By-the-Wind Sailor: Anatomy, Habitat, Diet & Other Facts

By-the-wind sailors are commonly known as Velella. Vevella is a single species, and Velella Velella is the name of that species in science.  These species are members of the Hydrozoa class’s monospecific genus.  They belong to the Porpitidae family and are frequently referred to as smaller species of jellyfish. But they are not true jellyfish.

The by-the-wind sailors are cosmopolitan hydrozoans that drift freely on the surface of the open ocean. You can call them simply Velella, little sail, purple sail, by-the-wind sailor, and simply sea raft. Their purple colors are attractive and captivating. Furthermore, their unique characteristics make them more fascinating creatures of the ocean.

Are you anxiously waiting to know some crazy facts about these sailors of the waters? Do you have curiosity about how they live, develop, and behave? You’re welcome here to unfold the secrets of these specialized species of jellyfish. Just sit back, eat your snacks, and read the article to get in-depth information about the by-the-wind sailors. Let’s begin now!

By-the-Wind Sailor

About By-the-Wind Sailor – A Quick Biology Table

Before deep diving into the ocean for insights about these marine animals, take a look at these quick bibliographical facts:

Scientific nameVelella velella (Linnaeus, 1758)
GenusVelella (Lamarck, 1801)
SpeciesV. velella
Habitat and geographical rangeCoasts of the Atlantic OceanCape HatterasCoasts of the Pacific Ocean
DietSmall plankton
Weight1 to 10 grams
Size6 to 20 centimeters in length
PredatorsPurple snails, ocean sunfish
LifespanFew months

Description and Anatomy of By-the-Wind Sailor

By-the-wind sailors have interesting anatomy. These are small cnidarians that belong to one of the specialized and important communities of the ocean surface. We are talking about cnidarian siphonophores here. Yeah, these are better known as the Portuguese man o’ war, according to the research of WildlifeTrust. ~ source

The bodies of the sea sailors are filled with gas that helps them float on the ocean surface. They have a stem-like structure located underneath the pneumatophore. This structure is known as hydrocaulus. Above all, their bodies are 95 percent water. Quite a surprising fact! 

Physical Characteristics of By-the-Wind Sailor

The by-the-wind sailors have unique physical characteristics. They can be recognized easily for their appearance and color. Every individual is part of a hydroid colony. Their length is only a few centimeters. This may range from 1 cm to 7 cm. Their colors are purple or deep blue. 

However, apart from all these characteristics, they have a unique feature that makes them stand out from the rest. We are talking about their small stiff sail. Yup, they can easily catch the wind. They can also propel it over the sea’s surface.

According to BBC News, these sea sailors can be stranded in thousands on specific beaches. They do this under certain weather or wind conditions. Their bodies are in the shape of a disk. This shape helps them to drift on the ocean surface. ~ source

They have multiple tentacles just like other species of sea jellies. The by-the-wind sailors also have a central mouth that is located underneath the float. Their sizes can also reach a few inches in diameter sometimes. Here are the photos and a short documentary film about by-the-wind sailors: 

Behaviors of By-the-Wind Sailor

Here are a few commonly known behaviors of by-the-wind sailors:

Buoyancy regulation

By-the-wind sailors have a gas-filled float that helps them stay afloat and move along with the winds. They can adjust the size and shape of their body to remain stable in windy and choppy conditions. This allows them to remain near the ocean surface. This also maximizes their exposure to sunlight for photosynthesis.


By-the-wind sailors possess tiny nematocysts, or stinging cells, which help them defend against predators. When threatened, they release these nematocysts, which can cause a painful sting to potential predators. They can also roll up their tentacles for self-protection.

Group behavior

By-the-wind sailors are known to form large aggregations or swarms that can cover vast areas of the ocean surface. These swarms are thought to serve several functions including the following:

  • Increasing the efficiency of reproduction
  • Enhancing the animals’ buoyancy
  • Providing protection against predators
See also  Sailfish Vs Marlin: What are the Differences?

Sensitivity to environmental factors

By-the-wind sailors are sensitive to changes in temperature, salinity, and other environmental factors. This behavior affects their buoyancy, movement, and overall survival. For example, changes in water temperature may cause the animals to migrate to different areas of the ocean. They do this in search of more favorable conditions.

Antifouling behavior

By-the-wind sailors have developed antifouling behaviors. This helps them to prevent the growth of other organisms on their float or tentacles. For example, they may shed their mucus strands or use their tentacles to remove unwanted organisms. This behavior helps to keep them clean and reduces the risk of infection.

Hope you like reading about the unique and amazing behaviors of these jellyfish. You can also read their hunting behavior and reproductive behavior in our following discussion. 

Adult By-the-Wind Sailor

Habitat, Range, and Distribution

By-the-wind sailors’ habitat includes warm and temperate waters. They are living in all oceans all over the world. They can survive in the water and air combo. 

It means they half sink in water and half in the air the water. In simple words, their floats are positioned above the waters. Also, their polyps dangle about a centimeter beneath the water’s surface.

