In recent weeks there were several reports
of large numbers of Velella velella
floating close to the shore in several parts of Malta and Gozo. I also read
about large numbers invading the sea in southern Italy.
I had been seeing small numbers of this
interesting hydrozoan since late winter but a few days ago I was amazed to see
tens of thousands floating at the Blue Lagoon in Comino.
Velella
velella is a scientific name. It is commonly known
as by-the-wind-sailor or velella which is the name I prefer. The velella is also known as
sea raft, by-the-wind sailor, purple sail or little sail.
The velella is found in all warm and
temperature waters of all the oceans. The organism is like an oval,
translucent, deep-blue plastic with a transparent sail on top. It lives on the water surface and is at the
mercy of the wind, tides and currents for transport. It is often found in large
numbers and sometimes hundreds of thousands become stranded along the coast.
Each individual velella is a colony of
hydrozoans. It is made up of specialised polyps attached to a floating
structure. The various polyps in the colony have different structures and
responsabilities including feeding and reproduction.
The velella is carnivorous. It feeds on
small plankton which it catches by means of stings found on the tentacles of
some of its polyps. These stings are strong enough to immobilise very small
creatures but have no effect on man this species is does not sting and is
totally harmless.
The velella is preyed upon by a number of predators including
a purple snail. This snail has a very thin delicate shell and floats by
anchoring itself to a raft consisting of small air bubbles. Very often purple
snails are stranded together with the velella.
I got to know about the velella about
fifteen years ago when I photographed it in St Julians Bay. I do not recall
having ever seen it before then and I had spoken to many people about it to find
out whether they were familiar with this species. Many seemed to be unaware of
its existence.
Since I
first saw it, it seems to have become more common and nowadays I see it in
large numbers nearly every year. The increase in numbers of velella seems
to follow the increase in number of jellyfish to which the velella is related.
This article was published in The Times of Malta on 15 May 2014.
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