Polka Dotted Nudibranch
Photo credit: Kevin McLoughlin at Rawa Island, Malaysia

Nudibranchs are soft-bodied, marine gastropod molluscs, which are noted for their wide variety of extraordinary colours and forms. Many scuba divers fall in love with these creatures and it’s easy to see why. There are roughly 3000 valid species of nudibranch, but the one I would like to look at in a bit more detail is Jorunna funebris, aka the dotted or polka-dotted nudibranch.

Apart from its interesting markings (which remind some divers of Oreo cookies!) it also has an interesting diet! It appears that this nudi is an extremely picky eater, apparently only eating a particular blue sponge. The sponge helps it to retain its toxicity, which provides it with a chemical defence, meaning they taste bad to predators and might even be toxic when ingested.

Jorunna fenebris nudibranch
Photo credit: Chelsea Clements at Rawa Island, Malaysia

The term nudibranch comes from the Latin “nudus” meaning naked, and the Greek “brankhia” meaning gills, because generally their breathing apparatus is exposed. This can quite clearly be seen on the Jorunna by the black edging on the feathery gills at the back.

Jorunna funebris can grow to approximately 70 mm and is found in the Indo-West Pacific. I have seen these guys in a few different spots, but my latest sighting was on the island of Pulau Rawa, Malaysia.

So next time you see some blue sponges, keep an eye out for these guys!