Author: Rudman, 1980

Order: Nudibranchia  Family: Facelinidae

Maximum Size: 40 mm

Sightings: Sunshine Coast

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Sakuraeolis nungunoides  Rudman, 1980

A number of species of the Facelinidae are aggressive sea slugs and Sakuraeolis nungunoides certainly can be grouped with those. It has also been termed pugnacious due to its tendency of suddenly erecting and straightening of its cerata and the directing of them in a quivering manner at a perceived threat. This is deimatic behaviour, or startle display, but it is not all bluff as the ceratal tips bear cnidosacs containing nematocysts (stinging cells) obtained through their diet of “stinging” hydroids.

Sakuraeolis nungunoides is a large aeolid, reported up to 40 mm in length. Body shape is elongate and relatively high, the foot is much wider than the body and the tail is short but tapered. Cerata are long as are rhinophores and the oral tentacles are yet longer still and tapered. The anterior corners of the foot are very well-developed into long propodial tentacles. The rhinophores are wrinkled and sometimes, on close examination, appear covered with very small protuberances. The cerata are arranged in a series of raised arches down each side of the length of the notum, the first and second arch separated significantly by the pericardium. The genital aperture is situated on the right side between the first and second ceratal arch in the inter-hepatic space.

Colouration described here relates to specimens found on the Sunshine Coast of Queensland, Australia. The body is semi-translucent with the internal viscera somewhat visible. The foot is translucent, the substrate being visible beneath. The head carries an orange patch from between the bases of the oral tentacles posteriorly to the base of the rhinophores. The oral tentacles have opaque white pigment to the basal two thirds being translucent on the distal third. The propodial tentacles are orange on the dorsal surface. The rhinophores are watery translucent orange to the basal third, white pigmented to the middle third and orange to the distal third with a small white tip. The cerata are mostly translucent such that the unbranched brown digestive gland is visible. There is an orange band of varying width towards the tip followed by some white pigment not always arranged as a band, however the extreme tip is translucent. The tail is white. Rudman mentions on the Sea Slug Forum that the cerata sometimes have “….a dusting of white” and examples of that are given in the image gallery.

There are some differences between the specimens found on the Sunshine Coast, Queensland and the description given by Rudman, 1980, concerned only with colouration. The characteristic orange patch is present upon the head from base of oral tentacles to base of rhinophores.The adults on the Sunshine Coast however are more vivid in their orange colouration, the notum is a little more opaque white than translucent. The oral tentacles are translucent at the distal third rather than orange (although close examination will at times reveal a hint of orange upon them ventrally), the basal two thirds being white rather than translucent. Rhinophores bear an opaque white section to the middle third rather than the upper two thirds being orange. The tip of the tail lacks the mentioned orange colouration. The Sea Slug Forum shows a specimen collected from New Caledonia by Rudman that exhibits some of these variations in colouration although overall those specimens are quite pale. Are these just geographical variations or a different species? (personal musings) The holotype and paratypes used for the original description were collected in Tanzania, East Africa, western Indian Ocean.

The example given in Nudibranch & Sea Slug Identification – Indo-Pacific, 2018 (NSSI 2nd Ed. p. 324) shows a specimen with cerata that are covered in opaque white pigment.

Known to feed on a number of different hydroids including Eudendrium sp.

The spawn is laid as a crenulated egg coil upon its hydroid host.

Sakuraeolis nungunoides has a wide Indo-West Pacific distribution.

The author states that the specific epithet of nungunoides is derived from the Swahili name for the porcupine (nungunungu) being an allusion to the bristling of its cerata when aggravated. Swahili is a native language of the Bantu people and also a lingua franca for much of East Africa including Tanzania where the author worked at the time. The genus Sakuraeolis was raised by Baba in 1965, Sakura = cherry or cherry blossom in Japanese being the national flower of Japan.

David A. Mullins – February, 2021

References:

– Baba, K. & Hamatani, I. (1965). The anatomy of Sakuraeolis enosimensis (Baba, 1930). n.g. (=Hervia ceylonica (?) Eliot, 1913) (Nudibranchia-Eolidoidea). Publication of the Seto Marine Biological Laboratory, 13; 103-113.

– Rudman, W. B. (1980). Aeolid opisthobranch molluscs (Glaucidae) from the Indian Ocean and the south-west Pacific. Zoological Journal of the Linnean Society, 68: 139-172.

– Rudman, W. B. (2003 May 10) Sakuraeolis nungunoides Rudman, 1980. [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/sakunung and associated messages.

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