Jellyfish life cycle

Jellyfish Life Cycle – Life stages, Death & Fascinating Facts

What have you heard about the jellyfish life cycle? Most likely, when you see a jellyfish, you picture a translucent, bell-shaped creature with long, slender tentacles. Although famous, it simply represents the “Medusa” phase of a true scyphozoan jellyfish before it expires. 

The only jellyfish that most people have ever seen are fully mature ones – the eerie. Bell-shaped animals that sporadically wash up on sandy beaches. However, jellyfish have intricate life cycles in which they pass through a minimum of six distinct growth phases.

Jellyfish have much more intriguing and lengthy lives than you might have thought! If you are interested in finding out more about the jellyfish life cycle, keep reading. The jellyfish life cycle, from fertilized egg to fully developed adult, will be covered in the following article. 

What Is a Jellyfish?

In the ocean, jellyfish are among the most unusual animals. They use their lengthy, sting-capable tentacles and bell-shaped bodies to catch their prey. In contrast to other creatures, the jellyfish life cycle is long and diversified, one characteristic that sets them apart. Let’s find out more about the various stages of growth a jellyfish experiences!

Stages of a Jellyfish Life Cycle

A jellyfish’s appearance frequently changes throughout its lifetime. A baby jellyfish doesn’t resemble an adult jellyfish. It can no longer swim at one point, and while some changes happen quickly, others take a little while. 

Let’s find out more about each stage in the jellyfish life cycle.

The Egg

The jellyfish life cycle begins similarly to our own: a male and a female searching for an opportunity to mate. Adult jellyfish, also known as Medusae, congregate in large numbers at twilight or dusk to reproduce. As a result, they spew copious quantities of sperm and unfertilized eggs into the water surrounding them. 

These spawning activities continue throughout the adult jellyfish life cycle and are brought on by factors such as proximity to other jellyfish, light, and a large food supply. How much offspring an adult jelly can produce during this period depends on how big it grows

Most jellyfish leave fertilized eggs to float freely on the ocean, while some jellies go to greater lengths to protect their eggs. Moon jellies, for instance, permit the fertilized eggs to stick to their oral arms and provide protection for them until they are prepared to survive the next stage of the jellyfish life cycle.

Planula Larva

A planula is the next developmental stage of the jellyfish life cycle. When the egg matures into the planula, which resembles a small flatworm and has cilia on its surface, it can swim freely. It can move due to the cilia’s regular beating. The planula keeps growing until it is large enough to search for a suitable solid surface to cling to.

The planula often locates a piece of stable seafloor to adhere to, with various species favoring various types of terrain. Sometimes, they will even cling to other creatures, especially the bodies of other mature jellyfish. Planula enters the next step once the ideal location has been identified. The embryonic development of all animals after fertilization by the male’s sperm occurs in the female jellyfish’s eggs.


The attached planula grows into the polyp, which is the next stage of the jellyfish life cycle. A polyp can be compared to a little stalked mammal with one end attached to the ground and the other projecting into the water, the mouth/anus is surrounded by a ring of tentacles. The jelly can efficiently catch prey at this phase since it has a fully developed digestive system

The jellyfish polyp resembles corals, anemones, and hydroids in the ocean. These creatures actually share a close genetic relationship with true jellyfish, and they have thus far gone through the same lifecycle. In contrast, an animal like an anemone will essentially mature into an “adult polyp,”  whereas a jellyfish will progress through several phases after the polyp.

Depending on the species, jelly can stay in this polyp stage for years. As a result, the jelly can wait until the right conditions arise for it to mature or for a significant number of its species to reproduce before achieving its ultimate adult form. 


When conditions are right, the polyp starts duplicating itself to reproduce asexually. The polyp stretches out and develops segments that will eventually bud off to create separate animals or even more polyps to hasten this process. The polyp that is strobilating is referred to as a scyphistoma, and the process is known as strobilation. The polyp’s tentacles are reabsorbed into its body to begin strobilation.

