Appearance
The medusa is translucent, usually about 25–40 cm in diameter, and can be recognized by its four horseshoe-shaped gonads, easily seen through the top of the bell. It feeds by collecting medusae, plankton and mollusks with its tentacles, and bringing them into its body for digestion. It is capable of only limited motion, and drifts with the current, even when swimming.
Distribution
The genus "Aurelia" is found throughout most of the world's oceans, from the tropics to as far north as latitude 70°N and as far south as 40°S. The species "Aurelia aurita" is found along the eastern Atlantic coast of Northern Europe and the western Atlantic coast of North America in New England and Eastern Canada. In general, "Aurelia" is an inshore genus that can be found in estuaries and harbors. It lives in ocean water temperatures ranging from 6 °C to 31 °C; with optimum temperatures of 9 °C to 19 °C. "A. aurita" prefers temperate seas with consistent currents. It has been found in waters with salinity as low as 6 parts per thousand.
Food
"A. aurita" and other "Aurelia" species feed on plankton that includes organisms such as mollusks, crustaceans, tunicate larvae, rotifers, young polychaetes, protozoans, diatoms, eggs, fish eggs, and other small organisms. Occasionally, they are also seen feeding on gelatinous zooplankton such as hydromedusae and ctenophores. Both the adult medusae and larvae of "Aurelia" have nematocysts to capture prey and also to protect themselves from predators.The food is caught with its nematocyst-laden tentacles, tied with mucus, brought to the gastrovascular cavity, and passed into the cavity by ciliated action. There digestive enzymes from serous cell 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" can process carbohydrates, proteins and lipids.
Predators
"Aurelia aurita" is known to be eaten by a wide variety of predators including the Ocean Sunfish ", the Leatherback Sea Turtle ", the scyphomedusa "Phacellophora camtschatica", and a very large hydromedusa ". Moon jellies are also fed upon by sea birds, which may be more interested in the amphipods and other small arthropods that frequent the bells of "Aurelia", but in any case, birds do some substantial amount of damage to these jellyfish that often are found just at the surface of bays."Aurelia" jellyfish naturally die after living and reproducing for several months. It is probably rare for these moon jellies to live more than about six months in the wild, although specimens cared for in public aquarium exhibits typically live several to many years. In the wild, the warm water at the end of summer combines with exhaustive daily reproduction and lower natural levels of food for tissue repair, leaving these jellyfish more susceptible to bacterial and other disease problems that likely lead to the demise of most individuals. Such problems are responsible for the demise of many smaller species of jellyfish. In 1997, Arai summarized that seasonal reproduction leaves the gonads open to infection and degradation.
Some metazoan parasites attack "Aurelia aurita", as well as most other species of jellyfish.
Uses
These jellyfish are popularized as pets.References:
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