Goniobranchus vibratus (Pease, 1860)

Description

A small to medium-sized dorid reaching about 25 mm in body length. At rest the body is oblong, becoming oval when active. The mantle is smooth, convexly rounded above, rounded and somewhat dilated in front, acutely rounded behind, with thin margins not concealing the foot. The gill consists of seven small, sub-erect, linear, quadrangular plumes, ciliated along their whole length on the angles, retractile into a common simple cavity and decreasing in size posteriorly. The anal papilla is prominent. The rhinophores are short, ovate, obliquely lamellate and retractile into simple cavities. The oral tentacles are small and cylindrically tapering. The foot is elongate, almost as wide as the mantle, obtusely rounded in front and tapering to an acutely rounded point behind, projecting beyond the posterior end of the mantle. In life the dorsum is yellow with irregular white spots; it is paler towards the margin, which is dotted and edged with purple. The gill is edged with violet, the rhinophores are violet with uncoloured peduncles, and the foot is white. In captivity Pease observed the species to vibrate its gill continuously, both at rest and when crawling.

Distribution

Central Pacific. Type locality: Sandwich Islands (Hawaiian Islands), based on Pease's observations of Hawaiian specimens. Subsequently recorded from the Hawaiian Islands, Johnston Atoll and the Line Islands.

Etymology

The specific epithet vibratus is the past participle of Latin vibrare ("to vibrate, to set in tremulous motion"), in reference to the continuous vibrating motion of the gill that Pease observed in captive specimens.

Remarks

Originally placed by Pease in Doris as the representative of "a group with simple, linear, quadrangular branchiae" together with Doris propinquata and Doris picta. The species was later transferred to Goniobranchus; the parentheses in the author citation reflect this generic transfer. The Japanese name "エラフリイロウミウシ" ("gill-shaking colour-slug") refers, like the specific epithet, to the constant vibration of the gill described by Pease.

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References

• Doris vibrata Pease n. sp., Pease W.H. (1860). Descriptions of new species of Mollusca from the Sandwich Islands. Part I. Proceedings of the Zoological Society of London. 28: 18-36.
• クロモドーリス・ウィブラータ, 小野篤司. (2004). 沖縄のウミウシ. ラトルズ.
• クロモドーリス・ウィブラータ, 中野理枝. (2004). 本州のウミウシ. ラトルズ.
• クロモドーリス・ヴィブラータ, 小野篤司 & 加藤昌一. (2009). ウミウシ. 誠文堂新光社.
• Goniobranchus vibratus (gender corrected from vibrata), Johnson R.F. & Gosliner T.M. (2012). Traditional taxonomic groupings mask evolutionary history: a molecular phylogeny and new classification of the chromodorid nudibranchs. PLoS ONE 7(4): e33479.
• Goniobranchus vibratus, Terrence Gosliner, Ángel Valdés and David Behrens. (2015). Nudibranch and Sea Slug Identification Indo-Pacific. New World Pubns Inc.
• エラフリイロウミウシ（新称）, 中野理枝. (2018). 日本のウミウシ. 文一総合出版.