Slugs on land aren’t known for their color. But once you dive into the ocean, you’ll find that sea slugs are among the most striking creatures on earth! From electric blue to bright orange to hot pink, you can find all manner of incredible shades on the countless species of sea slugs.
Here’s our list of the world’s most colorful sea slugs:
1. Lettuce Sea Slug
- Latin name: Elysia crispata
- Habitat: Tropical parts of the western Atlantic and the Caribbean
- Size: Between about 1.2″ and 2″ long
- Diet: Mostly different types of algae, though it is often able to make its own food
- Colorful feature: The lettuce sea slug is sometimes green. But as you can see in the picture, it comes in a range of colors. It is often bluish or yellowish with pink accents.
Though it’s named after a humble piece of edible vegetation, the lettuce sea slug is much more colorful. If you’re familiar with sea slugs at all, you might expect every one on the list to be a nudibranch. However, while it is colorful like a nudibranch, the lettuce sea slug is actually classified as a sacoglossan.
2. Blue Velvet Headshield Slug
- Latin name: Chelidonura varians
- Habitat: Shallow, tropical reefs in much of the Indo-Pacific region
- Size: Up to about 2.8″ long
- Diet: Entirely flatworms
- Colorful feature: This lovely slug looks illuminated by neon lights! Its base color is deep, velvety black. Much of its body appears to be outlined in thin lines of electric blue.
This beautifully colored creature is a type of “headshield slug.” A quick look at it tells you how it earned that name! It’s also set apart from other sea slugs due to its dual “tails.” It has two pointed tails that split off like a fork. One tail is always longer than the other. This slug is especially useful to aquarium owners as well. Thanks to its flatworm diet, it can be used in aquariums to get rid of flatworm infestations.
3. Nembrotha aurea
- Latin name: Nembrotha aurea
- Habitat: Much of the western Indo-Pacific Ocean
- Size: At least 1.2″ long, though they are often longer
- Diet: Small marine creatures called ascidians or “sea squirts”
- Colorful feature: This nudibranch is probably one of the most colorful sea slugs on the list. Its body has a soft yellow base color marked with dark brown, pinstripe-like lines. The branches reaching off its body are usually a mixture of white and bright blue, while parts of the gills are intense red.
Some species of sea slug have not been discovered until recently. And despite its dazzling and seemingly very noticeable colors, this species was not scientifically described until 2008. Like other nudibranchs, even though it doesn’t have a shell, it is still classified as a mollusk.
4. White-Speckled Headshield Slug
- Latin name: Chelidonura fulvipunctata
- Habitat: Many parts of the Pacific and Indian Oceans, though it also can be found in the Mediterranean Sea
- Size: Between about 0.4″ and 0.8″ long
- Diet: Small aquatic worms
- Colorful feature: This creature, interestingly enough, does not usually have white spots. Instead, it is covered in small yellowish or orange spots. Its base color is quite eye-catching too: it’s deep brown or black with a faintly bluish sheen.
You might not think of sea slugs as becoming invasive species, but this small headshield slug traveled to the Mediterranean Sea in 1961. Prior to that, it had never been recorded there. Luckily, its invasion of the Mediterranean does not seem to have caused noticeable environmental issues.
5. Ruppell’s Warty Slug
- Latin name: Phyllidia rueppelii
- Habitat: Has been found in the Red Sea and the Gulf of Oman
- Size: Up to about 1.6″ long
- Diet: Various types of small marine life
- Colorful feature: This interesting sea slug is both colorful and textured. It has a black base color and is dotted with light blue tubercles, each of which is topped with bright yellow.
Many of the sea slugs on the list have smooth surfaces, making species like Ruppell’s warty slug that much more interesting. Like many slugs on the list, it has a body shaped like a long oval.
6. Hypselodoris infucata
- Latin name: Hypselodoris infucata
- Habitat: Various parts of the tropical Indo-West Pacific, including the Red Sea and the Mediterranean Sea
- Size: At least about 2″, though they are frequently longer
- Diet: Various types of sea sponges
- Colorful feature: This bright sea slug has a whitish base color. It is covered in blotches of deep blue and light blue. It also has large spots of yellow and small dots of black. Its fin-like protrusions are a semi-translucent red.
This is another nudibranch species that has invaded the Mediterranean Sea via the Suez Canal. This type of migration is so common that it has its own name: Lessepsian migration. Creatures that migrate this way almost always come from the Red Sea to the Mediterranean; they rarely migrate in the other direction.
