Browse sea slugs by color
Twelve primary colors as entry points into the nudibranch and sea slug catalog. Each card explains how that color works biologically — aposematism, structural color, kleptoplasty, crypsis — and shows a representative species. For the full primary-literature take, see Are nudibranch colors really "structural"?.
Red赤
Red sea slugs are textbook examples of aposematism. By feeding on sponges and cnidarians, they sequester carotenoid pigments and chemical defences, advertising their unpalatability with vivid red. Phyllidiidae and Hypselodoris are classic exemplars of this honest-signal strategy.
Browse species in this color →Brown茶
Brown serves both algal mimicry and benthic camouflage. Aplysiidae blend into seaweed while many Aglajidae and Doridoidea melt into muddy or sandy substrates. Despite its plain appearance, brown is the most taxonomically diverse colour group.
Browse species in this color →Orange橙
Orange in sea slugs typically reflects sequestered β-carotene-class pigments. Plocamopherus and Trapania species display vivid orange accents on processes and rhinophores, advertising sequestered chemical defences to potential predators.
Browse species in this color →Pinkピンク
Pink hues typically originate from sponge-derived carotenoids or from structural colour. Tritoniidae and Cratena wear soft pinks while feeding on cnidarians whose nematocysts they recycle into their own cerata for defence.
Browse species in this color →Yellow黄
Yellow comes from carotenoid pigments sequestered from sponges or algae. The lemon yellow of Phyllidia and the sulphur yellow of Notodorididae have evolved as aposematic warning colours, signalling chemical defence.
Browse species in this color →Green緑
Green sea slugs are mostly Sacoglossa. They suck chloroplasts from algae and keep them functional inside their own cells — a phenomenon called kleptoplasty. Some Elysia species can survive on photosynthesis alone for months.
Browse species in this color →Blue青
True blue pigments are rare in the sea. The vivid blues of Chromodoris and Hypselodoris come from pixel-organised guanine nanocrystals in the skin — a matte, angle-independent structural colour sharpened as an aposematic signal. The pelagic Glaucus atlanticus instead floats upside-down at the surface, exposing its blue ventrum to the sky and its silvery dorsum to the depths in an inverted countershading.
Browse species in this color →Purple紫
Purple emerges either by blending blue and red pigments or by sequestering dietary pigments. The purple bands of Chromodoris and Hypselodoris are derived from sponge pigments and pair with strikingly symmetrical patterning to form clear aposematic signals.
Browse species in this color →White白
White sea slugs are not as plain as they look — black, orange or red edging on rhinophores, cerata and gills sharpens contrast and turns white into an aposematic signal. The white grounds of Chromodoris and Goniodoridae have evolved repeatedly as minimal but loud warning colours.
Browse species in this color →Gray灰
Grey acts as cryptic camouflage on sandy and muddy substrates and algae-covered rocks. Aglajidae and Discodorididae often combine grey grounds with fine speckling, blending into the substrate and matching their relatively sedentary lifestyle.
Browse species in this color →Black黒
Black ground colours work in concert with vivid blue, yellow or orange bands to create high-contrast warning signals. The blue-black bodies of Tambja and Nembrotha with yellow or orange bands advertise chemical defences sequestered from bryozoan and other prey.
Browse species in this color →Transparent透明
Transparency is the open-water camouflage of pelagic sea slugs. Pteropods (Thecosomata / Gymnosomata) and Glaucus atlanticus dissolve into the surrounding seawater and drift through the open ocean nearly invisible to predators.
Browse species in this color →