Nudibranchs & sea slugs

Nudibranchia

The jewels of the sea — nudibranchs come in every colour combination imaginable and reward slow, careful searching. Check under overhangs, on sponges, and along hydroids. Once you spot your first, you'll start finding them everywhere.

Last updated April 2026

Species

Spotted sea slug

Discodoris atromaculata(30 photos)

Up to 12 cm5–40mRocky reef

A flat, oval nudibranch — creamy white to pale yellow body covered in distinctive dark brown or black spots and rings. Looks like a cow-print cookie.

Glides slowly over rocky surfaces grazing on sponges — easy to photograph thanks to its slow movement and bold pattern.

Observed at

Las Planetas(Sant Feliu de Guíxols)El Jardín y La Red(Sant Feliu de Guíxols)Túneles de Port Salvi(Sant Feliu de Guíxols)Dofí Nord(Illes Medes)Bajo de Dentro(Cabo de Palos)Pedra de Déu(Illes Medes)La Garita(Tarifa)Punta Cana(Costa del Maresme)El Trencat(Costa del Maresme)S'Adolitx(Sant Feliu de Guíxols)Els Canons de Tamariu(Begur)

Flabellinopsis affinis

Flabellinopsis affinis(19 photos)

Up to 5 cm5–40mRocky reef

A delicate, purple-violet nudibranch with clusters of cerata (finger-like projections) along its back tipped in white. Striking color against dark rocky surfaces.

Feeds on hydroids on rocky walls — often found in small groups. One of the most commonly photographed Mediterranean nudibranchs.

Observed at

Mar Menuda(Tossa de Mar)Las Planetas(Sant Feliu de Guíxols)Barreta d'en Serra(Costa del Maresme)S'Adolitx(Sant Feliu de Guíxols)Pedra de Déu(Illes Medes)La Calita(La Herradura)Isla de Santa Eulalia(Ibiza)Punta Cana(Costa del Maresme)Montseny(Costa del Maresme)Montelivi(Sant Feliu de Guíxols)Punta de la Mona(La Herradura)

Prostheceraeus roseus

Prostheceraeus roseus(13 photos)

Up to 4 cm3–30mRocky reef

A pale pink to rose-colored marine flatworm with a smooth, oval body and wavy edges. Similar to the pink flatworm but more uniformly colored.

Found under stones and in shaded crevices — slides gracefully over rocky surfaces, nearly transparent in bright light.

Observed at

Bajo Piles I(Cabo de Palos)El negre(Barcelona)Punta Cana(Costa del Maresme)Pedra de Déu(Illes Medes)Ancora del Negre(Costa del Maresme)La Calzada(Costa del Maresme)El Trencat(Costa del Maresme)Ferranelles(Illes Medes)Els Canons de Tamariu(Begur)

Violet sea slug

Hypselodoris picta(12 photos)

Up to 6 cm5–40mRocky reef

A beautiful nudibranch with a bright blue-purple body edged in yellow-gold, with yellow-tipped rhinophores and gills. One of the Med's most photogenic sea slugs.

Glides slowly over sponge-covered walls — look for the contrasting blue and yellow coloring against dark rock surfaces.

Observed at

La Calita(La Herradura)Montelivi(Sant Feliu de Guíxols)Punta de la Mona(La Herradura)

Cratera flatworm

Cratera peregrina(11 photos)

Up to 5 cm3–25mRocky reef

A terrestrial flatworm that has invaded Mediterranean gardens, but the marine sighting refers to Cratera peregrina — a flat, leaf-shaped worm with brown stripes on a pale body.

Glides across rocky surfaces using muscular contractions — paper-thin and surprisingly fast for a flatworm.

Observed at

Barreta d'en Serra(Costa del Maresme)Dofí Nord(Illes Medes)

Paraflabellina ischitana

Paraflabellina ischitana(5 photos)

Up to 4 cm5–40mRocky reef

A vivid Mediterranean aeolid nudibranch with a translucent pink-purple body and clusters of cerata tipped in white above an orange band. Named for the island of Ischia.

Observed at

Piedra del Hombre(La Herradura)Pedra de Déu(Illes Medes)Punta de la Mona(La Herradura)Las Planetas(Sant Feliu de Guíxols)Montelivi(Sant Feliu de Guíxols)

African chromodorid

Chromodoris africana(4 photos)

Up to 4 cm5–30mRocky reef

A striking chromodorid nudibranch with a blue-black body ringed in orange-yellow, endemic to West African and Macaronesian waters.

Crawls on sponge-covered rocks in Canary Islands waters — a special find for nudibranch enthusiasts visiting the eastern Atlantic.

Observed at

S.S. Thistlegorm(Sharm El Sheikh)El Malek(Hurghada)

Candy-striped flatworm

Prostheceraeus vittatus(4 photos)

Up to 5 cm1–30mRocky reef

A polyclad flatworm (not a true nudibranch) with a cream body finely lined with dark longitudinal stripes and a delicate ruffled margin. Two raised pseudotentacles mark its leading edge as it glides over rock with smooth, undulating motion.