The body of the polyp gets smaller and starts to produce easily seen segments. A fully distinct set of muscles, nerves, and the digestive system eventually split from these segments when the grooves between them grew deep enough.


The next stage is indeed one of the most interesting stages of the jellyfish life cycle. An ephyra, the forerunner of the adult jelly, emerges from the tiny, newly-budded section of a polyp as a free-living organism. The ephyra is currently only a few millimeters broad, but as it swims away, it eats and expands.

Though this jellyfish has begun a new phase of its life, it’s crucial to remember that it is only one among many clones. The original polyp and any copies of it that remain alive could very well outlive this new jelly. 


Surprisingly, jellyfish are often called psychedelic medusas. However, it’s just another phase of the jellyfish life cycle. The ephyra develops into its final form as it grows; as it does so, its bell, tentacles, and oral arms all take on distinctive shapes. 

The medusa takes this form as an adult. Even if the first adult is little, it is already a mature creature and capable of reproducing. Yet, there are several incentives to grow as big as possible, as early as feasible, for example:

  • Jellies such as compass jellies and moon jellies congregate in large numbers to reproduce. A jelly must grow more significantly than its competitors to produce more sperm or eggs, which is necessary for successful reproduction.
  • Since there are not many deep-sea jellies, they have an incentive to get big quickly to scare off predators and enable them to survive long enough to breed.

Death Of Jellyfish

Since jellyfish normally don’t live very long in this stage, the medusa’s primary goal is to survive long enough to reproduce. Many jellies we buy at the aquarium only have a short lifespan before they essentially reach “old age.” By now, you’ve hopefully realized that the medusa just symbolizes the end of the jelly’s life and not its entire existence. 

Jellies don’t need unreasonably long lives because they are extraordinarily good at figuring out the ideal environment to reproduce in. If the circumstances are right for it to develop into an adult medusa, it will probably be able to produce the following generation rapidly and successfully. 

You may have heard or read about an “immortal jellyfish,” which in theory might live forever due to the ability of its adult medusa to revert to the polyp stage. Although this is the case, Jelly has defeated death in other instances. 

Remember that clones of their polyps are still surviving on the seafloor while the adult medusae of most jellyfish are dying of old age. The majority of jellyfish could potentially enjoy extraordinarily long lives through cloning

What Are Comb Jellies?

Unlike true jellyfish, which reproduce asexually and irregularly, sea walnuts only sexually reproduce. Every adult generates both sperm and eggs, and self-fertilization is typical. Those are all released into the water, where they fertilize the egg and cause it to start growing. The larval comb jelly emerges from the egg after approximately a day and has two long, sticky tentacles to catch prey. 

When a larval comb jelly reaches a size of around 5 mm, it starts to absorb its tentacles and expand the lobes that it will utilize as an adult to catch prey. When the larval comb jelly grows to a length of around 15 mm, it has completely absorbed its tentacles and becomes an adult.  

True Jellyfish

Most of the larger and more vibrant jellyfish that interact with people are Scyphozoa, commonly referred to as “True Jellyfish” because of their familiarity. There are at least 200 species of Scyphozoans, and they are most frequently observed in their medusa body shape.

Do Jellyfish Sting?

Long tentacles on jellyfish are known as cnidoblasts, and these cells contain nematocysts, which are stinging thread-containing nematocysts. Nematocysts’ pressure inside the jellyfish forces threads to uncoil when they come into contact with a foreign object. 

The poison that causes stings comes from the jellyfish’s tentacle. Stinging jellyfish destroy their prey by paralyzing it and injecting venom into it in self-defense.  

You must first remove the part of the jellyfish adhering to your skin. Washing the sting area with fresh water could cause additional venom to be released. Instead, use some alcohol or ammonia to clean the area. 

Bottom Line

These incredible creatures have a unique life cycle. If you want to know them better, you can probably find jellyfish in every body of water on Earth, particularly in waters around the equator and in the Arctic. 

In essence, a jellyfish can be found wherever a polyp can attach and grow into an adult jellyfish. Now, you know more about the Jellyfish life cycle. However, try not to hurt them and be careful to avoid jellyfish stings.