Phylum Annelida Annelus = “ Little Ring” The Segmented Worms

3 Major Classes in Phylum Annelida Class Oligochaeta: the earthworms Class Hirudinea : The leeches Class Polycheata: The marine worms

Identifying Characteristics of the Annelids Have a TRUE COELOM (body cavity which allows them to have true organ systems and muscular layers) Have a TRUE COELOM (body cavity which allows them to have true organ systems and muscular layers) Posses complex digestive & circulatory systems as well as defined nervous and excretory systems Posses complex digestive & circulatory systems as well as defined nervous and excretory systems No developed respiratory system as they exchange O 2 and CO 2 via moist epidermis No developed respiratory system as they exchange O 2 and CO 2 via moist epidermis Are segmented into a sequence of compartments by septa. Segments are marked by rings called annuli Are segmented into a sequence of compartments by septa. Segments are marked by rings called annuli Reproduce sexually and some asexually by regeneration and fission Reproduce sexually and some asexually by regeneration and fission Are hermaphroditic with cross fertilization Are hermaphroditic with cross fertilization Are found in terrestrial, freshwater and marine environments Are found in terrestrial, freshwater and marine environments Can range in size from less than 1 mm to over 3 meters (the seep tube worm) Can range in size from less than 1 mm to over 3 meters (the seep tube worm)

Example: The Earthworm - Digestive system is a one way tube including a mouth and anus with specialization of digestive organs (esophagus, crop, gizzard, and intestines) - Closed circulatory system with blood contained in blood vessels. Presence of a primitive heart and hemoglobin in the blood to carry O 2 - Excretory system includes nephridia (primitive kidneys) which eliminate waste from the blood - Nervous system includes cephalization with a primitive brain and ventral nerve cord. No defined sensory organs

Earthworm Reproduction Although earthworms are hermaphroditic (produce both eggs and sperm) they must still copulate in order to mix their gametes Earthworms are also capable of re- growing amputated segments of their bodies Mating Earthworms

Ecological Importance of Annelids Form the base of many food chains Form the base of many food chains House parasites such as Protozoa, Platyhelminthes and Nematodes House parasites such as Protozoa, Platyhelminthes and Nematodes Aerate & mix the soil and are constructive to mineralization and nutrient uptake by vegetation Aerate & mix the soil and are constructive to mineralization and nutrient uptake by vegetation Certain species mix the surface and mineral soil by traveling between the two Certain species mix the surface and mineral soil by traveling between the two Oligochaete Worm

Biological Roles include: acting as composters and helping to create dead organic matter into fertile soil Chemical Roles include: helping to cycle nutrients and minerals through the soil through their casts (worm poop!) Increasing the levels of nitrogen, phosphates and potash Physical Roles include: burrowing and keeping the soil structure open (aerating the soil and providing a path for drainage)

Random Annelid Facts In the New Zealand Maori culture NOKE is an earthworm dish sold as a delicacy Lumbriculus and Aulophorus (species of annelids) are known to reproduce by the penis breaking into fragments and then forming whole new worms!