The life cycle of jellyfish for creatives

Jellyfish, though simple beings, are truly remarkable creatures. Just look at their life cycle and you know you hit gold. A jellyfish knows many forms, from larva, to polyp to fully grown medusa. Artist or not: This will be an interesting read!

Hi! My name is Tessa, I’m a Dutch artist, specializing in wildlife and creature designs. I love to share my passion for nature, art and fantasy, and do that by creating this archive and community, alongside my company Tez Art & Design.

Table of Contents (Click to collapse)

What are jellyfish?

The reason jellyfish belong to the cnidarian family.

So, what are jellyfish really? Well, they aren’t fish for sure. A fish is naturally centered around a backbone, while jellyfish have no bone at all and therefore are invertebrates.
Jellyfish belong to the cnidarian family, its closest relatives are corals, sea anemones, sea whips, and hydrozoa. This is because they share distinct features. One of the most remarkable ones, being their stinging cells. These stinging cells are called cnidocytes. which is the Greek word for ‘nettle’.

We all know jellyfish. These graceful creatures with a large round bell and enormous tentacles and float on the current in large groups. But in truth, this is only their final medusa state, after which they will die. For a brainless creature like the jellyfish, they have a remarkable life cycle. An artist can get a lot of inspiration from jellyfish.

Jellyfish for creatives

The jellyfish is an interesting pick for any creative that’s into creature designs in one way or another. Their life cycle is one that opens new dimensions of what is possible and, on its own, is very inspirational. They look a lot different, or even unrecognizable in most of their stages, they live their lives in many different ways and even clone themselves. There are even jellyfish out there that are biologically immortal, like the turritopsis dohrnii.
Jellyfish simply are one of the most remarkable examples of what is possible. When a creative is looking to make a new and believable design, jellyfish are the last creature you should ignore and one of the first you should take into consideration, simply because they will open up your mind with possibilities and provide you with a lot of inspiration.

Fun fact
Did you know that many jellyfish are bio-luminescent? They glow up in the dark to communicate and catch their prey.

The life cycle of jellyfish described

There are many species out there. They look different from each other as adults, but also when they’re in their other stages. As there are over 2000 known jellyfish stages and even more to be discovered, there will only be a few examples here. Don’t be shy to use google, reference is key and knowledge even more so!

In this article we mostly focus on the rhizostoma luteus jellyfish. This is simply because this is one of the best documented species out there. Remember that every jellyfish species has a slightly different speed and way of development.

The fertilization

Male jellyfish release their sperm when they are in close proximity to many other jellyfish.
Photo by Krysten Merriman on Unsplash

Eggs are technically no jellyfish yet, but it’s an important part of their life cycle nonetheless. Male jellyfish release their sperm when they are in close proximity to other jellyfish. Females then collect the sperm and fertilize their eggs. This event happens during several days in a row at dusk and dawn. But food is also a very important factor. The larger the jellyfish they more offspring it likely will have.

From this point on the eggs are released to drift with the current and turn into a larva. Some species, like the moon jelly take a bit more effort. They allow the eggs to stick to the oral arms till they become larva and go their own way to find some good soilto attach on.

Planulae, the jellyfish larva stage

Planulae stage of the Rhizostoma luteum jellyfish.

This is the first stage in which a jellyfish starts to fend for itself. Most species move in groups in this stage to latch onto some solid and decent soil on the ocean floor in huge groups. Some species go their way alone, but this is a rarity, because, when it comes to jellyfish, survival comes in numbers.
Interestingly, some jelly species are born in their young medusa state. These belong to the scyphozoans, while the majority attaches to a solid substrate. They are called anthozoans. To appreciate the jellyfish for what they are, we will continue on with the anthozoans. The scyphozoans will catch up with us later again!

When in their planulae stage, some species cannot eat and some can. Nearly all of them will make a run for a suitable substrate to latch on as soon as they can to develop into a polyp. Most jellyfish planulae are simple oval forms with some hair-like extensions to the side with which they can propel themselves forwards.

The scyphistomae, or polyp stage

Images provided by research through Plos One.
The different polyp stages of the Rhizotoma luteum jellyfish.

This is where things become interesting. Here we are looking at the phase which comes after the planulae attached itself to some suitable soil.
This phase is known as the ‘polyp stage’. In the early polyp stage, it’s called ‘scyphistomae’. Even the polyp stage knows many different stages.
The listed images on this topic and the following below are graciously provided by researchers as creative commons images after extensive research on the Rhizostoma luteum jellyfish.

