10 Interesting Facts About Jellyfish

Most children are fascinated by these colourful, translucent and beautiful sea creatures and you can see them crowding round the displays in an aquarium. Jellyfish are amazing creatures, can be dangerous as well and range in size from small ones which you can hardly see to gigantic ones.

Here are 10 interesting and astonishing facts about these fascinating aquatic beings.

1. Jellyfish is not a fish

The name is misleading and Jellyfish is not really a fish. Fish are vertebrates which breathe through gills. Jellyfish has no bones at all and breathes (or absorbs oxygen) through membranes. Thus they are gelatinous zooplanktons.

2. Jellyfish do not have brain or heart

Yes, you read correctly. Jellyfish do not have a brain and neither do they have a heart! Instead of a brain, they have a basic nervous system – a nerve net – which helps them sense environment changes and respond accordingly. They don’t need a heart for providing oxygen throughout their body. Their gelatinous body can do it through diffusion.

3. Jellyfish predate the dinosaurs by hundreds of millions of years

Jellyfish do not have bones and therefore not many fossils have been found making it difficult to determine since when they have been in existence. In 2007, however a fossil was found in Utah which is thought to be over 505 million years old confirming that jellyfish have been on Earth since millions of years before the dinosaurs (dinosaurs lived from around 245 million to 66 million years ago. Read 10 Interesting Facts About Dinosaurs).

4. Atleast one type of Jellyfish is Immortal

Jellyfish has 2 main phases of life – the polyp stage where it is stationery which then develop into the Medusa stage where it is mobile. Most of the Jellyfish that we refer to are the medusa stage jellyfish. Turritopsis nutricula is a type of jellyfish which, in times of stress or as it ages undergoes cellular transdifferentiation. It settles on the sea floor and goes back to the polyp stage, which in turn spawns new, genetically identical jellyfish. It is thus theoretically immortal.

5. 95% of Jellyfish is water

With only 5% of a jellyfish is made of proteins, nerve cells and muscles. The remaining 95% is water. As a result, if a jellyfish is washed ashore, in a few hours itself, most of it will be evaporated and barely any trace will remain behind. It is also for this reason that jellyfish fossils are so hard to come by.

6. Largest Jellyfish could be the longest animal

Lion’s Mane Jellyfish is the largest known jellyfish. It varies a lot in size. Its bell can range from 50cm to 2.5 metres across. However, its tentacles can stretch over 30 metres (about the same length as that of a blue whale). The sting of lion’s mane jellyfish is not lethal for humans. It causes only some mild reactions.

7. Jellyfish have travelled to space

It sounds odd, but its true. NASA has been sending jellyfish to space since early 1990s. In 1991 NASA sent over 2000 jellyfish polyps into space in flasks filled with artificial seawater. The reason for this was that jellyfish and humans both use calcium crystals to orient themselves to gravity, and scientists wanted to study the effect on space-born jellyfish. Towards end of the mission the polyps had spawned into over 60,000 jellyfish. However, when the space born jellyfish returned to Earth, they could not orient themselves well to gravity showing that space born human babies could also face the same problem.

8. Jellyfish candies anyone?

Believe it or not, but there are over 25 types of jellyfish which are edible and are considered a delicacy in places like Japan and Korea. In Japan jellyfish has been made into candies – to make use of the huge number of jellyfish that plague the water there.

9. Box Jellyfish can kill a human

Box jellyfish is one of the most venomous marine animals in the world. Its tentacles have poison covered darts. A few types of box jellyfish have venom which is so dangerous for humans that if a person is stung by these, he can have a cardiac arrest or die within a few minutes.

10. Jellyfish like how humans are changing the ocean

As humans pollute the oceans and cause global warming, most animals on Earth are finding it difficult to survive. Not the Jellyfish! They are thriving in the polluted waters because they need much less oxygen than fish. Their numbers are increasing so rapidly that power plants in many countries like Sweden, US, Philippines have been affected by blooms of jellyfish. In Philippines, so many jellyfish were swept into the power system that power in a large part of one of the islands was shut down. Nuclear reactors usually rely on ocean water intake and if swarms of jelly fish enter these pipes and clog them, it can cause a temporary halt in operations.