The 10 Strangest Types Of Nudibranch

They’re already classed as one of the oceans most bizarre critters, but have you ever wondered what the strangest types of nudibranch look like? These decadent shell-less mollusks are found in textures, shapes and colors that you never knew existed.

Blue glaucus
Glaucus atlanticus

Nudibranch Type Glaucus Atlanticus
This impressive sea slug is often referred to as a ‘blue dragon’ due to its mythical looks. Photo: Daniel Coleman.

Meet the blue glaucus, a captivating ocean dweller that may be small (reaching a maximum length of just 1 inch), but it never fails to grab attention. Unlike other nudibranchs, the blue glaucus breaks the mold by spending most of its time floating upside down on the water's surface, rather than dwelling on the seabed.

Surviving solely with the help of waves and currents, these enchanting creatures sustain themselves by feasting on jellyfish. While their soft bodies may seem tempting to touch, it's important to note that the blue glaucus can be potentially dangerous.

What makes them even more fascinating is their defense mechanism. By ingesting jellyfish, they store the stinging cells and employ them as a protective shield against predators!

Scientific Name Glaucus atlanticus
Common Name Blue glaucus, blue dragon
Size (Max Length) 1.2 inches (3 cm)
Habitat Atlantic, Pacific and Indian Ocean

Janolus sp.
Janolus flavoanulatus

Nudibranch Type Janolus SP
The distinguishing feature of the janolus flavoanulatus includes a brightly colored stubby cerata, covering their bodies.

Say hello to the Janolus flavoanulatus nudibranch, a sea slug belonging to the Protonotidae family. Its specific name, flavoanulatus, cleverly describes the yellow subapical ring found on its cerata (the Latin words flavus for yellow and anulatus for ringed).

Interestingly, their main predator is the Navanax, a sizable sea slug that, despite its resemblance, does not fall under the nudibranch category.

When sensing danger, the Janolus flavoanulatus adopts a self-defense strategy reminiscent of a hedgehog, rolling into a protective ball and proudly displaying its spiky cerata.

While these charming sea slugs can be found worldwide, they particularly thrive in warm, shallow waters throughout the Indo-West Pacific region, spanning from the Philippines, Indonesia, and Papua New Guinea to Japan, Solomon Islands, Vanuatu, and Australia.

Scientific Name Janolus flavoanulatus
Common Name Janolus sp.
Size (Max Length) 1.9 inches (5 cm)
Habitat Indo-Pacific

Spanish dancer
Hexabranchus sanguineus

Nudibranch Type Hexabranchus Sanguineus
Among the 3,000 nudibranch species, this is the sole one capable of actual swimming.

Meet the Spanish dancer, a remarkable nudibranch known for its impressive size and exceptional swimming abilities.

Gracefully drifting through the water, they perform mesmerizing twists and turns, resembling a flamenco dancer captivatingly swirling her dress. It's no wonder they are commonly referred to as Spanish dancers.

These captivating displays usually occur during nocturnal hours, so if you desire to witness their enchanting movements, a night dive is the way to go.

Dance-offs serve as a means of attracting mates, although Spanish dancers also glide along the reef bottom like other nudibranchs.

While their dominant hue is red, rare sightings of yellow and occasionally patterned individuals have been reported, adding to the allure of these fascinating creatures.

Scientific Name Hexabranchus sanguineus
Common Name Spanish dancer
Size (Max Length) 23 inches (60 cm)
Habitat Indo-Pacific

Leaf sheep
Costasiella kuroshimae

Nudibranch Type Hexabranchus Sanguineus
Measuring a mere 5 mm in length, these tiny leaf sheep can be found in the waters surrounding Japan, Indonesia, and the Philippines.

Introducing the charming leaf sheep (Costasiella kuroshimae), one of the world's cutest nudibranchs.

With its adorable appearance, it may remind you of a certain cartoon character called "Shaun the Sheep," as affectionately named by divers in the Philippines.

They're not found in coral reefs but in areas next to coral reefs, the leaf sheep spends its whole life on a species of algae, its source of nourishment.

What truly sets the Leaf Sheep apart is its extraordinary diet. These fascinating creatures primarily graze on algae and have a remarkable ability to incorporate the algae's chloroplasts into their own tissues, storing them in their cerata for up to 10 days.

By utilizing this unique adaptation, the leaf sheep can supplement its diet through photosynthesis, a process typically associated with plants. This makes them one of the rare examples in the animal kingdom capable of performing photosynthesis, showcasing their remarkable biological versatility.

Scientific Name Costasiella kuroshimae
Common Name Leaf sheep, Shaun the sheep, leaf slug, salty ocean caterpillar
Size (Max Length) 0.2 inches (1 cm)
Habitat Japan, Philippines, Indonesia

Pikachu Nudibranch
Thecacera pacifica

Nudibranch Type Thecacera-Pacifica
The nudibranch Thecacera pacifica, is also compared to a certain cartoon character, but can you guess who?

For anime enthusiasts, the adorable Thecacera pacifica, affectionately known as Pikachu nudibranch, is a delightful find. Its yellow and black jelly-like translucence bears a striking resemblance to the beloved character.

Being a rare species, encounters with the Pikachu nudibranch are considered special and cherished by underwater photographers. They eagerly seek out these unique nudibranchs, including Pikachu, to capture them in their portfolios.

