Phylum AnnelidaPhylum AnnelidaAnnelus = “ Little Ring”Annelus = “ Little Ring”

The Segmented WormsThe Segmented Worms

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3 Major Classes in Phylum Annelida3 Major Classes in Phylum Annelida

Class Oligochaeta: the earthworms

Class Hirudinea : The leeches

Class Polycheata: The marine worms

Identifying Characteristics of the AnnelidsIdentifying Characteristics of the Annelids Have a Have a TRUE COELOMTRUE COELOM (body cavity which allows them (body cavity which allows them

to have to have true organ systems and muscular layerstrue organ systems and muscular layers)) Posses complex Posses complex digestive & circulatory systemsdigestive & circulatory systems as well as well

as defined as defined nervous and excretorynervous and excretory systems systems No developed No developed respiratory systemrespiratory system as they exchange O as they exchange O22

and COand CO22 via via moist epidermismoist epidermis Are Are segmentedsegmented into a sequence of compartments by into a sequence of compartments by

septasepta. Segments are marked by rings called . Segments are marked by rings called annuliannuli Reproduce Reproduce sexually and some asexually sexually and some asexually by by

regeneration and fissionregeneration and fission Are Are hermaphroditichermaphroditic with with cross fertilizationcross fertilization Are found in Are found in terrestrial, freshwater and marineterrestrial, freshwater and marine

environmentsenvironments Can range in size from less than Can range in size from less than 1 mm to over 3 meters1 mm to over 3 meters

(the seep tube worm)(the seep tube worm)

Example: The EarthwormExample: The Earthworm- - Digestive systemDigestive system is a one way tube including a is a one way tube including a mouthmouth and and anusanus with with specialization of specialization of digestive organsdigestive organs (esophagus, crop, gizzard, and intestines) (esophagus, crop, gizzard, and intestines)- - Closed circulatory systemClosed circulatory system with blood contained in with blood contained in blood vesselsblood vessels. Presence . Presence of a of a primitive heart and hemoglobinprimitive heart and hemoglobin in the blood to carry O in the blood to carry O22

- - Excretory systemExcretory system includes includes nephridianephridia (primitive kidneys) which eliminate (primitive kidneys) which eliminate waste from the bloodwaste from the blood

- - Nervous systemNervous system includes includes cephalization with a primitive braincephalization with a primitive brain and ventral and ventral nerve cord. No defined nerve cord. No defined sensory organssensory organs

Earthworm ReproductionEarthworm ReproductionAlthough

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 AnnelidsEcological Importance of Annelids Form Form the base of many the base of many

food chainsfood chains House House parasitesparasites such as such as

Protozoa, Protozoa, Platyhelminthes and Platyhelminthes and NematodesNematodes

Aerate Aerate & mix the soil& mix the soil and and are constructive to are constructive to mineralization and mineralization and nutrient uptake by nutrient uptake by vegetationvegetation

Certain species Certain species mix the mix the surface and mineral soilsurface and mineral soil by traveling between the by traveling between the twotwo

Oligochaete Worm

Biological Roles include:Biological Roles include:acting as composters and acting as composters and helping to create dead organic helping to create dead organic matter into fertile soilmatter into fertile soil

Chemical Roles include:Chemical Roles include:helping to cycle nutrients and helping to cycle nutrients and minerals through the soil minerals through the soil through their casts (worm through their casts (worm poop!) poop!) Increasing the levels of Increasing the levels of nitrogen, phosphates and nitrogen, phosphates and potashpotash

Physical Roles include:Physical Roles include:burrowing and keeping the soil burrowing and keeping the soil structure open (aerating the structure open (aerating the soil and providing a path for soil and providing a path for drainage)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!