What Do Jellyfish Eat? 9 Unbelievable Facts

To get the answer to the question “What do jellyfish eat“, we have to dive into detail. The jellyfish and sea jellies are free-swimming marine animals. It is one of the most strange and fascinating spectacles on earth. With the odd bell-shaped body and attractive luminescent glow of jellyfish, this creature rarely looks like an animal at all, instead, it seems like some kind of unusual alien life.

How do jellyfish reproduce

Nevertheless, some qualities are shared by this strange creature in common with other animals, which includes the ability to use oxygen and symmetrical body plan. 

Jellyfish belong to the phylum of Cnidaria amongst all the species of sea anemones, corals and all 200 existing species of jellyfish.

Jellyfish do show an enormous diversity in shape of tentacles, color, size, and number,  although every adult jellyfish has the same bell-shaped body which is symmetrical. 

This strange creature is found in just about all the wild marine environments around the globe; but only a few of these species are known to exist exclusively in freshwater ecosystems.

About 600 million years ago, the first true jellyfish evolved on our planet (the exact date is unknown because the soft parts of jellyfish do not fossilize properly). It can be assumed as representative of the initial forms of multi-organ animal life on earth.

Jellyfish relatively have a simple body structure with no circulatory  or respiratory system. They have only basic neurological and digestive functions. Their body is composed of a high amount of water which is more than 95% (by comparison, we humans have only 60% water in our body).

When jellyfish first evolved on the lap of mother nature, the species were more limited to very basic or primary organisms floating through water; and they had more limited dietary options. 

Now, the species feeds on a huge variety of various marine plants and animal life in the oceans. The diet composition of jellyfish highly influences their color, turning it red, pink, or purple, with various pigments.

Despite the jellyfish being calm and simple, in reality the species are amongst the most efficient swimmers in the marine world.

They get power by contracting and expanding the motion of the bell. It squirts water in the other direction of where the jellyfish are headed.

In order to produce energy, the relatively simple digestive system of the jellyfish is used, and actually it is a fascinating study. This will be discussed here in this article. 

Again, this is also a very fascinating subject of how the digestive system of jellyfish could have evolved in early days.

Types of Jellyfish

What do jellyfish eat?

It depends on the species. The jellyfish has an eclectic and wide variety of diet, consisting of small fish (which includes both egg and larval stages), other jellyfish, plants, crustaceans, and even plankton. 

Majority species of the jellyfish are purely carnivorous – imagine a very big jellyfish eating a crab or a large lobster

However, there are some facts which are more interesting. The spotted species of jellyfish grows algae inside of their stomach. Nutrients are derived by the jellyfish from the resulting photosynthesis.

Jellyfish belong to the voracious eaters category regardless of their food habit. Many times you can see them congregating together groups of millions known as blooms.

These groups or blooms eat a lot of food that they actually hollow out the whole fisheries, leaving few behind for the people to catch. 

Unfortunately, experts and scientists believe that climate change may raise the likelihood of blooms or groups appearing throughout the oceans in the near future. Further it could decimate various ecosystems.

How Often to Feed Your Jellyfish

Usually speaking, you should feed your jellyfish every day, however your jellies don’t require food in the exact manner as we do – instead they need food for their overall growth!

So, put your jellyfish on a diet, if they are getting too big in size – feed them once every alternate day, and you’ll notice them shrink in size.

On the other hand, if you want your jellyfish to grow in size, try feeding twice every day.

What do the SMALL jellyfish eat?

Smaller jellies feed on all the various little organisms you will notice floating around in the ocean. That’s why they are called “Carnivorous”.

These things include:

  • Plants
  • Lots of other tiny creatures
  • Fish eggs (full of proteins)
  • Plankton
  • Tiny fish

Places with lots of jellies, it could be a big problem for the tiny fish because the jellies will consume everything that is small and full of nutrition.

So to find food, finally the smaller fish have to move somewhere if there are lots of jellies. As the small fish are smart enough and are able to figure this out very quickly, that’s not a big problem. The Jellies are not that smart, and will float around in a large fog of unconsciousness. So they will not follow after the small fish.

