Jack Sail-by-the-Wind or Velella Velella
Words by Maureen McCoy
Photography by Paul McCambridge
A strange creature has been washing up on the beaches of Donegal, at first sight I, and many others on the beach, thought they were mussels. Why would mussels, usually holding so firmly on to rock or rope, have detached themselves from their beds? On closer inspection these dark blue shells were perhaps only half the mussel, broken apart by stormy seas? As each wave flushed more to be stranded in the sun, it looked as though the top layer of shell was peeling off. Like fine clear silicone with a spider web pattern, but this wasn’t mother of pearl with its rainbow colours and pearlescent sheen. This was transparent and it was not a layer peeling off but a tiny sail atop a tiny raft. Twisting slightly as it stretched over the length of the shell in a long thin S shape with fine spokes fanning out connecting a series of concentric growth rings, a delicate pattern so like the spiders web.
I picked one up and as I set it on my hand I was surprised to feel its soft underbelly on my skin. I immediately thought of oh-so-innocent looking jellyfish with their vicious tentacles and decided that perhaps it was not a good idea to handle them – I wasn’t stung though.
No-one seemed to know what they were, so snaps were taken and google was activated, I introduce you to –Jack Sail-by–the-Wind (or Velella velella)
The science bit;
About 6cm long they are widespread in the oceans where they float on the surface with their tiny sails driven by the wind. There are two kinds with the sails running in the opposite diagonal across the raft, so some will always sail to the left of the wind, some always to the right.
The little raft is a float, filled with many air sacks, on its underside are attached a colony of cnidarians – (specialized ocean surface animals which include the Portuguese man o’ war) but although they do possess nematocysts – (the stinging bits of jellyfish) they are relatively harmless to humans – (some people can be irritated by contact so best not to rub your eyes or face after handling them). They are related not only to jellyfish but to anemones and coral.
Also known as Sea raft, purple sail, little sail.