How big is a Box Jellyfish? How big do they get? Also read about their eyes and venom
Here in this post, we will know about the Box Jellyfish species and about how big they are. And, not only these we’ll also know much more related things about them.
So, just keep reading!
The Box jellyfish belong to the Cass Cubozoa of the Phylum Cnidaria of the animal kingdom.
They are extensively marine invertebrates distinguished by their cube-shaped umbrella-like body along with many tentacles coming out of the umbrella part of the body.
Some of the box jellyfish species are also venomous in nature as they can produce extremely potent venom that is painful and can be fatal to humans. Like for example, Chironex fleckeri (Sea wasp or Australian box jellyfish), etc.
They can be mostly seen in the warm coastal waters around the world. Most probably the coastal waters from northern Australia and New Guinea to Malaysia.
The Philippines and Vietnam coastal regions also hosts a lot of them.
The fatal species of the box jellyfish varieties are found primarily in the Indo-Pacific region and northern Australia parts. This includes the Australian box jellyfish (Chironex fleckeri) which is considered the most venomous marine animal.
(Image Source: Avispa marina.jpg: Guido Gautsch, Toyota, Japanderivative work: Mithril / CC BY-SA)
How big is a box jellyfish? How big do they get?
The species of box jellyfish are really big and the adult jellyfish are 2 to 3 times larger than an adult human being.
The body of a jellyfish exhibits radial symmetry and is divided into three main parts: the umbrella, the oral arms (around the mouth), and the stinging tentacles.
The total length of an adult box jellyfish can measure up to 320 cm in length which includes the length of the Umbrella which is 20 cm in length along with the length of the tentacles which is about 300 cm in length.
Each side of its umbrella body-portion can have a diameter of about 30 cm at least. Its umbrella portion can be comparable to the size of an adult human head.
That’s why it is said that an adult box jellyfish that has fully grown can get amazingly bigger than us when we measure it including its 300 cm long tentacles along with its 20 cm long umbrella part of the body.
There are about 15 tentacles on each corner of the umbrella portion, attached to it. Each tentacle can have more than 500,000 cnidocytes (stinging cells), containing microscopic nematocysts that can inject venom into the victim.
All due to such a huge size, the weight of the box jellyfish can reach only a maximum of 2 kg which equals 4.4 pounds as a whole.
How big is the biggest box jellyfish?
Chironex fleckeri, also known as the Sea wasp or Australian box jellyfish, is the largest species of the box jellyfish.
They are the most well-known marine stingers, that live primarily in the coastal waters off Northern Australia and throughout the Indo-Pacific regions.
They are pale blue and transparent in color and get their name from the cube-like shape of their bell (umbrella-like body).
Its body size can get reaching up to one foot (30 cm) in diameter and thickness. It has around 60 shoelace-like tentacles with each one that can go up to a length of about 10 feet (30 cm) long.
Its umbrella part of the body can grow to about the size of a basketball and that’s even a bit large than the human head. From each of the four corners of the umbrella comes out a cluster of 15 tentacles.
Due to their large body and large-sized tentacles, they are capable of achieving propulsion speeds of up to 1.5 to 2 metres per second or about 4 knots (7.4 km/h; 4.6 mph) that move them forward in the water.
And also due to this, they are considered fast swimmers, and studies have shown that the big box jellyfish can swim faster than any Olympic swimmer. That’s incredible, right?
They can very rapidly squeeze their umbrella-like bodies in order to push jets of water from the bottom of their bodies to propel the jellyfish forward at a rapid speed.
How their size ranges from larva to adult?
The life cycle of box jellyfish includes the Planula larval stage, Polyp stage, Ephyra stage, and Medusa stage.
The planula stage is the tiny larval stage of the jellyfish that shows an oval structure with the outer layer being lined with minute hairs called cilia. The planula larva floats for a few days on the surface of the water.
The diameter of each planula larvae can range between 0.50 mm to 0.60 mm. This size may vary depending on the species.
Next, after settling to the seafloor, the planula larva will form a cylindrical, stalk-like structure that attaches to a hard surface and transforming it into a polyp stage.
Large polyps are 10 millimeters (mm) or larger in diameter. The polyp stage is also known as scyphistoma.
Next comes the Ephyra stage of development. Ephyra stage is the free-swimming jellyfish stage that comes before full-grown medusa. It is the stage of the larval jellyfish after it has been separated from the scyphistoma (polyp stage).
Each Ephyra can range from only a few millimeters to a few centimeters in diameter and length. They are much larger than Polyps, but will feed and grow, and if it survives then it will become a mature box jellyfish, possibly weighing and lengthening as that of an adult.
