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Interesting Facts about Box Jellyfish
[Box Jellyfish Phylum: Cnidaria] [Subphylum: Medusozoa] [Classification: Cubozoa (cube jellyfish)]
There are about 50 box jellyfish species, free-swimming cnidarian invertebrates that are easily distinguished from other sea jellies by the cuboid medusae (box-like body).
This section contains essential facts about box jellyfish (class Cubozoa) including where they are found, what they eat, and how these pelagic cubozoans reproduce.
Box Jellyfish Geographic Range and Habitat
Cubozoans have a fairly significant distribution worldwide, but they are more abundant in the Indo-Pacific regions, especially:
- Australia (Queensland, the Northern Territory, and Western coasts)
- PNG and Malaysia (including Indonesia, Philippines, and Thailand)
- Pacific Islands (Fiji, Hawaii, Micronesia, and Polynesia)
- India, Sri Lanka, Maldives, Seychelles, (and parts of East Africa)
- Eastern Pacific (Central America, Panama, and South America)
- Western Atlantic (e.g., Caribbean Sea, Gulf of Mexico, and Florida)
There are about two hundred different types of jellyfish around the world. But the box jelly tends to inhabit shallow coastal waters where seawater clashes with freshwater, such as estuaries, mangrove creeks, and lagoons.
Despite the infamous notoriety, not all of the box jellyfish species are poisonous. However, the harmful toxins from the Australian box jelly (Chironex fleckeri) make it one of the most venomous of all creatures.
Pro Tip: In many parts of Southeast Asia and northern Australia, the "stinger season" for dangerous box jellyfish occurs most during the warmest months, typically between October and May.
Box Jellyfish Characteristics Cubozoa
Some of the funniest fish names also relate to the common names of Cubozoa jellyfish. For example, people often call them sea nettles, sea wasps, or marine stingers.
As they move through water, the movement differs to that of most pulsating jellyfish. Box jellies are able to propel themselves, sometimes jetting around at seven kilometres per hour.
Here's the thing:
They are lightweight marine predators with long venomous tentacles. The medusa, a cuboid bell, is usually clear or transparent with a hint of pale blue colour.
So, it creates superb camouflage for clear tropical waters and it means they are almost invisible to snorkelers and scuba divers.
The anatomy of a jellyfish is basic, and there is no central nervous system to process what they see. Instead, they have a cluster of 24 eyes (20 of which are eye spots) located on each of the four sides of the bell.
Their complex system for vision, and for image formation, is made of an advanced retina, cornea, and an iris with a sophisticated lens.
Box Jellyfish Size and Weight
Most species of box jellyfish have up to fifteen (15) tentacles that dangle from each corner of the bell margin. But, being contractile means box jellyfish tentacle length varies from a few centimetres long or up to three (3) metres.
Even though the gelatinous body can be up to three (3) metres long and 25 centimetres across, it's mostly water. So, even the biggest box jellyfish (Chironex fleckeri) rarely weigh more than a few kilograms (4 pounds).
What Do Box Jellyfish Eat?
Unlike some jellyfish types that drift with ocean currents and filter their food, the distinctive box jellyfish anatomy is one that's well suited for an active hunter.
By and large, the primary diet of box jellies is one that includes small fish, shrimps, crustacean larvae, and other tiny invertebrates that drift with planktonic matter.
Interesting Fact: They use powerful stinging barbs and deadly venom to stun and paralyse their prey - followed shortly after by death.
Types of Box Jellyfish Species
Australian Box Jelly (Chironex fleckeri)
The quantity of venom that the victim is subjected to correlates to the extent of the damage received and the seriousness of the injury. The box jellyfish species Chironex fleckeri is attributed to more than 100 known deaths.
This jellyfish has toxins so immensely poisonous, marine biologists suggest that one death-dealing animal can kill 60 adults.
In fact, biochemists have discovered exactly how the Chironex fleckeri delivers its fatal venomous sting.
The lethal blow is delivered by a proteinous chemical which makes the victim's cell walls leak potassium directly into the bloodstream.
Excessive potassium is called hyperkalemia. It causes almost immediate death.
Within three minutes of a sting attack, the victim suffers shortness of breath combined with intense pain and probable cardiac arrest often resulting in death.
Urgent medical attention is needed after being stung by this box jellyfish. You can treat the wounded area with vinegar to reduce the pain and to inhibit firing of further nematocysts.
Use tweezers or gloves (not bare hands) to remove the visible tentacles. You should contact EMS while monitoring the victim's vitals and administer CPR if necessary.
Preventing the Sting
Even if you suspect Chironex fleckeri may be present at your favorite dive site, you may not necessarily need to cancel your dream diving holiday to the Great Barrier Reef. Jellyfish stings need pressure and a chemical on the skin to trigger the nematocysts.
Without direct contact with the chemical, the tentacles do not fire the stinging cells. Try to cover all bare skin as much as possible with a full body wet suit or dive skin with booties and gloves.
Curiously, biologists have found that almost all jellyfish dislike the color red. Red wet suits are not popular or fashionable but you could wear a red rash guard, skin top or your favorite red t-shirt over your normal thermal protection.
