Class Turbellaria

Class Turbellaria - The flame cell system functions in...

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Class Turbellaria The class Turbellaria includes freshwater planaria such as Dugesia that feed on small organisms or the remains of small creatures, as well as often colorful marine forms. Their small size and ease of care also make Dugesia a common animals in introductory biology labs. The planarian head is normally arrow-shaped, with side extensions that are sensory organs for detection of food and the presence of other organisms. Flatworms have two light-sensitive eyespots that have pigmentation making them look cross-eyed. The presence of three muscle layers facilitates varied movement. Gland cells secrete a mucous material upon which the animal slides or glides. The animal captures food by wrapping itself around its prey, entangling it in slime, and pinning it down. The pharynx is a muscular tube that extrudes from the mouth and through which food is ingested. Often in biology labs the "prey" can be liver and students can watch the pharynx extend out of the worm's body.
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Unformatted text preview: The flame cell system functions in excretion and consists of a series of interconnecting canals that run length of the body on either side of the longitudinal axis and side branches of the canals, each ending in a flame cell. The flame cell is a bulb-shaped cell containing a tuft of cilia within the hollow interior of the bulb. The cilia move back and forth, bringing water into the canals that empty through pores at the body surface. This flame-cell system functions in both water excretion and osmotic regulation in a typical freshwater, free-living flatworm. Planaria can reproduce both sexually and asexually. They can constrict beneath the pharynx and each half will grow into a whole animal by the process of regeneration. Planaria are hermaphroditic, possessing both male and female sex organs, and can cross-fertilize each other. Fertilized eggs are enclosed in a cocoon and hatch in two to three weeks....
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