Hexabranchus giganteus Tibiriçá, Pola & Cervera, 2023

MORPHOLOGY

Commonly up to 500 mm (with some reports to 700 mm in Madagascar). The notum of resting, mature animals is evenly pustulate (“quilted”). The body of mature animals is oval. The mantle is wide, expanding, and rolled on the sides and posteriorly (but not anteriorly). The foot extends slightly beyond the mantle. There are five to eight multi-pinnate gill branches separated in gill pockets. The anus is on an elevated papilla located in the center of the gill branches. The kidney pore is on the right side of the anus. The rhinophore clubs are elongate and slightly bent with approximately 80 lamellae (in large, mature individuals). The oral tentacles are large, fleshy, and elongated.

DISTRIBUTION

Western Pacific and Western Indian Ocean. Red Sea (Yonow, 2008), Djibouti, Yemen (Debelius, 1996), Mozambique (Tibiriçá et al., 2017), Seychelles, Madagascar (Debelius & Kuiter, 2007), Tanzania (Debelius, 1996), South Africa (pers. obs.), Hong Kong (Yonow, 2008), New Caledonia (Hervé, 2010), Indonesia (Tonozuka, 2003; Valdés, 2002), Papua New Guinea (Colin & Arneson, 1995; Debelius, 1996), Japan (Nakano, 2018) including Okinawa (Coleman, 2008). On-line sources: Oman, Philippines (iNaturalist), Emirates Arab (MedSlug), Mayotte (South-west Indian Ocean Seaslug site), Vanuatu (Underwater Australasia), and Fiji (Sea Slug Forum).

ETYMOLOGY

The specific name refers to the gigantic size of this species, one of the largest nudibranchs in the world.

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References

• ミカドウミウシ, 殿塚孝昌. (2003). ウミウシガイドブック〈3〉. TBSブリタニカ.
• ミカドウミウシ, 中野理枝. (2004). 本州のウミウシ. ラトルズ.
• ミカドウミウシ, 中野理枝. (2018). 日本のウミウシ. 文一総合出版.
• Hexabranchus giganteus sp. nov., Tibiriçá Y., Pola M., Pittman C., Gosliner T.M., Malaquias M.A. & Cervera J.L. (2023). A Spanish dancer? No! A troupe of dancers: a review of the family Hexabranchidae Bergh, 1891 (Gastropoda, Heterobranchia, Nudibranchia). Organisms Diversity & Evolution. 23(4): 697-742. https://doi.org/10.1007/s13127-023-00611-0
• エンテイウミウシ（新称）, 西田和記. (2024). ウミウシの生態観察図鑑. 誠文堂新光社.