The annelid phyla includes animals such as earthworms, polychaete worms, and leeches. All members of this group have segmented body parts that divide the body cavity. Each segment contains different body systems such as the circulatory, nervous, and excretory systems. The body is made up of both circular and longitudinal muscle fibers that is surrounded in an epidrmal layer. Annelids have a true coelom which allows the pressure to be maintained across segments. This means that annelids can bend and contract the body withouth collapsing it. Annelids have well developed internal organs. They have a closed circulatory system, a complete digestive system with mouth and anus and gases are either exchanged through the skin or through gills. The nervous system has a pair of ganglia that attach to nerve cords and run the length of the organism. Some annelids even have eyes. Annelids can reproduce sexually or asexually.
medicinal leech (Hirudo medicinalis )
Myers, P. 2001. "Annelida" (On-line), Animal Diversity Web. Accessed February 28, 2011 http://animaldiversity.ummz.umich.edu/site/accounts/information/Annelida.html.
