Plocamopherus tilesii Bergh, 1877
- Location
- Red Beach, Okinawa Island (East coast), Okinawa, Japan
- Date
- 2013/01/27
- Length
- 60mm
- Depth
- 13.0m
- Water temperature
- 22.0℃
Description
A large nudibranch reaching 9-11 cm in length, with body height about 2 cm at mid-back and the caudal fin about 2.5 cm tall; the oral veil reaches about 4.5 cm wide. Ground colour pale brownish-grey, spotted with dark purple-brown and golden-yellow. The purple-brown forms small dots, scattered or densely aggregated into larger sharply-outlined patches; in particular, a forward-pointing triangle and a similar but less sharply-defined backward-pointing triangle between the rhinophores; an elongate patch on each side of the front of the back; and several on the sides of the tail and the fin. The golden-yellow appears as larger, rounded spots, most numerous on the edge of the oral veil and the sides of the body. The processes of the oral veil are pale grey with yellow and purple-brown dots; the rhinophore club is dark purple-brown, white at the tip with dark dots. The dorsum bears three pairs of branched lateral appendages, the posteriormost beside the gill and reaching 8 mm in height. The gill is three-leaved (the lateral leaves so deeply divided that they appear five-leaved). The anterior edge of the oral veil is beautifully rounded, bearing a fringe of about 20-25 short, branched or knobby processes.Distribution
Type locality: Nagasaki, Japan. Widely distributed across the western Pacific.Etymology
The specific epithet tilesii honours the German naturalist Wilhelm Gottlieb Tilesius von Tilenau (1769-1857), naturalist on the first Russian circumnavigation under Krusenstern (1803-1806), who illustrated many Pacific and Japanese marine animals.Remarks
The Japanese name "Hikari-umiushi" ("light-emitting sea slug") refers to the strong bluish-white light emitted from the tips of the dorsal lateral appendages when the animal is disturbed — a characteristic feature of Plocamopherus.References
- Plocamopherus tilesii, Rüppell E. & Leuckart F.S. (1828-1830). Atlas zu der Reise im nördlichen Afrika von Eduard Rüppell. Erste Abtheilung. Zoologie, Neue wirbellose Thiere des Rothen Meers. Frankfurt am Main: H.L. Brönner. iv + 47 pp., 12 pls.
- ヒカリウミウシ（新称）, Baba, K. 1930. Studies on Japanese nudibranchs (1). Polyceridae. Venus 2(1)
- ヒカリウミウシ, Baba K. (1949). Opisthobranchia of Sagami Bay collected by His Majesty the Emperor of Japan (相模湾産後鰓類図譜). Iwanami Shoten, Tokyo. 4+2+194+7 pp., pls. 1-50.
- Plocamopherus tilesii Bergh Hikari-umiushi, Baba, K. 1957. A revised list of the species of Opisthobranchia from the northern part of Japan, with some additional descriptions. J. Fac. Sci., Hokkaido Univ.,ser. 6, Zool. 13(1-4):8-14.
- ヒカリウミウシ, 小野篤司. (1999). ウミウシガイドブック. TBSブリタニカ.
- ヒカリウミウシ, 鈴木敬宇. (2000). ウミウシガイドブック〈2〉. TBSブリタニカ.
- 高岡生物研究会. (2002). 日本海のウミウシ. 第2版.
- ヒカリウミウシ, 殿塚孝昌. (2003). ウミウシガイドブック〈3〉. TBSブリタニカ.
- ヒカリウミウシ, 小野篤司. (2004). 沖縄のウミウシ. ラトルズ.
- ヒカリウミウシ, 中野理枝. (2004). 本州のウミウシ. ラトルズ.
- Plocamopherus tilesii Bergh, 1877, Vallès Y. & Gosliner T.M. 2006. Shedding light onto the genera (Mollusca: Nudibranchia) Kaloplocamus and Plocamopherus with description of new species belonging to these unique bioluminescent dorids . The Veliger 48(3): 178-205
A Kindle field guide by the site author
Kimoto N. (2026). Sea Slugs of Japan & the Indo-Pacific, 2nd Edition.
Kindle Edition
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Photos of Plocamopherus tilesii
Tag:
Same Genus Nudibranchs
Similar Colors Nudibranchs
Academic Database
Sea slug observation data is available in international marine biodiversity databases.