Platyhelimenthes

=Phylum Platyhelimenthes (means "flat worms")= Flatworms are unsegmented, bilaterally symmetrical worms that lack a coelom (acoelomate) but that do have three germ layers. Some forms are free living but many are parasitic. Flatworms have a cephalized nervous system that consists of head ganglion, usually attached to longitudinal nerve cords that are interconnected across the body by transverse branches. Excretion and osmoregulation by flatworms is controlled by "flame cells" located in protonephridia (these are absent in some forms). Flatworms lack a respiratory or circulatory system; these functions take place by absorption through the body wall. Nonparasitic forms have a simple, incomplete gut; even this is lacking in many parasitic species.

Movement in some flatworms is controlled by longitudinal, circular, and oblique layers of muscle. Others move along slime trails by the beating of epidermal cilia. The development of directional movement is correlated with cephalization. In some flatworms, the process of cephalization has included the development in the head region of light-sensitive organs called ocelli. Other sense organs found in at least some members of this group (not necessarily on the head) include chemoreceptors, balance receptors (statocysts), and receptors that sense water movement (rheoreceptors). Most flatworms can reproduce sexually or asexually. Most are monoecious. Most of these have developed ways of avoiding self-fertilization. Development may be direct (eggs hatch into tiny worms that resemble the adults) or indirect (with a ciliated larval form).

Flatworms include a large number of parasitic forms, some of which are extremely damaging to human populations.


 * Classes of Platyhelimenthes:**
 * Turbellaria-** free living flatworms.
 * Cestoda-** tapeworms
 * Monogenea-** parasitic flukes
 * Trematoda-** parasitic flukes

**Student Zoo Keeper Pages of Species: (Enter Your Species Pages Below)**
Blue Lined Flatworm (Zookeeper: Sidney Baker) Blue Flatworm (Zookeeper: Taylor Cebuly) Dog Tapeworm (Zookeeper: Kenzie Davidson) Blood Fluke (Zookeeper: Shaiann Etwara) Tiger Flatworm (Zookeeper: Erin Holbert) Pseudoceros dimidiates (Zookeeper:Syed Islam) Pork Tapeworm (Zookeeper: Marissa Jenkins) Freshwater Planarian (Zookeeper: Hannah Jones) Beef Tapeworm (Zookeeper: James K. Kanthachack) Fish Tapeworm (Zookeeper: Savannah Kelley) Clonorchis sinensis (Zookeeper: Tori Lopez) Penis-Fencing Flat worm (Zookeeper: Whopper) Persian Carpet Flatworm (Zookeepr: Heath McGreogor) //Eurylepta sp//. (Zookeeper: Lindsey Rafus) Broad Fish Tapeworm (Zookeeper: Sarah Reimer) Divided Flatworm (Zookeeper: Paco Rodriguez) Flat Worm (Zookeeper: Paige Ryder) Blood Fluke //Schistosoma intercalatum// (Zookeeper: Haley Shelton) __Orsaki Flatworm__ (Zookeepeer: Jeffrey Slape) Hydatigera taeniaeformis (Zookeeper: Riley Stewart) __Marine Flatworm-Pseudoceros Ferrugineus__(Zookeeper: Jessica Tolliver) Ferris Polyclad Flatworm (Zookeeper Rachel Tolliver) Leopard Flatworm (Zookeeper: Ashley Veilleux) Horseshoe Crab Flatworm (Zookeeper: Hannah Williams) Gigantolina elongata (Zookeeper: Jayme Willingham) Chinese Liver Fluke (Zookeeprer: Katie Woolen) Hancocks Flatworm (Zookeeper: Elisabeth Young)

Myers, P. 2002. "Platyhelminthes" (On-line), Animal Diversity Web. Accessed March 06, 2011 http://animaldiversity.ummz.umich.edu/site/accounts/information/Platyhelminthes.html. islandwood.org synergysci0809.wordpress.com madasamarinebiologist.tumblr.com :
 * Information and Photo References:**