Reticulidia fungia Brunckhorst & Gosliner, in Brunckhorst, 1993

Many nudibranch lovers are confused and frustrated by the phyllidiids - all lumps and bumps and mostly grey and black. I know of a couple of divers who even refuse to photograph them. I find them a bit of a challenge myself but a challenge to be met and mastered rather than avoided. However sometimes along comes a phyllidiid that no one can ignore and Reticulidia fungia falls into that category.

Reticulidia fungia is one of just four described species in the genus. Externally the main features distinguishing them from the other phyllidiids are the absence of any tubercles (lumps and bumps) on the notum and the presence instead of smooth reticulate ridges that have given their name to the genus. At first glance they can be mistaken for species of Halgerda with those dramatic steep sided ridges but the absence of dorsal gills soon sets the record straight.

Reticulidia fungia has fewer ridges that are rather more broadly based than those of the larger and similarly distributed Reticulidia halgerda. They are orange in colour with a white line along the crest and outlining the base. There is a main longitudinal medial ridge that bifurcates behind the rhinophores and from which most of the other transverse ridges arise. In between the ridges the notum is black with the mantle margin a blue/grey colour, that hue being created by a myriad of white specks overlaying a translucent base. It grows to a recorded size of 45 mm but is more typically seen around 30 mm with the juvenile illustrated here being 15 mm long.

Brunckhorst and Gosliner gave it the specific name of fungia due to the resemblance of its ridges to the septae of the Fungia solitary corals.

Reference:

Brunckhorst, D.J. (1993) The Systematics and Phylogeny of Phyllidiid Nudibranchs (Doridoidea). Records of the Australian Museum, Supplement 16: 1-107.

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