7. Caloria indica
- Latin name: Caloria indica
- Habitat: Many parts of the Indo-West Pacific, though it is also an invasive species in the Mediterranean Sea
- Size: Between about 1″ and 2″ long
- Diet: Various types of small marine life
- Colorful feature: This striking, porcupine-like sea slug varies in color. Most individuals are some combination of orange, blue, and white. The one in the picture has especially colorful blue and white “spikes.”
This species was first found off the coast of India’s picturesque Ambon Island, but it has an impressively wide range. Like many of the colorful sea slugs on the list, this one has also become an invasive species in the Mediterranean. However, it seems to be confined to the part of the Mediterranean close to Israel. It was first spotted there in the 1980s, but another sighting in 2016 confirmed that it was still a resident species.
8. Purple-Line Unidenitia
- Latin name: Unidentia angelvaldesi
- Habitat: Various parts of the Indo-Pacific and East Pacific Oceans
- Size: Up to about 0.4″ long
- Diet: Various types of small marine life
- Colorful feature: These beautiful creatures are often semi-translucent with accents of solid purple. As you can see in the photo, some of them appear to be lit up!
This beautiful creature has not been as extensively researched and documented as some of the other sea slugs on the list. Still, it is one of the most beautiful slugs on our list! The purple-lined unidentia is one of the tendril-covered sea slugs that looks like a tiny sea anemone at first glance.
9. Goniobranchus verrieri
- Latin name: Goniobranchus verrieri
- Habitat: Various parts of the Indo-West Pacific
- Size: Between 0.7″ and 1.2″ long
- Diet: Various types of sea sponges
- Colorful feature: This pretty little sea slug looks a little like a rabbit! Its body is creamy white with a reddish or burnt-orange outline. It has two red gills that look like rabbit ears as well as a puff-like protrusion at the rear.
Most of the sea slugs on our list are bright, rainbow-like colors! But while this one looks a bit like a small rabbit, its coloration is a lot like that of a toasted marshmallow. Its body is rich white, while the reddish accents look a lot like the toasted or burnt part of a marshmallow.
10. Nembrotha lineolata
- Latin name: Nembrotha lineolata
- Habitat: Many parts of the Indo-Pacific Ocean
- Size: Up to about 2.8″ long
- Diet: Mostly marine invertebrates called tunicates
- Colorful feature: These colorful sea slugs can appear in a variety of different patterns. They usually are off-white with dark brownish lines. Many individuals also have jewel-like accents of blue, purple, and yellow.
This pretty sea slug is shaped a lot like the slugs you usually see on land! They also have some of the most distinctive eggs on the list. Nembrotha lineolata lays its eggs in a distinctive bright orange “spiral,” often on sea squirts or other types of marine life.
11. Dendrodoris guttata
- Latin name: Dendrodoris guttata
- Habitat: Tropical waters off the coast of Australia
- Size: At least 2″ long
- Diet: Mostly sea sponges
- Colorful feature: This bright sea slug varies somewhat in color. The most colorful individuals are a bright, lively orange. They have black spots that appear ringed in a soft, whitish glow.
Some species on this list look more like land slugs than others. This unique species is especially amorphous, as it looks like a glistening, spreading blob. Nonetheless, its very bright pattern sets it apart from many of the other sea slugs on our list.
12. Phyllidia varicosa
- Latin name: Phyllidia varicosa
- Habitat: Much of the Indo-West Pacific region including the Red Sea
- Size: Up to about 4.5″ long
- Diet: Mostly sea sponges
- Colorful feature: This colorful, caterpillar-like sea slug is covered in a number of soft blue-gray ridges. The points of these ridges are bright yellow or orange. The base color of the slug’s body is a striking jet black.
This striking nudibranch’s bright colors serve as a warning for predators. It is toxic if consumed. The sea cucumber uses mimicry to fool predators into thinking it’s also toxic. Juvenile sea cucumbers look a lot like this species, especially if you aren’t too familiar with the differences between the two.
13. Thuridilla gracilis
- Latin name: Thuridilla gracilis
- Habitat: Various parts of the Indo-Pacific
- Size: Up to about 1″ long
- Diet: Mostly various types of algae
- Colorful feature: As you can see in the picture, this nudibranch species is covered in a mesmerizing pattern of bright lines on a dark background. Typically, the base color is black and the lines are white, but the lines can also be very bright yellow. It usually also has some accents of orange. Individual coloration varies somewhat, as is the case with many types of nudibranchs.
