorded from the Kii Peninsula and Yamaguchi Prefecture westward into the East China Sea, on sandy-muddy bottoms with macroalgae at depths of about 5–30 m, with additional records from Amami-Ōshima (Kagoshima). It has also been reported from Singapore, suggesting a broader Indo-West Pacific range.

Etymology

The specific epithet okamotoi is a Latinised personal name honouring a Mr. Okamoto.

Remarks

Originally described in 1952 by Habe as Limulatys okamotoi in the family Atyidae (now Haminoeidae). Oskars et al. 2019, in their molecular phylogenetic revision of Haminoeidae, transferred this species to the newly erected genus Vellicolla, yielding the current combination Vellicolla okamotoi (Habe, 1952).

It has long been confused with the externally similar Weinkauffia ukulele (Too, Carlson, Hoff & Malaquias, 2014) in Japanese field guides, but the two are distinct species in different genera, separable on shell shape, soft-body details, and known geographic range.

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References

• Limulatys okamotoi n.sp., Habe T. (1952). Atyidae in Japan. In: Kuroda T. (ed.) Illustrated Catalogue of Japanese Shells, 1(20): 137-152.
• ホソタマゴガイ？, 中野理枝. (2004). 本州のウミウシ. ラトルズ.
• ウクレレタマゴガイ（新称）？, 中野理枝. (2018). 日本のウミウシ. 文一総合出版.
• Atys ukulele, Terrence Gosliner, Ángel Valdés and David Behrens. (2018). Nudibranch and Sea Slug Identification Indo-Pacific 2nd Edition. New World Pubns Inc.
• Oskars T.R., Too C.C., Rees D., Mikkelsen P.M., Willassen E. & Malaquias M.A.E. (2019). A molecular phylogeny of the gastropod family Haminoeidae sensu lato (Heterobranchia: Cephalaspidea): a generic revision. Invertebrate Systematics 33(3): 426-472.
• ウクレレタマゴガイ, 小野篤司 & 加藤昌一. (2020). 新版 ウミウシ. 誠文堂新光社.