Reproduction
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.
(scyphozoans.tripod.com)
OVERVIEW
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
(tolweb.org)
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.jpg)
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.)
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