Box Jellyfish, are marine creatures belong to the Cubozoa class and are renowned for their cube-shaped bells and potent venom. Unlike their other jellyfish cousins, box jellies have a distinct allure. With various species scattered across our oceans, each one has its unique charm and mysteries, and many have a notorious sting that can be very dangerous for humans.
Within their distinctive class, there are two orders of box jellyfish – Carybdeida and Chirodropida, each with their own defining characteristics. Within the order Chirodropida there are three different families, and within Carybdeida there are five. Across this range of families there are a number of different genera and at least 51 species of box jellyfish that are known to exist today. It is believed though, that there are more yet to be discovered, as we explore more of our vast and virtually unobserved, deep oceans.
Most species are found in the warm tropical and subtropical waters around the central Atlantic and Pacific Oceans, particularly around the Indo-Pacific biogeographical region.
Appearance & Characteristics of the Box Jellyfish
Imagine a transparent, cube-shaped bell floating in the water, trailed by tentacles – that’s the box jellyfish for you! They can vary enormously in size, with the smallest species – Carukia barnesi having a bell diameter of around two thirds of an inch, while the largest, – Chironex fleckeri can have a bell reaching up to 30 cm in diameter.
But that’s not all; their tentacles can stretch out to an astonishing 3 meters! These tentacles, though delicate and almost invisible, are equipped with specialized cells called nematocysts. When triggered, these cells release venom, making the box jellyfish a formidable predator in the ocean. Their venom is used primarily to catch prey but can also come in handy for defence.
Larger species of box jellyfish are known to be incredibly good swimmers, rather than drifters like their ‘true jellyfish’ relatives. They use their swimming skills to actively hunt, and can reach speeds up to around 4.5 miles per hour (7.4 km/h)!
Another class defining feature the box jellyfish display, is that they have a total of 24 eyes, across several rows, with each set having it’s own role, design and function.
The box jellyfish, or Cubozoans, are primarily divided into two main orders: Carybdeida and Chirodropida. Here’s a breakdown of the differences between the two:
Tentacles: Carybdeida species typically have four tentacles, one hanging from each corner of their bell.
Size: They are generally smaller than Chirodropida species.
Bell Shape: The bell is usually more cube-shaped.
Venom: While they can deliver painful stings, most species in this order are not considered as dangerous to humans as some Chirodropida species. However, there are exceptions, such as the Irukandji jellyfish (Carukia barnesi), which can cause the potentially fatal Irukandji syndrome.
Distribution: Found in various parts of the world, including the Pacific and Indian Oceans.
Families: This order includes five families: – Alatinidae, Carybdeidae, Carukiidae, Tamoyidae, and Tripedaliidae.
Tentacles: Chirodropida species have multiple tentacles (more than four) hanging from each corner of their bell.
Size: They are generally larger, with some species having a bell diameter of up to 30 cm.
Bell Shape: The bell is more elongated and boxy.
Venom: Contains some of the most venomous species of jellyfish, including the infamous Australian box jellyfish (Chironex fleckeri). Their stings can be extremely painful and potentially fatal to humans.
Distribution: Predominantly found in the waters of the Pacific region, especially around Australia and Southeast Asia.
Families: This order is primarily made up of the family Chirodropidae, but also includes two more families: – Chiropsalmidae and Chiropsellidae.
While both orders belong to the class Cubozoa and share many similarities, they can be distinguished based on their tentacle number, size, venom potency, and distribution.
Five Common Species of Box Jellyfish:
Chironex fleckeri: Often referred to as the Australian box jellyfish, this species is known for its potent venom and is considered one of the most dangerous jellyfish in the world.
Carukia barnesi: Commonly known as the Irukandji jellyfish, its sting can lead to the potentially fatal Irukandji syndrome.
Alatina alata: Found in the waters of the Pacific and Atlantic Oceans, this species is known to cause Irukandji syndrome but is less potent than Carukia barnesi.
Chiropsalmus quadrumanus: Also known as the four-handed box jellyfish, it is found in the western Atlantic Ocean and has a potent sting.
Tripedalia cystophora: A smaller species found in the Caribbean and known for its unique habitat among mangrove roots.
Distribution – Location and Habitat
Box jellyfish can be found around the world, mostly in warm, tropical and subtropical waters. Most species thrive in the warm waters of the Pacific Ocean, making their homes from the coasts of Australia to the shores of Thailand and even up to Japan. Some species though, can be found as far south as New Zealand, or as far north as Hawaii or the coastal waters of California.