Neuston is the term used to describe organisms that inhabit both the surface of the water and the air. By-the-wind sailors that partially float above and below the water are also known as neuston. On occasion, offshore boaters may come across vast numbers of wind sailors floating on the ocean surface.

The by-the-wind sailor has a small but stiff sail. It extends into the air and helps them to catch the wind. Its sail always aligns with the wind. It allows it to act like an airplane wing or aerofoil. Plus, it enables the creature to sail downwind at a slight angle.

Since by-the-wind sailors lack any means of propulsion besides their sail, it relies on prevailing winds to move across the ocean. It is consequently prone to becoming stranded en masse (all together) on beaches worldwide. Let’s take an example of this habitat here.

Mass Stranding Example:

A mass stranding event takes place along the West Coast of North America every spring. This phenomenon occurs annually. It started from British Columbia and moved progressively south over the course of several weeks. The event typically affects vast numbers of by-the-wind sailors. It led to their mass stranding on the beaches of California.

Occasionally, the number of stranded by-the-wind sailors is so high that the animals pile up on the tide line as the waves recede. The resulting line of dying and decomposing creatures can be several centimeters deep. It stretches along hundreds of kilometers of shoreline.

Reports of mass strandings of by-the-wind sailors have come from various parts of the world. The west coast of Ireland is one such location where these events have been observed. Hayle, located on the west coast of Cornwall in England, is another area where mass strandings have been observed and reported by a senior reporter, Lisa Letcher in the CornWallLive news.

Feeding Habits/ Diet of By-the-Wind Sailor

The by-the-wind sailors are carnivorous just like many sea jellies. They are capable of catching their prey/food easily with the help of their tentacles. Generally, they catch plankton which is their favorite dinner.

They are smart predators of plankton and they catch prey by hanging down their tentacles in the water. Their tentacles contain cnidocytes which are also known as nematocysts. These nematocysts contain toxins that help them hunt their prey.

All species of cnidarians have tentacles with toxins and nematocysts. However, only a few have powerful toxins as compared to other species of sea jellies in cnidarians. This feeding behavior is very common in jellyfish.

According to the researchers, by-the-wind sailors have nematocysts that are not typically harmful to humans. However, individual reactions to their toxins may vary. So, it’s best to avoid touching your face or eyes after handling them. Exposure to the nematocyst toxin can cause itching on the skin.

See also  Pajama Cardinalfish: Habitat, Diet, Anatomy & Fun Facts

Life Cycle and Reproduction System

The life cycle of by-the-wind sailors is characterized by two distinct stages. This is known as bipartite. This is a feature common to many Hydrozoa. The generations of these creatures exhibit a form of an alternation. This is where the life cycle switches between two different forms.

Many beachgoers recognized these deep blue sailors in their phase of a polyp. This is the one phase of the life cycle. These sea creatures may appear to be a single entity with a sail. But, it is actually a colony of hydroids consisting of numerous polyps that feed on plankton in the ocean.

A canal system interconnects the polyps within the hydroid colony. It allows them to share the food that any individual polyp consumes. Let’s see what we have found about these creatures from a research study.

“These wind sailors are composed of colonies that consist of only male or female polyps. The colonies of these sailors are made up of various types of polyps. Gonozooids are polyps responsible for reproduction and feeding purposes. On the other hand, dactylozooids of these jellyfish serve as a protective function.”

The gonozooids in a Velella colony create countless small organism. They do this via a process known as asexual budding. This means that the colony is capable of generating thousands of tiny purple sail within a short time. Each of the small sail measures approximately 1 mm in height and width.

Each tiny medusa produced by the gonozooids contains multiple zooxanthellae. These are single-celled organisms that live inside another organism in a mutually beneficial relationship. Zooxanthellae can harness sunlight to provide energy for the creature. Similar endosymbiotic organisms are found in corals and some sea anemones.

Conaria – planktonic larvae

It has been researched that healthy by-the-wind sailors in captivity are known to release many medusae. Still, it remains a mystery as to whether they do the same in the wild or not. It is because these medusae are rarely observed in the plankton. This scarcity of data makes it difficult to gain insights into the natural history of Velella.

However, laboratory experiments have shown that Velella medusae reach sexual maturity within a span of three weeks. Upon free-spawning, the fertilized eggs and sperm give rise to a planktonic larva. These planktonic larvae are known as conaria. These eventually develop into a new floating colony of Velella hydroids.

Cardiovascular and Nervous Systems

The cardiovascular and nervous systems of the by-the-wind sailor reflect its simple body structure. It also reflects relatively basic life functions. Let’s see how:

Cardiovascular system

The by-the-wind sailor does not possess a well-defined cardiovascular system. In other words, it does not have a complex nervous system. Instead, it relies on simple diffusion and movement of fluid to transport nutrients, gasses, and waste products throughout its body.

In addition, the by-the-wind sailor’s lack of a true cardiovascular system means something awesome. It is unable to regulate its internal fluid volume in response to changes in external pressure or temperature. This can make it more vulnerable to environmental stresses like fluctuations in salinity or sudden temperature changes.

