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 TRUE COELOM (body cavity which allows them Have a TRUE COELOM (body cavity which allows them

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

as defined nervous and excretory systemsas defined nervous and excretory systems No developed respiratory system as they exchange O2 No developed respiratory system as they exchange O2

and CO2 via moist epidermisand CO2 via moist epidermis Are segmented into a sequence of compartments by Are segmented into a sequence of compartments by

septa. Segments are marked by rings called annulisepta. Segments are marked by rings called annuli Reproduce sexually and some asexually by Reproduce sexually and some asexually by

regeneration and fissionregeneration and fission Are hermaphroditic with cross fertilizationAre hermaphroditic with cross fertilization Are found in terrestrial, freshwater and marine Are found in terrestrial, freshwater and marine

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

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

Example: The EarthwormExample: The Earthworm- Digestive system is a one way tube including a mouth and anus with - Digestive system is a one way tube including a mouth and anus with specialization of digestive organs (esophagus, crop, gizzard, and intestines)specialization of digestive organs (esophagus, crop, gizzard, and intestines)- Closed circulatory system with blood contained in blood vessels. Presence - Closed circulatory system with blood contained in blood vessels. Presence of a primitive heart and hemoglobin in the blood to carry O2of a primitive heart and hemoglobin in the blood to carry O2- Excretory system includes nephridia (primitive kidneys) which eliminate - Excretory system includes nephridia (primitive kidneys) which eliminate waste from the bloodwaste from the blood- Nervous system includes cephalization with a primitive brain and ventral - Nervous system includes cephalization with a primitive brain and ventral nerve cord. No defined sensory organsnerve cord. No defined sensory 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 the base of many Form the base of many

food chainsfood chains House parasites such as House parasites such as

Protozoa, Protozoa, Platyhelminthes and Platyhelminthes and NematodesNematodes

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

Certain species mix the Certain species mix the surface and mineral soil surface 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!) Increase the levels of poop!) Increase 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!