In the ocean, groups of jellyfish are swimming together. This group is known as a bloom. A Bloom contains millions of jellyfish. The jellies often create problems for fishermen and fish. When that occurs, you should have to wait till the current of the sea or ocean carries the bloom in another direction.

What do the large jellyfish eat?

With the poisonous sting, the bigger jellyfish can actively catch and kill large sized organisms, as we discussed above. By touching the highly long jellyfish tentacles floating around itself, they are able to shoot out this sting as and when any animal will trigger them.

Once the jellies successfully catch and kill an animal (or make it unconscious) they will try to get into the animal’s mouth.

Following are some of the animals bigger jellies eat:

  • Barnacles
  • Lobsters
  • Plants
  • Other Jellies (!)
  • Crabs
  • Shrimp etc..

The bigger jellyfish can also eat other small sized jellyfishes.

Cannibalistic behavior can be seen in the jellies. However, since jellyfish don’t have a brain, they’re not actually “aware” of what’s entering into their mouth. They have to feed on whatever thing floats around by.

Basically jellyfish can consume anything that comes by. Even though their digestion system is super-simple, it can easily eat a large variety of food!

What eats jellyfish?

Do jellyfish get eaten by anything? Jellyfish itself are also in constant danger of being caught and eaten by various animals such as:

  • Sea Turtles
  • Spade fish
  • Humans(!)
  • Other Jellyfish
  • Sunfish

Can you eat jellyfish? Yes, for humans, some jellyfish are considered a delicate meal. Sometimes at some expensive restaurants, the “Cannonball Jellyfish” is served as a meal. Particularly in Asia where jellies are considered as a part of the booming seafood industry.

For the U.S state of Georgia, jellyfish are also of high export value.

Jellies are being sold to seafood distributors across some Asian countries such as Thailand, China,Laos, Korea and Japan where the species will end up on the dining table of restaurants. Before jellies get shipped, they are properly dried and packaged.

Mexico alone harvested 20,000 tons of jellyfish. It is equivalent to US$3.5 million over a period of just 3 months (according to Wikipedia).

Do jellyfish have brains

How do jellyfish catch their food?

It partially depends on the life stage of the jellies. What is unknown to a lot of people is that the anatomy of the jellyfish radically changes across their four-part lifespan

By strategically converting between asexual  and sexual  jellyfish reproduction at various points in their lifespan, jellies are able to undergo a crucial transformation.

After reproduction, the first stage of jellyfish is called larva. Larva is produced from the jellyfish sperm and the egg of the adults. When a suitable surface is found by the parents, the larva produced by them will settle down and it can develop and transform into a sedentary polyp.

After passing a certain amount of time, jellies will then bud into a lot of free-swimming clones known as ephyrae. Eventually all the ephyrae will reach the complete “medusa” adult period. They only remain in the longer adult period for reproduction, and their larval stages are only transitional types.

Usually the polyp is the most enduring and longest amongst the four. Polyp can remain in the same form for so many years, awaiting perfect situations in order to complete its transformation into adulthood.

The polyp remains stuck to another surface or a rock, and unable to move. They have a completely developed digestive system. 

It is a passive predator, seizing on whatever organic matter or small animals that floats by with their tentacles to eat them.

When they reach the medusa adulthood stage,  jellies gain a few degrees of mobility. 

When jellies float through the water placidly (either by their own power or any water current), the jellyfish expend minimal effort to hunt down their food. Probably it is due to their limited muscular or neurological system that prevents them from maneuvering their prey or out-swimming.

Instead, the jellyfish spread out its tentacles. In the case of a few species (such as the lion’s mane jellyfish) the tentacles can reach up to 100 feet long, in order to help jellies collect some animals as food in the ocean as they pass by.

The tentacles of jellyfish have painful stinging cells that can easily stun or paralyze their prey. Along the tentacle length there are an uncountable number of these small tiny cells. 

