Box jellyfish

Box jellyfish are special kinds of creatures known as cnidarians, and they don’t have a backbone like humans do. They are called “box” jellyfish because their body looks like a cube. These animals have long, thin tentacles that can sting anything they touch.

Some box jellyfish have a very strong poison, or venom, in their tentacles. When they sting, this venom can hurt people a lot and, in some cases, be very dangerous. There are a few species, like Chironex fleckeri, Carukia barnesi, and Malo kingi, whose stings can be especially harmful. However, not all box jellyfish are the same—some, like Carybdea murrayana, can sting and cause pain but are not usually dangerous to humans.

Even though some box jellyfish can be dangerous, they are important parts of the ocean’s ecosystem. They eat small fish and other tiny sea animals, helping to keep the balance of life in the sea. Scientists study them to learn more about their venom, which might help in making new medicines one day.

Taxonomy and systematics

Historically, box jellyfish, also known as cubozoans, were grouped with other jellyfish until 1973. That year, scientists realized they were different enough to give them their own class because of how they develop and their body shape.

As of 2018, there were at least 51 known species of box jellyfish. They are organized into two main groups called orders and eight families. Scientists continue to discover new species, so there are likely more out there waiting to be found.

The box jellyfish class, Cubzoa, includes:

• Order Carybdeida
  • Family Alatinidae
  • Family Carukiidae
  • Family Carybdeidae
  • Family Tamoyidae
  • Family Tripedaliidae
• Order Chirodropida
  • Family Chirodropidae
  • Family Chiropsalmidae
  • Family Chiropsellidae

Description

The box jellyfish has a unique square-shaped body, which gives it its name. From each corner of this box hangs a long, thin tentacle that can deliver venom. These jellyfish can move very quickly, up to 1.5 metres per second, by pulsing their bell-shaped body.

Box jellyfish have a complex nervous system and special eyes that help them see. They possess true eyes with retinas, corneas, and lenses, arranged in clusters on sensory structures called rhopalia. This allows them to navigate their environment, avoid obstacles, and swim in specific directions. Depending on the species, a box jellyfish can be up to 20 cm (8 in) across, with tentacles that can stretch up to 3 m (10 ft) long. Even small species, like the thumbnail-sized Irukandji, can be dangerous due to their venomous tentacles.

Distribution

Box jellyfish live in tropical and subtropical oceans all around the world, from about 42° N to 42° S. You can find them in places like the Indo-Pacific, the Atlantic Ocean, and the east Pacific Ocean. Some have even been seen as far north as California and as far south as South Africa and New Zealand.

Recently in 2023, scientists discovered a new type of box jellyfish in the Gulf of Thailand. Named Gershwinia thailandensis after scientist Lisa-ann Gershwin, this species stands out because it has special sensory horns and a different digestive system than other box jellyfish.

Detection

Detecting box jellyfish, also known as cubozoans, can be challenging because they are transparent, come in different sizes, and have two life stages. Traditional methods like watching for them, using nets, or attracting them with light can work but have limits.

A newer, easier way to detect box jellyfish is by using environmental DNA (eDNA). This method collects water samples and looks for tiny bits of genetic material left behind by the jellyfish. By studying this DNA, scientists can tell if box jellyfish are present in an area, helping to monitor their numbers in a cost-effective way.

Main article: Environmental DNA

Ecology

Box jellyfish have a fascinating way of growing. Researchers can tell their age by looking at special structures in their bodies, called statoliths, which grow in layers each day. For example, the Chironex fleckeri species grows about 3 mm each day and can live up to three months in the wild.

These jellyfish are active hunters, unlike some other jellyfish that just drift along. They can swim quickly, up to 2 meters per second, and can even avoid obstacles. They catch their food, like small fish and prawns, by using their tentacles and a special venom that helps them catch prey and stay safe from predators like certain fish and turtles.

Box jellyfish have interesting ways of reproducing. Some species release eggs and sperm into the water, while others transfer sperm directly inside the female. Recent studies suggest that some box jellyfish might be able to reproduce more than once in their lifetime, which is different from what was previously believed.

Genetics

Box jellyfish have a special kind of DNA found in their cells that is arranged into eight linear chromosomes. As of 2022, scientists have fully studied the DNA of only two box jellyfish species, Alatina alata and Morbakka virulenta. The species A. alata has a very large number of genes, more than any other similar creature. The DNA of box jellyfish is arranged in a unique way, with each chromosome containing a few genes, including two extra ones that help make important proteins. Only a few studies have looked closely at how these genes work in box jellyfish.

Danger to humans

Box jellyfish are known for their powerful sting, which can be very dangerous to humans. Some species, like Chironex fleckeri and Carukia barnesi, have venom that can be deadly. Their venom contains many toxic proteins, which can cause skin irritation, heart problems, and in some cases, can be fatal.

In Australia, the Chironex fleckeri jellyfish is responsible for many serious stings. This species has caused many deaths since the 1880s. In other places like the Philippines, Malaysia, and parts of the United States, other box jellyfish species have also caused fatalities. To help protect people, some beaches use nets to keep jellyfish away and provide vinegar for first aid after a sting.

Protection and treatment

Wearing pantyhose, full body lycra suits, dive skins, or wetsuits can help protect against box jellyfish stings. These clothes work because the stinging cells on the jellyfish’s tentacles react to chemicals on human skin, which are not found on the clothing material.

If a box jellyfish stings you, flushing the area with vinegar can help stop more venom from being released. It’s important to carefully remove any tentacles with a towel or gloved hand, as even detached tentacles can still sting. Some treatments like urine or heat packs may help with pain, but many other home remedies have not been proven to work. Scientists are researching possible antidotes, including creams that might neutralize the venom.