This real-life Pokemon inhabits the coastal waters off Africa and is particularly abundant around the renowned muck dive sites of Tulamben in Bali.

Scientific Name Thecacera pacifica
Common Name Pikachu Nudibranch
Size (Max Length) 0.8 inches (2 cm)
Habitat Indo-Pacific

Spanish shawl
Flabellinopsis iodinea

Nudibranch Type Flabellinopsis Iodinea
The Spanish shawl, Flabellinopsis iodinea, is commonly found in the shallow waters of the Pacific Ocean.

Prepare to be mesmerized by the Spanish shawl, as it is undoubtedly one of the most captivating nudibranchs you'll encounter!

These remarkable nudibranchs boast vibrant bodies, usually in shades of purple or blue, adorned with a splendid cerata "shawl" adorned with fluorescent, squishy orange spikes.

Similar to the Spanish dancer, this nudibranch's nickname is inspired by its graceful movements. It has the ability to swim and sway its body from side to side, showcasing its impressive "mane."

Feeding on a particular species of hydroid, the Spanish shawl gains a special pigment called astaxanthin, which contributes to its vibrant hues and adds to its visual allure.

Scientific Name Flabellinopsis iodinea
Common Name Spanish shawl
Size (Max Length) 2.8 inches (7 cm)
Habitat Pacific

Sap-sucking sea slug
Cyerce elegans

Nudibranch Type Cyerce Elegans
The Cyerce elegans nudibranch is indeed a sight to behold, with its ethereal appearance and fascinating anatomical features.

The Cyerce elegans nudibranch truly lives up to its name, as it is undeniably one of the most enchanting and peculiar species among its nudibranch counterparts!

Its otherworldly body showcases a range of color variations, spanning from light orange to a deeper shade of brown. Upon closer inspection, you'll notice delicate white polka dots scattered internally.

The broad, oval-shaped cerata resemble soft pillows and are adorned with cream, gold, or white flecks along their edges. Interestingly, under specific lighting conditions, these cerata reveal an iridescent internal spot, shimmering in hues of blue or green.

Upon further scrutiny, the cerata can be observed divided into distinct sections, forming a mesmerizing network of transparent vein-like lines.

Scientific Name Cyerce elegans
Common Name Sap-sucking sea slug, Flower butterfly sea slug
Size (Max Length) 1.6 inches (4 cm)
Habitat Indo-Pacific: Arabian Sea to Hawaii

Batangas sea slug
Halgerda batangas

Nudibranch Type Halgerda Batangas
Halgerda batangas almost looks good enough to eat!

The Batangas nudibranch, named after the region in the Philippines, is a species of Halgerda found across the coral triangle in South East Asia.

As a dorid nudibranch, it relies on gills located on its backside for respiration.

One can easily identify the Batangas species by the intricate network of orange lines that adorn its body, stretching between the raised tubercles.

What sets this nudibranch apart are its striking orange patterns and the delightful rounded bumps that dot its body, giving it a unique and jelly-like texture. Its ornate markings truly make the Batangas nudibranch a captivating and unusual sight to behold.

Scientific Name Halgerda batangas
Common Name Batangas sea slug
Size (Max Length) 1.6 inches (4 cm)
Habitat Philippines, Indonesia, Papua New Guinea, Solomon Islands

Hopkin's rose nudibranch
Okenia hopkinsia rosacea

Nudibranch Type Okenia Hopkinsia
A vibrant and eccentric nudibranch that showcases a stunning hot pink coloration.

The Hopkin's rose nudibranch stands out with its numerous long papillae on its back, drawing attention with their eye-popping appearance. These papillae taper to a rounded white tip and can grow up to an impressive inch in length.

Much like other types of nudibranchs, the Hopkin's rose has both male and female reproductive organs meaning that they are able to mate with any other Hopkin's.

To add to its allure, the Hopkin's rose lays pink spiral-shaped eggs that beautifully complement its vibrant exterior.

You can often find this nudibranch species along the coastlines of California, Oregon, and Mexico, where it adds a splash of vibrant pink to the marine ecosystems.

Scientific Name Okenia hopkinsia rosacea
Common Name Hopkin's rose nudibranch
Size (Max Length) 1.2 inches (3 cm)
Habitat North America, Central America

Solar-powered nudibranch
Phyllodesmium magnum

Nudibranch Type Phyllodesmium Magnum
The color of Phyllodesmium magnum is greatly influenced by the coral it is feeding on.

The Phyllodesmium magnum, a remarkable aeolid nudibranch, is predominantly found in sandy areas and has a diet consisting of soft corals and anemones.

This nudibranch species possesses unique cerata, the spikes on its back, which serve multiple functions including respiration, digestion, and defense. However, these cerata have an additional extraordinary feature — they function as solar panels!

By consuming algae from within the anemones and corals, these nudibranchs absorb the algae and store them in their cerata. The algae, still capable of photosynthesis, continue to provide a constant source of food and sugars for the nudibranch.

Due to their ability to derive nutrients from photosynthesis, the Phyllodesmium magnum is often referred to as a "solar-powered" nudibranch.

Scientific Name Phyllodesmium magnum
Common Name Solar-powered nudibranch
Size (Max Length) 5.1 inches (13 cm)
Habitat Indo-West Pacific

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the blue dragon has always been my favorite

Bakiri February 26, 2024

I love these little guys

M October 16, 2023

Very Cool!

Tim and Elizabeth March 09, 2023

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