They are able to piercing the skin of its victim by exploding with a total pressure of higher than 2,000 pounds each square inch while making any contact. 

In the case of some species,  sometimes the sting is more strong to cause immense pain in the human body and even result in death to humans. However it is the result of self-defense or accidental contact on the part of jellies rather than aggressive behavior.

With the power of the swimming motion, jellyfish can easily draw food inward toward its tentacles. It means jellyfish expend no extra energy than otherwise they would by normally swimming through water.

An interesting fact comes out from this story is that some jellyfish species share a symbiotic relationship with different creatures. The scientific term “symbiotic” is used for when two or more species living in the same proximity share a mutually profitable relationship. 

In practical terms it means that some juvenile fish and smaller animals will live close to the bell of jellyfish, either somehow avoiding the long jellyfish tentacles or naturally immune to its poison, with a view to protect themselves against some common predators.

What benefits does the jellyfish gain? It’s assumed that the symbiotic creatures may perform as a lure to draw in prey for the jellies with the intent to consume.

These kinds of symbiotic relationships don’t always end in a nice way, however; in some cases the jellyfish may betray its nearby passenger and consume it instead. This risk is worth taking for the tiny animal because the odds of survival in water are normally huge near the jellies than outside. 

A symbiotic relationship is shared by the cannonball jellyfish with more than 10 various other marine species, which includes juvenile long nose spider crab. They live inside of the bell (this is not clear what benefits this confers to jellyfish).

What do jellyfish eat

How do jellyfish digest food?

In spite of their more simplistic anatomy, like any other common animal, all the marine jellyfish possess a primary set of digestive organs. 

After their quarry is paralyzed or killed, with a set of oral arms some of the jellyfish will push the food toward their mouth. Their mouth is located on the underside of the bells. The arms of jellies have a range of various movements and primarily resemble short tentacles. 

The mouth of a jellyfish is nothing more than a tiny hole. Simultaneously it performs as a normal opening for water to enter and leave the body, anus, and mouth.

This is the place where the jellyfish anatomy becomes most apparent. The stomach and the mouth are directly connected by a very little entry. There is no other organ or throat in between.

The digestive system of the jellies are very simple so that it lacks intestines, pancreas and liver, which absorbs nutrients and generates essential chemicals in the majority of other animals. 

Typically it’s only a big cavity that generates all the necessary things to break down their food on its own. Naturally, the nutrients are diffused into the water throughout the whole body of jellyfish because they lack a circulatory system of any type.

When the feeding is done, jellyfish will expel the undigested food out again with the help of their mouth. It is a very efficient and fast process because they cannot consume it again until and unless the previous eaten food has left their body. 

Providing the importance of specialized digestive organs such as the liver and intestines in the evolution process of highly complex animals, this simple digestive system probably limits it to only basic behaviors and functions. 

After almost 600 million years the jellies are still thriving. For their part, jellyfish seem to  just fine without them. 

 Jellyfish facts

  • Jellyfish don’t have lungs, hearts, brains, or even eyes
  • Jellyfish are supposed to be the oldest multicellular animal on the planet
  • Jellyfish can create their own clone
  • Some species of jellyfish have teeth
  • Jellyfish never get tangled
  • Jellyfish can be very attractive and colorful
  • Jellyfish are almost fully comprised of water
  • Jellyfish aren’t actually fish
  • There are more than 25 types of edible jellyfish
  • Some jellyfish can generate their own internal glow, they are called bio luminescent.

FAQs

How many Jellyfish types are there? 

There are more than 200 known existing types of jellyfish. Some are bigger jellyfish and some are smaller. The majority of them are not so dangerous to us. However,  if you touch the jellyfish tentacles they can still cause irritation.

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Dibyajyoti Bordoloi is the creator and author of FishCampRehab.com, a third-generation experienced fish keeper and owner of a successful pet breeding farm. He is also a member of the Center for Wildlife Rehabilitation And Conservation (Assam), the Marine Aquarium Societies of North East India, and the Kaziranga Nature Conservancy of Assam.

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