Nembrotha purpureolineata O'Donoghue, 1924

Description

Body length around 4–5.5 cm. The dorsum is deep chrome yellow, while the sides are paler yellow, with a large orange-yellow patch in the centre of the dorsum and another near the middle of the tail. The chestnut-brown longitudinal stripes are bolder and fewer in number than in Nembrotha lineolata: one mid-dorsal stripe, one along the mantle margin, and three on each side of the body. The integument between the stripes shows fine wrinkled corrugations. The rhinophore club is vermilion, and the three bipinnate gills are also vermilion-tinged. The rhinophore sheath, gill base, anal papilla, oral tentacles and foot margin can be blue to purple depending on the individual. The species closely resembles N. lineolata but differs in the thickness and number of stripes and in the deeper yellow ground colour.

Distribution

Indo-West Pacific. The type locality is the Houtman Abrolhos Islands, Western Australia. Records also include eastern Australia and southern Japan (from the Kii Peninsula southward), with a new colour morphotype reported from East Timor by Pola et al. 2026.

Etymology

A Latin compound of purpureus (purple) and lineatus (lined).

Remarks

Known to feed on ascidians. Nembrotha rutilans Pruvot-Fol, 1931 is treated as a junior synonym of this species (Pola, Cervera & Gosliner, 2008). Baba 1976 first reported the species from Japan based on specimens from Seto, Kii, and proposed the Japanese name Seto-ryugu-umiushi. Baba commented on the strong similarity to Nembrotha lineolata, suggesting the two might prove conspecific.

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References

• Nembrotha purpureolineata n.sp., O'Donoghue C.H. (1924). Report on Nudibranchiata from the Abrolhos Islands, Western Australia, with description of a new parasitic copepod. Journal of the Linnean Society of London, Zoology, 35(237): 521-579, plates 27-30.
• セトリュウグウウミウシ Nembrotha purpureolineata O'Donoghue, 1924, Baba, K. 1976a. Two species of Nembrotha (s.s.) new to Japan (Nudibranchia: Doridoidea: Polyceridae). Veliger 19(2):131-134.
• Pola M., Cervera J.L. & Gosliner T.M. (2008). Revision of the Indo-Pacific genus Nembrotha (Nudibranchia: Dorididae: Polyceridae), with a description of two new species. Scientia Marina. 72(1): 145-183. https://doi.org/10.3989/scimar.2008.72n1145
• Nembrotha purpureolineata (new color morphotype), Pola, M., Paz-Sedano, S., Guisado Martín, P., Warren, L., Noble, K. & Martín-Hervás, M.R. (2026). The most wanted! Gorgeous, delicate and surprising description of three new polycerid species (Mollusca, Heterobranchia) from East Timor. Zootaxa, 5793(1), 193-217.