Annelida

=Phylum Annelida (means"ringed ones)= The annelids include earthworms, polychaete worms, and leeches. All members of the group are to some extent segmented, in other words, made up of segments that are formed by subdivisions that partially transect the body cavity. Segmentation is also called metamerism. Segments each contain elements of such body systems as circulatory, nervous, and excretory tracts. Metamerism increases the efficiency of body movement by allowing the effect of muscle contraction to be extremely localized, and it makes possible the development of greater complexity in general body organization. Besides being segmented, the body wall of is characterized by being made up of both circular and longitudinal muscle fibers surrounded by a moist, acellular cuticle that is secreted by an epidermal epithelium. All annelids except leeches also have chitonous hair-like structures, called setae, projecting from their cuticle. Sometimes the setae are located on paddle-like appendages called parapodia.

Annelids are schizocoelous and with a large and well-developed true coelom (i.e., one that is lined with mesoderm). Except in leeches, the coelom is partially subdivided by septa. Hydrostatic pressure is maintained across segments and helps maintain body rigidity, allowing muscle contractions to bend the body without collapsing it.

The internal organs of annelids are well developed. They include a closed, segmentally-arranged circulatory system. The digestive system is a complete tube with mouth and anus. Gases are exchanged through the skin, or sometimes through specialized gills or modified parapodia. Each segment typically contains a pair of nephridia. The nervous system includes a pair of cephalic ganglia attached to double nerve cords that run the length of the animal along the ventral body wall, with ganglia and branches in each segment. Annelids have some combination of tactile organs, chemoreceptors, balance receptors, and photoreceptors; some forms have fairly well developed eyes, including lenses.

Annelids may be monoecious or dioecious. Larva may or may not be present; if present they are of the trochophore type. Some forms also reproduce asexually. They are protostomes, with spiral cleavage. Members of the Phylum Annelida can be found throughout the world, in marine, freshwater, and terrestrial environments. Ecologically, they range from passive filter feeders to voracious and active predators.


 * Classes of Anelida:**
 * //Polychaeta-//** most diverse and predominately marine
 * //Aelosomata-//** small group of small worms that live in fresh and brackish water
 * //Clitellata-//** super class contains three subclasses

**Student Zoo Keeper Pages of Species: (Enter Your Species Pages Below)**
Spaghetti worm (Zookeeper: Sidney Baker) King Ragworm (Zookeeper: Taylor Cebuly) Tiger Leech (Zookeeper: Kenzie Davidson) Bloodworm (Zookeeper Shaiann Etwara) Giant Gippsland Earthworm (Zookeeper: Erin Holbert) Sabellastarte Indica (Zookeeper:Syed Islam) European Nigtcrawlers (Zookeeper: Marissa Jenkins) Diopatra (Zookeeper: Hannah Jones) Giant Palouse Earthworm (Zookeeper: James K. Kanthachack) Fan Worms (Zookeeper: Savannah Kelley) Aphrodita aculeata (Zookeeper: Tori Lopez) Hirudo Medicinalis leech (Zookeeper Whopper) Hemiclepsis marginata (Zookeeper: Heath McGregor) Clam Worm (Zookeeper: Ramon Prieto) Fire Worm (Zookeeper: Lindsey Rafus) Medicinal Leech ( Zookeeper: Sarah Reimer) Green Bristle Worm (Zookeeper: Paco Rodriguez) Tubeworm (Zookeeper: Paige Ryder) Samoan Palolo Worm (Zookeeper: Haley Shelton) __Lugworm__ (Zookeeper: Jeffrey Slape) Chaetogaster diaphanus (Zookeeper: Riley Stewart) Red Tubeworm-Serpula Vermicularis (Zookeeper:Jessica Tolliver) Polychaete Worm (Zookeeper Rachel Tolliver) Christmas Tree Worm (Zookeeper: Hannah WIlliams) Aeolidia papillosa (Zookeeper: Johnta Williams) Oregon Giant Earthworm (Zookeeper: Jayme Willingham) __Chloeia Fusca__ (Zookeeper: Jesse Wilson) Red Tubeworm (Zookeeper: Katie Woolen) Feather Duster Worm (Zookeeper: Elisabeth Young)

Myers, P. 2001. "Annelida" (On-line), Animal Diversity Web. Accessed March 06, 2011 http://animaldiversity.ummz.umich.edu/site/accounts/information/Annelida.html. http://www.earthlife.net/inverts/annelida.html craze4.edu.glogster.com sciencephoto.com
 * Information and Photo References:**