By-the-wind sailor
Velella velella
IUCN Status:Not Evaluated
Often mistaken as a jellyfish, they're actually a pelagic (open-water) colony of hydrozoan (Cnidaria) polyps, which serve different functions: feeding, by trapping prey using stinging cells (known as nematocysts), cells which contain zooxanthellae (producing nutrients from sunlight in a mutualistic relationship), and reproductive polyps.
What do they look like?
Their bright blue characteristic sail gives them their name: by-the-wind sailor, velum being the latin for 'sail'.
Where can they be found?
Typically southern and western coasts, and occasionally as far north as the Hebrides. November is often the best month for beach finds, as the month often brings the first of the the winter storms.
Did you know... The lifecycle is complex, going from polyp-medusa-egg-planula-polyp. The reproductive polyps “bud” off tiny medusae, which look like small jellyfish, then the medusae sink to deeper waters and produce sperm and eggs released into the water column for fertilization. Once fertilised, the planula larvae develops into a polyp and the life cycle begins again.
Key facts
They're passive in nearly everything they do - they have little independent form of movement and drift at the whim of the wind, literally sailing through life. They tend to aggregate in swarms and can be found washed up in their hundreds or even thousands after stormy weather.
They use stinging tentacles to prey on young fish and other small animals while they travel. Thankfully, their venom is considered harmless to humans, but some people may react to it.
| IUCN status | Not Evaluated |
|---|---|
| Habitat | Strandline, pelagic / open ocean |
| Diet | They feed on young fish, zooplankton and fish eggs. |
| Sting strength | Unlike the Portuguese man o' war, a sting from a by-the-wind sailor is mild and their venom is considered harmless to humans. |
| Length | A small creature at 7-10cm long, with the sail standing at around 5cm tall. |
| Weight | Being so small they're incredibly light, with a 0.09g dry land weight. |
| Speed and distance | By-the-wind sailors can travel thousands of miles as they are completely reliant on the current of the ocean. |
| Lifespan | A very short life span of a couple of months, with a maximum of one year. |
