Saint Anselm College

BI338 Invertebrate Zoology, Fall 2011

Brian K. Penney, Ph.D.

Goulet 2320, Ph 641-7149, email: bpenney (at)
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  1. Name and describe features unique to Annelida
  2. Describe the level of integration and general animal characters seen in Annelida
  3. Diagram and label a cross section through a typical annelid, and list features in which other classes or subclasses may differ
  4. Diagram and describe segmentation and its functional consequences
  5. Describe teloblastic segmentation as found in annelids and arthropods

    Neither are “true segments”

  6. Use a table to compare the classes and subclasses of Annelida

    download table here

  7. Describe how annelids approach the basic functions of animals
    1. Movement in Annelida ()
    2. Support in Annelida ()
    3. Feeding in Annelida (Carolyn)
      • Just posterior to the mouth opening is the muscular pharynx.
      • When these muscles contract, food particles are sucked into the mouth.
      • The esophagus is posterior to the pharynx.
      • The esophagus expands into a thin-walled storage structure, the crop.
      • Just posterior to the crop is the muscular gizzard, which is a grinding structure.
      • Food is passed from the gizzard to the intestine, where further digestion and absorption occur. The intestine ends at the anus.


    4. Reproduction in Annelida ()
    5. Circulation in Annelida (Molly)
      • Circulatory system present for internal transport and distribution of nutrients. For gas exchange, their structures are limited to particular body regions; thus they depend on the circulatory system for internal transport of gases. The entire body surface functions in gas exchange. Special has exchange structures, or branchiae, are found in the form of filaments, anterior gills, and crowns on the head. There are no special hearts or pumping organs. The circulatory system is greatly reduced and has become fused with the coelom remnants.


    6. Gas exchange in Annelida ()
    7. Excretion/water balance in Annelida ()
    8. Growth and development in Annelida ()
    9. Sensation and coordination in Annelida (Molly)
      • The fundamental plan of the central nervous system in annelids includes a dorsal cerebral ganglion, paired circumentric connectives, and one or more ventral longitudinal nerve cords. Their nervous system arose from a ladder-like system.


    10. Defense against predators and pathogens in Annelida (Carolyn)
      • Many worms have the ability to burrow to escape prey.
      • Some worms produce chemical defense in their mucus.
      • Clam worms have pinchers.
      • Some worms can regenerate body parts when attacked.

updated: 12/7/11all writing and graphics, copyright Brian K. Penney and the 2008- 2010 years' classes, unless otherwise noted