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The Phylum Annelida is divided into 3 classes, one of which the Clitellata could really be called a Superclass, it contains three subclasses, the Oligochaeta, the Branchiobdella and the Hirundinea. The other two classes are the Polychaeta which contains the largest number of species and the Aelosomatida which contains very few.


1. Symmetry and Size. 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). Also within Eunicida may be found the largest of annelids.


Annelids share the common characteristics of size and symmetry and have body walls and coeloms. Although they vary widely in habitat area and live in different environments around the world, annelids have structured nervous systems, sense organs, circulation and respiratory structures and segmented organs.


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 polychates, has a pair of parapodia that many species use for locomotion.


Invertebrates Facts. Invertebrates are multi-cellular and all the cells have different responsibilities to keep the animal alive. ... Characteristics of Annelids. The common characteristics of annelids are as follows: Annelids have a long cylindrical body;


Annelida is a medium-sized phylum with distinctive features, comprising over 9000 species. This article provides information about the characteristics of the phylum Annelida.


10 main characteristics of Phylum Annelida are given below: Bilaterally symmetrical and vermiform. Body has more than two cell layers, tissues and organs. Body cavity is a true coelom, often divided by internal septa. Body possesses a through gut with mouth and anus. Body possesses 3 separate sections, a prosomium, a trunk and a pygidium.


Classification of Phylum Annelida Phylum Annelida is divided into four main classes, primarly on the basis of setae, parapodia, metameres and other morphological features. Class 1 Polychaeta


Annelida: Annelid Characteristics. Segmented Bodies . The fundamental characteristic of the phylum is the division of the body into a linear series of cylindrical segments, or metameres. Each metamere consists of a section of the body wall and a compartment of the body cavity with its internal organs. The external divisions, which may be seen ...


Characteristics of Annelids. Annelids are found in many different areas and environments. We dig earthworms up in damp soil, and may find leeches attached to our body after swimming in a lake.