Fontandraui's chromodoris

Hypselodoris fontandraui(4 photos)

Up to 5 cm5–40mRocky reef

A vibrant nudibranch with a blue-white body, two bright yellow dorsal stripes, and yellow-tipped rhinophores. Similar to the violet sea slug but with more pronounced yellow markings.

Found on sponge-encrusted rocky walls in the Mediterranean — a prized macro photography subject.

Observed at

Punta de la Mona(La Herradura)La Calita(La Herradura)

Brown flatworm

Yungia aurantiaca(4 photos)

Up to 6 cm2–30mRocky reef

A flat, oval marine flatworm (not a true nudibranch) with a velvety brown surface, often with lighter margins. Paper-thin and remarkably flexible.

Glides over rocky surfaces and under stones — can swim briefly by undulating its body edges like a magic carpet.

Observed at

Pedra de Déu(Illes Medes)

Edmundsella pedata

Edmundsella pedata(4 photos)

Up to 4 cm5–40mRocky reef

A small Mediterranean aeolid nudibranch with a translucent violet body and clusters of cerata tipped in orange-red. Slender oral tentacles and rhinophores. Long known as Flabellina pedata and Coryphella pedata.

Feeds on hydroids on rocky walls, typically in shaded areas — often overlooked due to its small size.

Observed at

Bajo de Dentro(Cabo de Palos)El Jardín y La Red(Sant Feliu de Guíxols)S'Adolitx(Sant Feliu de Guíxols)

Argo dorid

Platydoris argo(2 photos)

Up to 7 cm3–35mRocky reef

A large, flat dorid nudibranch with a firm, leathery rust-brown to reddish body finely mottled with paler blotches and a granular surface. Mostly shelters beneath stones by day.

Villafranca sea slug

Felimare villafranca(2 photos)

Up to 3 cm3–35mRocky reef

A small dark-blue chromodorid speckled with rounded yellow spots and rimmed by a yellow margin. A Mediterranean species of rocky reefs and Posidonia meadows.

Dondice

Dondice banyulensis(2 photos)

Up to 6 cm5–35mRocky reef

A striking aeolid nudibranch with a translucent white body and dense clusters of brown-orange cerata tipped in white. Named after Banyuls-sur-Mer where it was first described.

Feeds on hydroids and anemones on rocky walls — stores stinging cells from its prey in its cerata for self-defense.

Observed at

Punta de la Mona(La Herradura)

Flabellina babai

Flabellina babai(2 photos)

Up to 3 cm5–35mRocky reef

A small, delicate nudibranch with translucent white body and clusters of cerata. Very similar to Flabellina affinis but typically smaller with subtle differences in cerata arrangement.

Found on hydroid colonies on shaded rocky walls — requires close inspection to distinguish from related flabellina species.

Observed at

La Calita(La Herradura)

Tricolour sea slug

Felimare tricolor(1 photos)

Up to 4 cm5–40mRocky reef

A small Mediterranean chromodorid with a deep blue body crossed by fine cream-yellow longitudinal lines and edged with a bright yellow margin. Slimmer and smaller than the violet sea slug.

Orsini sea slug

Felimare orsinii(1 photos)

Up to 3 cm5–40mRocky reef

A small blue-violet chromodorid marked with a fine yellow midline and a yellow margin. One of the smaller Felimare species of the Mediterranean.

Red Sea nembrotha

Nembrotha megalocera(1 photos)

Up to 12 cm5–30mCoral reef

A large, spectacular nudibranch with a black body decorated with vivid red-orange patches and spots. One of the most dramatic nudibranchs in the Red Sea.

Crawls on tunicates (its food source) on reef walls — large, bold, and slow-moving, making it an outstanding photography subject.

Observed at

Gorgonian Garden(Hurghada)

Armina

Armina tigrina(1 photos)

Up to 8 cm5–40mSandRocky reef

A flattened, elongated nudibranch with a velvety texture and distinctive tiger-stripe pattern — dark lines on a pale body. Has feathery gills on the underside.

Burrows in sandy sediments near rocky reefs — occasionally found on night dives crawling across open sandy areas.

Observed at

Badalona(Barcelona)

Log your dives

Track every dive with depth, duration, conditions, and marine life sightings. Join a club and share your underwater experiences.

Try DiveLog — it's free

Taxonomy

Class: invertebrate
Order: Nudibranchia
Family: Nudibranchia

21 species · 122 photos

Spotted sea slugDiscodoris atromaculata30
Flabellinopsis affinisFlabellinopsis affinis19
Prostheceraeus roseusProstheceraeus roseus13
Violet sea slugHypselodoris picta12
Cratera flatwormCratera peregrina11
Paraflabellina ischitanaParaflabellina ischitana5
African chromodoridChromodoris africana4
Candy-striped flatwormProstheceraeus vittatus4
Fontandraui's chromodorisHypselodoris fontandraui4
Brown flatwormYungia aurantiaca4
Edmundsella pedataEdmundsella pedata4
Argo doridPlatydoris argo2
Villafranca sea slugFelimare villafranca2
DondiceDondice banyulensis2
Flabellina babaiFlabellina babai2
Tricolour sea slugFelimare tricolor1
Orsini sea slugFelimare orsinii1
Red Sea nembrothaNembrotha megalocera1
ArminaArmina tigrina1

Habitat

Rocky reefCoral reefSand