Nudibranch 101

Where seen? This brilliant nudibranch is often seen on many of our shores, in coral rubble and near reefs.



3-5cm. Long, narrow, soft body with finger-like projections (called cerata) arranged in hand-like clusters along the length of the body. Although those encountered were mostly blue, this nudibranch reportedly comes in various colours from yellow to green. It is identified by the purple bands on its long oral tentacles. It has a pair of shorter feathery rhinophores.

What does it eat? It eats hydroids. A large solitary hydroid, Ralpharia sp. is among the adult’s favourite food. Young ones have been seen among short ‘turfing’ hydroids. The blue dragon nudibranch can also store symbiotic algae (zooxanthellae) within its cerata and body. Here, the zooxanthellae get protection and in turn provides the nudibranch with much of the nutrients produced through photosynthesis. Young animals are white as they have yet to develop their crop of zooxanthellae. Older ones may be brown. Adults often can go without feeding for sometime, possibly living off the nutrients provided by the zooxanthallae.

Pteraeolidia species have a habit of staying near their eggs once they’ve laid them. Several individuals may stay near the eggs for several weeks. But it is not clear whether they are actually caring for their eggs.

Text & Photo Contributed by Our In-House Instructor and UW Photographer Mr Zulkarnain Ng


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