Pernapasan:
The earthworm prossesses no respiratory system, but obtains oxygen and gets rid of carbon dioxide through the moist outer membrane. Many capillaries lie just beneath the cuticle, making the exchange of gases easy. The oxygen is combined with the hemoglobin.
Habitat:
It is common in such widely separated areas as the United States, England and New Zealand.
Pencernaan:
The alimentary canal consists of a mouth cavity or buccal pouch, a thick muscular pharynx, a narrow, straight tube, the esophagus, a thin-walled enlargement, the crop or proventriculus, a thick muscular-walled gizzard, and a thin-walled intestine. The intestine is not simple sylindrical tube; but its dorsal wall is infolded, forming an internal longitudinal ridge, the typhlosole. this increases the digestive surface. Surrounding the alimentary canal and dorsal blood vessel is a layer of chloragogen cells. The function of these cells are somewhat comparable to those of the liver of higher animals as centers of glycogen and fat synthesis and storage.Three pairs of calciferous glands lie at the sides of the esophagus; they produce calcium carbonate, which they excrete into the digestive tract when the component ions are overly abundant in the body fluids.
Reproduksi:
Both male and female sexual organs occur in a single earthworm. The female systems consists of a pair of ovaries, a pair of oviducts which open by a ciliated funnel, enlarge into an egg sac, and then open to the exterior; and two pairs of seminal receptacles or spermathecae. The male organs are two pairs of glove-shaped testes and two vasa deferentia which lead from ciliated funnels to the exterior, and three pairs of seminal vesicles, and two central reservoirs. Self-fertilization does not take place, but spermatozoa are transfered from one worm to another during a process called copulation. Two worms come together; slime tubes are formed, and then a bandlike cocoon is secreted about the clitellar region. Eggs and spermatozoa are deposited in the cocoon, but fertilization does not occur until the cocoon is slipped over the head.
Peranan:
Darwin (1881) has contributed greatly to the understanding of the importance of earthworms in soil formation. More recent information on the subject has been assembled by Rodale (1961). They improve the soil by burrowing through it and increasing its porosity while mixing organic and inorganic materials and making some of the inorganic materials available to the plants. An interesting side effect of some species voiding their earth containing feces on the surface has been the gradual burial of such things as abandoned Indian cities in Central America.
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