Among the most beautiful of all molluscs, what did we find in French Polynesia?

Simply slugs - Bornella irvingi
Simply slugs - Bornella irvingi Photographer: Ian Skipworth © Auckland Museum Image: Ian Skipworth
© Auckland Museum

Nudibranchs, or sea slugs, are a scuba divers dream. Not only are they small, colourful, attractive, and often elusive, which makes their discovery exciting, they are perfect photographic subjects. They don’t move anywhere quickly so are almost guaranteed to provide you with at least one good shot.

Besides that, the colours and patterns are important for species identification. After they are preserved for scientific study in formalin or alcohol they lose their beautiful colours making them look like pieces of used chewing gum. A good photograph is essential when collecting nudibranchs in the field.

We found eight nudibranch species during our expedition, though many more undoubtedly occur among the islands we visited. Our photographer, Ian Skipworth, took all of the fabulous images you see here.

Among our findings, we discovered a species we have called Ceratosoma cf. amoenum; ‘cf.’ meaning it is a species that is similar to the ‘true’ Ceratosoma amoenum that is found in Australia and New Zealand. Being a southern temperate endemic species, it is unlikely that the animal we found in French Polynesia is really the same species. When we have the actual specimens back in Australia, experts will be able to examine its morphology and DNA in detail to see if it is, indeed, a new species.

Nudibranch, Chromodoris cf. amoenum Photographer: Ian Skipworth © Auckland Museum Image: I. Skipworth
© Australian Museum

A second significant find was the exquisite Bornella irvingi featured in the main picture. This species was previously known only from two specimens from the Pitcairn Islands upon which the original species description was based, so its discovery provides a range extension record for the species.

The Phyllidiella pustulosa will be useful for a study being conducted by student Patricia Oristanio Vas de Lima from the University of Sao Paulo who is trying to determine whether this taxon, thought to be a single widespread species, is indeed, a single species or more than one.

Phyllidiella pustulosa
Phyllidiella pustulosa. Photographer: Unknown. © Australian Museum Image: -
© Australian Museum

Other researchers are using some of our tissue samples for a broader study of the evolutionary relationships among the mollusc Class Gastropoda to which nudibranchs belong.

Doriprismatica sibogae
Simply slugs - Doriprismatica sibogae Photographer: Ian Skipworth © Auckland Museum Image: Ian Skipworth
© Auckland Museum

So, not only are these creatures beautiful, but they will be very useful for a range of scientific studies by researchers at the Australian Museum and elsewhere.

Elysia rufescens
Simply slugs - Elysia rufescens Photographer: Ian Skipworth © Auckland Museum Image: Ian Skipworth
© Auckland Museum