Goniobranchus trimarginatus (Winckworth, 1946)

Description

Body length reaches about 30 mm. The mantle is translucent white with irregular reddish spots and blotches scattered over the dorsum. The most characteristic feature is the mantle margin: an inner band of white mantle glands bordered outside by three narrow lines of yellow, deep red, and white. The gill and rhinophores are translucent white with opaque white edges. The gill consists of eleven unipinnate branchial leaves, and the rhinophores bear about 20 lamellae.

Distribution

Type locality: Bombay (now Mumbai), India. Distributed from India through the northern Indian Ocean to Malaysia and Singapore.

Etymology

From the Latin tri (three) and marginatus (margined), referring to the three coloured bands along the mantle edge.

Remarks

Originally described as Glossodoris trimarginata Winckworth, 1946, later transferred to Chromodoris by Rudman 1985 and subsequently to Goniobranchus.
Distinguished from the similar Goniobranchus preciosus (Kelaart, 1858), which has reddish rhinophores and gill leaves and a much wider white border, and from Goniobranchus sinensis (Rudman, 1985), which has regular minute orange-brown dorsal spots and red-edged rhinophores and gill. Goniobranchus trimarginatus further differs from Goniobranchus sinensis in possessing a vestibular gland in the reproductive system, illustrated for the first time by Valdés, Mollo & Ortea 1999.

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References

• Glossodoris trimarginata n.sp., Winckworth, R. (1946). Glossodoris from Bombay. Proceedings of the Malacological Society of London. 26: 155-160.
• Chromodoris trimarginata (Winckworth, 1946), Valdés Á., Mollo E. & Ortea J. (1999). Two new species of Chromodoris (Mollusca, Nudibranchia, Chromodorididae) from southern India, with a redescription of Chromodoris trimarginata (Winckworth, 1946). Proceedings of the California Academy of Sciences. 51(13): 461-472.
• Goniobranchus trimarginatus, 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 trimarginatus, Terrence Gosliner, Ángel Valdés and David Behrens. (2018). Nudibranch and Sea Slug Identification Indo-Pacific 2nd Edition. New World Pubns Inc.