Beautiful Nudibranchs: Colorful Sea Slugs
Speaking of Nudibranchs:
"Of all the creatures in the sea, these are the high fashion models." ~David Doubilet, photographer for National Geographic
I have had several salt water 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.
Nudibranch is a Latin word that literally means “naked gills”. This name refers to the feathery gills and horns that most have on their backs. Most nudibranchs are around one inch in length, but they pack a lot of intricate beauty in that small size.
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 could be found.
I found a child’s description, “It is something like a flatworm that looks tie dyed”, both amusing and apt.
Although there are more than 3000 nudibranch species throughout the world’s oceans, divers are often able to spot species that have not been previously scientifically identified.
Over 160 different species have been identified along the California coast alone!
They most often inhabit shallow, tropical waters.
Nudibranchs, however, can be found in both shallow and deep waters. Some nudibranchs navigate the oceans by swimming, either by undulation of their entire bodies or by flapping fin-like structures along 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.
Nudibranchs are Carnivores
Most nudibranchs are carnivores eating soft corals, snails, anemones, hydroids, and sponges. Most eat sponges. 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 creatures.
Some species have developed a way to harness energy from the sun. They have been able to develop a symbiotic relationship with very small algae, zooxanthelle. The nudibranch stores the 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.
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.
Their Defense Mechanisms
Because they lack a shell to protect themselves, nudibranchs have had to develop fascinating ways of defending 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.
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
"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
Nudibranchs share a trait with their land cousins, the snail and slug.
Nudibranchs leave slime trails which other nudibranchs use to find a mate. They also use it to warn other nudibranchs of danger in the area. They do the latter by releasing chemicals into their slime when they are attached.
"The cure for anything is salt water - sweat, tears, or the sea." ~Isak Dinesen
"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
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 type mass. Many times the egg mass is larger than the Nudibranch laying them!?!
Upon hatching, some species of nudibranchs emerge as a crawling juvenile; however, most hatch out as free swimming larvae who float and/or swim for a time until settling down to the bottom of the ocean floor.
"Nudibranchs have a marvelous sex life. They are hermaphrodites."
Watch a Video of Nudibranch in the Ocean Depths
Watch and listen to ...
... National Geographic photographer David Doubilet introduce the Nudibranch here.
© 2011 Cindy Murdoch