Like many types of sea slugs, this one lives primarily in coral reefs. You can usually find it on the slopes of reefs and in nearby shallow water. It uses aposematic coloring, meaning that its bright coloring serves as a warning to predators. Like other sacoglossans, this one can convert parts of the algae it consumes into various types of toxins.
14. Cabangus regius
- Latin name: Cabangus regius
- Habitat: Many parts of the tropical Indo-Pacific
- Size: Up to about 1.2″ long
- Diet: Various types of sea sponges
- Colorful feature: This distinctive nudibranch has a body that is largely translucent, though it often has a surface that appears white, pink, orange, or yellow. It has dark-colored, pointy tubercles and some dark spots. The color varies a good bit between individuals, and the brightest individuals are largely orange.
As the scientific name indicates, this particular species of nudibranch looks especially regal! Its body is covered with raised tubercles, many of which look a lot like tiny trees. There are two especially imposing, antler-like tubercles atop the head region. Scientists have noticed a similar-looking sea slug with an overlapping range, but this lookalike is believed to be a different species that has yet to be named.
15. Hypselodoris sagamiensis
- Latin name: Hypselodoris sagamiensis
- Habitat: Waters off the shore of India and Japan
- Size: At least 1.2″ long
- Diet: Mostly sea sponges
- Colorful feature: This very colorful nudibranch includes a whole range of bright shades. Its body has a snowy white base color, but the mantle is ringed with a line of yellow spots and a line of purple spots. The mantle itself is dotted with dalmatian-like black spots. And the brush-like tubercles atop the head are accented with intense burnt orange.
Most literature on this strikingly beautiful sea slug asserts that it can only be found in Japan and India. However, divers and researchers have reported seeing large numbers of Hypselodoris sagamiensis off the coast of Queensland, Australia as well. It’s possible that, like some other sea slug species on the list, this one has slowly but steadily expanded its range.
16. Hypselodoris zephyra
- Latin name: Hypselodoris zephyra
- Habitat: Parts of the western and central Pacific Ocean
- Size: At least 0.8″ long
- Diet: Sea sponges in the Dysidea genus
- Colorful feature: This bright sea slug’s body has a base color ranging from white to soft yellow. The bottom of the mantle is ringed in electric purple, while the body is crossed in vein-like black lines. Its rhinophores (ear-like sensory organs) are a lively burnt orange.
Here’s another sea slug from the Hypselodoris genus. Hypselodoris contains many of the most dazzling sea slugs the ocean has to offer. This species also bears a striking resemblance to another member of the genus, Hypselodoris nigrostriata. As you likely could guess from the name, Hypselodoris nigrostriata is also striped with black lines.
17. Opalescent Sea Slug
- Latin name: Hermissenda opalescens
- Habitat: Along much of the Pacific coast
- Size: About 2″ long
- Diet: Various small marine organisms including sea squirts and sea anemones
- Colorful feature: This striking sea slug has a mantle that, appropriately, is about the same color as an opal. Its back is covered in fiery, spine-like protrusions that are orange with yellow-white tips.
The opalescent sea slug is one of the most mesmerizing on the list, but it’s also been very useful in research. In particular, scientists have used it to study neural circuits, associative learning, and memory consolidation. Scientists also have used it to better understand the behavior and reproduction of countless related species.
18. Tambja sagamiana
- Latin name: Tambja sagamiana
- Habitat: Parts of the West Pacific Ocean, especially around Korea, Japan, and Taiwan
- Size: At least 4.3″ long
- Diet: Various types of small marine organisms
- Colorful feature: This especially striking sea slug almost looks more like a sculpture than it does an animal! Its body is bright blue and dotted with irregular, black-lined orange spots. The foot is lively yellow.
This brightly-colored sea slug has not been researched as extensively as some of the others on the list. Though its bright colors may serve to warn predators of its toxicity, researchers have not investigated how toxic it may be to humans or other organisms.
19. Purple Mediterranean Sea Slug
- Latin name: Flabellina affinis
- Habitat: Parts of the Atlantic Ocean off the coast of Europe, as well as in the Mediterranean Sea
- Size: About 2″ long
- Diet: Hydrozoa (very small, predatory marine animals) in the Eudendrium genus
- Colorful feature: This magical-looking sea slug has a body that appears to be lilac or lavender in color. Like some other species on the list, it is covered in orangish, spine-like protrusion with glowing yellow-white tips.
As you likely gathered from the name, this sea slug is especially common in the Mediterranean Sea. It’s not too hard to see when snorkeling or diving, as it mostly stays in waters with a depth of 50 m or less.
