Sea Wasp: Characteristics, Morphology, Habitat, Reproduction

The sea ​​wasp or Chironex fleckeri is a jellyfish that belongs to the cubozoa class of the phylum Cnidaria. It is famous worldwide for the toxicity of its venom, which has been responsible for the death of some bathers on the Australian coast.

It was first described in 1956 by Australian physician Ronald Southcott. The scientific name derives from the Greek word cheiro which means “hand” and from the Latin nex which means “murderer”. The second word in the name is in honor of Dr. Hugo Flecker, a native of Queensland, who studied the effects of jellyfish poisons.

Chironex fleckeri specimen. Source: Sea Wasp.jpg: Guido Gautsch, Toyota, Japanderivative work: Mithril [CC BY-SA 2.0 (]

Despite the fact that its venom is quite powerful, there have been cases of animals that are immune to it, such as some species of sea turtle.

Article index

  • one


  • two


    • 2.1

      They are multicellular eukaryotes

    • 2.2

      They are diblastic

    • 23

      Half life

    • 2.4

      They show radial symmetry

    • 2.5

      Produce toxins

  • 3


    • 3.1


    • 3.2


    • 3.3

      Receptor organs: ocelli and statocysts

    • 3.4

      Digestive system

    • 3.5

      Nervous system

    • 3.6

      Reproductive system

    • 3.7

      Respiratory system

  • 4

    Habitat and distribution

  • 5


  • 6


  • 7


  • 8

    Chironex fleckeri sting: signs and symptoms

  • 9



– Domain: Eukarya.

– Animalia Kingdom.

– Phylum: Cnidaria.

– Class: Cubozoa.

– Order: Cubomedusae.

– Family: Chirodropidae.

– Gender: Chironex.

– Species: Chironex fleckeri.


They are multicellular eukaryotes

Chironex fleckeri is an organism that is made up of eukaryotic cells. This means that its genetic material is located in a cellular organelle known as the cell nucleus, delimited by a membrane.

Similarly, the tissues of this jellyfish are made up of various types of cells, each with its specific characteristics and functions, which gives it the name of a multicellular organism.

They are diblastic

In its embryonic development stage, two germ layers appear: ectoderm and endoderm. These layers are fundamental, since all the tissues and organs that make up this animal are differentiated from them.

Half life

The half-life time of the sea wasp is quite short, compared to other species of jellyfish. According to studies, it has been established that these jellyfish can live up to three months.

They show radial symmetry

The jellyfish of the Chironex fleckeri species show radial symmetry. This means that all parts of the body are arranged around a central axis. This is a characteristic common to all organisms of the phylum cnidaria.

Produce toxins

The Chironex fleckeri, to the same as the other members of the phylum cnidaria presents cells called cnidocitos that are responsible for synthesizing a toxic substance used to paralyze and kill their prey. The toxin from this jellyfish has multiple effects on various organs, since it acts at the level of the muscles, the nervous system, the heart muscle and the blood level.


As in all jellyfish, during their lifetime sea wasps present two appearances, that of a polyp and that of a jellyfish itself. This will depend on the phase of its life cycle in which the animal is.


The Chironex fleckeri polyp is similar to the other polyps that occur in the phylum cnidaria. They are fixed to the substrate and present an oral region, the body and the basal area.

Through the basal area the polyp is fixed to the substrate. At the upper end are tentacles that it uses to catch its prey and bring it to its mouth.


Taking into account that the Chironex fleckeri belongs to the class cubozoa, it is not surprising that it shares the same morphology as the rest of the members of that class. This jellyfish is characterized by its cube or square box shape.

The umbrela is translucent and also has bioluminescence, so it has the ability to glow in the dark. It can reach measurements of up to 24 cm. Likewise, in terms of weight, it can weigh up to 2 kg.

In the lower part of the umbrella you can see the typical jellyfish manubrium, at the end of which the oral opening is located. The mouth opens the way to the so-called gastrovascular cavity, which occupies almost the entire internal part of the umbrela of this jellyfish.

