How Do Jellyfish Reproduce?

How Do Jellyfish Reproduce?
Photo by Jeffrey Hamilton

Jellyfish are gelatinous invertebrates with a dome form. Most of us have come into contact with this fascinating animal somehow.

Despite its popularity, this intriguing species remains relatively unknown. For example, have you ever thought or asked, “how do jellyfish reproduce?”.

Surprisingly, the reproduction of Jellyfish does not occur within the female Jellyfish’s body as in mammals. In this article, you’ll learn how Jellyfish reproduce!

What Are Jellyfish Characteristics?

The Jellyfish are members of the “Cnidaria” phylum, which has over 10,000 species; only 20 are freshwater, while the rest are marine.

Jellyfish have radial primary symmetry (splitting an animal into equal halves along the body’s longitudinal axis).

Jellyfish come in many different shapes, sizes, and colors. Although most of us think of Jellyfish as clear blobs in the sea or washed up on the beach, this is not the case.

Many of the large Jellyfish have colors such as reds, browns, yellows, mauve, and even numerous hues of blue. 

The sea nettle, for example, is frequently orange or light brown, Octopus jellyfish are blue/gray in hue, and Lion’s Mane jellyfish are golden in color—just like their namesake!

Many other Jellyfish are transparent, allowing you to see their four stomachs. Jellyfish can be colored by the water they live in and their unique farming method.

Some jellyfish, such as Cassiopeia xamachana, are vegetarians who generate food and transport it with them. 

These Jellyfish produce algae inside their bellies, providing sustenance as they float across the oceans. The algae can vary in color, giving the Jellyfish a wide range of hues.

Others are still influenced by their diet in terms of color. Moon jellies, for example, are typically pink to purple in hue while feeding on a large number of larval crustaceans high in specific pigments. And in the Aquarium of the Americas, brine shrimp are frequently used as jellyfish food.

As a result, the orange-colored brine shrimp may be seen inside the Jellyfish’s four stomachs after they feed.

A jellyfish’s body is structured as a blind sac with a single opening for food entrance and waste outflow.

In addition, jellyfishes have a digestive chamber known as a “gastrovascular cavity,” which digests food and transports nutrients and oxygen to the rest of the organism.

Because Jellyfish lack a brain and a heart, they are distinguished by highly developed organ senses in their bell.

These sensors exist so that Jellyfish can detect a change and coordinate their movements within their environment. In addition, their visual organs (ocelli) and static organs can be found there (statocysts). 

Jellyfish can be predatory or filter feeders. Filter feeding occurs when they filter the water around them, capturing minute food particles for feeding. They also have “cnidocytes,” which are specialized cells.

There are various varieties of these cells, but the most frequent is the nematocyst, which is why jellyfish sting: to hunt and defend themselves. Its tentacles contain these stinging nematocysts. 

Ptychocyst, an explosive cell, is another way Jellyfish hunt. Ptychocyst is a sticky surface used by Jellyfish to capture prey.

Another distinguishing feature of Jellyfish is that they have two physical forms: polyps (which live tethered to the seafloor) and colonial forms. 

The second bodily form, the planktonic form, is when they live in water and become solitary. Some species are built entirely of polyps, while others are composed of both. You might still be wondering, “how do jellyfish reproduce?” read on to find out!

How Do Jellyfish Reproduce?

To understand how these animals reproduce, we must first understand where they dwell.  Cnidarians all exist in salt freshwater aquatic environments. Internal fertilization (the merger of the ovum and sperm) is uncommon in this medium. 

As a result, cnidarians are subjected to external fertilization. This means both males and females expel ovules and sperm from their bodies.

However, individuals in hermaphroditic species will produce both eggs and sperm. As we indicated in the text, some jellyfish species only have the polyp form, but others have both.

The majority of jellyfish species are hermaphrodites. Other species are dioic and have distinct sexes; however, they are difficult to distinguish.

Jellyfish take on two body forms throughout their lifecycle: medusa and polyps. Polyps can reproduce asexually by budding, while medusae spawn eggs and sperm to reproduce sexually.

The jellyfish medusa (with its bell-shaped body and long tentacles) is merely one stage in the jellyfish life cycle. Jellyfish evolve into a variety of various species.

The lagoon jelly area in the Tropical Pacific exhibit now includes a small ephyra bowl, thanks to a recent intern project, to give Aquarium visitors a peek at another stage of the jellyfish life cycle. Ephyra is the free-swimming jelly stage that occurs before full-grown medusa.

How do Jellyfish reproduce? Male moon jelly (Aurelia aurita) medusas, which may be seen in the Ring of Life exhibit, emit sperm trails that moon jelly females suck up orally and fertilize internally.

