Skip to primary navigation Skip to content Skip to footer
Back to Blog

Animal feature – the Fabulous Nudibranch, Sea slug survey coming to Perth!

a blue bird sitting on a rock

Perth Nudibranch news, facts and how you can get involved in citizen science to discover new nudies!

Perth Nudibranch captured by Salty Dragon

Image by Salty Dragon

It’s a crystal clear day. You’re gliding through the water. Familiar browns, greens and blues of the kelp, sea grass and ocean are immersing you. Sandy coloured limestone formations promise hidden secrets.

You and your buddy get into a familiar rhythm, taking turns to lead and investigate nooks as the familiar ripple of light patterns in the water paint a steady visual tempo.

Something catches your attention, from the corner of your eye. A shock of colour. Sitting on the coral, a few meters below the surface, is a slug like creature so fabulous it could be dressed for a disco. You’ve just found a Nudibranch.

WA Pikachu Nudie by Dive.By.Nature

WA Pikachu Nudie by Dive.By.Nature

Recognising a Nudibranch

Almost everyone who spends time in the ocean will meet one of these colourful critters. There’s no mistaking them, with so many different varieties there is a recognisable structure.

The Scientific name Nudibranchia is a combination of Latin and Greek words meaning “Naked Gills”. Unlike many other marine creatures, the gills Nudibranch use to breathe are out in the open. Nudibranch have been observed retracting this branchial plume if they sense a potential threat.

Nudibranchia - Image identifying Rhinophores (antennae for smelling), Gills (branchial plume) and foot (base of the slug).

Nudibranch behaviour

Nudies are carnivores known to eat coral, sponges and even each other. They are also known to take on properties of their food, such as stinging nematocytes. Many are hermaphrodites and can mate with any other mature nudie of their species. They lay a spiralling ribbon of eggs, usually on a food source.

Using their Rhinophores (the two antennae like structures on the top of their head) nudibranch can detect “scent plumes” in the water and act based on what they smell. A 2006 study found that if a mate or suitable food was “smelt”, a nudie would move upstream towards it. If it caught the scent of a predator, a nudibranch would slowly crawl downstream, potentially allowing it to escape while keeping tabs on the location and direction of the threat.

ID Please! How to get an ID on your Perth Nudie sightings provides information and useful resources on the over 3000 species you might encounter. There is also an app you can download and recommended reading to help you ID them yourself. The app lets you search for nudibranch based on only their colours.

You might have seen recent articles on Nudibranch citizen science where the public has been invited to participate in a survey to identify new species.

We spoke with Dr Lisa Kirkendale, Head of Aquatic Zoology and Curator (Mollusca) at WA Museum, who stated that Exmouth and the Pilbara were included in this year’s survey. The survey expansion organised by Professor Stephen Smith was a soft roll out to Western Australia, with the intention of including Perth next year. 

Tips for Nudi ID Photos


Perth Nudibranch enthusiasts can look forward to next year’s survey, so it’s exciting times ahead. While Dr Kirkendale and WAM resident Nudibranch expert Dr. Nerida Wilson encourage unique or potentially new sightings to be submitted to  for posterity.

iNaturalist Dashboard


Survey Coordinator Professor Stephen Smith tells us that uploading an image of any nudibranch you find to is the best thing you can do.

(on iNaturalist) “…The identity of difficult species can and will be crowd sourced by a large range of taxonomists and talented amateur enthusiasts…. the submission process includes providing locality information so people can easily check to see what species have been found in their area of interest…

…substantiated records are automatically added to global databases which allows anyone to look at distribution ranges (e.g. in Australia, Atlas of Living Australia). This means that local divers can really make their finds have more relevance for a range of research projects. The value of images lives on long after the “likes” on Facebook are a distant memory.”


Image By Karena Gonsalves

Image By Karena Gonsalves

iNaturalist is great because you can sign up to receive regular emails. These show all the pictures submitted in your area. You can also view all your own sightings, dates, and locations in your own dashboard. All submissions are reviewed and verified to confirm their ID.

Want to spot a Nudie? Join us on a free shore dive, or book a ticket on dive boat Moonshine II to meet the Nudibranchs of the Marine Reserve at Rottnest Island.