The warty pleurobranch (Pleurobranchaea bubala) has at times been a regular feature on these pages. They are one of the most common sea slugs seen on shallow dives in Cape Town, and despite their unprepossessing appearance are enjoyable (and quite easy) to observe performing a range of behaviours. In contrast to their more colourful cousins, they are frequently spotted on the move. Perhaps they are aware that they can’t just rely on their good looks to get by. Warty pleurobranchs are side-gill slugs, so named for their single gill which is on the right hand side of their bodies. The specimen above was sitting on a rock in a fairly heavy current (we were diving the Cape Matapan) which caused its gill to be exposed.
The picture below shows a warty pleurobranch busy laying eggs. Their egg ribbons have a filmy appearance and can be quite large. The characteristic side-gill is also visible here, as in the first picture above. These creatures are only found from Saldanha to Jeffrey’s Bay.
The warty pleurobranch is a vigorous predator, preferring to eat its own kind – sea slugs, sea hares and the like. There is a similar-looking relative, usually found in deeper water, known as the dwarf warty pleurobranch. I’ve never reliably identified one of these – apparently they have smoother skin (and are smaller, hence the name).
All useful knowledge of these creatures is found in Nudibranchs of the Cape Peninsula and False Bay by Guido Zsilavecz.
