Author: Undescribed

Order: Nudibranchia  Family: Chromodorididae

Maximum Size: 35 mm

Sightings: Sunshine Coast

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Goniobranchus sp. 04 Undescribed

This is a species that we see from time to time on the Sunshine Coast reefs of southern Queensland. It is one of a group of several Goniobranchus species that present with a red reticulation on the notum. It is most often encountered upon a distinctive brown sponge that grows, branching in a finger-like manner, giving us reasonable cause to assume that the sponge is this nudibranch’s preferred food source. It has also been recorded a little further south at Flinders Reef off Cape Moreton, Moreton Is. (Harasti, 2002) and at Flat Rock off Point Lookout, North Stradbroke Is. (Wilkie, 2006) on the same species of sponge. Its distribution would seem to be rather restricted.

Our separation of it into a distinct undescribed species has been justified by the subsequent molecular sequencing work of Soong et al, 2020, who recognized it as a distinct species, although it has not yet been formally described and named. In that paper it is identified as Goniobranchus sp. 4.

Goniobranchus sp. 04 is oval in shape, rounded and high in profile, with the mantle overhanging the foot. The tail may or may not be visible past the posterior of the mantle. The body is white as is the notum, however the notum is covered by a tight and dense reticulation of deep red such that the white is visible as small spots, some of which appear raised. The mantle margin carries a golden-yellow band followed by a submarginal band of white the two bands being of mostly of equal width. The edge of the red reticulation is regular where it meets the white submarginal band. The edge of the foot and tail are without coloured bands but the tail carries a non-reticulated patch of red centrally. The rhinophores are deep red in colour with white edging to the lamellae. The gills are translucent white but are red-lined on the edges and have red tips.

The observable features that originally convinced us to separate Goniobranchus sp. 04 as a distinct species include:
– The tightness and consistency of the reticulation
– The deep red colour of the reticulation
– The red patch on the tail
– The finger-like brown sponge food source it is consistently found upon

In the past this species had often been confused with Goniobranchus reticulatus or Goniobranchus tinctorius, both previously in the Chromodoris genus.

David A. Mullins – August 2023

References:
– Harasti, D. (2002, Oct 23) Chromodoris tinctoria from Sthn Queensland. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/8248

– Wilkie, B. (2006, Jun 6) Chromodoris tinctoria feeding. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/16786

– Soong, G. Y., Wilson, N. G. & Reimer, J. D. (2020). A species complex within the red-reticulate Gonio- branchus Pease, 1866 (Nudibranchia: Doridina: Chromodorididae). Marine Biodiversity 50: e25. https://doi.org/10.1007/s12526-020-01048-w