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 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 called cubozoans, were grouped with other jellyfish. In 1973, scientists found they were different enough to give them their own class. This was because of how they develop and their body shape.

As of 2018, there were at least 51 known species of box jellyfish. They are sorted into two main groups called orders and eight families. Scientists keep finding new species, so there are probably more to discover.

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 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 have true eyes with parts like retinas, corneas, and lenses. These eyes are arranged in clusters on structures called rhopalia. This helps them 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 warm oceans around the world. You can find them in 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.

In 2023, scientists found a new type of box jellyfish in the Gulf of Thailand. Named Gershwinia thailandensis after scientist Lisa-ann Gershwin, this one looks different because it has special sensory horns.

Detection

Detecting box jellyfish, also called cubozoans, can be hard because they are clear, come in different sizes, and have two life stages. Old ways to find them include watching, using nets, or attracting them with light, but these ways have problems.

A new and easier way to detect box jellyfish is by using environmental DNA (eDNA). This method takes water samples and looks for tiny bits of genetic material left by the jellyfish. By studying this DNA, scientists can know if box jellyfish are in an area, helping to watch their numbers in a cheaper 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. These 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. They can swim quickly, up to 2 meters per second, and can even avoid obstacles. They catch their food, like small fish and prawns, using their tentacles and special venom. This venom 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.

Genetics

Box jellyfish have special DNA in their cells arranged into eight chromosomes. As of 2022, scientists have studied the DNA of only two box jellyfish species, Alatina alata and Morbakka virulenta. The species A. alata has more genes than any similar creature. The DNA of box jellyfish is arranged uniquely, 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 have a very strong sting that can be dangerous to humans. Some species, like Chironex fleckeri and Carukia barnesi, have venom that can be deadly. Their venom can cause skin irritation and heart problems. In some cases, it can be fatal.

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

Protection and treatment

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

If a box jellyfish stings you, flushing the area with vinegar can help. 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 home remedies have not been proven to work. Scientists are researching possible antidotes.