Details
Glaucus atlanticus
The blue glaucus is a tiny nudibranch that floats near the sea surface with blue, winglike lobes. It eats stinging animals and stores their defenses in its own body.
Map: Ecoregions 2017 © RESOLVE (CC BY 4.0) · Natural Earth (PD)
It drifts in warm surface waters of the Atlantic, Pacific, and Indian oceans, both offshore and near coasts. Winds and currents sometimes strand it on beaches.
Length 2-4 cm; weight 0.1-3 g. A deep blue underside and silvery back provide countershading at the surface. Fingerlike cerata spread from the sides, giving it a starry outline.
Cathemeral and solitary, it floats upside down by holding air in the body. Waves and surface currents carry it between patches of prey.
A carnivore, it feeds on floating cnidarians such as Portuguese man-of-war. Stinging cells from prey are stored in the cerata and reused for defense.
Individuals are hermaphrodites and lay strings of eggs after mating. Eggs may be attached to floating material or prey remains, and larvae drift in the plankton.
It is listed as Least Concern, but it can still sting through stored nematocysts. Stranded animals should not be handled bare-handed.
