Body System
Aurelia 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 covering its body. 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. The large surface area membrane to volume ratio helps Aurelia to diffuse more oxygen and nutrients into the cells.
The basic body plan of Aurelia consists of several parts. The animal lacks respiratory, excretory, and circulatory systems. The adult medusa of Aurelia, with a transparent look, has an umbrella margin membrane and tentacles that are attached to the bottom. It has four bright gonads that are under the stomach. Food travels through the muscular manubrium while the radial canals help disperse the food. There is a middle layer of mesoglea, gastrodervascular cavity with gastrodermis, and epidermis. There is a nerve net that is responsible for contractions in swimming muscles and feeding responses. Adult medusa can have a diameter up to 40 cm. The medusae are either male or female. The young larval stage, a planula, has small ciliated cells and after swimming freely in the plankton for a day or more, settles on an appropriate substrate, where it changes into a special type of polyp called a "scyphistoma", which divides by strobilation into small ephyrae that swim off to grow up as medusae. There is an increasing size from starting stage planula to ephyra, from less than 1 mm in the planula stage, up to about 1 cm in ephyra stage, and then to several cm in diameter in the medusa stage.
Read more about this topic: Aurelia Aurita
Famous quotes containing the words body and/or system:
“And everything is gone, the body is gone
completely under, gone, entirely gone.”
—D.H. (David Herbert)
“The North American system only wants to consider the positive aspects of reality. Men and women are subjected from childhood to an inexorable process of adaptation; certain principles, contained in brief formulas are endlessly repeated by the press, the radio, the churches, and the schools, and by those kindly, sinister beings, the North American mothers and wives. A person imprisoned by these schemes is like a plant in a flowerpot too small for it: he cannot grow or mature.”
—Octavio Paz (b. 1914)