Author: Miller & Haagh, 2005

Order: Nudibranchia  Family: Polyceridae

Maximum Size: 35 mm

Sightings: Sunshine Coast

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Tambja tenuilineata Miller & Haagh, 2005

This is a small species of polycerid nudibranch with a limited temperate distribution, reportedly growing to a length of 35 mm. It tends to be larger in cooler climes but typically seen much smaller, around 10 mm in length in the more northern extent of its range, the warmer waters of south east Queensland.

The distinguishing features of Tambja tenuilineata are, the green limaciform body, bearing longitudinal integumentary ridges with many longitudinal narrow black lines that traverse its entire length, together with the green rhinophores and green gills all with bluish/purple apices. Occasionally the rhinophore stalk is similarly coloured. The notum is not delineated from the side of the body with a brim, however the head region does have a distinct ridge extending anteriorly around its edge from rhinophore to rhinophore. Also note there are no extrabranchial, extrarhinophoral or velar processes. The rhinophores can retract into pockets with raised sheaths. The 5 or 6 gills are simple, sparsely branched and non-retractile (phanerobranch) being carried in a high cluster mid-length on the dorsum and arranged in a semicircle around the anus. Not obvious, but nevertheless present, is the “sensory” lateral slot, possessed by all Tambja, situated horizontally between rhinophore and oral tentacle, both sides under the brim. The function of the lateral slot is currently conjectured to be sensory due to the substantial connections to the rhinophore nerves.

Very occasionally it is found without any of the black lines, a situation that allows the integumentary ridges to be more apparent. Also known to be yellow in colour instead of green it being suggested that these individuals change colour to green as they mature into adults but this has not been proven. I have noticed in certain regions that some specimens look more blue than green even though being found in the same population as the standard green versions.

Tambja tenuilineata feeds upon arborescent bryozoans including Virididentula dentata (also known as Bugula dentata).

The spawn is laid as a white spiral coil.

Tambja tenuilineata is preyed upon by the larger polycerid Roboastra luteolineata by being engulfed whole (personal observation).

Distribution is limited to the eastern Australian coast of southern Queensland and New South Wales, Lord Howe Island and northern New Zealand.

The specific epithet of tenuilineata means fine-lined.

Tambja amakusana is sometimes misidentified as a form of Tambja tenuilineata without the black lines, especially the green and yellow variants but that species only possesses three gills that although tipped in purple have white bases. It has also been misidentified as Tambja affinis.

References:
– Miller, M.C. & Haagh, J.M. (2005) A new species of the dorid nudibranch genus Tambja Burn, 1962 (Gastropoda, Opisthobranchia) from Australasia. Vita Malacologica, 3: 55-60.

– 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(5):491-530.

– Coleman, N. (2008) Nudibranchs Encyclopedia. Neville Coleman’s Underwater Geographic Pty Ltd, Springwood, Qld.

– 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.

– This Species Profile has been modified from:
– Opisthobranch of the Week, Week #846, Tambja tenuilineata (16/09/2013), Mike Miller’s slugsite.tierranet.com by David A. Mullins
– A previously published article in Dive Log Magazine’s – Critter ID with NudiNotes Column, Issue: #358 (May 2018): 12 by David A. Mullins

David A. Mullins, March 2020