Soon they will reach, the adult medusa stage of their life cycle, where they will gain a maximum of 320 cm in body length with its umbrella part being 20 cm in length and the tentacles being 300 cm in length only. Their umbrella will gain a diameter of about 30 cm at least.
Box jellyfish do not have long lives. They may spend less than a year in the medusa form and only a few months as a polyp.
And, this entire cycle can take place over the course of two years or less.
Do they shrink in size if they don’t eat?
Box jellyfish feed on small fishes, arrow worms, annelid worms, mantis shrimps, and prawns. They can even feed on other crustaceans as well, and even on other jellyfish as well.
Box jellyfish are usually seen to eat at least two to three times a day or more. Small ones are seen to most often eat prawns and big ones have been noticed to eat meaty fishes.
It has also been seen that, if they don’t feed on anything, or they are being caged and deprived of feeding then they will gradually shrink in size within a day or two. In general, if they don’t eat they will surely shrink.
It has been estimated that a big box jellyfish can lose up to 30% of its body weight within 24 hours if it doesn’t eat.
So, you may not know if the box jellyfish is feeding well or not in the open sea. So, looking at its size won’t give you a better indication of its age.
So, that’s why you will often notice researchers and scientists studying their eyes rather than their full bodies in the best way possible to tell the age of a jellyfish.
The fact is that the box jellyfish’s eyes are the best organs to notice in order to measure their age and not by looking at the size of their body.
If they are hungry, or whenever their size have shrunk for not feeding well, then they will actively hunt their prey by finding it and chasing after it very fast. During that time, they will eat whatever they can get their tentacles on as they are carnivores.
Are box jellyfish the most venomous jellyfish in the world?
Australian box jellyfish (Chironex fleckeri) which is also known as the sea wasp is the most venomous jellyfish in the world.
Not only in the list of jellyfish, but the Australian box jellyfish is considered the most venomous marine animal as well.
All jellyfish will sting you with venom if their tentacles come in contact with you but only about eight or nine species of jellyfish are dangerous. Australian box jellyfish is the one which is in the list of the most venomous.
They can be very easily seen in coastal waters from Northern Australia and New Guinea to Malaysia, to the Philippines and Vietnam as well.
Their 60 of the tentacles contain millions of cnidocytes (stinging cells) with nematocysts. These nematocysts attached to each cnidocyte are with tiny microscopic darts loaded with deadly toxic.
The large-sized adults are more venomous than the smaller ones. Their sting once touched with the human skin can produce an intense pain action accompanied by an intense burning sensation as well.
The pain is like that of being ironed and burned with an extremely red hot iron rod.
Once stung by a box jellyfish, it will soon result in a high-level increase of the Potassium ions in the blood. This can cause initial symptoms of severe stomach pain, nausea, and vomiting along with headache, muscle pain as well.
If an extreme level of envenomation occurs then this can often lead to cardiovascular arrest and death as quickly as within two to five minutes. But, it has been seen that most encounters appear to result only in mild envenomation.
Their venom is considered to be among the most deadly in the world, containing toxins that attack the heart, nervous system, and skin cells.
It is so overpoweringly painful that the human victims have been known to go into shock and drown or die of heart failure before even reaching shore.
Do box jellyfish have eyes?
Yes, box jellyfish have eyes. In fact, box jellyfish are the only species that have eyes. Big box jellyfish like the Chironex fleckeri (Australian box jellyfish) and other Chironex sp. have 24 eyes in total.
Till now we have learned about the fact that jellyfish don’t have eyes. But this is one of the most bizarre facts that only the Big box jellyfish have eyes and moreover not two or four eyes, that’s a total of 24 eyes.
Strange, isn’t it?
In common with other box jellyfish, Chironex fleckeri has four eye-clusters (eye-structures) with 24 eyes. That is their every eye-structure has 6 eyes.
The eyes of a box jellyfish are located on the circular structure in the middle of the bottom edge of the jellyfish’s bell. The jellyfish has four such structures. Regardless of the jellyfish’s position, the upper lens eyes are well-oriented so they look upward.
The two of the eye structures i.e. the upper and lower lens eyes can form images and resemble the eyes of vertebrates like humans. The other eyes are more primitive.
Some of these eyes seem capable of forming images, but whether they exhibit any object recognition or object tracking is still being a topic of debate and further research.
It has been already known that box jellyfish’s vision allows them to perform simpler tasks, like responding to light and avoiding obstacles.
It is a bizarre fact that they do have eyes because scientists are still confused about how they process information from their sense of touch and eye-like light-detecting structures without even having a central nervous system.