At the corners of the umbrella there is a structure known as a pedal. From it the tentacles emerge. Approximately 15 tentacles emerge from each pedal, giving a total of 60 tentacles for each specimen. The tentacles can be up to 3 meters long.

The tentacles are full of nematocysts (millions), which are made up of cnidocytes. These are cells that have the ability to synthesize and release the toxins of this jellyfish. Because of this, it is claimed that this jellyfish is one of the most poisonous and toxic in the world.

Chirnonex fleckeri nematocysts. Source: Brinkman DL, Aziz A, Loukas A, Potriquet J, Seymour J, Mulvenna J [CC BY-SA 3.0 (]

Likewise, they present a structure known by the name of velario. This is located along the entire length of the lower edge of the umbrella. The function of the velario is twofold: to restrict the opening of the umbrella and help in the displacement of the jellyfish, creating a jet when the umbrella hits a surface.

Receptor organs: ocelli and statocysts

Similarly, sea wasps have a structure known as a ropalio on the umbrella. They have four in total, which have a preradial location. The ropalios carry ocelli (simple eyes) and statocysts.

With regard to the ocelli, in number of 24, they present certain structures similar to those of the eyes of more developed animals. They have a vitreous body, retinas, and lenses. With these receivers they cannot perceive their surroundings clearly and clearly, differentiating shapes and colors, but only distinguish light or dark.

In this way, using the ocelli the sea wasps can orient themselves during their movement by the marine currents. Likewise, they can perceive some contours, which makes it easier for them to capture their prey.

On the other hand, statocysts are common organs in invertebrate animals and their function is to help the body maintain balance at all times during its movement.

Digestive system

It is quite simple, just like in the rest of the jellyfish. Features a single opening at the end of the handlebar. This opening has a double function: that of the mouth and anus. This hole communicates with a space called the gastrovascular cavity. This is where the digestion of nutrients takes place.

The gastrovascular cavity is divided by four septa into four gastric pouches and a central stomach.

Nervous system

The sea wasp’s nervous system is made up of an intricate network of nerve fibers that have both multipolar and bipolar neurons. They also have a large number of receptors that are arranged throughout the umbrella.

Among the receptors, the ropalios and the statocysts already mentioned above stand out. In addition, it is important to mention that they have another type of receptors, the cnidocilia, which are responsible for perceiving signals related to tactile stimuli.

Reproductive system

It is made up of four gonads that are located in pairs on both sides of each septum in the gastrovascular cavity. In these gonads the gametes or sex cells are produced, which are later released for reproduction.

Respiratory system

The Chironex fleckeri you lacks organized structures and specialized to carry out the process of breathing. This is because, since they are such simple organisms, oxygen diffuses directly through the body wall.

Habitat and distribution

Chironex fleckeri is a jellyfish found almost exclusively on the north coast of Australia. It has been located mainly in Exmouth, the Gulf of Carpentaria and on the coast of Queensland. It constitutes a great threat to bathers on the beaches of these towns.

However, although it was believed to be unique to Australia, specimens have also been found in other areas of the Indo – Pacific Ocean, such as the Philippine Islands, Vietnam and Papua – New Guinea.

It is believed that sightings in these distant areas may be due to a fortuitous event, because these jellyfish can move and cover great distances in short periods of time.


The jellyfish of this species are heterotrophic. They are also carnivorous, and feed mainly on small fish and crustaceans that they get in shallow waters where there is a high density of potential prey.

The way the feeding process occurs is as follows. The jellyfish identifies, through its receptors located in the clothing, the possible prey. Immediately, with the help of the tentacles, it inoculates the toxin to the prey, which dies almost instantly. This is due to the powerful toxicity that the venom of this jellyfish has.

Once this is done, the jellyfish, with the help of its tentacles, directs the prey towards the mouth, introducing it there to be digested.

In the gastrovascular cavity, the prey is subjected to the action of a wide variety of digestive enzymes that process it and convert it into nutrients that are absorbed. Subsequently, the waste from this digestion is expelled through the mouth.


