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Velella velella (Family Porpitidae)

By-the-wind Sailor

Distribution

Distribution:

Occurs all around Australia and widely occurring around the world. The By-the-wind Sailer is not an intertidal dweller, but is an occasional visitor, brought in by ocean currents from the tropical north, and is then blown ashore by prevailing north-easterly winds (QLD, NSW, VIC, TAS, SA, WA, NT).

Features:

The By-the-wind Sailer is a blue coloured colonial polyp that consists of a floating-oval-shaped disc about 10-15 mm across, with a thin, transparent, S-shaped, obliquely positioned sail across the top. Although there are no tentacles, it does contain bands or masses of nematocysts on the zooids. These are used like tentacles for trapping food while the By-the-wind Sailer is blown along.

The floating disc contains a set of air chambers, which keep the colony afloat and upright. The sail is thin, erect and transparent

Ecology/Way of Life:

The By-the-wind Sailer is most usually seen lying stranded and dying on the shore after heavy weather. It is only seen occasionally, but when they are blown ashore it is in very large numbers. It normally moves from place to place across the water using its sail that is driven by the wind. There are right and left handed forms of how the sail crosses the disk. The result of this is that the two forms are blown by the wind in different directions, so that they are not all blown ashore together. The floating disk is full of concentrically positioned air chambers that ensure that the By-the-wind Sailer always remains at the water's surface and is incapable of being submerged for long. The By-the-wind Sailer is often associated with the other pelagic drifter, the Portuguese man-o'-war or Blue Bottle. By-the-wind Sailers are preyed upon by two groups of pelagic molluscs of the families Glaucidae and Ianthinidae.

Preferred Image

Interaction with Humans/Threats:

Because this species is widespread throughout the world and around all Australian shores, it appears to be under no threat from human activities.

Other Comments:

Velella velella, (Linnaeus, 1758). Velella comes from the Latin word velum meaning a curtain, veil or sail.

Further Reading:

Bennett, I. (1987). W. J. Dakin's classic study: Australian Seashores: a guide to the temperate shores for the beach-lover, the naturalist, the shore-fisherman and the student. p.167, Angus & Robertson.

Davey, K. (1998) A Photographic Guide to Seashore Life of Australia. New Holland Press, p.34, Sydney.

Edgar, G.J. (1997). Australian Marine Life: the plants and animals of temperate waters. p.123, Reed.

Acknowledgments:

Text, map & photograph by Keith Davey.

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Images and Multi-media:  
Attached Image  
image/jpeg 115540 bytes By-the-wind Sailer
Distribution Map  
image/gif 1115 bytes Distribution of By-the-wind Sailer

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