The polyp stage is the stage where a single, free-swimming organism becomes an organism that’s attached to the soil and starts copying itself into free-swimming organisms again. But this polyp stage knows many stages as well. Let’s list them out, or simply have a look at the provided images.

Note that we are no scientists, below is a description based on visual observation. Also know that many species develop in different ways (colors and shapes) but this common jelly gives you a very good idea of all the stages you can expect from a polyp forming jelly species.

You can find the meanings of the letter combinations in the table below.

First phase

In this early phase, the hypostome develops (‘hy‘ the mouthpart) and so does the nematocyst (‘ne‘ stinging cells within the tentacles) and so does the tentacular ring (‘tr’). After a few days, a clear cone begins to form on top of the stolon (‘st‘) which is attached to solid soil. In this first final stage (F) the polyp is ready to start cloning.

Second phase

The polyp is ready to make its first ephyra disk (G). The ephyra disk is the young jellyfish stage, only now it’s still attached to the polyp along with its brother- or sister clones. The polyp gets slightly brown at the top and starts forming more and more disks, each of which will turn into an individual jellyfish. Image (J) represents a polyp of 4 days old and has two ephyra disks, representing two young jellyfish ready to detach themselves and let the currents take them.

Ephyra stage

Young ephyra, early stage.
Image from Plos One.

The first ephyra let go of the polyp and is now floating around like a little star amongst thousands of others. The next one in line will follow soon after. The average polyp can shed up to 15 ephyrae. The first in line starts contracting, the second does so too soon after, but is weaker, to begin with. All the other ephyra in line don’t really move that much yet and are often still disks. When the first one let’s go, the second one starts contracting more and the third starts doing the same, slightly. And so it goes on until there is only a polyp stalk left.

Stage 0

The image shows four phases, each of them at a different angle. Stage 0 is a newly released ephyrae, in this stage they weakly move around by contracting the edges of their bells. A is a drawing of the gastric system, B is the oral view, C the aboral view, and D is the mouth without oral tentacles present. Many parts of the jellyfish are already developed, but some of them aren’t, like, for example, the tentacles.

Stage 1

As the jellyfish grows, the bell is still turned inside out. The oral tentacles become slightly visible, the gastric system and the nerves start to develop. The stage one ephyra is roughly 48 hours old.

Stage 2

The little ephyra continues to grow, developing its nerve and gastric system, everything simply becomes larger and better developped. The stage two ephyra is roughly three to four days old.

Stage 3

The bell of the ephyra starts to thicken and the oral arms are now clearly visible. Now it looks unmistakenly like a jellyfish, but just one that’s inside-out as the bell didnt curl in- and downwards yet. The ephyra is about 6 to 7 days old in this stage,

Stage 4

Developed stage of ephyra form.
Image from Plos One.

The ephyra becomes more complex, developing its gastric system and nerve system even further. The gastric filaments, used to produce enzyms to digest and paralize caught prey, are now clearly visible.The nerves of a jellyfish detects light and gravity. However, even when swimming it can’t change its direction. The current will take it and that’s it.

Stage 5

The oral arms develop epaulettes, or mouth folds in this stage. The velar lappets in the bell develop even further to form a nearly fully formed bell and the four oral tentacles devide into eight. The ephyra is now 9 to 15 days old.

Stage 6

The bell starts to turn down- and inwars, resembling more of the final form. The tentacles start to form a J-shape, typical for this species. The ephyra is now 16 to 20 days old.

Stage 7

The final ephyra stage. The mesoglea in the bell thickend massively and turned it into a very recognizable shape. The nerve- and gastric systems are now fully developped. This species doesn’t have the long strands of stingint tentacles like many others have, but it does have stinging cells, this species has them all over the oral arms.

Explaining the markers

hyHypostomeThe oral tip surrounded by tentacles.
neNematocystCycst with undeployed harpoon-like stinging cells.
trTentacular ringThe ring of which the tentacles grow.
stStalkThe stalk on which the polyp is attached.
caCalyxBasal portion of the upper tentacular part of a polyp.
edEphyra diskStacked individual ephyra in an early stage.
tenTentaclePolyp tentacles.
mlMarginal LappetSensing organs fringing the bells edge.
rhRhopaliumExtensions of the sensing organ. Detect light and gravity.
rcRhopalium canalThe sensing canal leading to the rhopalium.
vcVelar canalPart of the gastric system.
rlRholapar lappetsThe outer end of the rhopalium sensor.
maManubriumThe tube that leads from the mouth to the stomach.
gfGastric filamentsAn opening in the stomach that releases enzymes to digest and paralyze caught prey.
lbLappet budEncase the rhopalium on both sides.
otOral tentaclesThe non-stinging oral tentacles leading to the mouth.
prcPrimary ring canalFused velar and rhopalia canals.
epEpauletteMouth folds.
Description of the letters displayed in the images.