20. Nembrotha purpureolineata
- Latin name: Nembrotha purpureolineata
- Habitat: Much of the western region of the tropical Indo-West Pacific Ocean
- Size: Up to about 4.7″ long
- Diet: Mostly sea squirts and related species
- Colorful feature: This colorful sea slug has patchwork coloring similar to that of a paint horse. Its base color is white and it is covered in large patches of red or brown. It has large and eye-catching rhinophores that range from reddish-orange to red.
Nembrotha purpureolineata is one of the older species discoveries. It was first described in 1924. Though it seems like it would be very easy to identify, this species looks a lot like two other nudibranch species, Nembrotha aurea and Nembrotha chamberlaini.
21. Swallowtail Headshield Slug
- Latin name: Chelidonura hirundinina
- Habitat: Western parts of the Indo-Pacific as well as the Caribbean Sea
- Size: Up to about 1.6″ long
- Diet: Almost entirely flatworms
- Colorful feature: This brilliantly-colored sea slug has a black base color (though it is sometimes another dark color). Its body has pinstripe-like markings of blue, orange, and/or green.
Even a quick look at this sea slug can tell you how it got its name. Its tail is forked much like that of a swallow. And of course, like other “headshield slugs,” this one also has a distinctly shield-shaped head.
22. Sea Clown Triopha
- Latin name: Triopha catalinae
- Habitat: Parts of the Western Pacific ranging from Alaska to Mexico, though it has also been found off the coasts of South Korea and Japan
- Size: Up to about 6″ long
- Diet: Various types of bryozoans, or small aquatic organisms
- Colorful feature: This brightly-colored nudibranch has a body that is largely snowy white. It is covered in a range of orange protrusions that appear hairlike at first. Its cheerful appearance makes its name especially appropriate!
Many of the bright sea slugs on the list have interesting scientific names. This one’s name is a reference to Catalina Island, California, one of the first places it was discovered.
23. Hypselodoris roo
- Latin name: Hypselodoris roo
- Habitat: Seems to only be found off the coast of the Philippines and in some parts of Indonesia
- Size: At least about 1.8″ long
- Diet: Various types of small marine organisms
- Colorful feature: This lovely creature has distinctive patterning that makes it look a bit like the ocean floor when it’s dappled by sunlight. Its base color is blue-gray, and it’s spotted with blue, yellow, black, and white. Its rhinophores add an unexpected burst of red, too.
This bright, blob-like nudibranch is definitely one of the more colorful ones on our list! Its rhinophores are especially intriguing, as they look a bit like pointy horns.
24. Clown Nudibranch
- Latin name: Ceratosoma amoenum
- Habitat: Intertidal zones of parts of Australia and New Zealand
- Size: At least 2.4″ long
- Diet: Various types of sea sponges
- Colorful feature: This bright nudibranch is marked with spots of yellow to orange and pink to purple, while its base color is bold white.
Interestingly enough, this colorful sea slug’s patterning varies by location. Slugs that live near New Zealand tend to have spots that are bigger than those farther away. But regardless of spot size, these are still some of the most beautiful sea slugs on the list!
25. Nembrotha mullineri
- Latin name: Nembrotha mullineri
- Habitat: Only off the coast of the Philippines
- Size: At least about 2″ long
- Diet: Primarily sea squirts
- Colorful feature: This striking slug is usually black and white, though its patterning is stunning. Its base color is whitish and marked with many thin dark lines and spots. The end result is a pattern that looks close to that of a blue roan horse or a blue merle dog. Some individuals, like the one in the picture, are marked with broader and/or paler lines.
This slug may not be colorful in the sense of being extremely bright, but its intricately beautiful pattern earns it a spot on the list. And as you can see in the picture, its hind end is covered with uniquely beautiful, tree-like protrusions.
26. Gem Sea Slug
- Latin name: Goniobranchus geminus
- Habitat: Coral reefs in the Red Sea and in the Indian Ocean (from Kenya to Sri Lanka)
- Size: Up to about 2″ long
- Diet: Various types of sea sponges
- Colorful feature: This strange sea slug looks like something out of an abstract painting! It has a whitish base color, and the mantle is ringed with pale bluish-purple and yellow. The center of the body has a rosy hue and many purple spots. Each spot is surrounded with a ring of white that makes it look as if it’s glowing.
This appropriately-named sea slug looks as if it’s encrusted with dark, amethyst-like gems. It does look a bit like some other species of sea slug, mostly those in the same genus.
