Moon Jelly
Scientific classification
(Rodriguez, 1996)
Kingdom:Animalia
Phylum:Cnidaria
Class:Scyphozoa
Order:Semaeostomeae
Family:Ulmaridae
Genus:Aurelia
Species:Aurelia aurita
Binomial name
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Moon Jelly (Aurelia aurita) are the most common Jellyfish species found in the genus Aurelia. Other species found in the genus Aurelia besides Aurelia Aurita are: Aurelia labiata, Aurelia limbata, Aurelia sp. You can find them in the Chesapeake Bay, Atlantic Ocean, Arctic Ocean, Pacfic Ocean, and other places in the U.S .1-MND-2003, Aurelia sp. 2-MND-2003, Aurelia sp.3-MND-2003, Aurelia sp. 3-MND-2003, Aurelia sp. 4-MND-2003, and Aurelia sp. 5-MND-2003 (NCBI. 2003).

General biology

Aurelia aurita lives in tropical places and usually all around the coasts of British Isles (Russell, 1953). In general, A. aurita is an inshore species but they could well live in places like estuaries and harbors (Russell, 1953). They are a "cosmopolitan species with a worldwide distribution in neritic waters between 70° N and 40° S" (J.E. Purcell, et al. 2001).  They live in ocean water temperature that range is from -6° to 31° Celsius; the optimum temperature would be 9-19° Celsius (Rodriguez, 1996). The environment for A. aurita has to be mildly cold salt water with current flowing (Rodriguez, 1996).  They can be found in 3% salinity water but are limit to 6% salinity (Russell, 1953).

Features

A. aurita has a complex life cycle that consists of several stages. Their asexual stage is scyphistoma while the sexual adult stage is medusa (J.E. Purcell, et al. 2001). The reason why A. aurita species live worldwide is due to their varying habitat conditions that allow then to survive (J.E. Purcell, et al. 2001). Medusa stage appear more frequently in shallow water that is opened to the ocean with limiting waves than in deep water with strong waves (J.E. Purcell, et al. 2001).  The young stage planula also stays in water that is around 20 feet in depth (J.E. Purcell, et al. 2001). The scyphistomas can live in mussel bed (Russel, 1953). Medusa A. aurita can survive in polluted, anoxic water environment that has low nutrients supply (J.E. Purcell, et al. 2001). The polyps stage of A. aurita can survive oxygen level that is three time normal for several days, giving it a higher chance of survival in case of a sudden change in the water oxygen level (J.E. Purcell, et al. 2001).

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." (Rodriguez, 1996). Occasionally, they would be 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 (Arai, 1997). 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 (Arai, 1997). 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, lung, 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 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 travel 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 40cm (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 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).

Life cycle

A. aurita first starts out with an ovum from a female medusa and a sperm from a different medusa to form a zygote (sexual reproduction) (Gilbertson, 1999). Zygote then turned into blastula, then gastrula, and then planula (Gilbertson, 1999). The planula settles on bottom and attaches itself onto a reef for a while (Gilbertson, 1999). Planula then grows and changes into a small polyp called a scyphistoma (Gilbertson, 1999). The scyphistoma grows and becomes strobila with small buds on the top layers (Gilbertson, 1999). Each of the buds breaks off and forms an ephyra. Ephyra enlarges and matures to become the last stage, adult medusa (Gilbertson, 1999). The strobila stage can reproduce by asexual fission (Gilbertson, 1999). From mid July to October is when the growth of A. auritaat its highest (Aria, 1997). The ephyra and medusa stage can last approximately 14 moths, although some medusae died earlier in the winter (Aria, 1997).

Predators

The death of the organism sometimes is brought by after reproduction, leaving the gonads open to infection and degradation (Arai, 1997). A. auritahave been food for a wide variety of predators including the ocean sunfish, Mola mola, loggerhead turtles, Caretta caretta, and the hydromedusae Aequorea victoria (Arai, 1997). Another cause of death is by fisheries of A. aurita for food in countries such as China, Philippines, Thailand, Malaysia, and Indonesia . Their hunted by birds also. They defend themselves by stinging with their tentacles. (Arai, 1997).

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

Aurelia aurita interaction

Beside from being a source of food for human consumption, A. aurita species also "represent an important step in pelagic organic matter transformations" (Rodriguez, 1996). On the bad side, A. aurita species could ruin the fish markets for human, creating a tidal effect that may hurt the fish population either indirectly or directly by eating on fish larvae (Arai, 1997).

References