Reproduction and Life Cycle of The Tapeworms
True tapeworms are exclusively hermaphrodites; they have both male and female reproductive systems in their bodies. The reproductive system includes one or many testes, cirrus, vas deferens and seminal vesicle as male organs, and a single lobed or unlobed ovary with the connecting oviduct and uterus as female organs. There is a common external opening for both male and female reproductive systems, known as genital pore, which is situated at the surface opening of the cup-shaped atrium. Even though they are sexually hermaphroditic, self-fertilization is a rare phenomenon. In order to permit hybridization, cross-fertilization between two individuals is often practiced for reproduction. During copulation, the cirrus of one individual connects with that of the other through the genital pore, and then exchange their spermatozoa.
The life cycle of tapeworms is simple in the sense that there are no asexual phases as in other flatworms, but complicated in that at least one intermediate host is required as well as the definitive host. This life cycle pattern has been a crucial criterion for assessing evolution among Platyhelminthes. Many tapeworms have a two-phase life cycle with two types of host. The adult Taenia saginata lives in the gut of a primate such as a human, but more alarming are Taenia solium, which can form cysts in the human brain. Proglottids leave the body through the anus and fall onto the ground, where they may be eaten with grass by animals such as cows. This is known as the intermediate host. The juvenile form migrates and establishes as a cyst in the intermediate hosts body tissues such as muscles, rather than the gut. They cause more damage to this host than it does to its definitive host. The parasite completes its life cycle when the intermediate host passes on the parasite to the definitive host, this is usually done by the definitive host eating an infective intermediate host, such as possibly a human with a preference for raw meat—in whose gut the adult Taenia establishes itself.
Read more about this topic: Cestoid
Famous quotes containing the words reproduction, life and/or cycle:
“Although Samuel had a depraved imagination—perhaps even because of this—love, for him, was less a matter of the senses than of the intellect. It was, above all, admiration and appetite for beauty; he considered reproduction a flaw of love, and pregnancy a form of insanity. He wrote on one occasion: “Angels are hermaphrodite and sterile.””
—Charles Baudelaire (1821–1867)
“Art is only a means to life, to the life more abundant. It is not in itself the life more abundant. It merely points the way, something which is overlooked not only by the public, but very often by the artist himself. In becoming an end it defeats itself.”
—Henry Miller (1891–1980)
“The Buddha, the Godhead, resides quite as comfortably in the circuits of a digital computer or the gears of a cycle transmission as he does at the top of a mountain or in the petals of a flower.”
—Robert M. Pirsig (b. 1928)