27. Goniobranchus splendidus
- Latin name: Goniobranchus splendidus
- Habitat: Shallow waters off the coast of southeastern Australia
- Size: Around 3″ long
- Diet: Sea sponges and some other types of marine life
- Colorful feature: This shiny, striking sea slug has a pearly white backdrop. It’s marked with big red spots, and the mantle has an outline of bright yellow. Its rhinophores are electric purple!
This especially pretty sea slug looks a lot like some other species. These species have overlapping ranges and form a “mimicry ring” around parts of the Australian coast.
28. Mexichromis multituberculata
- Latin name: Mexichromis multituberculata
- Habitat: Has been found off the coast of Southeast Asia, parts of northern Africa, and Japan
- Size: About 1.2″ long
- Diet: Specific types of sea sponges
- Colorful feature: This unusual sponge is primarily white in color, though it is covered with purple-tipped tubercles. Its mantle is also lined with purple spots.
As you can likely tell from the scientific name, this species stands out because it is covered in multiple tubercles. These unusual, bulbous protrusions give it an alien-like appearance. If you happen to see one on a dive or a snorkeling trip, you certainly won’t forget it!
29. Spanish Shawl
- Latin name: Flabellinopsis iodinea
- Habitat: Shallow waters off the west coast of North America and parts of Mexico; it’s also found in the Galapagos Islands and in the Gulf of California
- Size: Up to about 2.75″ long
- Diet: Eudendrium hydroids
- Colorful feature: This memorable sea slug’s mantle has a base color of electric purple. The body is covered in cerata, or appendages that extract oxygen from the surrounding ocean. The cerata are neon orange. This species also has relatively short, scarlet rhinophores.
This pretty sea slug is one of the relative few on the list that has a common name. And thanks to its bright cerata, it does look a bit like a shawl. Experts think the bright orange cerata are meant to help it camouflage among its prey as it eats.
30. Cristate Neon Slug
- Latin name: Nembrotha cristata
- Habitat: Tropical parts of the Indo-West Pacific Ocean
- Size: At least 2″ long
- Diet: Various types of tunicates (small marine invertebrates)
- Colorful feature: This high-contrast sea slug has a black base color. It’s covered in raised, bright green spots. Its black, ear-like rhinophores are lined in green.
Like many of the sea slugs on the list, this one is toxic to predators. Its unusually bright coloring is meant to warn predators that it is dangerous to eat.
31. Dendrodoris krusensternii
- Latin name: Dendrodoris krusensternii
- Habitat: Tropical parts of the Indo-Pacific Ocean
- Size: Up to about 1.5″ long
- Diet: Various types of small marine life
- Colorful feature: This striking and unusual sea slug is primarily a clearish, glowing white to translucent brown. It’s covered in raised tubercles. But as you can see in the picture, it also has patches of warm olive that are dotted with irregular streaks of electric blue.
This highly unique sea slug is one of the more recently discovered species; it was first discovered and formally described in 1972. It is considered to be somewhat rare, though it can often be found in relatively open, unprotected parts of the ocean.
32. Hypselodoris pulchella
- Latin name: Hypselodoris pulchella
- Habitat: Found in the Red Sea and some parts of the tropical Indian Ocean
- Size: Up to about 4.3″ long
- Diet: Various types of sea sponges
- Colorful feature: This stunning sea slug has a white base color with a purple-lined mantle. The back has a faint purplish case, and it is dotted with sunny yellow spots. The rhinophores are also bright medium purple.
If you spot one of these sea slugs in the wild, you will likely see another one close by. That’s because this species exhibits a behavior called “trailing.” This is when one slug swims ahead and another follows closely behind. These slugs also have a distinctive swimming style where they raise and lower their heads repeatedly.
33. Hairy Norse God
- Latin name: Aegires villosus
- Habitat: Found throughout much of the Indo-West Pacific Ocean
- Size: Up to 0.5″ long
- Diet: Some types of sea sponges
- Colorful feature: This striking creature has a whitish base color. Much of the top of the mantle is mottled in pink and yellow. It also sometimes has black-tipped tubercles and a few spots of black on the body as well.
As the common name of this species tells you, this sea slug has a vaguely hairy appearance. It’s one of the smaller species on the list, but its very bright colors mean that it’s easy to spot in its natural habitat.
34. Thorunna horologia
- Latin name: Thorunna horologia
- Habitat: Warm waters off the coast of South Africa and Réunion
- Size: Up to about 0.8″ long
- Diet: Various types of smaller marine life
- Colorful feature: This pretty sea slug is mostly white in color. Its mantle is lined in bright purple. And like many species on the list, it has bright orange rhinophores that look especially striking against the white body. Some individuals have a faint purple cast reaching over part of the mantle.