Chirodectes Maculatus Jellyfish
[Phylum: Cnidaria] [Class: Cubozoa] [Family: Chirodropidae] [Species: C. maculatus (spotted)]
A worthy candidate for the rarest species of jellyfish is the Chirodectes maculatus - a monospecific genus of the box jellyfish.
In fact, divers who were diving off the coast of Queensland in Australia on 2nd of May 1997 were the only humans that had seen it and they filmed this extremely rare spotted box jellyfish - an extraordinary and exceptional creature discovered underwater.
Chirodectes Maculatus Size
It has four separate and distinct groups of tentacles that trail behind its translucent body. It also contains a bright red organ inside the center of the bell, which measures about fifteen (15) centimetres in height (5.9 inches).
Scientists believe it is the gastrovascular cavity, used as the primary organ for digestion and circulation in jellyfishes.
Here's the good news:
An observational study carried out in 2005 suggests that the Chirodectes maculatus is not venomous. This is still unknown because zoologists were reluctant to dissect it.
The animal failed to sting or adhere to a human hand or forearm during the examination. As a result, there are no recorded cases of a human sting from Chirodectes.
Related Information and Help Guides
Note: The main section contains a marine invertebrates list with detailed information about animal species that do not possess a vertebral column or spine.
Bonaire Banded Box Jellyfish (Tamoya ohboya)
Carukia Barnesi
Carybdea Confusa
Fire Jelly (Morbakka fenneri)
Four-handed Box Jellyfish (Chiropsalmus quadrumanus)
Gershwinia Thailandensis
Gorilla Box Jellyfish (Chirodropus gorilla)
Habu Box Jellyfish (Chironex yamaguchii)
Irukandji Jellyfish (common kingslayer)
If you want to learn about a rare box jellyfish, the Malo kingi and the Carukia barnesi are some of the least spotted box jellyfish in any of the seas and oceans.
Mangrove Box Jellyfish (Tripedalia cystophora)
Mediterranean Box Jelly (Carybdea marsupialis)
Pelagia Noctiluca
Sea Wasp (Alatina alata)
South African Box Jellyfish (Carybdea murrayana)
Tamoya Haplonema
Box Jellyfish Venom
The venom of the box jellyfish ranks as one of the world's most deadly poisons. These rapid-acting, protein-based toxins attack skin cells, heart muscle, and the nervous system.
As a consequence of that, contact with the box jellyfish's tentacles may lead to severe shock symptoms, weeks of excruciating pain, skin scarring, heart failure, and death.
However, the stinging cells (called nematocysts) are "fired" by physical contact with a chemical - and not by touch alone.
How Do Box Jellyfish Reproduce?
Like many other cnidarians, such as corals and sea anemones, box jellyfish reproduction also includes sexual and asexual stages.
Asexual Reproduction (Polyp Stage)
Some polyps reproduce asexually - either through a process of budding or by dividing itself into smaller segments (known as strobilation).
- Budding polyps can produce new polyps that can either remain attached by the stem or they can completely detach and form new individuals.
- In strobilation, the polyp segments into ephyrae - which are disc-like sections that form immature medusae. They eventually detach themselves and develop into adult medusae to complete the life cycle.
Sexual Reproduction (Medusa Stage)
Depending on the species, there are some adult jellyfish that release sperm and eggs into the water column. This process means fertilisation can either occur internally inside the female jellyfish or externally in the water.
Once fertilised, the tiny eggs start to develop into a free-swimming planula larva - a phenomenon copied by some coral species and sea anemones. The larvae eventually find a suitable surface to settle on and develop into polyps.
Threats and Predators
It would be unusual for any of the box jellyfish species to live for much more than one (1) year. But, in spite of the "danger" they pose to humans, they still remain as an important part of the food web that face natural predators and threats to the oceanic environments in which they live.
Box Jellyfish Predators
- Sea turtles (especially the hawksbill sea turtle and the loggerhead turtle)
- Fish (e.g., batfish, butterflyfish, and rabbitfish)
- Crustaceans (especially crabs)
- Other jellyfish (some of the large jellyfish species consume box jellyfish polyps and juveniles)
- Seabirds (feeding on stranded medusae that wash ashore)
Localised scientific research suggests jellyfishes do better than most other marine invertebrates in areas affected by human activities.
Nonetheless, typical examples of human-induced threats to the long term survival of box jellyfish include garbage pollution, habitat destruction, climate change, coastal development (such as artificial and unnatural lighting), and overfishing.
Interesting Fact: The IUCN list of endangered species does not see any specific risk to the conservation status of box jellyfish (Cubozoa).
Related Information and Help Guides
- Best Home Treatment for Jellyfish Stings and Bites
- Common Jellyfish Species List with Pictures
- Jellyfish Anatomy: Parts of a Jellyfish Explained for Beginners
- Fun Fact: Portuguese Men-of-War are Not Jellyfishes
- Symptoms of Box Jellyfish Sting and First Aid Treatment
Pro Tip: The short video [2:05 minutes] presented by "Deep Marine Scenes" contains even more box jellyfish facts with some amazing footage of Chironex fleckeri swimming in their natural habitat.