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Beautiful Nudibranchs: Colorful Sea Slugs

Cindy has always been fascinated by life in the sea and has had several saltwater aquariums, one a natural reef.

Unidentified Nudibranch 1 - This one reminds me of a dragon.

Unidentified Nudibranch 1 - This one reminds me of a dragon.

Dirona albolinieata at Ogden Point in Victoria BC.

Dirona albolinieata at Ogden Point in Victoria BC.

Of all the creatures in the sea, these are the high fashion models.

— ~David Doubilet, photographer for National Geographic

Colorful nudibranch in shallow water off Whyalla, South Australia

Colorful nudibranch in shallow water off Whyalla, South Australia

I have had several saltwater aquariums over the years, and have always been fascinated with the life forms that can be found in the ocean. I envy those who have traveled to exotic locations and have taken all these fantastic pictures. I never had much luck keeping Nudibranchs (pronounced “noo-dee-branks”), also known as Sea Slugs, in any of my aquariums, but have always admired their exquisite beauty.

Frosted Nudibranch can reach up to 7" long.

Frosted Nudibranch can reach up to 7" long.

Naked Gills

"Nudibranch" is a Latin word that literally means “naked gills”. This name refers to the feathery gills and horns that most nudibranchs have on their backs. Nudibranchs are generally only around one inch in length, but they pack a lot of intricate beauty into a small space.

As you browse through this article, if you would like to see a larger image of the nudibranchs, just click on the picture. In my search for images, I was overwhelmed by all the shapes, sizes, forms, colors, textures and patterns that are exhibited by the nudibranch.

It is something like a flatworm that looks tie-dyed.

— ... a child’s description of the nudibranch that is both apt and amusing

Bonisa nakaza in a Kelp bed on the Cape Peninsula, South Africa

Bonisa nakaza in a Kelp bed on the Cape Peninsula, South Africa

Although there are more than 3000 previously identified nudibranch species throughout the world’s oceans, divers are often able to spot species that have not been previously scientifically identified.

They most often inhabit shallow, tropical waters.

Nudibranch (Pteraeolidia Ianthina) taken in Egypt

Nudibranch (Pteraeolidia Ianthina) taken in Egypt

Nudibranch - Berthella (?)

Nudibranch - Berthella (?)

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Nudibranchs, however, can be found in both shallow and deep waters. Some nudibranchs navigate the oceans by swimming, either by the undulation of their entire bodies or by flapping fin-like structures along the length of their bodies. Most move through ocean habitats using a sticky foot located along the full length of their body.

The typical lifespan in the wild is approximately one year; although, some live less than one month.

Nembrotha Kubaryana - Close-up of Head

Nembrotha Kubaryana - Close-up of Head

Nudibranchs are Carnivores

Most nudibranchs are carnivores eating soft corals, snails, anemones, hydroids, and sponges; however, sponges are the mainstay of their diets. Some nudibranchs eat other nudibranchs. Some even eat algae which they then utilize as a continuing food source. (See solar power below for more information.) Generally, a species of nudibranch will feed exclusively on one type of prey, rather than consuming all of the aforementioned food sources.

Flabellina iodinea, Spanish Shawl Nudibranch - Photograph taken at North Point, Morro Strand State Beach, Morro Bay, CA

Flabellina iodinea, Spanish Shawl Nudibranch - Photograph taken at North Point, Morro Strand State Beach, Morro Bay, CA

Nudibranchs Can Harvest Energy from the Sun

Some nudibranch species have developed a method to harness energy from the sun. These nudibranchs have developed a symbiotic relationship with very small algae called zooxanthellae. The nudibranch stores the zooxanthellae algae in its tissues and lives off the sugars produced by the algae’s photosynthesis.

Another nudibranch is able to save and use chloroplasts found in the algae it consumes.

White and Blue Nudibranch

White and Blue Nudibranch

The Nudibranch is a Mollusk

The nudibranch is an invertebrate and a shellfish, but unlike other shellfish such as snails and clams, does not have a hard shell. Some hatch out with a small shell still intact but lose this shell as they mature.

They can range from less than .5 inches (a few millimeters) to over 12 inches (30 centimeters) in length. One nudibranch, the sea lemon, can reach lengths of 20 inches.

Hermissenda crassicornis, Opalescent Nudibranch - Photograph taken at North Point, Morro Strand State Beach, Morro Bay, CA

Hermissenda crassicornis, Opalescent Nudibranch - Photograph taken at North Point, Morro Strand State Beach, Morro Bay, CA

Nudibranchs have been known to weigh up to 3.3 lbs (1.5 kg)!