Nervous system

Similarly, the by-the-wind sailor’s nervous system is quite primitive. It lacks a centralized brain. It has a nerve net that runs throughout its body. This network allows it to detect changes in the environment and coordinate basic responses. It consists of interconnected neurons that are distributed throughout the body and can communicate with each other.

One of the key functions of the by-the-wind sailor’s nervous system is to detect changes in the environment. It helps them to coordinate appropriate responses. For example, these marine animals may use their nerve net to detect the presence of predators or other potential threats. They can initiate defensive behaviors such as rapid movement or the release of toxins.

Threats and Conservation Status

By-the-wind sailors are generally not considered to be threatened by human activities. However, their populations can be impacted by the same threats that affect other marine species. These threats include the following:

  • Pollution
  • Climate change
  • Ocean acidification

In some regions, populations of these marine animals have been observed to wash up on shore in large numbers. They are potentially indicating a mass die-off event. This could be caused by factors such as changes in ocean currents or temperature. However, more research is needed to understand the underlying causes of such events.

See also  20 Deepest Sea & Ocean Creatures [with Photos]

Now, let’s talk about the conservation status of by-the-wind sailors. As a whole, there are no known conservation efforts specifically targeting by-the-wind sailors. However, their unique and fascinating biology makes them an important subject for scientific research. This can contribute to our understanding of marine ecosystems as a whole.

By-the-Wind Sailor on sand

Predators of By-the-Wind Sailor

The predators of the by-the-wind sailors are also specialized just like its community. Special gastropods mollusks prey on these aquatic animals. The two of these popularly known predators are: 

  • Sea slugs (nudibranchs)
  • Purple snails

Here, sea slugs belong to the genus Glaucus and the purple snails belong to the genus Janthina. Additionally, certain species of seabirds and fish also eat the by-the-wind sailors.

According to the researchers, quacks were found snacking on smacks. Here, they mean to say that Mallard ducks were found eating the by-the-wind sailors on the beach of Santa Margherita Ligure. 

Relationship with Humans 

By-the-wind sailors have a limited direct impact on humans, both positive and negative. Here are a few examples:


  • They are an important part of the ocean’s ecosystem. They serve as a food source for many marine animals.
  • Some people find them fascinating to observe. They may enjoy seeing them washed up on the shore.


  • When large numbers of by-the-wind sailors wash up on the beach, they can create an unpleasant smell as they decompose.
  • There have been reports of people experiencing skin irritation or allergic reactions. These reactions were observed after coming into contact with the tentacles of by-the-wind sailors. However, such cases are rare.

Systematics of the By-the-Wind Sailor

The Porpitidae family is composed of a group of hydrozoans that are characterized by their floating lifestyle on the ocean surface. The family consists of two genera named:

  • Velella
  • Porpita

Both of these families are known for their ability to live freely without attachment to any substrate. Taxonomists have been working on the systematic position of these genera. During the mid-to-late 19th century, the classification of the three genera under discussion was a matter of debate among scholars.

Some researchers grouped them with athecate hydroids. Others placed them under the category of Siphonophorae. In 1954, Totton introduced a new taxonomic order, Chondrophora, to accommodate the three genera. However, other scholars at that time still debated whether they should be classified under Anthomedusae/Athecatae or not.

Over the last four decades, the prevailing view among researchers has been that these creatures are distinctive floating colonial athecate hydroids. It is said that they release medusae that are unequivocally categorized under the Anthomedusae group. There are uncertainties about the placement of Porpitidae in the Athecatae/Anthomedusae classification. Hydrozoan systematists have ceased using the taxonomic order Chondrophora.


Can by-the-wind sailor sting you?

No. By-the-wind sailors do not usually sting humans. There are no reports that state about them that they sting a human or that harmful results are shown due to their sting. However, they belong to the venomous family that possesses nematocysts.

The nematocysts of these organisms are not powerful enough to penetrate human skin. They do not produce venom that could cause any significant harm. However, it is still recommended to avoid handling these creatures with bare hands. It is best to observe these creatures from a safe distance.

Can by-the-wind sailors survive out of the water?

No, by-the-wind sailors cannot survive out of the water for long periods. It is because they require seawater to stay hydrated.

Can by-the-wind sailors be kept in aquariums?

Yes, by-the-wind sailors can be kept in aquariums. However, they require specific environmental conditions and feeding requirements. It is recommended to leave them in their natural habitat.

Are by-the-wind sailor poisonous?

No. By-the-wind sailors are usually not poisonous to humans. They are not friendly or aggressive towards humans. However, they have algal symbionts. It means they can cause allergic reactions to your skin, as we have mentioned before.


By-the-wind sailors are like the cool kids of the oceans. They float around on their little sailboats. They love catching a tan and riding the waves like they’re at a beach party. We are sure they know how to live the sweet life on the high seas.

Hope you enhanced your knowledge about these aquatic friends!

Leave a Comment