These creatures have a penchant for shallow waters, especially those near coastlines and river mouths, where they can easily find their prey. Some are known to prefer mangroves and kelp forests, where prey is abundant.
The Lifestyle & Behaviour of the Box Jellyfish
As mentioned above, unlike many other jellyfish that drift with the currents, box jellyfish can propel themselves forward, reaching speeds that rival a leisurely human walk. Their advanced navigation skills are attributed to their cluster of eyes, which help them avoid obstacles and predators. As night falls, these nocturnal hunters ascend closer to the water’s surface, hunting and feeding in the moonlit waters.
Little is known about the behaviour or any habitual acts that these jellyfish perform, other than for the purpose of hunting or reproducing.
Box Jellyfish Sting
How dangerous are they? Well, not all box jellyfish are dangerous, but many from the order Chirodropida are extremely dangerous! Their venom is potent enough to be fatal, even for humans!
How painful are they? Immensely! Many victims have described it as the most excruciating pain they’ve ever felt.
Which ones have the worst sting? The crown goes to the Australian Box Jellyfish (Chironex fleckeri) for having the most venomous sting.
Are they dangerous to humans? Absolutely, especially the Chironex fleckeri. Their sting can cause serious harm and even be lethal if not treated promptly. Vinegar is known to help deactivate or prevent the release of further venom, and in areas where venomous jellyfish are common, it is often made available to public beaches.
Research continues to find an antidote to the venom of these jellyfish, as in severe cases, a sting can cause death in as little as 2 to 5 minutes. The venom can cause hyperkalaemia, which can ultimately lead to cardiovascular collapse and death.
Diet & Nutrition of the Box Jellyfish
Box jellyfish are carnivorous hunters. The specific diet does vary by species, but across the range, they are known to feast on small marine invertebrates, as well as other small jellyfish of other species. They also enjoy crustaceans like prawns, and other tiny marine creatures. They use their venomous tentacles to immobilize their prey. Once captured, the prey is transported to their mouth-arms, where it’s consumed.
Predators & Threats to the Box Jellyfish
Despite their venomous reputation, box jellyfish do have their threats. Some species of sea turtles, with their thick shell and skin, are immune to their stings and are known to eat them quite contently. Some species of crab – particularly the blue swimmer crab – again with a good armour to the sting, are also fond of a box jelly meal. There are a few species of fish too though, including batfish and butterfish, that are brave enough to prey on box jellyfish.
Humans, though mostly unintentionally, pose the biggest threat by ensnaring them in fishing nets or polluting their habitats.
The Box Jellyfish Reproduction
The world of box jelly reproduction is fascinating and it varies depending on the order. In both cases, when it is time to reproduce, the jellyfish move to shallower, coastal inland waters to lay and fertilize eggs. This usually happens in spring, and box jellyfish only produce one hatch of offspring.
Those of the Chirodropida order are oviparous, and reproduce through external fertilization. For these jellyfish, the female releases her eggs, and the male releases sperm into the water at the same time, to fertilize the hatch.
Those of the Carybdeida order reproduce ovoviviparously through internal fertilization, where the male transfers sperm to the female. Eggs eventually hatch into larvae and these larvae, called planulae, float in the ocean until they find a suitable spot to settle. Once settled, they transform into polyps and eventually mature into the box jellyfish we recognize.
Lifespan of the Box Jellyfish
The life of a box jelly is fleeting yet full. They live for about a year, transitioning from minuscule larvae to the tentacled creatures we are more familiar with. Each stage of their life, from larvae to polyp to mature jellyfish has it’s own season.
Interestingly, like the mayfly, once mature box jellyfish have spent their spawn, they don’t live for very much longer.
Population and Conservation
Box Jellyfish are not currently listed as a species of interest or concern by the IUCN. However, as with all marine life, they play a vital role in the ecosystem and their well-being is intertwined with the health of our oceans.
5 Fun Box Jellyfish Facts for Kids
- Box jellies have up to a whopping 24 eyes!
- They’re speedsters, swimming as fast as we walk.
- Sea turtles munch on them without any worries.
- They’re mostly water, with a dash of mystery.
- Some box jellyfish can light up, glowing beautifully in the dark!