This species is one that has not been extensively researched, and even experts don’t know much about its life history. However, as is the case with most smaller sea slugs, it likely lives a few months.
35. Goniobranchus reticulatus
- Latin name: Goniobranchus reticulatus
- Habitat: Various parts of the Indo-West Pacific Ocean
- Size: Up to about 4″ long
- Diet: Various types of small marine life
- Colorful feature: This species has a mesmerizing pattern. Its back is covered in spots of red and lacquer. The pattern of smallish spots make it look beautifully textured. The white foot also creates a beautiful contrast with the rest of the body.
This nice-looking nudibranch is the subject of some debate in the scientific community. Some experts believe that there are actually distinct species that are currently being lumped together as Goniobranchus reticulatus. Of course, time and more research will tell.
36. Chelidonura livida
- Latin name: Chelidonura livida
- Habitat: Parts of the tropical Indian Ocean (between the Philippines and northern Australia), as well as in the Red Sea and off the coast of Madagascar
- Size: Up to about 2″ long
- Diet: Different types of flatworms
- Colorful feature: This lovely sea slug has an especially eye-catching pattern; it is dark brown to black with bright, electric blue spots.
This is another of the oddly-shaped headshield slugs. Though its body looks like that of many sea slugs, its head is shaped like that of a hammerhead shark! It is especially easy to spot in the wild, as you can often find it in shallow, intertidal areas throughout its native range.
37. Hypselodoris whitei
- Latin name: Hypselodoris whitei
- Habitat: Parts of the tropical western Pacific Ocean between Australia and Hawaii
- Size: At least 1.7″ long
- Diet: Primarily sea sponges
- Colorful feature: This sea slug is especially pretty thanks to its scheme of complementary colors. Its body is pale yellow with lavender lines. Its mantle also has a ring of purple along the bottom.
This nudibranch’s coloring is soft and light enough that it often appears to be glowing! It also has striking orange gills that top the body in a kind of crown. Though it is small, it’s definitely a sea slug worth seeing!
38. Nembrotha chamberlaini
- Latin name: Nembrotha chamberlaini
- Habitat: Off the coast of the Philippines and Indonesia
- Size: Up to about 4″ long
- Diet: Sea squirts and various types of tunicates
- Colorful feature: This splashy sea slug has a white body with a burst of color streaked across the upper mantle. That color can be black, orange, green, or yellow. It is easily set apart from other sea slugs by its bright red rhinophores and gills.
Though this sea slug certainly looks unique, it can be easy to confuse with other Nembrotha species if you are unfamiliar with various types of sea slugs. Experts believe that its bright colors are meant to warn predators of its toxicity.
39. Goniobranchus leopardus
- Latin name: Goniobranchus leopardus
- Habitat: Can be found off the coast of parts of Australia and Southeast Asia
- Size: Up to about 2.4″ long
- Diet: Certain types of sea sponges
- Colorful feature: True to the name, this sea sponge is patterned a bit like a leopard. Its largely flat mantle is a golden tawny color. It is marked with black spots or rings surrounded by an aura of white, while the edge of the mantle is skirted with a line of blue or purple.
It’s always interesting to see sea slugs that look like other animals; this is one of the few that does. Its leopard-like coloration makes it stand out from many other members of the genus.
40. Thorunna florens
- Latin name: Thorunna florens
- Habitat: Tropical waters off the coast of Indonesia, Australia, and Thailand
- Size: Up to about 0.5″ long
- Diet: Mostly sea squirts and various types of tunicates
- Colorful feature: This sea slug has a bright white base color marked with streaks and spots of yellow or purple. It also has bright red to red-orange rhinophores.
This striking sea slug is one that has not been too extensively researched. Currently, experts believe it may more properly be described as a complex of different species rather than a single species. This is partially due to its large range and many variations in color.
41. Painted Doris
- Latin name: Felimare picta
- Habitat: Rocky sea floors in the Mediterranean Sea, off the coast of Spain and Portugal, the Gulf of Mexico, and eastern parts of the Atlantic Ocean
- Size: Up to about 5.1″ long
- Diet: Specific types of sea sponges
- Colorful feature: These striking nudibranchs have an intense blue base color with bright yellow markings. The amount of yellow varies greatly between individual sea slugs.
This sea slug is one of the many whose coloration varies based on location. Individuals in the Atlantic have dark blue gills. But those found in the Mediterranean have violet blue gills. The exact patterning will often vary based on location as well.
