Jellyfish Life Cycle

Introduction:

Once in a while, we all go to the beach and if we are lucky enough, we spot a jellyfish. As beautiful as they are in their appearance, it is just as painful if a jellyfish stings you. Jellyfish are bell-shaped, jelly-like creatures with long trailing tentacles that are found at shores.

Jellyfishes are marine invertebrates with around 200 species that fall under the class Scyphozoa and the phylum Cnidaria.

The size of a jellyfish varies from 2 cm to 40 cm in diameters and there are certain larger creatures that measure up to 6 feet.

Now, let’s look at the life cycle of a jellyfish for a better understanding.

Life Cycle of a Jellyfish:

Jellyfishes are organisms that reproduce sexually with reproductive organs known as gonads.

1) The Egg – Stage 1 –

During the time of dusk, large groups of jellyfishes gather and start spawning. During this process, jellyfishes release large amounts of sperm and eggs into the ocean. The fertilized eggs float in the ocean.

2) Planula Larvae – Stage 2 –

The fertilized eggs grow in a planktonic spore called the planula. After some time, the eggs hatch and planula larvae emerge from the female’s mouth. A planula is tiny and oval-shaped with minute hair called cilia that line outside the body of larva. The planula larva floats in the water, if not eaten by intriguing predators. After a while, the planula larvae swim down and settle on the underlying surface to develop into a polyp. The polyp is the next stage after planula.

3) Polyp (Scyphistoma) – Stage 3 –

When the planula settles down, it attaches its body to a hard surface and develops into a polyp. A polyp is also known as Scyphistoma, which has a cylindrical structure. A polyp’s base has a disc to aid in attaching to surfaces and mouth on top with tentacles around it. Depending on the species, the polyps can be in this stage for a long period. Since the polyp has a fully developed digestive system and one part of polyp is attached, it spends most of its time feeding. The polyp forms hybrid colonies in which the polyps are linked together through feeding tubes. Here they enter the next stage of their life cycle called medusa.

4) Medusa – Stage 4 –

The process through which new medusas are formed is called strobilation. In this process, the end of Scyphistoma metamorphosis into an ‘ephyra’, which is called immature medusa. It eventually detaches and swims away. Depending upon the species, a polyp is able to produce one or several ephyrae, at once with many intervals. The free-swimming ephyrae develop and grow larger in size and gradually transform into an adult jellyfish.

Conclusion:

Jellyfishes appear to be a transparent, bell-shaped invertebrate with long trailing tentacles, that we might notice washed up at the shore. The life cycle of a jellyfish is complex and jellyfish have the ability to adapt to extremely harsh living conditions.