Velella Velella

By Curt Beebe (bio)   Updated 6-5-02

Mike Baird and I collected some fresh Velella velella as they blew up on the beach. I floated these in a pan, and took photo Number 1. Notice the tentacles hanging down at the bottom of the picture.

The jellies’ mantle is water repellent on its upper surface. This causes the organism to right itself if tipped over by a wave.  

Jellies are very fragile. As autolysis began the tentacles were shed first. They can be seen lying on the bottom of the pan in picture Number 2.

My understanding is that Velella medusae are communal hydroids, and each tentacle is an individual. The clear base of the tentacle contains a branch of the communal stomach, which is how each individual gets its share of the catch.

When autolysis was complete only the chitinous sail mechanism remained.

Number 3 shows the rectangular
base of the sail mechanism, that
attached to the jelly. I am gripping the “sail.” 
Number 4 records growth rings
particularly well.

Number 5 shows the sail base
from its side.  
The base has a twist in it, as
shown further in Number 6.

When the wind blows on the sail, Velella first turn sideways, and begins to drift downwind. The twist of the base makes drag greater on the left; that twists the organism counterclockwise, and the Velella begins to sail!

Velella live in the open ocean. Off our coast Velella sail 45 degrees to the left of downwind, at mild and moderate wind velocities. (1) During the winter southwesterly blows this helps keeps them off our shore. However, with the advent of prevailing northwesterlies in spring, large numbers can be blown ashore. The same phenomena occur in Australia, in the winter and spring of the southern hemisphere.

Biologically, it is a simple trick to reverse symmetry. Velella off the coasts of Japan and Chile tack in the opposite direction! The winds blow in opposite directions from here, and the twist of the base is opposite. (One of you world travelers PLEASE bring me a picture.)

[Editor's note: here is an example from the UK, where the twist appears to be opposite] velella_co.jpg (37022 bytes)

Massive beachings of Velella are not common. The last one in this area was in ’89 or ’90. (2)

1. Lane Community College web site (Oregon) 
2. Central Coast Audubon hotline

Addendum by Mike Baird
Here are some additional related Internet references:

PBS - The Voyage of the Odyssey - Voice from the Sea  (this is a pretty good article)

By-the-Wind Sailor Velella velella  (this contains a neat 360 degree image)

Jack-Sail-By-The-Wind (Velella velella  

Okinawa Slug Site

Monterey Bay National Marine Sanctuary "special Velella link" at (link may have expired)

Waste Magazine (in Spanish) article 


Fisheries Centre, The University of British Columbia 

Dock Watch Identification Chart for Jellies 

British Marine Life Study Society Jellyfish Page 

eNature article (click here) (more info

Hydrozoa by Peter Schuchert 

Australian "southernshores"

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