By-The-Wind-Sailor - Velella velella

Photograph by Peter Parks

This relative of the Portuguese Man-O-War (Physalia), another siphonophore, is known as a By-The-Wind-Sailor or Jack-Sail-By-The-Wind. Like the Man-O-War, it is not a single animal but a colony of individual hydroid polyps, known as 'persons'. Stinging persons, which fringe the central disc, numb its prey. The large mouth, below the disc, is surrounded by reproductive persons. The air-filled buoyancy chambers of the disc create a float (usually less than 6 cm long) which bears a triangular sail and causes this planktonic animal to remain on the ocean surface, drifting with the currents. These floating hydroids are cosmopolitan in warm to warm-temperate waters, they often become stranded on beaches all along the west coast of America, usually in late spring or early summer. Velella eats a variety of other planktonic forms such as fish eggs and copepods, and is in turn eaten by other surface drifting animals such as the Blue Sea Slug (Glaucus) and the Purple Bubble Raft Snail (Janthina). More images of the whole surface drifters community can be viewed in the Surface Drifters Catalogue pages.

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