Author: (Kelaart, 1858)

Order: Nudibranchia  Family: Chromodorididae

Maximum Size: 30 mm

Sightings: Sunshine Coast, Capricorn/Bunker Group GBR; Anilao Philippines, Bali Indonesia

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Goniobranchus preciosus (Kelaart, 1858)

In November of 2021 The Team undertook a live-aboard dive trip to the Capricorn Group, Great Barrier Reef. During that trip we recorded a specimen of Goniobranchus preciosus at Tryon Island. Upon return, this find had us thinking that perhaps some specimens we had found previously on the Sunshine Coast, that we had identified as Goniobranchus verrieri, might actually be Goniobranchus preciosus. A review of our data and closer examination of our G. verrieri images uncovered a number of misidentified examples.

Rudman’s 1985 description tells us that in Goniobranchus preciosus the mantle overhangs the sides and only a small posterior portion of the foot is left exposed. The smooth mantle is creamy-white and may carry diffuse spotting of red or brown sometimes creating a mottled appearance where parts of the mantle are translucent. There are three bands to the mantle margin – outermost – bluish-white, central – deep red, and innermost – orange/yellow. These bands are of similar width. (Our observations reveal that sometimes the outermost bluish-white band may be a little narrower.) Some of our specimens also exhibit a blue border to the tail similar to that of Gosliner et al, 2018, (NSSI 2nd Edition), P.152 bottom right image.

The rhinophores have translucent stalks and red clubs, the lamellae bearing opaque white to the edges. The gill is red with opaque white to the edges.

Distribution: Eastern Indian Ocean, Western and Central Pacific Ocean

This species has had a confused history due mainly to the somewhat ambiguous original description by Kelaart and a subsequent, “apparently”, inaccurate illustration of Kelaart’s published by Eliot, 1906. Rudman, 1985, undertook a redescription of this and similar looking species. Rudman states that the illustration of Doris preciosa published by Eliot: “… bears little relationship to Kelaart’s earlier description and should be considered inaccurate.” However Eliot had stated: “The drawings consist of figures of about 55 species of Nudibranchs made from life by Kelaart in Ceylon. Thirty-five of these figures are now reproduced.” These included Doris preciosa. What are we to make of this? Rudman is correct, the illustration does not reflect Kelaart’s description. So we are best to ignore it and make the most of the word picture instead. Rudman seems to have the running with this and made the greatest effort to sort it all into some semblance of sense. We could do worse than accept and use the descriptions, redescriptions and nomenclature of his 1985 paper.

Previously known as Chromodoris preciosa it is included in the species listed as having been sequenced and subsequently removed from Chromodoris and placed in Goniobranchus by Johnson & Gosliner, 2012.

Originally described as Doris preciosa.

David A. Mullins – January, 2022

References:
– Kelaart E. F., (1858). Description of new and little known species of Ceylon nudibranchiate molluscs, and zoophytes. Journal of the Ceylon Branch of the Royal Asiatic Society. 3: 84-139.

– Eliot, C. N. E., (1906). On the nudibranchs of Southern India and Ceylon, with special reference to the drawings by Kelaart and the collections belonging to Alder & Hancock preserved in the Hancock Museum at Newcastle-upon-Tyne. Proceedings of the Zoological Society of London. 636-691

– Rudman, W. B., (1985). The Chromodorididae (Opisthobranchia: Mollusca) of the Indo-West Pacific: Chromodoris aureomarginata, C. verrieri and C. fidelis colour groups. Zoological Journal of the Linnean Society. 83: 241-299.

– Rudman, W. B., (2000, July 2). Chromodoris preciosa (Kelaart, 1858). [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/chroprec and associated messages.

– 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)

– Gosliner, T. M., Valde ́s, A ́. & Behrens, D. W. (2018). Nudibranch & Sea Slug Identification – Indo-Pacific, 2nd Edition. New World Publications, Jacksonville, Florida, USA.