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are by the wind sailors jellyfish ?

# Are By-the-Wind Sailors Jellyfish?

A recent invasion of bright, blue, sail-like creatures along the beaches of Southern California has brought a renewed fascination with one of the sea’s most unique inhabitants: the By-the-Wind Sailor, or Velella velella. But what are these organisms, and are they really jellyfish? As it turns out, although they share some characteristics with jellyfish, the by-the-wind sailor is in a class of its own.

## What Are By-the-Wind Sailors?

By-the-wind sailors, scientifically known as Velella velella, are hydrozoans, a class of organisms that belong to the same larger group as jellyfish, anemones, and corals. Found floating on the surface of the open ocean, these creatures rely on the ocean’s currents and the wind to drift along, hence the common name, ‘by-the-wind sailors.’ They get their scientific name, Velella, which means ‘to sail’ in Latin, from the characteristic sail-like appendage that enables them to harness the wind to navigate the seas.

The by-the-wind sailor’s sail and distinctive blue color are some of its most obvious features, but it is its colonial structure and unique lifecycle that further set it apart. Velella velella have both polyp and medusa forms, which is not common in the jellyfish world. However, in contrast to jellyfish, they do not have a single bell that pulsates for movement. Instead, the individual organisms collectively form a colony with a sail, and they appear to travel as a single unit.

## Velella velella and Jellyfish: Relations and Differences

Although they are not true jellyfish, by-the-wind sailors belong to the same phylum as jellyfish—Cnidaria. They contain the same type of stinging cells or cnidocytes, which they use to catch small fish and plankton. However, the stinging cells of Velella are significantly less potent than those of some jellyfish species and are considered harmless to humans.

True jellyfish, like moon jellies and sea nettles, have a single, pulsating, bell-shaped body that propels them through the water. In comparison, Velella velella do not swim, they drift. The sail function primarily allows them to drift along wind-lines, effectively catching the wind in a manner similar to a sailboat, a mechanism that is not found in traditional jellyfish.

## The Environmental Factor

The phenomenon of vast numbers of by-the-wind sailors washing ashore, like what was observed recently in southern California, is not uncommon due to the weather conditions and the wind. These creatures can be pushed ashore in large numbers when winds are strong, and this event often results in enormous ‘wash-ups’. Beach visitors might be intrigued, and sometimes alarmed, by the sight of hundreds of these small, blue, sail-like bodies on the shore.

## Are They A Harmful Species?

While the stinging cells they possess can paralyze small fish and invertebrates for feeding, for humans, they’re mostly harmless. The presence of their stinging cells can sometimes cause irritations or allergic reactions on human skin, so it’s advisable to handle them with caution. However, despite the ability to sting, they are generally considered harmless and are more of a fascinating sight than a threat.

## Conclusion

In summary, the by-the-wind sailor or Velella velella might appear to be a jellyfish at first glance, but they are a fascinating and distinct group in the vast marine ecosystem, classified under the Hydrozoa suborder Velellidae. While sharing some anatomical features with jellyfish, they diverge in several key aspects, from their method of locomotion (sailing the surface) to their multi-form colonies. These enchanting creatures are a tangible example of the complex and varied evolutionary responses to marine pressures, all the more fascinating for their unusual adaptations and movements across our planet’s oceans. The stories of these small blue creatures add another layer to the mystery and wonder of our vast oceanic world.