The moon jellyfish, as well as other jellyfish in the phylum Scyphozoa, uses the alternation of generation life cycle to reproduce. There is a sexual and asexual stage to their life cycle, meaning they switch off on which form (polyp or medusa) is formed, although medusa is the dominant form. The sexual stage starts off with the medusa form (the dominant form). Moon jellyfish exists as male or female (they are dioecious); the female jelly produces its eggs and releases them into the pits of the oral arms, while the male produces sperm and releases them into the water. The sperms make their way into the mouth of the jellyfish and to the chamber of the oral arms to fuse with the egg. After fertilization occurs, the planulae is formed and attaches itself to the edge of the bell of the female jelly until it can swim. Next the cilia (hair-like structures) covering the planulae allows it to attach and swim to a rock or seaweed, where it transforms into the polyp (or other known as scyphistoma) and the stage where the tentacles and mouth form.  The polyps can use the asexual reproduction called “budding” to form new polyps. These new polyps have identical DNA or are “daughter” polyps of the original parent because basically the first polyp just spilts into two polyps, but they are unequal in size. No sperm and egg are needed therefore, the same DNA is used and replicated to make the new polyp. The polyps then form grooves (or are now called stroblia), which will become disk-like structures called ephyra larvae. The larvae grows and is now simply called the ephyra, which looks like a young form of medusa  (photos to the above are courtesy of Alexander Semenov). These ephyra starts to mature into the final adult medusa form after detaching from the other polyps.  (

The above explanation is pretty long and boring, but here's the important steps you need to know. The video will give a more visual explanation and enhance your understanding of reproduction among the Moon Jellies (hopefully).

                      (the above video of of courtesy of the marinebiologychannel on youtube)

1.) female jelly produces eggs & male jelly produce sperm
2.) sperm swims inside the female jelly to fertilize the egg
3.) after fertilization, it becomes the planula and grows on the edge of the bell
4.) when the planula is able to swim it uses cilia to swim and attach to a substrate
5.) the planula develops by growing tentacles and forms a mouth, now called the polyp
6a.) budding occurs, where it looks like one polyp splits into two (identical); asexual
6b.) grooves start to form on the polyp and it is now called a stroblia; sexual
7b.) the grooves form deeper and deeper inside the stroblia and become disk-like structures called ephyra larvae
8b.)  the ephyra larvae grows to become the ephyra and lastly the adult medusa form

                                Effects of Temperature and light on the reproduction cycle
        At different stages of the moon jellyfish’s life cycle the water temperature necessary for the highest reproduction outcome changes. There have been many experiments on the correlation between water temperature and rate of asexual reproduction amongst moon jellyfish. Look back to the habitat page for an experiment also relating water temperatures andasexual reproduction in the moon jelly.  a comparison of the different water temperatures needed during the stage of a planula and the stage of a forming polyps. In 2008 an experiment was conducted to look at the effects of temperature and light intensity on the asexual reproduction of the moon jelly. Nine tanks of jellyfish were observed in this experiment at 3 different temperatures of water (20 degrees Celsius, 25 degrees Celsius, and 30 degrees Celcius), three different light intensities (0 lux, 56 lux, 372 lux), and in 12 hour light and 12 hour dark toation periods. The results show that “warm temperature accelerated strobilation and increased the daily production of ephyrae.” (Liu, W., et al. 2008.)  In the other lab, the results found that in higher temperatures caused more types of asexual reproduction, but this lab shows that the transformation from a planula to a polyp, called strobilation, is results in a higher count of eyphra produced.  The temperatures in the med-high range tend to have the greatest results because the moon jelly would not be able to function in areas of the water where there is too much light or the water temperature is too high although, high temperatures increase the rate of transformation from a planula to a polyp due to the production of new bud; the low temperatures were found to result in a very low rate of transformation. Temperature and light intensity greatly affect the life cycle of the Aurelia aurita. (Liu, W., et al. 2008.)