Platyhelminthes (Flatworms)

Platyhelminthes (Flatworms)

Flatworms are the simplest of the worm groups and are found in marine and fresh water. They can be free living parasites. One example of a well known parasitic flat worm is a Tapeworm. Flatworms are also the simplest animals to have bilateral symmetry and are triplobastic, which means they are composed of 3 fundamental cell layers. Flatworms are flat because of their lack of a body cavity. They also lack an anus, the same pharyngeal opening expels waste as well as taking in food. Because they only have a gut and no real digestive system they must respire by diffusion. They are also flat because no cell can be too far from the outside.

Most Platyhelminthes have reproductive systems that produce gametes. The majority of flat worms are hermaphroditic, simultaneously male and female. Because of this many reproduce asexually.

Some other examples of flat worms are tapeworms, planarians, and flukes.

tapeworm

 

Planarian

Fluke

 

Cite:

Pictures:

 http://www.starfish.ch/c-invertebrates/flatworms.html

 http://curezone.com/ig/i.asp?i=1358

http://web.mit.edu/neuro/planaria.html 

 http://www.whatsthelatest.net/health/10-human-adversaries/

Info:

http://faculty.fmcc.suny.edu/mcdarby/animals&plantsbook/animals/03-Flatworms.htm

http://www.ucmp.berkeley.edu/platyhelminthes/platyhelminthes.html

http://www.mcwdn.org/Animals/Flatworm.html