Nudibranchs are related to abalone, sea hares, octopus, squid, scallops, mussels, oysters, clams, chiton, snails, and limpets, all of which are also mollusks.

phyllidia sp. - Photograph taken in Malaysian waters.

phyllidia sp. - Photograph taken in Malaysian waters.

Their Defense Mechanisms

Because they lack a shell to protect themselves, nudibranchs have had to develop fascinating ways to defend themselves. One such defense is to produce a very distasteful secretion to deter their predators.

Some nudibranchs are also able to store special stinging cells, also called nematocyst cells, from the creatures they eat, such as sea anemones, jellyfish, and corals. When eating one of these creatures, rather than digesting the nematocyst cells, the nudibranch will attach these stinging cells to their own skin and tentacles. Then, when attacked, the nudibranch will discharge the stinging cells causing their predators to retreat.

Hypselodoris Bullocki (2 cm)

Hypselodoris Bullocki (2 cm)

Dragon Tail Nudibranch in the South Pacific Ocean

Dragon Tail Nudibranch in the South Pacific Ocean

Still, others use camouflage to help them blend into the colorful corals they inhabit in order to hide from their predators. But most nudibranchs have very intricate and vivid color patterns to let their predators know that they might want to think twice about taking a bite.

Common predators are other nudibranchs, sea hares, inexperienced fish, and humans (collectors).

The sea, once it casts its spell, holds one in its net of wonder forever.

— Jacques Cousteau

Nudibranch (Flabellina) in Indonesia

Nudibranch (Flabellina) in Indonesia

Ardeadoris egretta on the Great Barrier Reef, Australia

Ardeadoris egretta on the Great Barrier Reef, Australia

It is an interesting biological fact that all of us have in our veins the exact same percentage of salt in our blood that exists in the ocean, and therefore, we have salt in our blood, in our sweat, in our tears.

We are tied to the ocean. And when we go back to the sea--whether it is to sail or to watch it--we are going back from whence we came.

— John F. Kennedy

Phyllidiopsis Fissuratus (2.5 cm)

Phyllidiopsis Fissuratus (2.5 cm)

Nembrotha Kubaryana in Indonesia

Nembrotha Kubaryana in Indonesia

Orange Peel Nudibranch taken at Resurrection Bay

Orange Peel Nudibranch taken at Resurrection Bay

Slime Trails

Nudibranchs share a trait with their land cousins, the snail and slug.

Nudibranchs leave slime trails so that other nudibranchs can locate them for the purpose of mating. Additionally, they use slime trails to warn other nudibranchs of danger in the area by releasing chemicals into their slime when they are attacked.

Unidentified Nudibranch 3 in Niu Valley, Honolulu, HI

Unidentified Nudibranch 3 in Niu Valley, Honolulu, HI

Janolus or Phidiana Close-up

Janolus or Phidiana Close-up

Dendronotus frondosus, Bushy-backed Nudibranch taken at Morro Strand State Beach, Morro Bay, CA.

Dendronotus frondosus, Bushy-backed Nudibranch taken at Morro Strand State Beach, Morro Bay, CA.

The cure for anything is salt water - sweat, tears, or the sea.

— Isak Dinesen

Redmargin Nudibranch - Hypselodoris ? purpureomaculosa

Redmargin Nudibranch - Hypselodoris ? purpureomaculosa

Chromodoris Leopardus - You can definitely see the leopard spots from which it has derived its name.

Chromodoris Leopardus - You can definitely see the leopard spots from which it has derived its name.

Opalescent Nudibranch taken at the Kenai Fjords National Park

Opalescent Nudibranch taken at the Kenai Fjords National Park

Janolus sp. - This one reminds me of a porcupine!

Janolus sp. - This one reminds me of a porcupine!

My soul is full of longing

For the secret of the sea,

And the heart of the great ocean

Sends a thrilling pulse through me.

— Henry Wadsworth Longfellow

Nudibranch Eggs - The yellow ribbon like mass is nudbranch eggs laid in a long string.

Nudibranch Eggs - The yellow ribbon like mass is nudbranch eggs laid in a long string.

Nudibranch Egg Cluster (pink)

Nudibranch Egg Cluster (pink)

Nudibranchs have a marvelous sex life. They are hermaphrodites.

— David Doubilet

Nudibranch Reproduction

All nudibranchs are hermaphroditic, meaning that they act as both male and female. This helps "even the odds" of such a small creature in such a large ocean being able to find a mate. Eggs are usually deposited in a coiled ribbon-shaped mass. Many times the egg mass is larger than the nudibranch that originally laid them.

Upon hatching, some species of nudibranchs emerge as a crawling juvenile; however, most hatch out as free-swimming larvae that float and/or swim for a period of time until settling down to the bottom of the ocean floor to continue its growth and development.

Glossodoris Atromarginata in Indonesia

Glossodoris Atromarginata in Indonesia

Watch and listen to ...

