Aurelia aurita

Aurelia aurita (the  jelly, moon jelly fish, moon jellyfish, common jellyfish, saucer jelly or swimming jellyfish) is the most common jellyfish species found in the genus Aurelia. Other species found in the genus Aurelia besides A. aurita are: A. labiata and A. limbata. There are at least 13 species in the genus Aurelia including those that are still not described (Dawson, 2003). They can be found in the Atlantic Ocean, the Arctic Ocean and the Pacific Ocean, and are common to the waters off California, Japan, the East Coast of the United States as well as Europe. The animal is translucent, can be 25-40 cm across, and has characteristic patterns of color within its body. It feeds by stinging small medusans, plankton and mollusks with its tentacles and bringing them into its body for digestion, but is capable of only limited motion; like other jellies it drifts with the current.

General biology
The cosmopolitan Aurelia aurita is found throughout the tropics and as far north as 70° latitude and as far south as 40°. (J.E. Purcell, et al. 2001). In addition to frequenting the North American coast, they are usually found all around the coasts of the British Isles (Russell, 1953). In general, A. aurita is an inshore species that can be found in places like estuaries and harbors (Russell, 1953). They live in ocean water temperatures that range from &minus;6 °C to 31 °C; with optimum temperatures of 9 °C to 19 °C (Rodriguez, 1996). A. aurita prefers mildly cold salt water with consistent currents (Rodriguez, 1996). They can be found in 3% salinity water but are typically found only in water with 6% salinity (Russell, 1953). Their ectreme range is Gulf of Botnia, Baltic sea, where salinity is 0.6%

Feeding
A. aurita species feed on zooplankton that includes organisms such as mollusks, crustaceans, tunicate larvae, copepods, rotifers, nematodes, young polychaetes, protozoans, diatoms, eggs, fish eggs, and other small jellies. Occasionally, they are also seen feeding on hydromedusa and ctenophores (Rodriguez, 1996). Larvae of A. aurita have special nematocysts to capture prey and also to protect themselves from predators. The food is tied with mucus, and then it passed down by ciliated action down into the gastrovascular cavity where digestive enzymes from serous cell would break down the food. There is little known about the requirements for particular vitamins and minerals, but due to the presence of some digestive enzymes, we can deduce in general that A. aurita species consume carbohydrates, proteins, and lipids (Arai, 1997).

Body system
A. aurita does not have respiratory parts such as gills, lungs, or trachea. Since it is a small organism, it respires by diffusing oxygen from water through the thin membrane. Within the gastrovascular cavity, low oxygenated water can be expelled and high oxygenated water can come in by ciliated action, thus increasing the diffusion of oxygen through cell (Rees, 1966). The large surface area membrane to volume ratio helps A. aurita to diffuse more oxygen and nutrients into the cells.

The basic body plan of A. aurita  consists of several parts. The species lack respiratory, excretory, and circulatory systems (Arai, 1997). The adult medusa of A. aurita, with a transparent look, has an umbrella margin membrane and tentacles that are attached to the bottom (Russell, 1953). It has four bright circular gonads that are under the stomach (J.E. Purcell, et al. 2001). Food travels through the muscular manubrium while the radial canals help disperse the food (Russell 1963). There is a middle layer of mesoglea, gastrodervascular cavity with gastrodermis, and epidermis (Solomon, 2002). There is a nerve net that is responsible for contractions in swimming muscles and feeding responses (Aria, 1997). Adult medusa can have a diameter up to 40 cm (Arai, 1997). The sexes are can be differentiated between males and females in the medusa stage (Arai, 1997). The young stage, planula, has small ciliated cells and would settle at the bottom of the water where it would change into strobila and then float off as ephyra (Gilbertson, 1999). There is an increasing size from starting stage planula to ephyra, from less than 1 cm in planula stage to 1 cm in ephyra stage (Russell, 1953).

Predators
The death of the organism sometimes is brought about after reproduction, leaving the gonads open to infection and degradation (Arai, 1997). A. aurita have been food for a wide variety of predators including the Ocean Sunfish (Mola mola), the Leatherback Sea Turtle (Dermochelys coriacea), the hydromedusae (Aequorea victoria) (Arai, 1997) and the scyphomedusa "(Phacellophora camtschatica)" (Towanda and Thuesen, 2006).

A. aurita is food in countries such as China, Philippines, Thailand, Malaysia, and Indonesia. They are hunted by birds also. They do not have tentacles that sting, so they must hide. (Moon jellys can be recognized by the clover symbol on their backs.)

There are possible metazoan parasites that attack A. aurita (Arai, 1997).

Aurelia aurita interaction
Besides being a source of food for human consumption, A. aurita species also "represent an important step in pelagic organic matter transformations" (Rodriguez, 1996).