Locomotion in Annelida. Before we discuss the details of locomotion in annelids, we have to recapitulate the major subdivisions of the phylum Annelida.
The digestive system of annelids consists of an unsegmented gut that runs through the middle of the body from the mouth, located on the underside of the head, to the anus, which is on the pygidium. The gut is separated from the body wall by the body cavity, called the coelom. The segmented compartments of the coelom are usually separated from each other by thin sheets of tissue, called septa, which are perforated by the gut and by blood vessels.  2)Body has more than two cell layers, tissues and organs. 3)Body cavity is a true coelom, often divided by internal septa. 4)Body possesses a through gut with mouth and anus. 5)Body possesses 3 separate sections, a prosomium, a trunk and a pygidium. 6)Has a nervous system with an anterior nerve ring, ganglia and a ventral nerve chord.  Locomotion in Annelida Before we discuss the details of locomotion in annelids, we have to recapitulate the major subdivisions of the phylum Annelida. Phylum Annelida contains Polychaeta, Oligochaeta and Hirudinea. Locomotor structures. So, Locomotion is the result of co-ordinate effort of all these. Locomotion in Annelida. The annelids are bilaterally symmetrical, triploblastic, coelomate, invertebrate organisms. They also have parapodia for locomotion. Most textbooks still use the traditional division into polychaetes (almost all marine), oligochaetes (which include earthworms) and leech-like species. Annelids are considered members of the Lophotrochozoa, a super-phylum of protostomes that also includes molluscs, brachiopods, flatworms and nemerteans. The basic annelid form consists of multiple segments. Each segment has the same sets of organs and, in most polychaetes, has a pair of parapodia that many species use for locomotion 2. Nearly all annelids have a fluid-filled cavity between the outer body wall and the gut, and this is referred to as a coelom (Figure 1). The coelom is often used as a storage area for gametes and acts as a hydrostatic skeleton for locomotion. Annelids are all bilaterally symmetrical animals. They range in size from much less than 1 mm in length to more than 3 m. The smallest annelids described to date would appear to be Neotenotrocha (Dorvilleidae, Eunicida) reaching only a few hundred microns in length (Eibye-Jacobsen and Kristensen, 1994). Coelom. Nearly all annelids have a fluid-filled cavity between the outer body wall and the gut, and this is referred to as a coelom (Figure 1). The coelom is often used as a storage area for gametes and acts as a hydrostatic skeleton for locomotion. Annelids are all bilaterally symmetrical animals. They range in size from much less than 1 mm in length to more than 3 m. The smallest annelids described to date would appear to be Neotenotrocha (Dorvilleidae, Eunicida) reaching only a few hundred microns in length (Eibye-Jacobsen and Kristensen, 1994). Phylum Annelida The phylum Annelida is constructed on a tube within a tube body plan. The digestive tract with terminal mouth and anus runs more or less through the center of the body. Annelids are characterized by external and internal segmentation.  By Phil Myers. 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.  The annelids (Annelida, from Latin anellus, little ring), also known as the ringed worms or segmented worms, are a large phylum, with over 17,000 extant species including ragworms, earthworms, and leeches. Annelids are considered members of the Lophotrochozoa, a super-phylum of protostomes that also includes molluscs, brachiopods, flatworms and nemerteans. The basic annelid form consists of multiple segments. Each segment has the same sets of organs and, in most polychaetes, has a pair of parapodia that many species use for locomotion
http://www.infoplease.com/encyclopedia/science/annelida-annelid-characteristics.html http://www.earthlife.net/inverts/annelida.html http://www.expertsmind.com/questions/locomotion-in-annelida-30131568.aspx https://en.wikipedia.org/wiki/Annelid http://www.tolweb.org/accessory/Characteristics_of_Annelida?acc_id=57 http://www.tolweb.org/accessory/Characteristics_of_Annelida?acc_id=57 http://www.bigelow.org/mitzi/images/teacher%20resources/Phylum%20Annelid.pdf http://animaldiversity.org/accounts/Annelida/ https://en.wikipedia.org/wiki/Annelid
describe locomotion in annelids