Author: Pola, Cervera & Gosliner, 2005

Order: Nudibranchia  Family: Polyceridae

Maximum Size: 60 mm

Sightings: Sunshine Coast, Capricorn/Bunker Group GBR

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Tambja victoriae Pola, Cervera & Gosliner, 2005

Tambja victoriae is classified as a phanerobranch dorid nudibranch as it cannot retract its gills into a pocket below the mantle. It is placed in the Polyceridae family and interestingly, these are considered more closely related to the cryptobranchs than other phanerobranchs.

The body is limaciform with the head slightly expanded and just below the rhinophores is an anterior distinct remnant of the notal brim. The tail of the body has a long taper, terminating in a point. The surface of the body is smooth but naturally prone to wrinkling when contracted. The large rhinophores are perfoliate and contractile into raised sheaths. Below the rhinophores but above the oral tentacles are the characteristic horizontal lateral slots (one per side) of Tambja species, thought to be of a sensory capacity due to its enervation branching from the rhinophoral nerve. The oral tentacles are small and located under a vestigial frontal veil. There are no velar processes or any tentacular processes of any kind. The three multipinnate gills are non-retractile, carried as a high prominent cluster and are arranged in a semicircle around the anal papilla, approximately halfway along the body length.

The background colour is a bright blue, of an azure shade, with orange to golden yellow longitudinal lines or stripes each outlined in black. Some lines are almost continuous for the entire length of the body whilst others are discontinuous or just long dashes. Between the rhinophores is a wide patch of light green outlined in black that changes into a typical orange/yellow line. Posterior to that patch are two translucent blue patches each side of the midline, possibly providing a pigment-free window to the eye-spots. Leading up to and away from the gills the lines turn from orange/yellow to light green. These green lines may coalesce into a green patch around the base of the gills. As the lines continue up the gills they turn back to orange/yellow in colour once again. The inside surface of the gills is blue/black but exhibits a green line running up the axis of each rachis. The remnant of the anterior notal brim is also orange/yellow, outlined in black. The rhinophores themselves appear to be black but are a very dark green with an extremely small blue tip. The rhinophore sheaths are rimmed in orange/yellow with black below. The oral veil vestige is orange/yellow, outlined in black and continues as a line right around the mantle margin. This line is typically the widest of all the lines and often of the brightest orange/yellow as well. The foot is orange/yellow. There are sometimes variations to this most common theme.

Reported as feeding upon arborescent bryozoans of the family Bugulidae including Virididentula dentata. Certain species of Bugulidae are known to possess secondary metabolites called tambjamines that are toxic alkaloid compounds. Many of the Tambja species, including Tambja victoriae, are brightly coloured and it has been hypothesised that these species may have sequestered some of these toxic compounds through their diet to use for their own defence, the bright colours being aposematic to warn off predators. The many Tambja species with these bright colours and similar patterns could therefore be considered Mullerian mimics.

The spawn of Tambja victoriae is an apricot coloured ribbon laid on edge as an irregular ring.

Distribution is Western Pacific from the Philippines to the east coast of Australia.

The specific epithet of victoriae is dedicated to the wife of the second author of the describing paper.

A number of Tambja species including some putative examples look quite similar in external appearance to Tambja victoriae having a blue or black background colour with orange, yellow or green longitudinal lines or stripes. Until this species was described it was often misidentified as Tambja affinis or Roboastra arika the latter now listed as taxon inquirendum on MolluscaBase (WoRMS). This is the Roboastra arika Burn, 1967 of Willan & Coleman, 1984, Coleman, 2001 and Marshall & Willan, 1999. Burn, 1967 described Roboastra arika from a preserved specimen collected from Lord Howe Island. A close reading of that description reveals it is not Tambja victoriae, although confusion may have arisen because there was no colour photo or illustration accompanying the description and that Burn merely surmised the live colouration of the species. Also, Rudman 2005, in saying that Roboastra arika was certainly Roboastra gracilis (Bergh,1877) is difficult to believe as Burn also redescribed Roboastra gracilis in the same paper. In general, the more time that passes since an identification guide is produced the more discrepancies will be generated by the mere greater pool of additional knowledge that has accumulated.

Above: A pair of Tambja victoriae in the latter stages of mating. Here the simultaneous sperm transfer is completed and the penis stylets can be seen to disengage as they separate.

Above: Tambja victoriae moves across the substrate testing it in the search for its bryozoan prey.

David A. Mullins – May 2021

References:

– Burn, R. F. (1967)  Notes on an overlooked nudibranch genus Roboastra Bergh 1877, and two allied genera (Mollusca: Gastropoda). Australian Zoologist, 14: 212-221.

– Willan, R. C. & Coleman, N. (1984). Nudibranchs of Australia, Neville Coleman, AMPI: 26-27

– Marshall, J. G., Willan, R. C. (1999). Nudibranchs of Heron Island, Great Barrier Reef: A survey of the Opisthobranchia (sea slugs) of Heron and Wistari Reefs; Backhuys: Leiden, The Netherlands, 1999.

– Coleman, N. (2001). 1001 Nudibranchs, Catalogue of Indo-Pacific Sea Slugs. Neville Coleman’s Underwater Geographic Pty Ltd.

– Pola, M., Cervera, J. L. & Gosliner, T. M. (2005). Four new species of Tambja Burn, 1962 (Mollusca, Nudibranchia, Polyceridae) from the Indo-Pacific. Journal of Molluscan Studies, 71 (3), 257–267.

– Rudman, W. B., (2005 August 15). Tambja victoriae Pola, Cervera & Gosliner, 2005. [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/tambvict and associated messages.

– Pola, M., Cervera, J. L. & Gosliner, T. M. (2006).Taxonomic revision and phylogenetic analysis of the genus Tambja Burn, 1962 (Mollusca, Nudibranchia, Polyceridae) Zoologica Scripta, 35, 491-530.

– Pola, M., Padula, V., Gosliner, T. M. & Cervera, J. L. (2014). Going further on an intricate and challenging group of nudibranchs: description of five novel species and a more complete molecular phylogeny of the subfamily Nembrothinae (Polyceridae). Cladistics (2014) 1-28.

– Nimbs, M. J., Smith, S. D. A. (2017). An illustrated inventory of the sea slugs of New South Wales, Australia (Gastropoda: Heterobranchia). Proceedings of the Royal Society of Victoria 128: 44-113.

– Willan R. C. & Chang Y. -W. [Yen-Wei]. (2017). Description of three new species of Tambja (Gastropoda, Nudibranchia, Polyceridae) from the western Pacific Ocean reveals morphological characters with taxonomic and phylogenetic significance for traditional Polyceridae and related ‘phaneorobranch’ nudibranchs. Basteria. 81(1-3): 1-23.

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

– MolluscaBase eds. (2021). MolluscaBase. Roboastra arika Burn, 1967. Accessed through: World Register of Marine Species (WoRMS) at: https://www.marinespecies.org/aphia.php?p=taxdetails&id=456736 on 2021-05-23