Thuridilla lineolata (Bergh, 1905)

Description

A small thuridilline sacoglossan, 4.5-10 mm long. In life the coloration is splendid: parapodia blue with red inner and outer margins, head blue, rhinophore tips red. In preserved material the head is whitish, the upper surface (dorsum with spread parapodia) is otherwise blackish-grey with whitish parapodial margins and a black line just inside them. The front edge of the rather small front foot is bordered by a black line; the foot is grey, edged with a black band, outside which lies a broader whitish band. Each rhinophore carries a black transverse band at mid-height, often with another near the tip. The bold black longitudinal lines along dorsum, parapodial margins and foot are the key external character distinguishing this species from congeners.

Distribution

Type locality: reef off Saleyer (Selayar Island), south of Sulawesi, Indonesia (Siboga station 213). Now known to range widely across coral-reef habitats of the Indo-West Pacific.

Etymology

The specific epithet lineolata is a Latin compound of lineola ("small line") and -atus ("bearing"), meaning "with fine lines", in reference to the conspicuous black longitudinal lines along the dorsum, parapodia and foot.

Remarks

The species was originally described in Elysia with a question mark on the generic assignment, and later transferred to Thuridilla; the parentheses in the author citation reflect this transfer.

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References

• Elysia? lineolata Bgh. n. sp., Bergh R. (1905). Die Opisthobranchiata der Siboga-expedition. https://doi.org/10.5962/bhl.title.11223
• ツリディラ・リネオラータ, 殿塚孝昌. (2003). ウミウシガイドブック〈3〉. TBSブリタニカ.
• Thuridilla lineolata, Terrence Gosliner, Ángel Valdés and David Behrens. (2018). Nudibranch and Sea Slug Identification Indo-Pacific 2nd Edition. New World Pubns Inc.
• ソライロミドリガイ（新称）, 中野理枝. (2019). 日本のウミウシ. 第二版. 文一総合出版.