Living Color

Chromodoris sp.

Photographer David Doubilet introduces the glamour slugs of the sea.
Toxic nudibranchs—soft, seagoing slugs—produce a brilliant defense.

Yes, the first looks like a Pokemon, doesn’t he?

Mexichromis mariei
Size: 1.2 in (3 cm)

Nembrotha cristata
Size: 4.7 in (12 cm)

Phyllidia ocellata
Size: 2.4 in (6 cm)

Hypselodoris sp.
Size: 2 in (5 cm)

Nembrotha kubaryana
Size: 2.4 inches (6 centimeters)

Common hitchhiker, an imperial shrimp (Periclimenes imperator) feeds—perhaps on sea debris or fecal pellets—where its host, a Ceratosomanudibranch, has laid a ribbon of eggs. The shrimp benefits from the relationship, gaining a ride and access to food, but scientists don’t know whether the slug profits from the shrimp’s cleanup behavior.

Hypselodoris kanga, 1.6 inches long, uses its sticky foot to secure an egg ribbon extruded from an oviduct on its side; hatchlings by the thousands will soon disperse with the currents.

As adults, nudibranchs can be finicky eaters: A zebra-striped species ofArmina, a genus that ranges to 8 inches long, plays tug-of-war with its sole prey, the burrowing sea pen. A tiny blenny bystander picks the safer perch.

Photograph by Jennifer Hayes

Built to feed exclusively on corals like this spindly gorgonian, a translucent 1.7-inch-long Phyllodesmium iriomotense houses its branching digestive gland within tentacle-like cerata—outgrowths the animal can shed if under attack. This species is one of the few colorless nudibranchs.

Looking more flora than fauna, a plate-size “solar powered” nudibranch—Phyllodesmium longicirrum—farms zooxanthellae algae within its own body. Feeding on the soft coral Sarcophyton, the nudibranch pilfers algal cells and hoards them within its digestive system, which fills the paddle-shaped appendages called cerata. Stored just beneath the skin, the algae capture light energy, producing nutrients that can sustain the nudibranch for months. The same chemicals that feed the animal are also exuded from its skin as a defensive shield.

Flabellina exoptata
Size: 1.2 in (3 cm)

Cuthona sp.
Size: 0.7 in (1.8 cm)

Bornella anguilla flees danger by folding in its appendages and swimming like an eel.
Size: 2.8 in (7 cm)

Chromodoris annae compensate for their tiny size with loud, contrasting hues—warning predators of a toxic snack.
Size: 0.8 in (2 cm)

Chromodoris sp.
Size: 2.4 in (6 cm)

A hard body and thick skin help armor Halgerda batangas against predators. Any that persist learn that the sponge-eater also exudes a toxin.
Size: 1.6 in (4 cm)


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