But with the Aurelia we have here, it can be very hard to tell the difference between males and females. The best way to tell is to take a small amount of the gonad from the animal and look under a microscope. It is very easy to see the eggs and sperm of the jellies under a good microscope. In other jellies it can be we very easy to tell the difference. Up north it is easy to see the difference in color between males and females.
Jellyfish can live a wide variety of ages.
Some are very short lived and some can live for many years. The Aurelia we have typically live for one year, but it is not uncommon to see animals in a population that are two years old. In aquariums, kept in very unnatural conditions, jellies can live for many years in good health. But there is another issue we have to talk about. They are actually immortal as far as the genes are concerned.