42. Nembrotha megalocera
- Latin name: Nembrotha megalocera
- Habitat: Only found in the Red Sea
- Size: Up to about 4″ long
- Diet: Some types of sea squirts
- Colorful feature: This bright sea slug has a whitish body with a large yellowish-orange patch along the back. That patch is streaked with black. This species also has a very bright blue foot.
Like many of the sea slugs on the list, this one has a striking “crown” of gills at the center of the back. This crownlike structure is often red with orange and white stalks. That adds another burst of color to this already bright creature!
43. Hypselodoris tryoni
- Latin name: Hypselodoris tryoni
- Habitat: Parts of the tropical western Pacific ranging from the Philippinesto Australia
- Size: At least 2.4″ long
- Diet: Various types of sea sponges
- Colorful feature: This bright sea slug is another species whose white-ringed spots appear to be glowing. Its mantle is largely rosy brown with black spots. Those spots are surrounded by off-white rings. The mantle edge has a thin, clear blue line.
This is one of the species of sea slug that has been studied somewhat closely by scientists. Researchers have observed that these sea slugs are often followed by shrimp as they feed on sponges. The shrimp appear to feed alongside Hypselodoris tryoni.
44. Hypselodoris maculosa
- Latin name: Hypselodoris maculosa
- Habitat: Tropical parts of the Indo-Pacific Ocean
- Size: At least about 1.3″ long
- Diet: Some types of sea sponges
- Colorful feature: This species has a wide variation in color. Some of the more colorful individuals like the one in the picture have a soft orange base color accented with white streaks and small patches of magenta.
Hypselodoris maculosa has much more color variation than most species on the list. Scientists now believe that these different individuals may actually be different species. Ongoing DNA studies are helping to determine how many sea slug species are currently grouped in with Hypselodoris maculosa.
45. Tenellia melanobrachia
- Latin name: Tenellia melanobrachia
- Habitat: Has been found off the coast of the Philippines, Japan, Hong Kong, Australia, and Malaysia
- Size: Up to about 1.6″ long
- Diet: Some types of corals
- Colorful feature: This unusual sea slug comes in an orange form and a black form. The brighter orange forms have fiery coloration like the one in the picture. There are also softer-colored individuals whose coloration is closer to being pink.
This sea slug looks a bit different from many on the list. And as you saw above, it also has a different diet: it feeds on coral. Its many appendages help it to remain camouflaged as it feeds on coral reefs.
46. Dotted Nudibranch
- Latin name: Jorunna funebris
- Habitat: Many parts of the Indo-Pacific region
- Size: Up to about 3″ long
- Diet: Various types of sea sponges
- Colorful feature: This pretty nudibranch combines high-contrast color with interesting texture. Its base color is white. It has colored-in raised spots that are marked with short dark brown to black hairlike protrusions.
This striking sea slug has some potential in the world of chemistry. Researchers have discovered that the dotted nudibranch includes two compounds that are structurally very similar to anti-tumor drugs or alkaloids with anti-tumor properties. Though it has not yet been used in the pharmaceutical industry, this slug may one day be used to manufacture anti-tumor drugs.
47. Favorinus japonicus
- Latin name: Favorinus japonicus
- Habitat: Can be found throughout much of the Indo-Pacific region
- Size: Up to about 0.7″ long
- Diet: Mostly the eggs of other sea slug species
- Colorful feature: This is one of the stranger sea slugs on the list. It has a narrow, translucent body surrounded by curled or whirling pinkish-orange tendrils. Sometimes, the tendrils appear to be coated in powdery white.
You might sometimes hear this creature called the “egg-eating nudibranch.” That’s because it has an unusual diet; it feeds on the large egg masses left by some other sea slug species. Oddly enough, it even lays its own eggs atop these foreign egg masses.
48. Purple-Tipped Janolus
- Latin name: Janolus savinkini
- Habitat: Shallow waters in parts of East Asia
- Size: Up to about 3″ long
- Diet: Various types of hydroids
- Colorful feature: This stunning sea slug resembles a bright porcupine. It is bright yellow in color, though some individuals have an orange tint. It is covered in many cerata, and these cerata are tipped in purple. Some have tips closer to blue.
This lovely sea slug is hard to miss. But if you see one, don’t touch it! It feeds on stinging hydroids and is able to retain the stinging cells. As a result, it is able to sting predators or curious divers.
49. Goniobranchus kuniei
- Latin name: Goniobranchus kuniei
- Habitat: Shallow waters in many parts of the western Pacific Ocean and the eastern Indian Ocean
- Size: Up to about 1.6″ long
- Diet: Largely sea sponges
- Colorful feature: This beautiful species has a mantle that is between cream-colored and yellow. It is spotted with dark blue, and each spot is ringed in white or pale blue. The outline of the mantle is especially beautiful, as it includes a blue line and a purple line.
