How do Jellyfish mate? Do Jellyfish die after mating?
What is the difference between mating and reproduction?
Well, many people often confuse the term mating with reproduction, but mating and reproduction are the two very different concepts.
Reproduction is the process of making a biological copy of something, that is the production of offspring by a sexual or asexual process.
Whereas, mating is the process of the pairing of either opposite-sex or hermaphroditic organisms, usually for the purposes of sexual reproduction.
There are two forms of reproduction: Asexual and Sexual reproduction. Mating is the biological process that leads to Sexual reproduction.
Sexual reproduction is a broad term that involves various processes like attracting the opposite sex, mating, fertilization, zygote, and embryo formation, and the formation of larvae.
Whereas, mating is just one of the most important processes during sexual reproduction in which the sexual union leading to the fusion of male and female gametes is seen.
Mating is an act that may or may not lead to the formation of offspring, meaning that the success rate of mating leading to reproduction is not always 100%. Whereas, reproduction is a very complex process that always leads to the formation of offspring.
The mating process of animals depends on their social behaviour and how they physically contact each other to transfer the male gamete into the female reproductive part.
Whereas, reproduction is a very broad and complex process that involves various biochemical, biophysical, and physical processes. Mating is one of the physical processes of sexual reproduction.
How do Jellyfish mate?
Jellyfish mate using their tentacles that is by touching the stinging cells of the two sexes. The cubozoa Jellyfish species, Copula sivickisi, shows the mating behavior that has been well-studied so far by marine biologists.
Copula sivickisi, has a very different mating tactic, which involves a courtship dance.
In this species, during the mating process, a male will use his tentacles to grab a female’s tentacles after attracting her.
He will then drag her around for a while before pulling her close to him to release the sperms.
As both are in close physical contact with each other, the male will release a package of sperms into the oral arms and mouth of the female. The female will then consume the sperm package.
The sperm package consists of the male sperm cells along with some non-poisonous stinging cells that will help the sperm to anchor to the female gonads.
As soon as the sperms get inside the female, the female’s digestive enzymes start to act on those sperm cells and partly digest it. This releases the nuclei from the sperms.
The nuclei are then carried to the egg cell of the female where it goes and fuses. The DNA of the male sperm nucleus fuses with the DNA of the female egg nucleus.
This results in the formation of zygote which remains inside the female for a few days. This keeps them safe.
She then after a few days releases the underdeveloped eggs in a sticky strip called an “embryo strand” to the surface of the coral reef.
The development of the larva takes place out of the body of the female. So, after a few days, the Planula larva develops from the laid eggs and they crawl out of the sticky strip and swim away.
(Image: © Image courtesy of Alvaro E. Migotto, University of São Paulo)
How do Jellyfish attract mates?
Jellyfish can signal each other to attract mates. Jellyfish individuals can release some sort of chemical signals when it is about to mate.
Both males and females are probably attracted to each other by the chemical signals that they have released into the water that their cnidocytes or stinging cells can detect.
They have very simple sensory organs, and no brain to process any information. So, once the cnidocytes of the tentacles detect the mating chemical signal then the two sexes get attracted and the male grasps the female’s tentacles using his tentacles.
In fact, Box jellyfish species are those that even have advanced eyes that help them to see. That also helps them to better know their mates just after the chemical signals are released and have been detected.
Although, it’s pretty much clear that they use chemical signals to attract and detect their prey. As the scientists ‘sonar data’ revealed that the Jellyfish are capable of recognizing each other from a distance of two meters.
Yet, how they do so, and how and what type of chemical and chemical signals they release is still unknown and is a mystery.
Do all Jellyfish species mate?
No, not all Jellyfish species mate in order to reproduce. Those species that belong to the Box Jellyfish (Cubozoa) category mate which involves a courtship dance leading to physical contact between a male and a female.
All Jellyfish go through a series of stages during their life cycle. The stages in the life cycle of Jellyfish includes the Planula larva stage, Scyphistoma stage, Strobila stage, Ephyra stage, and then the fully-formed adult Medusa stage.
All those that do develops into an Adult Medusae stage fall into one of three classes: Scyphozoa also called “true jellyfish, Hydrozoa that are smaller than those of typical jellyfish, and Cubozoa that are also known as box jellyfish.
