Guardian Nature School Team Contact Blog Project Noah Facebook Project Noah Twitter

A worldwide community photographing and learning about wildlife

Join Project Noah!
nature school apple icon

Project Noah Nature School visit nature school

Blue Nudibranch

Glaucus marginatus


Tiny blue nudibranch with a 'wingspan' of under 1cm. The blue colours are actually on the ventral surface, as these creatures float upside down in the ocean using the 'foot' along the centre of their belly to hold the surface tension.


The Pacific Ocean. We found this one washed up on Yaroomba beach.


Not a great deal seems to be known about these tiny sea slugs, except that they eat bits of hydrozoans such as Portuguese Men o' War (blue bottles) and Porpita porpita (blue buttons) and store the stingers in their 'cereta' (the finger-like protusions along the side of their body). I think they're really cute. This series shows one in a variety of poses... in the second one you can see how small it is (check out the grains of sand around it on the surface of the water!) and the fourth one shows it flipped onto its front as the water goes out.

Species ID Suggestions

Sign in to suggest organism ID

31 Comments (1–25)

MichaelS 3 years ago

Hi ShannaB, These blue nudibranch photos are amazing! Be terrific to see some of your most recent discoveries here on Project Noah!

Jim Nelson
Jim Nelson 8 years ago

I suspected this one was a winner! Well Done, Shanna!

The MnMs
The MnMs 8 years ago

Indeed a beauty..congrats!

Mark Ridgway
Mark Ridgway 8 years ago

Such good shots.. cobgrats.

ShannaB 8 years ago

Thanks Lisa & Christiane!

Christiane 8 years ago

Congratulation Shanna.. I so hoe I can find one of these one day!

LisaPowers 8 years ago

Congrats ShannaB, your beautiful alien-like Blue Nudibranch placed 2nd in the "other" category for the Best of 2015! Here is the link for the '2016 Best Wildlife Photo mission so you can add more fantastic spottings for this year!

ShannaB 8 years ago

Thanks Ashley! Jim, Albert is right - we found these washed up on the beach. We scooped out a hollow in the sand so we could see these guys floating, and I took the photo from above. They are absolutely tiny - in the second shot you can see the grains of sand floating on the surface of the water.

Jim Nelson
Jim Nelson 8 years ago

All this time, I have been looking in the wrong places.

AlbertKang 8 years ago

@JimNelson, its more likely you will see this Nudibranch at the beach than when scuba diving.

Jim Nelson
Jim Nelson 8 years ago

Shanna...I have spent many years diving, and have never seen this one. Underwater macro sometimes takes time and patience. Great job on this one!

Christiane 8 years ago

Love this little cutie.. :)

AshleyT 8 years ago

Congrats Shanna, your unique Nudibranch has made the top 10 other spottings in the '2015 Best Wildlife Photo' mission! Rangers are voting on the top 10 other spottings, and the top 3 will be announced on February 7th. The top 3 spottings will be commented on here on the site, but make sure you keep a look out on our Facebook app page for the announcement as well! Congratulations on making the top 10!

Desmond.E.S.O 9 years ago


sunnyjosef 9 years ago

Congrats Shanna... great spotting...

Christiane 9 years ago

WOW.. Congrats Shanna. Great spotting..

DanielePralong 9 years ago

Congrats Shanna!

Leuba Ridgway
Leuba Ridgway 9 years ago

One of my favourite creatures. Great shots Shanna and a well deserved SOTD. Congratulations !

Neil Ross
Neil Ross 9 years ago

Congratulations, Shanna. This is a wonderful spotting. Awesome photos and info too.

VivBraznell 9 years ago

Stunning SOTD Shanna .. congratulations! Great set of images. The wings in image 4 look like a pair of feet :)

Mark Ridgway
Mark Ridgway 9 years ago

Congrats. I'd love to find one of these little beauties.

CalebSteindel 9 years ago

Yet another great sea slug shanna! Congrats

James McNair
James McNair 9 years ago

Exquisite and well deserved SOTD Shanna

ShannaB 9 years ago

Thank you, Yasser!

Yasser 9 years ago

Shanna, this spectacular sea slug is our Spotting of the Day! Thanks for sharing this incredible series with us and we look forward to a wonderful and wild 2015 filled with lots of awesome spottings, just like this one. Happy New Year and Congrats again!


Spotted by

Yaroomba, Queensland, Australia

Spotted on Jan 8, 2015
Submitted on Jan 10, 2015

Related Spottings

Atlantic Glaucus Blue Sea Slug Blue dragon Atlantic Glaucus

Nearby Spottings

Brahminy Kite Pink periwinkle Pigface Tawny Frogmouth family
Noah Guardians
Noah Sponsors
join Project Noah Team

Join the Project Noah Team