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Cestoda
Scolex of Taenia solium
Scientific classification
Kingdom: Animalia
Subkingdom: Eumetazoa
(unranked): Bilateria
Superphylum: Platyzoa
Phylum: Platyhelminthes
Class: Cestoda
Orders

Subclass Cestodaria:

  • Amphilinidea
  • Gyrocotylidea

Subclass Eucestoda:

Cestoda (Cestoidea) is a class of parasitic flatworms, commonly called tapeworms, that live in the digestive tract of vertebrates as adults and often in the bodies of various animals as juveniles. Taenia saginata, the beef tapeworm, can grow up to 12 m (40 ft); other species may grow to over 30 m (100 ft).[1]

Contents

Anatomy

Scolex

The worm's scolex ("head") attaches to the intestine of the definitive host. In some species, the scolex is dominated by bothria, which are sometimes called "sucking grooves", and function like suction cups. Other species have hooks and suckers that aid in attachment. Cyclophyllid cestodes can be identified by the presence of four suckers on their scolex.

Once anchored to the host's intestinal wall, the tapeworm absorbs nutrients through its skin as the food being digested by the host flows past it, and it begins to grow a long tail, with each segment containing an independent digestive system and reproductive tract. Older segments are pushed toward the tip of the tail as new segments are produced by the neckpiece. By the time a segment has reached the end of the tail, only the reproductive tract is left. It then drops off, carrying the tapeworm eggs to the next host.[2]

While the scolex is often the most distinctive part of an adult tapeworm, it is often unnoticed in a clinical setting as it is inside the patient. Thus, identifying eggs and proglottids in feces is important.

Body systems

The main nerve centre of a cestode is a cerebral ganglion in its scolex. Motor and sensory innervation depends on the number and complexity of the scolex. Smaller nerves emanate from the commissures to supply the general body muscular and sensory ending. The cirrus and vagina are innervated and sensory endings around the genital pore are more plentiful than other areas. Sensory function includes both tactoreception and chemoreception. Some nerves are only temporary. These are in the proglottids, and stop working with a detach.

Proglottids

The body is composed of successive segments (proglottids). The sum of the proglottids is called a strobila, which is thin, resembling a strip of tape, and is the source of the common name "tapeworm". Like some other flatworms, cestodes use flame cells (protonephridia), located in the proglottids, for excretion.

Mature proglottids are released from the tapeworm's posterior end and leave the host in feces.

Because each proglottid contains the male and female reproductive structures, they can reproduce independently. It has been suggested by some biologists that each should be considered a single organism, and that the tapeworm is actually a colony of proglottids.

The layout of proglottids comes in two forms, craspedote, meaning proglottids are overlapped by the previous proglottid, and acraspedote which indicates a non-overlapping conjoined proglottid.

Life cycle

Many tapeworms have a two-phase life cycle with two types of host. The adult taenia saginata, for example lives in the gut of a primate such as a human. Proglottids leave the body through the anus and fall onto the ground, where they may be eaten with grass by animals such as cows. In the cow's body the juvenile forms migrate and establish themselves as cysts in body tissues such as muscles, rather than the gut; they cause more damage to this host than the intestinal form to its host. The parasite completes its life cycle when the grass-eater is eaten by a compatible carnivore—possibly a human with a preference for rare meat—in whose gut the adult taenia establishes itself. .[3]

Taxonomy

There are fourteen recognised orders of Cestodes: the Amphilinidea, Gyrocotylidea and 12 orders belonging to the Eucestoda. Within the Eucestoda the Spathebothriidea appear to be a sister group to the remaining 11 orders.[4] The Pseudophyllidea and Haplobothriidea appear to form a clade as do Cyclophyllidea, Nippotaeniidea and Tetrabothriidea.

See also

Footnotes

  1. ^ "The Persistent Parasites". Time Magazine (Time Inc). 1957-04-08. http://www.time.com/time/magazine/article/0,9171,809356-1,00.html. 
  2. ^ http://www.marvistavet.com/html/body_tapeworm.html
  3. ^ http://www.mayoclinic.com/health/tapeworm/DS00659/DSECTION=risk-factors
  4. ^ Olson P.D., Caira J.N. (1999) Evolution of the major lineages of tapeworms (Platyhelminthes: Cestoidea) inferred from 18S ribosomal DNA and elongation factor-1alpha. J. Parasitol. 85(6):1134-1159

References

 This article incorporates public domain material from websites or documents of the Centers for Disease Control and Prevention.

External links


Gaming

Up to date as of February 01, 2010

From Wikia Gaming, your source for walkthroughs, games, guides, and more!

Tapeworm

Developer(s) Spectravision
Publisher(s) Spectravision
Release date Atari 2600:
1982 (NA)
Genre Maze
Mode(s) Single player
1-2 players alternating
Age rating(s) N/A
Atari 2600
Platform(s) Atari 2600
Input Atari 2600 Joystick
Credits | Soundtrack | Codes | Walkthrough



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Simple English

Tapeworms (often called Cestoda) are a class of segmented worms. They are parasitic, which means that they need another larger creature whose body they can live on. Tapeworms live inside the intestines of vertebrate animals (animals that have backbones). This includes humans. A creature that has a parasite living in or on its body is called the host, because it feeds the parasite. When a vertebrate creature or human has a tapeworm, they lose weight and become weaker.

Tapeworms can be up to 30 or 36 feet (10-12 metres) long. They eat what ever the host eats in. The head of a tapeworm has four suckers and two rings of hooks. The body of a Tapeworms is in segments (pieces that are like each other). Each segment can produce eggs . Little segments of the tapeworm sometimes break off and pass out through the stool of the host, with the eggs. Little segments of its body fall off. They go out of the host body and when they get into another host that segment becomes a tape worm.

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Common name: tapeworm.

Scientific name: Anoplocephala perfoliata.

Phyla: Platyhelminthes.

Class: cestoda.








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