Jellyfishes are exciting creatures. Scientists estimate that jellyfishes have been traversing our oceans for 600 million years. But how does this creature with no brain, heart, blood, or bone manage to reproduce?
Jellyfishes reproduce both sexually and asexually. The sexual stage of the jellyfish reproduction cycle involves the creation of planula from the release of eggs and sperm into the water. Consequently, the planula finds a hard surface – commonly the ocean bed – and grows into a polyp. Then the asexual reproduction stage is activated with the polyp self-multiplying into a colony of polyps. This matures into Ephyra. The ephyra is a young jellyfish that later develops into an adult medusa jellyfish.
The jellyfish has one of the most intriguing reproduction processes. It is one of the very few organisms that combine sexual and asexual reproduction. But more than this, how often do jellyfishes reproduce in a year? How many babies can one jellyfish make? What time does it take a jellyfish to hatch?
Let us find out the questions to these and more.
How Do Jellyfishes Reproduce?
Let us start the story by establishing that jellyfishes are cnidarians. These organisms commonly fertilize externally.
Here, adult male and female jellyfishes release sperm and ovules into the water. If hermaphrodite, the jellyfish will release both sperm and ovules.
Note that not all species fertilize externally. In some rare jellyfish species, the female retains their eggs and receives sperm orally.
The received sperm then fertilizes the eggs in the jellyfish’s body cavity. After this, it releases it into the water.
The Eggs Settles
This closes the sexual phase of reproduction. Now the fertilized egg in the water develops into a planula.
The planula is not easily visible to the human eyes – is round and swims around the water, leveraging its cilia for propulsion.
The planula resembles a significantly reduced sea anemone.
Within a week (or at most ten days), the planula settles on a rock or just any other hard surface. This is commonly at the bottom of the ocean bed.
Equipped with a solid base, the planula grows into a polyp, triggering the asexual reproduction phase. Here the polyp self-reproduces more polyps forming a colony.
The Ephyra Forms
These polyps now cumulatively form an ephyra. The latter is a bundle of baby jellyfishes (strobila) yet to develop fully.
Typically, the ephyra at the strobila’s top is the most mature and likely released first. Upon sufficiently maturing, the ephyra begins pulsing, ultimately ejecting itself from the strobila.
When each of the ephyrae that makes up that stack has matured, pulsed, and broken up, the polyp returns to its original state.
How about the ejected ephyra?
Now on their own, each ephyra stands the chance of maturing into an adult medusa jellyfish.
Do All Jellyfish Reproduce Asexually?
Yes, every jellyfish must undergo the asexual reproduction phase.
If the polyp doesn’t independently reproduce itself into a colony, the ephyra (from which an adult jellyfish arises) can never be formed.
How Often Do Jellyfish Reproduce?
A jellyfish’s reproduction rate depends on the existing conditions where they stay. If the conditions (nourishment, temperature, water salinity…) are suitable, jellyfishes reproduce daily.
How Many Babies Do Jellyfish Have?
While not much is known about the minimum babies a jellyfish can have at a time, scientists have discovered that some jellyfish species can lay up to 45,000 eggs in just one night!
How Long Does It Take for a Jellyfish Egg to Hatch?
It depends on the species. Some eggs hatch into larval comb jelly within 24 hours. Conversely, some can take weeks.
Why Do Jellyfish Reproduce Quickly?
Jellyfishes reproduce so quickly because they spurt out eggs and sperms at outstandingly high rates. For most species, their reproduction job ends almost as soon as the eggs and sperm are released in the water.
From there, the egg has to survive independently with zero parentage. It is way different for animals with gestation periods where they have to get pregnant and give birth after a while.
Next, after birth, such animals will have to nurse their little ones to maturity.
Take an animal like the elephant (or even humans) with enormous parenthood duties. The elephant can live up to 60 years but rarely gives birth to more than four babies all through its lifetime.
This is likely because of the enormous workload it takes to conceive and nurse their babies. The same applies to humans.
Do Jellyfish Reproduce in Captivity?
Yes, jellyfishes reproduce in captivity if you can masterfully replicate their reproduction cycle as they would in the wild.
A clean aquatic environment for the jellyfish to thrive is fundamental to the whole process.
Inevitably, you would need a set of polyps to trigger the process. If you already have some jellyfishes, you can investigate their aquarium and extract a handful of polyps from there.
If you don’t, you need to buy polyps from a jellyfish dealer. There is also the option of growing them from planula. But this process is overtly technical, and you may struggle to get it right.
Yes, getting polyps from a dealer can be expensive, and shipping can be a problem. Nonetheless, that is your best bet.
Having procured your polyps, transfer them to a culture dish or just any tiny aquarium you have and cover it. Covering your tank helps prevent water evaporation and the water salinity from being compromised.
The aquarium must be spacious enough for the polyps to bud off. If your tank’s water content is inadequate, there is the risk of the water being messed up within a day.
Keep the tank at room temperature. You can facilitate the process with an incubator nonetheless. If you get the conditions right, the polyps should independently grow into strobila within weeks and then into ephyrae.
It would help if you supplemented this polyp tank with another tank for housing the ephyrae.
The polyp tank should be built such that the ephyrae can flow into their designated tanks via an inlet hose (enhanced with filter) installed on the polyp tank.