Do All Jellyfish sting?

What is a Jellyfish and its Body Structure? What are Stinging Cells, and How do they work? Can they Sting each other? Which Jellyfish is a Stinger, and Which is not? What is a Group of Jellyfish called?
do all jellyfish sting
Photo by Jeffrey Hamilton on Unsplash

Jellyfish may sound similar to everyone’s favourite jelly, but they are not as sweet as jelly. Yeah, if you know what I am talking about is their sting. But have you ever just wondered do all jellyfish sting, and can jellyfish sting other jellyfish? Have you ever heard about jellyfish stinging cells? What are those waving and flowing long thread-like things? Seeing them you may have thought, do jellyfish have legs? Since we are on this topic, let’s find out about jellyfish body structure, and how do jellyfish stings work.

1. What is a Jellyfish?

The free-swimming umbrella-shaped marine animals in neon colours are the jellyfish. They look like bell-shaped umbrellas, and they have long floating tentacles that have stinging cells. They are also known as sea jellies, but the term jelly was incorporated into their names because of their locomotion and structure. However, some scientists consider scyphozoans only as the true jellyfish. The jellyfish belong to the phylum Cnidaria, which includes animals like sea whips, corals, and sea anemones. (See What Fish does Caviar come from?)

2. What is the Jellyfish Body Structure?

A jellyfish lacks many vital internal organs like the heart and brain but still, they are counted as living beings. The jellyfish body structure merely consists of 3 layers, namely

  • Epidermis, the outer layer
  • Mesoglea, the middle layer filled with jelly-like liquid
  • Gastrodermis, the inner layer. (See What Are Shark Teeth Made Of?)
do all jellyfish sting 2
Photo by Austin Loveing

3. What do They have in the Layers?

Still looking for an answer to how and why do all jellyfish stings, let’s first look at their structure. Their bell-shaped structure is hollow that is filled with mesoglea (a jelly-like matter) which is responsible for forming their hydrostatic skeleton. The mesoglea is made up of more than 95% of water and the other 5% is made of debris, bacteria, amoebocytes, and other fibrous proteins. (See 12 Catfish Whiskers Facts)

4. Do Jellyfish have Legs?

The margin of their bell-shaped body bears the tentacles. They are long dangling arms-like structures of jellyfish. The stage of jellyfish with tentacles is known as the medusa stage. However, there are some species without tentacles too.

5. What are Jellyfish Stinging Cells?

The stinging cell of jellyfish is known as nematocysts. Another name for these jellyfish stinging cells is cnidocytes because of the presence of the organelle known as cnidocytes or cnida. A jellyfish can have numerous stinging cells inside its tentacles, but these cells are also present around its mouth and stomach. The stinging cells have venom that can make a sting fatal. (See What is Blobfish (Psychrolutes marcidus)?)

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Photo by Mario Mendez

6. How do Jellyfish Stings work?

The stinging cells are like compartments which have a mini needle-like structure. So, how do jellyfish stings work? When something comes in contact with their tentacles, the stinger needle is activated. The cell is opened letting the ocean water inside. The rushing water causes it to shoot in the same direction and the venom is released after the stinger enters the skin. Their venom can be extremely painful and fatal (some jellyfish stings). (See Why are the Bottlenose Dolphins becoming endangered?)

7. Why do Jellyfish Sting?

They do not have a brain or heart, and their reflexes are amazing. They react to external stimuli instantly, so even before you realize they will sting you. This is their natural defence mechanism. They sting and release the venom to protect them and kill their prey. So, their reflexes are the reasons why do all jellyfish sting. (See How Do Fish Sleep with Their Eyes Open?)

8. Can Jellyfish sting other Jellyfish?

Jellyfish feed on fish, crabs, shrimp, and sometimes small plants. They sting and kill their prey and then digest them whole. However, there has not been any case of jellyfish stinging each other. This may be because they lack brains and do not have a territory-making requirement. Therefore, they do not have to kill or harm each other to survive and you don’t have to ponder how do all jellyfish sting other jellyfishes. (See How to Evade a Shark Attack?)