... National Geographic photographer David Doubilet introduce the Nudibranch here.

Spanish Dancer

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2011 Cindy Murdoch

Comments: "Beautiful Nudibranchs: Colorful Sea Slugs"

Greensleeves Hubs from Essex, UK on April 20, 2016:

Despite the unprepossessing common name of 'sea slug', nudibranchs certainly rival butterflies, birds and coral fishes as the most colourful creatures on our planet, and this collection of photographs with accompanying text is evidence of that. Beautiful hub Cindy.

TruthisReal from New York on January 17, 2016:

So many amazing sea creatures this is a very informative article, keep them coming and I just hit the follow button for more :)

Cindy Murdoch (author) from Texas on September 29, 2015:

Thanks so much Amanda6868. The ocean holds many wonderful sea creatures.

Cindy Murdoch (author) from Texas on September 29, 2015:

Thanks, Akriti. I am pleased that you enjoyed it!

Cindy Murdoch (author) from Texas on July 22, 2015:

Kristen - So glad to be able to open up a whole new world of beauty for you. Thanks so much for stopping by!

Amanda M from Unknown on May 21, 2015:

Very good description of this obscure sea animal. I now learned about an animal I never knew existed! Nice pictures too!

Akriti Mattu from Shimla, India on May 18, 2015:

Wow what a beautiful hub and what beautiful pictures .Voted up :)

Kristen Howe from Northeast Ohio on May 18, 2015:

Cindy, I never heard of nudibranches before. These are beautiful and amusing sea creatures. Your photos were fabulous! Nice descriptions too! Voted up!

Cindy Murdoch (author) from Texas on May 15, 2015:

poetryman6969 - your comment made me smile when you called nudibranchs "slimy critters". I am glad you enjoyed the hub and want to thank you for taking the time to comment. Have a great day!

poetryman6969 on March 09, 2015:

Voted up for exceptionally lovely photos of those slimy critters!

Cindy Murdoch (author) from Texas on January 30, 2015:

BlossomsB - Thanks so much. I love these creatures. Hope you have a chance to check out some of my sealife hubs.

Bronwen Scott-Branagan from Victoria, Australia on January 17, 2015:

The first time I saw these amazing creatures was on a school excursion to the Great Barrier Reef. What a great article you have written with so many examples of the wonderful variety. Thank you for all that research.

Cindy Murdoch (author) from Texas on January 16, 2015:

I am glad you enjoyed it mdscoggins. I truly love sealife.

Michelle Scoggins from Fresno, CA on September 06, 2014:

Beautiful pictures. Thank you for sharing the underwater world - something I am not all that familiar with :)

Cindy Murdoch (author) from Texas on April 18, 2013:

FlourishAnyway - they really are interesting, and beautiful. It is good to know that you enjoyed the quotes. I like to add variety to the hubs every now and then.

Cindy Murdoch (author) from Texas on April 18, 2013:

Peggy W - so glad you enjoyed it. I agree, they are truly beautiful. So glad to hear from another Texan!

FlourishAnyway from USA on April 17, 2013:

What interesting, beautiful creatures. I love not only your use of photos to accentuate the hub but also the quotes. The quotes about the sea were awesome. Voted up and more!

Peggy Woods from Houston, Texas on April 17, 2013:

Hi Cindy,

What an amazing array of beautiful photos of the various colored and types of Nudibranchs. It was interesting reading about them and learning more about them. The videos were also well worth watching. That Spanish Dancer one did remind me of a woman swirling her colorful skirt around her legs as she dances to music. All the up votes except funny and will share with my followers.

Cindy Murdoch (author) from Texas on April 13, 2013:

They truly where gorgeous outfits!

Thanks Crystal!

Crystal Tatum from Georgia on April 12, 2013:

Wow, these are beautiful creatures with a very odd name! I loved being introduced to the high fashion models of the sea!

Cindy Murdoch (author) from Texas on April 08, 2013:

I am pleased that you enjoyed this hub, as I find yours to be so inspiring and informative. Thanks, Sinea Pies!

Sinea Pies from Northeastern United States on April 05, 2013:

Not only is this such an interesting hub but the photos are spectacular. I pinned a few! :) Voted up, beautiful and awesome.

Cindy Murdoch (author) from Texas on November 01, 2012:

Astralrose - I am pleased that you enjoyed these beautiful creatures.

Cindy Murdoch (author) from Texas on November 01, 2012:

aykianink - I am pleased you enjoyed this hub. Yes I do have a hub about dividers that you can use. Here is the link for you: https://hubpages.com/community/Creating-Dividers-t... Enjoy!

aykianink on October 26, 2012:

I make it a point to read the text in hubs so I know what's going on. In this case, it was extra difficult because the pictures were so beautiful! And numerous!:-)

On another note, I got this info from "Suzie HQ"

"Hi aykianink, Thanks for the compliments! If you check out hubber homestead bound she has great dividers you are able to use once you give appropriate credit. The hub is about creating line dividers and tells you exactly how to do it, so check it out, it's excellent!"

