Reproduction

      Every organism in our vast universe reproduces. Some of the reproduction processes can be quite simple or very complicated. One complicated life cycle is the alternation of generations. In this life cycle fertilization can occur inside or outside of the organism, and the production of gametes can either come through mitosis or meiosis. The young offspring can be nurtured or not nurtured by their parents, and reproduction can occur sexually or asexually. Cassiopea xamachana is capable of both of these methods (Post et al. 2012).

     When Cassiopea xamachana reproduces sexually (both the male and female go through meiosis to produce their gametes), the male medusa will release its gametes or sperm into the water to be acquired by the proximate female medusa. The fertilization of the female’s gametes or eggs occurs inside of the female’s body. The adult female will internally incubate or brood the zygotes, which are covered with a mucus, until ciliated planula develop and start swimming. Planula are small mobile larvae. The planula will settle in a specific spot and grow and develop into a sessile asexually reproducing polyp, or scyphistomae (Post et al. 2012). Scyphistomae are the stage of Cassiopea xamachana’s life cycle that reproduce asexually by budding (Thornhill et al. 2006). The scyphopolyp will gain symbiotic photosynthetic algae once its oral opening is completely developed. Then, when nutrients and resources are abundant, the polyp will produce buds. Another wave of polyps are produced from each bud that settles onto the sediment (Post etal. 2012), or leaves that have fallen from the mangrove trees. These leaves might also provide cues to Cassiopea xamachana as to whether it should produce sexually or asexually (Holland et al. 2004). These secondary polyps will produce adult medusa by separating and squeezing the spicules which contain some of the tentacular portion of the polyp, a process known as monadisc strobilation, which only occurs during the winter, and occasionally fall months of the year. Monodisc strobilation will only occur after the scyphistomae form a bond with enough symbiotic photosynthetic algae, and when the temperatures are warm enough; temperatures must be at least 20 degrees Celsius. After monadisc strobilation, the polyp will grow the lost tentacular part from the strobilation, and will develop into an immature ephyra (Post et al. 2012). Ephyra are larval jellyfish after they have separated from the scyphistoma (McGill et al.  2008). They eventually grow and develop into a mature medusa that will reproduce sexually. Cassiopea xamachana do not care for their young, except for the brooding, and therefore they are not investing a lot of energy and resources into them (Post et al. 2012).