The rare night sky nudibranch Amanda armata
Photo by Dieter Stegemann
Another night sky nudibranch Amanda armata
Photo by Guido Zsilavecz
The rare black-dot nudibranch Caloria sp.1
Photo by Dieter Stegemann
Red-spotted dorid Chromodoris heatherae
Photo by Phil Parr
Ink-spot nudibranch Ceratosoma ingozi
Photo by Dieter Stegemann
Ink-spot nudibranch Ceratosoma ingozi and the Cape dorid Hypselodoris capensis
Photo by Phil Parr
A tiny candy nudibranch, Cuthona speciosa - insert shows it a bit better.
Photo by Dieter Stegemann
A not-so-tiny candy nudibranch.
Photo by Guido Zsilavecz
Blue-speckled nudibranch, Dendrodoris caesia
Photo by Dieter Stegemann
Four-colour nudibranch, Godiva quadricolor
Photo by Dieter Stegemann
This is a relatively uncommon species. I found it most often at the base of kelp in shallow water on offshore rocks - like at A-Frame. Occasionally one does find them in somewhat deeper waters though. Being a small species, it is easy to overlook, especially given that it is not particularly brightly coloured.
Black-dot nudibranch Caloria sp.1
One of the many undescribed species of nudibranch occurring in our waters, and is uncommon. Named black-dot because of there being a small dot near the tip of each of the cerata (not visible in the photo - it is a small dot), it is superfically similar to a number of other species - in which case the black dot is essential for distinguishing it.
Red-spotted nudibranch Chromodoris heatherae
This is a more common species, and can be found on both sides of the Peninsula. The white colour and bright red spots are quite distinctive. It inhabits most reefs.
Ink-spot and Cape dorid (Ceratosoma ingozi and Hypselodoris capensis)
These two species seem to have fluctuating populations - I remember that in the past we rarely saw either of them, and suddenly they were everywhere. At Castle Rocks the populations seem to fluctuate in opposite waves; if the one species is common, the other is not. Currently I am only seeing Cape dorids, but a few months ago they were rare.
Of the two the ink-spot is the larger species, as can be seen in the one photo, and the Cape dorid is slender and small in comparison.
Candy nudibranch Cuthona speciosa
With its highly edible colours it is still amazing how infrequently one spots one of these nudibranchs. The size, tiny, has much to do with that, as can be seen from the photos. The species is somewhat variable in colouration, as can be seen from the second photo. What unites them is their relatively short oral tentacles and rhinophores, as well as the short and stubby cerata. It can be found on most reefs.
Blue-speckled nudibranch Dendrodoris caesia
Not too long ago we were excited about seeing this species, but it is seen more often nowadays, even on shore dives. It is still not common, but because of its larger size quite conspicuous. It inhabits shallow inshore waters as well as deeper waters offshore.
Four-colour nudibranch, Godiva quadricolor
Another uncommon species, this brightly coloured nudibranch can be found on many reefs. It feeds on other nudibranchs and anemones.
For more details, see Nudibranchs of the Cape Peninsula and False Bay by Guido Zsilavecz, available (most likely) from July 2007 onwards for SURG and better diveshops in Cape Town.
Nudibranchs of Southern Africa - a guide to the opisthobranch molluscs of southern Africa, T Gosliner, 1987.