Uh...do I have the right person?

Ramilyn from India on October 25, 2012:

Only two months ago when I got to know these creatures. I read an article, not entirely about it, in exchristian.net and really they are very beautiful and extraordinary sea creatures.

Good thing you made an impressive and very useful hub about nudibranchs. Voted up and rated, except funny!

Cindy Murdoch (author) from Texas on August 27, 2012:

unknown spy - they truly are amazing creatures. I find much of the life in the ocean to be so fascinating. Thanks for stopping by.

DragonBallSuper on August 27, 2012:

those are great photos. what an amazing creature!

Cindy Murdoch (author) from Texas on August 20, 2012:

Lisa! So nice to see you again! We all get so busy - and times seems to fly by so much faster as technology is supposed to make our lives easier. I am not so sure about that! These creatures do give us a wonderful reason to stop and enjoy their beauty however, don't they? Thanks for the thumbs up and the share!

Liz Rayen from California on August 20, 2012:

Was browsing through your hubs again (I love doing that) and came across this hub. It's so beautiful Cindy! I love the vibrant photos of each creature and reading about their characteristics. I used to do a lot of diving and I never came across any of these beautiful specimens! Great job my friend! Thumbs up and shared :)

Cindy Murdoch (author) from Texas on March 25, 2012:

I think these creatures are so beautiful and amazing. This is one of my favorite hub. So glad to introduce you to nudibranch. Thanks so much!

Marcy Goodfleisch from Planet Earth on March 23, 2012:

This hub is amazing! I feel like I just visited the most wonderful aquarium in the world, or maybe I had a great scuba adventure among creatures far more beautiful than those on the surface of the earth. This is so well-researched and illustrated. Thanks for introducing us to this delicate and gorgeous creature.

Voted up, beautiful, awesome and interesting!

Cindy Murdoch (author) from Texas on March 05, 2012:

PDXKaraokeGuy - I thoroughly enjoyed mine, but it is 10 times more work and many times more expensive. Fish get sick and die easily because what you need to treat the fish iseases will often kill your invertebrates such as all these gorgeous creatures in this hub. If I had the money, I would definitely do it again. My last set up was a live reef, and that is the way to go. I also had an algae scrub tank/filter underneath for the water to cycle through. If you decide to do it, do a lot of research first.

Justin W Price from Juneau, Alaska on March 04, 2012:

cindy... i've only had tropical fish tanks... did you enjoy having a marine one?

Cindy Murdoch (author) from Texas on January 24, 2012:

BlossomSB - yes I do miss my fish tanks. I had several different kinds, but the saltwater live reef was fairly labor intensive. But I loved it! Thanks so much for stopping by!

Bronwen Scott-Branagan from Victoria, Australia on January 24, 2012:

I just noticed that you mentioned fish-tanks in one of your replies. I don't have any now, either, but they are really the most relaxing pets to have and they don't take a lot of work, either.

Cindy Murdoch (author) from Texas on January 24, 2012:

PDXKaraokeGuy - I agree with you there. It's like a whole new world - especially around the reefs.

Thanks so much for stopping by!

Justin W Price from Juneau, Alaska on January 23, 2012:

sea creatures in general are rather fascinating.

Cindy Murdoch (author) from Texas on January 22, 2012:

alvinalex - I am glad that you liked this hub. It is one of my favorites.

PDXKaraokeGuy - I thank you so much for sharing this hub. I really do find these creatures to be amazing!

rLcasaLme - It was indeed hard to pick which one should be first, but I was intrigued by the nudibranch's dragon appearance. But the second one is gorgeous as well.

Thanks to all of you for stopping by and sharing your thoughts!

Rael Casalme from Dubai, United Arab Emirates on January 20, 2012:

The first image was like a dragon, but my favorite is the second, Dirona albolinieata. It looks so awesome. If I'd be asked what would I prefer be like if given the same selection of creatures, I'd prefer be that.

Beautiful.

Justin W Price from Juneau, Alaska on January 20, 2012:

fascinating creature and mindblowing phots. another wonderful hub. up and shared!

alvinalex on January 17, 2012:

It's amazing! really nice Hub I am glad to appreciate for this. Voted up :)

Cindy Murdoch (author) from Texas on January 17, 2012:

Hi, lobobrandon! Yes they are real! They are amazing and gorgeous! Thanks so much for stopping by!

Cindy Murdoch (author) from Texas on January 17, 2012: