How Do Jellyfish Eat? (25 Jellyfish facts You Need To Know)

Most people from the centuries till today wondered How Do Jellyfish Eat? What Do Jellyfish Eat? and How Do They digest? Because they do not have complex organs and have only simple body parts that are even transparent.

So to answer these scientifically I have written many articles on it, one out of which is the most famous and most read is here.

How do jellyfish eat? Jellyfish use their tentacles for capturing food whenever the food accidentally reaches or touches these tentacles since these tentacles have nematocysts or stinging cells that contain a toxin to paralyze the prey later is carried to their mouth by using 4-8 oral arms situated around the mouth.

What do Jellyfish Eat?

The common food for jellyfish is planktons, small fishes, plants, smaller crustaceans, crabs, and other jellyfishes. However, the diversity of food varies according to the size of a jellyfish as the small jellyfish eat smaller prey whereas the bigger jellies can attack both smaller and bigger prey including other jellies as food. So let’s know the foods or diet of smaller and bigger jellies in detail.

The food for smaller jellyfishes are as follows:

  • Zooplanktons.
  • Phytoplanktons.
  • larvae.
  • Fish eggs.
  • planktonic eggs
  • Tiny fishes or hatched fishes.
  • Smaller crustaceans.

The food for bigger jellyfishes are as follows:

  • Fishes
  • Lobsters
  • Shrimps
  • Crabs
  • Other Jellyfishes. (cannibalism)

How do Jellyfish Eat Food?

Jellyfish eat foods using their oral arms and digest the food inside the cavity called the coelenteron cavity, where digestive enzymes are secreted in order to digest the food and are expelled out through the same part that is used to ingest the foods.

Note: To capture the food jellyfish paralyzes the prey by injecting toxic substances produced in the stinging cell that are all located on each tentacle.

Jellyfish mouth: The mouth of the jellyfish is located inside and below the body and is the part where both ingestion and excretion of food takes place.

How do Jellyfish digest their Food?

The jellyfish do not have an advanced digestive system. However, they have a very basic digestive system, where ingestion of food, digestion of food occurs in a single cavity. Later the digested food is excreted from the mouth as they do not have anus like other animals. 

The body of a jellyfish has a cavity called digestive cavity that is an extracellular cavity and is called coelenteron in biological standards this is why they are also called coelenterates since they possess the coelenteron cavity. 

This coelenteron cavity has only one aperture or simply one open that is where food is digested and is the only place that also expels the undigested food(faeces) which means it acts as both mouth for ingestion of foods and as the anus for egestion(excretion) of foods. Therefore they are said to have an Incomplete type of digestive system since there is only one opening meant for ingestion and egestion.

How Do Jellyfish Attack?

Defense and Offense parts of a jellyfish(The Stinging cells or Nematocyst)

Stinging cells are numerous in number(5,000 per tentacles) which is present on the tentacle. These stinging cells are unique features for jellyfish and are responsible for defending themselves from their own predators by stinging the predators through these numerous stinging cells.

The same stinging cells act as an offensive part for prey near jellyfish because the same stinging cells with their toxin attack the prey causing them to paralyze.

What problems do Jellyfish Cause?

  • Sometimes the rate of production or the density of jellyfish in an area increases so much that they all start to feed smaller food meant the smaller fish population for their own growth and development thus causing a lack of food and nutrition for these smaller fishes causing some to starvation, death and also to take migration. This leads to the unavailability of foods for those bigger fishes that usually depend on these smaller fishes thus this also causes the problem to fishermen because when they depend on bigger fishes.
  • When a lot of jellyfish live or swim together is called the blooms, that bloom makes transportation of ships difficult across the sea. 
  • The Bloom of a jellyfish can cause a lowered level of dissolved oxygen and less food available for other aquatic animals leading to their deaths.
  • They also cause problems to the fisherman in many ways such as it’s hard to capture the fishes in the bloom because jellyfish are interrupting for fishing as they are everywhere than those of fishes thus leading to capturing of jellies or both jellies and fishes in fishnet.
  • Another problem is the density of fishes available for fishing decreased due to the increased density of jellyfishes because you know jellies eat the fishes, Right!

Can a Jellyfish Eat Humans?

No, Jellyfish can’t eat humans because humans are so big. However, around the world, there are many people who get stung by jellyfish while swimming across them since they are mostly transparent, it is hard to find them in water. 

The humans who got stung by jellyfish develop reddishness of skin and pain. In some cases, Swimmers across the seashore who touched intentionally or unintentionally got stung by jellyfish’s tentacles containing stinging cells.  However, many people will have to bear the pain it gave them through their sting while some jellyfish such as  Australian box jellyfish (Chironex fleckeri) can be lethal as their venom or toxins can bring deaths to marine animals as well as humans.

What Animal Eats Jellyfish?

Jellyfishes have toxins present in their body capable of paralyzing both their prey and predators.  However, there are certain animals that evolved and adapted to eat these jellies irrespective of their toxin effects, and these are mentioned below

The Predators of a Jellyfish are

  • Sea Turtles
  • Sunfish
  • Spadefish
  • Other Jellyfish
  • Humans

Humans across the world consume the jellyfish as a delicacy. The commonly used edible jellyfishes as food are the “Cannonball Jellyfish” (Stomolophus meleagris) and jelly blubber (Catostylus mosaicus) , Some of the jellyfishes are dried, preserved, and packaged across countries like Japan, China.

Note: During processing, Edible Jellyfish’s tentacles or stinging cells have to be taken care of as they are rich in toxin or venom.

Do Jellyfish Eat Crabs?

Yes, jellyfish can eat crabs because they are carnivorous animals. However, this act of eating crab by a jellyfish is often seen in bigger jellyfishes that are relatively larger than the crab.  Larger jellyfishes can eat fishes, shrimps, crabs etc., whereas the smaller jellyfish can eat smaller creatures such as those smaller crustaceans, smaller fishes, hatched and unhatched eggs.

Read More : Is Jellyfish a Fish

25 Amazing Facts about Jellyfish:

1. Jellyfish can repair themselves: The Jellyfish can replace worn-out cells, that is power off regeneration, enable them to regrow the body parts such as their tentacles and other parts.

2. Jellyfish poop from the mouth: The digestive system of a jellyfish is an incomplete type i.e mouth serves as both for ingestion ( food intake) and egestion ( waste removal).

3. Jellyfish respire through the body surface: Jellyfish’s respiration is through their body surface, There are no nostrils like in frogs or no gills like in fish.

4. Jellyfish are edible and also used as a delicacy: Edible jellyfish are Cannonball jellyfish (Stomolophus meleagris) and jelly blubber (Catostylus mosaicus). During processing, Edible Jellyfish’s tentacles or stinging cells have to be taken care of as they are rich in toxin or venom. Mostly in China and Japan jellyfish is used as a delicacy. Some people across the world who consume them believe that they have medicinal values.

5. Jellyfish have Tentacles that act as an arm: The offense and defense part of a jellyfish containing stinging cells inject a toxin into the Prey(mostly small fishes and aquatic animals) paralyzing the prey thus it gets its food.

6. Jellyfish have very long Tentacles: Jellyfish can have about 15 tentacles. The length of each tentacles can reach about 10 feet to 100 feet in length which can have about 5000 stinging cells in a tentacle. 

7. Jellyfishes are danger, even the dead ones are danger: The dead jellyfish can produce a sting, this means the stinging cells of tentacles sometimes are active even after the jellyfish is dead. 

8. Jellyfish can bring heart attack, paralysis, or death by stinging humans: The venom or toxin of jellyfish can stop the heart (cardiac arrest) and brain activity of swimmers across them thus leading to drowning in water during swimming.

9. Jellyfish deadly jellyfish is the box jellyfish: The most dangerous Jellyfish in the world is the Australian box jellyfish, the most venomous Marine animal. Its toxic present in the stinging cells can be lethal.

10. Jellyfish sting cause skin redness and pain: Most humans got stung by jellyfish causing reddishness of skin and pain. Swimmers across the seashore who touched intentionally or unintentionally got stung by jellyfish’s tentacles containing stinging cells. 

11. Jellyfish have a very simple brain that can detect smell and touch: The jellyfish contain neural networks but not a brain like we humans do, which can perceive only smell and touch in water. So they may not feel emotions.

12. Sometimes only one jellyfish can give birth: They can reproduce asexually, that is, without sex cells or gonads,  which involves one jellyfish. While they can reproduce  sexually aslo, using sex cells or gonads, involving two jellyfish of the opposite sex. However, Some jellyfish can produce 45,000 eggs.

13. Jellyfish make glowing seashores at night: It is because of some protein present in the jellyfish which shows bioluminescence character. However, The glowing substance in jellyfish helped scientists to detect cancer cells. That is by inserting substances responsible for bioluminescence from jellyfish into cancer cells. Thus found bioluminescence activity in cancer cells while no bioluminescence activity in normal healthy cells.

14. A wide variety of colors of Jellyfishes possible: Some jellyfish are transparent, some are pink, yellow, blue, and purple, and often are luminescent. 

15. Jellyfish lifespan is 2 to 3 years under an artificial setup: Some jellyfish can live up to decades and some are even considered immortal, because they under asexual reproduction.

16. More the population of Jellyfish, the more problems it causes: Sometimes the Jellyfish population increases in a region so much that ships  found it difficult  to move and other aquatic animals, like fishes., die due to there being no food left by these jellyfishes.

17. Jellyfish have been sent to space: They have been sent to space to study about the effects of gravity on a jellyfish. The jellyfish which multiplied in space without gravity found it difficult to deal with earth Gravity when they were brought back to earth. In 1991 Space Shuttle Columbia sent moon jellyfish to space to study effects of microgravity.

18. Jellyfish can grow very very big: A lion’s mane is the Largest jellyfish whose tentacles can grow about 120 feet or about 71 meters, that is larger than a length of blue whale. There are Different colors of lion’s mane jellyfish such as red or purple.

19. Craspedacusta sowerbii is a freshwater jellyfish: Most of the jellyfish are found in marine and adapted to marine water. However, a few are freshwater jellyfish such as Craspedacusta sowerbii.

20. The Bloom of a jellyfish is a large number of jellyfish occurring in an area: A group of Jellyfish are called Bloom that contains millions of them. The reason for the bloom of jellyfish is Climate change, habitat modification, and decrease in population of jellyfish predators in a region. These blooms of a Jellyfish lead to a lowered level of dissolved oxygen and less food available for other aquatic animals leading to their deaths.

21. A box jellyfish is a deadly Jellyfish: A box jellyfish can be very dangerous as they produce Venom or toxic in stinging cells which are too fatal to humans. The Australian box jellyfish can kill a human as it is the most dangerous Box jellyfish. These  box jellyfish are more advanced than other jellyfishes. There are around 50 species of box jellyfish, that are responsible for more deaths of humans during swimming/diving in the sea. Some examples of a box jellyfish are Chironex fleckeri, Carukia barnesi and Malo kingi.

22. Green sea has immunity for Jellyfish sting: The Green Sea Turtles are the predators of box jellyfish which are immune to jellyfish’s venom. This Means the Venom or toxin produced by jellyfish does not kill a green sea turtle but it can kill other animals including humans. 

23. Jellyfish are crazy names of jellyfish possible: Cauliflower Jellyfish, Fried Egg Jellyfish, Crystal jellyfish, Bloodybelly Comb Jellyfish, Flower Hat Jellyfish. Pink meanie jellyfish, White-spotted jellyfish, Atolla jellyfish, Turritopsis dohrnii, Black Sea nettles Jellyfish, etc

24.Turritopsis dohrnii is called an Immortal Jellyfish: The Turritopsis dohrnii Is an Immortal jellyfish because of its ability to go back into its young stage from an adult under unfavorable conditions. 

25. Some marine animals live inside jellyfishes belly for protection: The small fishes and marine animals to hide from predators use the spaces present in between these tentacles of jellies because most animals do not come in contact with tentacles if they do so they will be paralyzed by jellyfish stinging cells.


How do Jellyfish Swim? The Jellyfish swims in water by contracting and relaxing the ring of muscles located around the body, that is they squeeze their body in order to push the water present at the bottom which causes moving forward. Thus they are said to use jet propulsion system movement for swimming in the water and are considered the most energy-efficient animals in the world.

How long are Jellyfish tentacles? The tentacle present in the jellyfishes is around 15 in number on each corner of the belly and each can grow as long as 75meters in length.  Each tentacle contains approximately 5,000 stinging cells in one tentacle and these stinging cells contain a paralyzing substance meant for attacking both its prey(food) and the predators(attackers or intruders).

Are dead jellyfish dangerous? The dead jellyfish can produce a sting, this means the stinging cells of tentacles sometimes are active even after the jellyfish is dead.  Venom or toxin of jellyfish can stop the heart (cardiac arrest) and brain activity of swimmers across them thus leading to drowning in water during swimming.