Cratena sp.4. Note the white oral tentacles and rhinophores.
Cratena sp.4. Note the dark cerata, with an orange apex.
Cratena sp.4, showing the orange "eye spots", ahead of the rhinophores
Above images Johan Swanepoel
Cratena sp.1, or the elegant nudibranchs. Also has dark cerata and orange "eye spots", but note the orange rhinophores.
Cratena capensis, or the orange-eyed nudibranchs. Has the orange "eye spots" but white tips on the cerata.
Aeolidiella indica, or the indian nudibranch. Has an orange spot between the rhinophores (a single blotch, rather than two separate "eye spots"), and white tips to the cerata.
Other images Guido Zsilavecz
Described in Gosliner's book from a collection of only two specimens in Algoa bay, at about the same depth as the one seen by Johan Swanepoel. It is only known from that area, and Gosliner did not find any food association, so it is not sure exactly what it feeds on.
A few similar species exist, as shown in the images. Visually they differ only in relatively small, but distinctive, details.
For more details on these nudibranchs (except Cratena sp.4, which does not occur in the Cape Peninsula), see "Nudibranchs of the Cape Peninsula and False Bay", available directly from SURG or better dive and book stores in Cape Town.
Nudibranchs of the Cape Peninsula and False Bay, G Zsilavecz, 2007
Nudibranchs of Southern Africa - a guide to the opisthobranch molluscs of southern Africa, T Gosliner, 1987