The lagoon jelly medusas (Mastigias Papua) on show at Ocean Oddities spawn directly into the water.

Fertilized eggs in both species develop into multicellular planula and eventually into polyps that reside on the sea floor.

Jellies resemble miniature anemones at the polyp stage and reproduce asexually by strobilation. Small ephyra is released into the water when a polyp strobilates (segments its body to reproduce).

Within a few weeks, a bell appears, and the ephyra is reclassified as medusa, restarting the entire process!

How Do Jellyfish Sting?

Your question, “how do jellyfish reproduce?” has been answered. Next is “how do jellyfish sting.” Jellyfish are transparent and composed of 95% water, so you’d assume there’s not much to them. 

However, Jellyfish are more complicated than you might believe, and one of their most intriguing features is their stinging cells.

Cnidocytes are jellyfish stinging cells that are found on their tentacles. They are tiny compartments that contain a needle-like stinger. The cell opens when an outside force activates a stinger, allowing ocean water to flood. 

This causes the stinger to dart out into the source of the activity, where venom is discharged. Everything happens in a millionth of a second. Though most jellyfish venom is harmless, some can be fatal.

The Indo-Pacific box jellyfish, for example, delivers venom that causes the heart to constrict. There is an antidote, but the toxin works quickly, so anyone stung should seek medical assistance immediately.

In addition, if you touch jellyfish nematocysts on your skin, you will most likely experience a burning, stinging, or tingling. 

Tentacle imprints, which can be red, brown, or purple track markings, are frequently left by the sting. The whole area might be pink, red, or purple.

Though it is often stated that humans get stung by Jellyfish 150 million times per year, it is unclear where this figure originates from or the true incidence.

Jellyfish stings, however, are common. Furthermore, most are minor and easily treated at home. However, jellyfish stings can cause a severe allergic reaction known as anaphylaxis in certain people.

In addition, some jellyfish species carry lethal venom even if you are not allergic to them.

The following are symptoms of a severe jellyfish sting that require emergency medical attention:

  • Shortness of breath
  • Wheezing
  • Chest tightness
  • Nausea or vomiting
  • Hives
  • Numbness or tingling
  • Muscle cramps
  • Blistering skin
  • Difficulty swallowing
  • Rapid heartbeat
  • Pain in various parts of the body
  • Dizziness or fainting

How to Avoid Jellyfish Stings?

Avoiding jellyfish stings is unquestionably preferable to treating them. You can protect yourself by doing the following:

  1. Prepare: Before stepping out into the sea, study which jellyfish species are abundant in the area, how hazardous they are, and what to do if stung.
  1. Plan: Jellyfish are drawn to warmer water and appear seasonally when the tidal flow changes. Inquire with local authorities or lifeguards about jellyfish season at your destination.
  1. Wear a protective suit: If you are visiting a jellyfish-infested location, you can protect yourself by purchasing a “skin suit” (also known as a “stinger suit”), which is available at many diving stores. They are light, yet they provide an excellent barrier if you come into contact with a jellyfish.
  1. Get a jellyfish repellent: Numerous commercially available lotions claim to repel you if you’re genuinely afraid of Jellyfish. However, even though it is uncertain how effective they are, many customers swear by them. Even suntan creams with jellyfish repellent are available.

How Do Jellyfish Die?

The medusa’s primary purpose in life is to reproduce; therefore, Jellyfish normally do not live very long in this stage.

Many jellies at the Aquarium live for only a few months before they reach “old age.” As you’ve probably figured out by now, the medusa does not symbolize the entire life of the jelly, only the end of it.

Apart from the question, “how do jellyfish reproduce?” It is also important to ask about the conditions for reproduction.

Jellies are extraordinarily good at recognizing the ideal conditions for reproduction; therefore, they don’t need to live for an inordinately long time.

If the conditions are favorable for it to mature into an adult medusa, it will certainly be able to spawn the next generation quickly and efficiently.

You may have heard of an “immortal” jellyfish that can theoretically live forever since its adult medusa can revert to the polyp stage. This is correct, but it is not the only jelly that has survived death. 

Remember that even when the adult medusae of most jellies die of old age, clones of their polyps continue to thrive on the seafloor. Most jellies can live extremely long lives if they are cloned.


In case you have been asking, “How do jellyfish reproduce” This article has taught you that Jellyfish reproduction occurs in numerous stages.

A jellyfish can reproduce sexually as an adult, or medusa, by releasing sperm and eggs into the water, forming a planula.

However, there is still so much to discover about these amazing organisms; thus, they remain a fascinating mystery.

Notify of

Inline Feedbacks
View all comments
You May Also Like