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Photo by Lazar Gugleta on Unsplash

9. Do All Jellyfish sting?

Not every floating creature in the depths of oceans is jellyfish. You may be confused about them. Moreover, not every jellyfish is a stinger. The venom of many jellyfish is not even harmful to humans. There are various species of jellyfish that don’t sting. So, to explain why and how do all jellyfish sting or not, let me tell you which one has the most and least fatal stings. (See 45 Types of Fish)

10. Who are Mild Stingers?

  • Cotylorhiza tuberculata: This round-headed reddish yellow jellyfish has a mild sting which is harmless.
  • Marivagia stellata: It is a rare species and hardly any stinging cases have been recorded from it so far. But researchers tell us that this is not a stinger specie.
  • Aequorea forskalea: It has a big transparent umbrella-like body with extremely thin tentacles. Their stinging cells are not harmful to humans, and they are categorized as mild stingers.
  • Aurelia Aurita: This spaceship-like jellyfish has marginal tentacles and these are often witnessed floating in many public aquariums too. These delicate jellyfish species are harmless to humans and in China, it is enjoyed as a meal.
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Photo by Ashleigh Robertson
  • Mnemiopsis leidyi: This jellyfish has a shooting star-like appearance as it has an egg-shaped lobate body. It is from the phylum ctenophora and does not have any stinging cells. Though it is harmless to humans, it can be fatal to fish larvae and fish eggs (roe) because it feeds on them.
  • Phyllorhiza punctata: It is a mushroom umbrella-like jellyfish covered with yellow spots. It will not harm humans unless the contact is intense. So, do all jellyfish sting, even if most of their stings are neither venomous nor painful? Not really.
  • Rhizostoma pulmo: It is one of the largest jellyfish and its body looks like a cauliflower. It has several small mouths, but their tentacles are short and filled with cnidocytes. But if you touch them, you can get mild rashes with slight painful stings.
  • Thalia democratic: They look like a transparent shooting star with an orange spot. They are herbivores and lack stinging cells. Therefore, they are harmless to humans. (See How Big is the Biggest Octopus?)
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Photo by Jonnathan Diemel

11. Which Jellyfish is a Stinger?

  • Rhopilema nomadica: It has the appearance of a huge cotton ball in a cyst with numerous thinner tentacles. They are a bad stinger and cause a painful sting.
  • Olindias phosphorica: It is a white transparent umbrella, with thin tentacles that catch the planktons while it falls back to the seabed. They are stingers, but their sting is not severe. However, they are painful enough.
  • Pelagia noctiluca: This luminescent jellyfish has 8 long tentacles that can leave scars on your skin if you get stung by them. They are the worst stinger, and their painful sting has long-lasting impacts.
  • Catostylus Tagi: It has the appearance of a large head with a bob haircut and several short tentacles that look like small brushes. Their stings are not fatal but painful, therefore, no need to touch them.
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Photo by Bruno Kelzer
  • Chrysaora hysoscella: Their head looks like a brown toadstool while their manubrium (the body parts hanging from their head) is hanging with 4 long arms (tentacles). Next, in all jellyfish stings, this one is a stinger but not as lethal as the Pelagia species.
  • Drymonema dalmatinum: This is a rare jellyfish species that is huge in terms of diameter. They mostly remain in the dark depths of the ocean but if you come in contact with one, they may be dangerous. They are termed strong stingers with huge bodies.
  • Cassiopea Andromeda: Its umbrella looks similar to the shell with its mouth and tentacles on top of its body, therefore, also known as upside-down jellyfish. Its singing cells will not cause painful stings but the mucus covering their stinging cells will cause irritation.
  • Carybdea marsupialis: It is a small, transparent jellyfish with a cubic umbrella and 4 tentacles. It is not a venomous jellyfish, but its stings can be extremely painful with lasting effects. Beware, because they are vigorous and swift. (See 21 Healthiest Fish for Fishetarians )
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Photo by Maksym Sirman on Unsplash

12. What is the Group of Jellyfish called?

As you already know do all jellyfish sting or note, let’s see their group names. Bloom, smack, or swarm are 3 terms that are used interchangeably for a group of jellyfish. But each term conveys a different meaning. Therefore, take a look below to get their meanings and use them as and when required while referring to a group of jellyfish.

  • Bloom: When a large group of jellyfish is seen in a small area, then the term bloom is used to define them. 
  • Smack: It is another collective word for a group of jellyfish. It is not a scientifically used term, but people usually use it.
  • Swarm: This term is used when the animals are actively living in a group. Jellyfish are often seen in a group, therefore, the swarm is a group of jellyfish called.

So, you finally got answers to do all jellyfish stings, how do jellyfish stings work, and can jellyfish sting other jellyfish. You also got to know about jellyfish stinging cells, jellyfish body structure, what is a group of jellyfish called, and do jellyfish have legs or arms like structures. (Also read What is a Group of Ants called?)

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