When this sea slug swims, it makes a beautiful sight! Its mantle spreads out with the semi-translucent foot beneath. Its gills form a pretty star-like shape on the back.
50. Hypselodoris kanga
- Latin name: Hypselodoris kanga
- Habitat: Various parts of the western Pacific and much of the Indian Ocean
- Size: Up to about 2.8″ long
- Diet: Primarily sea sponges
- Colorful feature: This beautiful sea slug is reminiscent of confetti or a formica countertop. Its body is bluish gray and covered in spots of yellow and black (or deep blue). The mantle has a lively blue border made up of smallish spots. Its rhinophores are dark orangish.
If this sea slug looks familiar, it may be because it looks a good bit like Hypselodoris roo. In fact, the two look so alike that researchers occasionally mistake members of one species for members of another. It’s made all the more confusing by the overlapping ranges of the different species.
51. Chromodoris quadricolor
- Latin name: Chromodoris quadricolor
- Habitat: Can be found in parts of the Indian Ocean, though it’s especially common in the Red Sea
- Size: Up to about 2″ long
- Diet: Some types of sea sponges
- Colorful feature: This nudibranch has an especially appropriate scientific name, as it is made up of four colors: blue, black, yellow (or orange) and white. These colors form eye-catching stripes and/or rings.
This four-colored sea slug is one of the most distinctive on the list. It makes a colorful sight when feeding on the red sponge (one of its preferred sources of food).
52. Nembrotha milleri
- Latin name: Nembrotha milleri
- Habitat: Tropical parts of the Indo-Pacific Ocean
- Size: At least 2.4″ long
- Diet: Various types of sea squirts and tunicates
- Colorful feature: Though it isn’t multicolored, this sea slug has a stunning blue-green color that earned it a mention. Thanks to its color, its multi-branched gills look a bit like leaves.
This sea slug has quite a pretty color, but there’s also another form that can be found in the wild. This form has a paler yellow-green background color. Both forms are marked with unusual dark-tinted wrinkles that reach lengthwise down the body. This is also one of the few nudibranch species named after a person; Nembrotha milleri is named after Michael D. Miller, a somewhat well-known nudibranch enthusiast.
53. Variable Neon Slug
- Latin name: Nembrotha kubaryana
- Habitat: Tropical parts of the western Pacific Ocean
- Size: Up to about 4.7″ long
- Diet: Some types of sea squirts
- Colorful feature: This colorful sea slug has a body with a black base color. It’s marked with bright green stripes running lengthwise. The foot, head, and rhinophores are marked with an especially bright fiery orange.
This sea slug is also sometimes called the “dusky nembrotha” thanks to its dark stripes. It is one of the species of slugs that can store toxins from its prey. If threatened, it is able to release these toxins in mucus.
54. Doriprismatica atromarginata
- Latin name: Doriprismatica atromarginata
- Habitat: Parts of the subtropical and tropical Indo-Pacific Oceans
- Size: At least about 2.4″ long
- Diet: Various types of sea sponges
- Colorful feature: This ruffle-like sea slug has an unusual pattern. Its body ranges from off-white to pale yellow to light brown. The edge of the curled-up mantle is black.
This pretty nudibranch has a very pretty way of moving. Its ruffled or frilly mantle seems to create a wavelike motion as the creature travels. Even though it looks delicate, it’s well equipped to defend itself. Like many nudibranch species, it is able to store toxins from its prey and use them against predators.
55. Hypselodoris variobranchia
- Latin name: Hypselodoris variobranchia
- Habitat: Generally is found off the coast of Australia, Indonesia, Malaysia, and Japan
- Size: Up to about 2″ long
- Diet: Various types of small marine life
- Colorful feature: This stunning sea slug has a body that is almost entirely electric purple. The mantle is surrounded by a broad white ring. Its gills and rhinophores create a pleasant burst of orange, too.
This striking species is very common and has a fairly large range. However, if you aren’t too familiar with sea slugs, it is easy to confuse this one with the very similar Hypselodoris bullocki and Hypselodoris apolegma, two species in the same genus.
Nature’s Brightly Colored Sea Slugs
You don’t spot sea slugs every day, but if you happen to dive in a coral reef or visit an aquarium, be sure to keep an eye out for these beautiful creatures. Though they may not be quite as famous as tropical fish, sea slugs are just as colorful!
