Blue choirboys Podoclavella sp., a species of ascidian or sea squirt
Photo by Stephanie
Egg case of the gasflame nudibranch Bonisa nakaza
Photo by Stephanie
Another egg case of the gasflame nudibranch
Photo by Guido Zsilavecz
Blue choirboys are colonial ascidians or sea squirts. Joined together at the base, they form a small cluster of individuals which can be recognized by having in inhalant and exhalant siphon. They are common in calm waters, and are often found under jetties in harbours and quiet bays - anywhere there is little wave action. They grow 5 to 10 cm tall.
The gasflame nudibranch is one of the most common nudibranchs in Cape Town waters. They lay their eggs, characteristically, on the branch of soft coral or even the local pink or purple hard coral Allopora nobilis, although less often so. The egg case consists of a tightly-wound string containing the individual eggs, which can be seen as the opaque white blobs.
Identifying nudibranch egg cases is generally not easy, and unless it is known what egg case a species lays it is not possible to deduce the species from the egg case, as there is high variability in the egg cases themselves, while at the same time very different species may lay very similar egg cases. For example, a spiral is very common, making it impossible to deduce the species accurately unless one has observed species laying the case!
Nudibranchs of the Cape Peninsula and False Bay. G. Zsilavecz, 2007.
Two Oceans, A guide to the marine life of Southern Africa, GM Branch, CL Griffiths, ML Branch and LE Beckley, 1994.
Nudibranchs of Southern Africa - a guide to the opisthobranch molluscs of southern Africa, T Gosliner, 1987.