Fully grown medusa

Fully-grown Rhizostoma luteus jellys reared in a laboratory.
Image from Plos One.

After 25 days, the ephyrae are called medusae, in the rhizostoma luteus species, this means that it continues growing in size and starts to change color. The bell becomes a milky white-bluish, and is somewhat translucent. It shows reddis-brown warts. The oral arms are violet with mustard colored frills and the appendages coming from between the oral arms were light purple-brown, if present. These appendages are known to have different sizes and count up to 8 in total. None of them are ever fully developped.

When fully grown the cycle will start again. During dusk and dawn, then together in big groups, they will start spawning sperm and release their eggs. Most species quickly die after this.

Different species

There are many different jellyfish species which all have slightly different timeframes they develop in. As stated before, some species skip the polyp stage. Others form many branches on a single polyp, to fall off at a certain point to become individual polyps.
When you use jellyfish in your design, don’t forget to google and collect examples of different species. They are a great source of inspiration!

Different colors of polyps and ephyrae

Different young ephyra shapes. 1: Scyphozoa jelly (class) 2: Lions mane jelly 3: A. aurita 4: Aurelia.
Art by: Tessa Geniets

Like adult jellyfish, polyps come in many colors. Nearly all of them start off as a white, or off-white color. Usually leaning towards the yellow-ish or orange-ish color spectrum. But as the polyp matures and starts to form ephyra disks, in some species the colors becomes darker. Though most polyps and disks keep a pastel color (white + color) some are a deep red or orange and warm yellow.
As soon as the ephyra disk releases itself from the polyp, it’s still mostly translucent, but still retaining the color from its polyp stage. Overtime the color will change into whatever color the adult jellyfish is.

The different polyp and ephyrae forms

When we talk about form, we talk about the 3d shape of an object, in this case, the polyp and ephyrae. The shape is the 2d form of anything that is flat or displayed on a flat surface.
The Rhizostoma luteum has been clearly described already, it’s worth checking the images and charts that come along with it. But many other species don’t only grow one stalk, they grow many side-branches on their stalks, making them look more like corals than an actual jellyfish polyp.
When the ephyra lets go, it’s really no more than a star-like shape, consisting of several lobes protruding from the edges, which, after about a month, will form into a bell. Some species have pointy loves, others are more rounded, or have little indentations at the ends of these lobes. The ephyra early bell is curled outwards instead of inwards and curling away from the gastric tube that’s already present. From this point on the ephyra will continue developing. In most species, this means their bell starts turning the right way, gastric- and nerve system develops, the jelly gets its stinging- and feeding tentacles and obtains the distinct features of an adult jellyfish.

The life cycle of jellyfish completed

Depending on the species we’re talking about, jellyfish live a few days, up to a year. During dusk and dawn, when grouped together, the males will release their sperm, which the females then collect to fertilize their eggs, which are released and either turn into small ephyrae after, or first go through their polyp stage to start the whole life cycle over again. Want to learn more about the adult stage? Read on right here: Adult jellyfish for creatives.

Several different jellyfish species.
Photos provided by Unsplash, photographs left to right by: Nikolay Kovalenko | Colin Viessman, James Lee, Hanson Lu, Nikolay Kovalenko | Colin Viessmann and Lucas Doddema


The jellyfish is an interesting animal in all its stages and it comes in many shapes and forms, making it to be a very inspirational animal to use in your designs. Don’t hesitate to use google or other search machines to find suitable visual reference material. There are so many species out there (over 2000 known, its thought there are 30.000 more to still discover) all with their own features. Although the polyp- and ephyrae stage are fairly simple forms, they still come in a wide variety. Have your design grow from them, or have them grow from your design, maybe your design is an ancient turtle, spending its time mostly resting on the ocean floor. How convenient is it to have your food source grow on your back? I mean, I know I would like one that keeps copying itself new money :p.
All I’m saying is, with simple lifeforms like these, coming in fairly simple shapes and nearly unlimited colors, you could apply them anywhere, be that as a hybrid, a single lifeform, or something else. Allow yourself to be inspired by these wonderful creatures and let them open up new dimensions for you.

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