The moon jellyfish is one of the most well-known species of jellyfish in the world. Belonging to the genus Aurelia, it is closely related to many other species of the genus. A few of its most easily distinguishable features include a translucent, circular body measuring between 25 and 40 cm in diameter, gonads shaped in the form of a horseshoe and the lack of any type of respiratory system. Members of the species don’t have any gills or lungs, but are instead able to diffuse oxygen from water through the use of their thin membrane. The species is resilient and extremely widespread, being present in all major oceans of the world and in waters with temperatures ranging from 6 to 31 °C.
The moon jellyfish is also known among researchers as Aurelia Aurita. Aside from its ability to efficiently extract water from oxygen, the body structure of this species of jellyfish confers many more advantages and surprises. The animal not only lacks a respiratory system, but also has no use for an excretory or circulatory system. The food it consumes is broken down by digestive enzymes in the gastro-vascular cavity, and the same cells that produce the digestive enzymes also trap nutrients and carry them throughout the body to wherever they are needed. While these creatures can reproduce sexually, their bodies are equipped for much more. According to a recent study, A. Aurita is capable of a process known as lifecycle reversal, where individuals grow younger rather than older.
Like most types of jellyfish, A. Aurita has a diverse diet consisting of crustaceans, tunicate larvae, protozoans, fish eggs, mollusks and other small creatures. Their nematocysts allow the jellyfish to protect themselves and hunt for food even from their youngest age. That being said, the species has a large number of predators that also include the leatherback sea turtle, a large medusa known as Aequorea victoria and the ocean sunfish.
The lack of any complex organs and its remarkable regenerative capabilities allow this jellyfish to thrive under the harshest conditions. While one might find the moon jelly in many tropical regions including the Pacific Ocean, the species is also prevalent in areas like New England and Eastern Canada on the North American coast, being able to withstand temperature drops even at latitude 70°N. The moon jellyfish generally thrives in temperate waters, and can exist in water that features a severe drop in salinity to 6 parts per thousand.