Cubozoa Jellyfish species have an almost transparent cube-shaped body with an upper umbrella portion, complex eyes, and stinging tentacles containing potent toxins in some species.
In many species, there aren’t even males or females as such. So, they don’t bother much about mating.
In fact, those of a few Box Jellyfish species like the Copula sivickisi shows a very different mating tactic, which involves a courtship dance.
Other species of Jellyfish don’t mate and reproduce in the simplest way possible. Males and females simply release their sperm and eggs into the water in huge numbers. Or, only the males release the sperm into the water in huge numbers, and as such fertilization can be either internal or external.
Do Jellyfish die after mating?
Yes, some species of the Jellyfish soon dies after mating and releasing the embryo out of the body of the female.
It has been seen that after the mating process and then soon after releasing the embryo, the life cycle of a few Jellyfish species ends, and then they die soon.
For example, many colorful Jellyfish species that are common in the coastal zones worldwide complete their life cycle within a year or so. The medusa of most species are fast-growing, and they rapidly mature within a few months and die soon after breeding.
Some species of Box jellyfish that shows mating ritual do not have long lives. They may spend less than a year in the medusa form and only a few months as a polyp. And, this entire cycle can take place over the course of two years or less.
It is also to be noted that there are some species that never dies as like the Turritopsis dohrnii (immortal jellyfish) after they have reproduced. They don’t die because they transform themselves back into their juvenile polyp stage which is long-lived.
When they transform themselves from their adult medusa stage to the juvenile polyp stage their tentacles retract, and their bodies shrink, and they sink to the ocean floor and start the cycle all over again. That’s why Turritopsis dohrnii is immortal.
Can they reproduce without even mating?
Yes, a majority of the jellyfish species can reproduce without even mating.
Reproduction without mating happens because the male can release his sperms and the female her ova (eggs) into the open water where both of the gametes fertilize.
Meaning that many jellyfish species reproduce by external fertilization, but in a few box jellyfish species like Copula sivickisi, fertilization can occur internally after the mating ritual has ended.
However in some species, internal fertilization can also occur with mating. Like for example in Aurelia jellyfish.
During non-mating reproduction, sperm cells swimming in the water reach the ova (eggs) and fertilize them either in the stomach of females or in the frills of the oral arm. This causes non-mating internal fertilization in females.
Or, the ova that are released in the water are also fertilized by the sperms that are also present in the open water. This causes non-mating external fertilization out in the open water.
As soon as the fertilization has completed, the life cycle of box jellyfish begins that includes the Planula larval stage, Polyp stage, Ephyra stage, and Medusa stage.
The planula stage is the tiny larval stage of the jellyfish. The polyp stage is also known as the Scyphistoma stage that settles down.
Next comes the Ephyra stage of development. Ephyra stage is the free-swimming jellyfish stage that comes before the full-grown adult medusa stage.
Soon, they will reach the adult medusa stage of their life cycle, where they will gain the maximum body length and diameter.
They may spend less than a year in the medusa form and only a few months as a polyp. And, then soon after the mature medusa stage their life cycle will end and they will die.
Do Jellyfish lay eggs or give birth?
A majority of the Jellyfish species can give birth to many under developing embryo if the fertilization is internal.
However, in a lot of species, the Jellyfish species can not lay eggs (fertilized ova), because the fusion of male and female gametes, that is fertilization, occurs out of the body of the female. This is external fertilization.
During the external fertilization phase the zygote and embryo formation, and also the planula larva develop out of the body of the female.
Whereas during the internal fertilization phase in the majority of the species, the planula larva also develops out of the body of the female, and only the zygote and embryo formation occurs inside the body of the female.
Now during internal fertilization that leads to laying of eggs, there are two different cases that has been seen.
In the first case, the zygote remains and develops inside the female body for a few days, and then the giving of birth to an under-developed embryo occurs soon after the zygote is fully developed. The blastula, gastrula, planula, and all other stages happen outside the female body. For example, in Copula sivickisi (Box jellyfish)
In the second case, as soon as the fertilization has occurred the giving of birth of the under-developed zygote occurs out of the female body. The zygote now turns into an embryo, blastula, gastrula, planula, and all other stages that also happen outside the female body. For example, in Aurelia Jellyfish