As regards the reproductive process, it takes place in the spring season. Although the habitat of this jellyfish is in the seas, reproduction occurs in fresh waters.

Fertilization in these jellyfish is external. Both the eggs and the sperm are released into the water and there they fuse, giving rise to a larva that has a flat shape, known as a planula.

This larva travels for a short period of time in the current, until it finds an ideal place in the substrate to establish itself with the help of its tentacles. There the polyp forms. It remains in this form for a time.

Finally, the polyp undergoes a metamorphosis until it becomes a small jellyfish, which begins to move until it is again in its natural habitat in marine ecosystems.

It is important to note that parental care is not contemplated in this type of jellyfish. Adult jellyfish simply release gametes to the outside for fertilization to occur.


The toxin synthesized and secreted by Chironex fleckeri is considered one of the most powerful and toxic on the planet. So much so that this jellyfish has been called the most dangerous and poisonous of all known species.

The deadly efficacy of this toxin lies in the fact that it is composed of chemical compounds that affect different organs of the body.

These compounds include:

– Myotoxin (T1 and T2). They directly affect muscle tissue. Specialists consider that they interfere with the transport of certain very important ions in the contraction process, such as calcium and sodium.

– Hemolysin. This is a substance that greatly affects the plasma membrane of red blood cells, causing the formation of pores in them. This results in the death of the cell by cell lysis.

– Neurotoxins. They are toxins that notably interfere with the conduction of nerve impulses, greatly hindering the proper functioning of the nervous system.

– Hemolytic toxin. It is a chemical compound that causes irreversible damage to red blood cells, destroying them entirely.

Those mentioned above are types of compounds found in the venom of Chironex fleckeri . However, only a few proteins have been completely sequenced. The best known and most studied are CfTX-A and CfTX-B. Both proteins are common in other members of the phylum cnidaria and have potent hemolytic activity.

Chironex fleckeri sting : signs and symptoms

Due to the fact that Chironex fleckeri abounds in beach areas, accidents involving contact with it are common, the bite being the most frequent.

The mere brushing with the tentacles of this jellyfish already causes a reaction to be triggered in the victim. Initially the signs and symptoms that may appear are:

– Shooting and uncomfortable pain.

– Marks that show contact with the tentacles. They can be purple, reddish, or even brown.

– Edema of the affected area.

– Unbearable burning.

– Uncontrollable itching

However, as the time elapsed after the bite progresses, the toxin begins to affect some body systems, generating specific reactions in them. Among the systemic symptoms caused by Chironex fleckeri toxin are the following:

– Difficulty breathing.

– Heart failure.

– Severe headache.

– Muscle spasms.

– Nausea and vomiting.

– Neurological effects: drowsiness, confusion, fainting.

It is important to mention that the sting of this jellyfish is so dangerous that it can cause death due to multi-organ failure, especially when affecting the heart and lungs.

Currently, specialists are working on the development of an antidote against the venom of this jellyfish. There have been promising advances, so it is hoped that in the future an antidote in the form of a spray or cream will be available to minimize the damage that sea wasps cause on the beaches of the Australian coast.


  1. Brinkman, D., Konstantakopoulos, N., McInerney, B., Mulvenna, J., Seymour, J., Isbister, G. and Hodgson, W. (2014). Chironex fleckeri (Box jellyfish) Venom Proteins. Journal of Biological Chemistry. 289 (8). 4798-4812.
  2. Curtis, H., Barnes, S., Schneck, A. and Massarini, A. (2008). Biology. Editorial Médica Panamericana. 7th edition.
  3. Fenner, PJ (2000). Chironex fleckeri  - the north Australian box-jellyfish.
  4. Hickman, CP, Roberts, LS, Larson, A., Ober, WC, & Garrison, C. (2001). Integrated principles of zoology (Vol. 15). McGraw-Hill.
  5. Ponce, D. and López, E. (2013) Jellyfish: the dancers of the sea. Biodiversitas. 109. 1-6
  6. Tobin, B. (2010) Dangerous marine animals of Northern Australia: Sea Wasp. Australian Institute of Marine Science.

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