Do Jellyfish lay eggs or give birth? Where do Jellyfish lay eggs?

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Do Jellyfish lay eggs?

An egg is actually a fertilized ovum (female gamete) fused with the sperm (male gamete). As soon as the fusion of ovum and sperm takes face the development of the offspring begins.

The offspring will first develop into a zygote, then into an embryo, then it will turn into blastula and gastrula, and then it will further develop to becoming a young jellyfish.

Now, if the whole series of zygote development to young jellyfish takes place inside the body of the female Jellyfish then, it will be termed as internal development.

And, if the zygote or the embryo comes out of the body of the female jellyfish and carries out its further developments then, the development of the jellyfish will be termed as external development.

Now, if the fusion of the ovum and sperm i.e fertilization takes place outside the body of the jellyfish, then it will be better known as external fertilization that will always lead to external development of the jellyfish.

So, Do Jellyfish lay eggs? What do you think? Here’s the answer provided below:

Jellyfish can lay an underdeveloped fertilized egg in the form of a zygote or an embryo into the open water. The egg equipped with the zygote or embryo will start its external development out of the body of the female jellyfish, which is in the open water.

For example, in a few Box Jellyfish species like Copula sivickisi fertilization can occur internally by mating. The male transfers a sperm package into the female’s stomach to fertilize the eggs after both jellyfish have entangled their tentacles.

In another example, of the Aurelia Jellyfish, the male sperms swimming about in the water will reach the ova and fertilize them in the stomach of the female jellyfish. Thus leading to internal fertilization.

However, in the majority of the species, the Jellyfish can neither lay eggs nor give birth to the young ones.

It’s because they will release the sperms and ovum into the open water where fertilization will take place by external fertilization, out of the body of the jellyfish. That is, many jellyfish reproduce using external fertilization.

A pair of jellyfish, Copula sivickisi, mating. In this cuboza species, the male (right) drags a female (left) through the water before pulling her in close and using his tentacles to pass a sperm packet to her tentacles. She then eats that sperm.
A pair of jellyfish, Copula sivickisi, mating. In this cubozoa species, the male (right) drags a female (left) through the water before pulling her in close and using his tentacles to pass a sperm packet to her tentacles. She then eats that sperm.
(Image: © Image courtesy of Alvaro E. Migotto, University of São Paulo)

Do Jellyfish give birth?

Giving birth means to take care of the fertilized eggs inside or outside the body of the female until it develops into young individuals.

The process of giving birth means to produce a well-developed young from the body of the female. Or, it also means sitting or keeping the eggs so as to hatch them by the warmth of the body of the mother.

Jellyfish don’t give birth to their young ones because they lay underdeveloped eggs in the form of zygote or embryo out of their body and leave them in the ocean bed and move ahead. They don’t even care about and nourish the laid eggs.

Another reason Jellyfish don’t give birth to their young ones is because, they do simply release the sperms and the unfertilized ovum into the open water and move on, and it is in the open water where fertilization and external development takes place.

In some species, it has been seen that some females carry fertilized eggs for a short time inside their stomach before releasing the developed embryo or planulae into the water.

At that point, when they keep the fertilized eggs inside, the adult jellyfish do provide a bit of care and nourishment for the development. But, as soon as the eggs are released no further care for their young is seen.

They simply release the eggs and move on. In fact, most species appear to die soon after fertilization occurs.

Giving birth to young ones also demands better nourishment and care from the parental side until the eggs develop into young ones. But, in the case of jellyfish, no such characteristics are seen.

In fact, they don’t even know which their eggs are, as they do release thousands to millions of eggs at a time.

And those that release the millions of gametes directly into the open water don’t even know if those have fused or have developed into young ones.

That’s how it usually occurs amongst the invertebrates inside the oceans. So, the final answer is that Jellyfish don’t give birth.


Where do Jellyfish lay eggs?

As already mentioned above in the post, there are only a few Jellyfish species that receive sperm through their mouths to fertilize the unfertilized eggs inside their body cavity. Then they do only lay the underdeveloped eggs.

But, it is also to be noted that most of the Jellyfish species are seen to just release sperm or eggs directly into the water where fertilization will take place.

Under the most favourable conditions, they release their gametes in millions once a day, usually synchronized to dawn or dusk.

Those few jellyfish that have performed the internal fertilization will lay the underdeveloped eggs in the form of zygote or embryo into the ocean water during their locomotory motion.

These released zygotes or embryos will flow into the open water along with the water current. Some will settle down on the ocean bed, and some will be still flowing due to the effect of the ocean current.

The zygote will form the 4-celled embryo, then many cells blastula, gastrula, and will eventually turn into the free-swimming ciliated planula larva.

The planula larva will then eventually turn into Scyphistoma stage and will form a stalk to attach to a substratum on the ocean bed.

Later on, the Strobila larva will also be formed and it will also remain attached to a substratum on the ocean bed using its stalk.

Sooner or later, the jellyfish will further develop and will eventually turn into a young Jellyfish (Ephyra stage) and will be detached from the substratum to start swimming freely.


What does a Jellyfish egg look like?

Jellyfish eggs are very microscopic and cannot be so easily seen with our naked eyes. And, these eggs flow along with the water current from one place to another.

The diameter of the newly released egg size differs from a size of 0.02 mm to 0.26 mm in size.

The egg size increases with the increase in the developmental stages. The embryo can be few millimeters large than that of the zygote.

As there are more than 2,000 different types of Jellyfish known so far. So, the egg size also do varies between the various species.

As there’s so much diversity in marine life, scientists do believe that there could be as many as 300,000 different species of Jellyfish yet to be discovered.

Just like the adult Jellyfish and adult Comb jellies vary greatly in size depending on the species. Most adult Jellyfish size range from being less than half an inch (1 cm) wide to about 16 inches (40 cm) wide, though the smallest ones are just 1 millimeter wide.

So, as you see, the size of the adult ones largely varies, so does the size of the egg as well.

Large Jellyfish species will have macroscopic eggs that can be easily seen by our naked eyes. While the small Jellyfish species will have extremely microscopic eggs that cannot be so easily seen by our naked eyes.

Jellyfish egg size is one of the most important aspects of the life history of these free-spawning marine organisms, and it is correlated with larval developmental mode and many other life-history characters.


Are there male and female jellyfish?

Yes, there are separate male and female Jellyfish. The males can release sperms and the females can release ova or eggs.

This answer can also be supported as the sperms of the male after being released in the water find its way into the female’s oral cavity or even at the female’s stomach where they will fuse together and form a fertilized egg or ovum.

It has also been seen that in a majority of the species the females carry their fertilized eggs in a brood pouch or in their stomach till they are being released into the open water.

Thus, this also proves that females are there that are distinct from the males in terms of having a brood pouch.

If you see the outer morphology you can’t so easily make out if the jellyfish is a male or a female. But, if you can see its anatomy then you can easily know its gender.

Both of the sexes will have their reproductive gonads inside the lining of the gut, also known as the gastrodermis.

Mature gonads are brightly colored and will vary in color depending on the state of the animal’s maturity and sometimes sex.

Depending on the species, it has been seen that the male gonads may be of a different color from the female gonads.

The very best way to say the gender of a Jellyfish is by looking at the adults.

Adult female jellyfish can be identified by the eggs she holds in her mouth or by brood pouches, while males don’t have such a type of biological system. Males are only able to release the sperms and nothing much.

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