Before we get started  Anterior: head-end  Posterior: tail-end  Dorsal: top-side  Ventral: bottom-side

Phylum Annelida  many marine, freshwater, and terrestrial worms  Ex) leeches and earthworms  “segmented worms” –division of rings or segments  septa/septum (walls) separate segments  setae: small, bristle-like appendages

Earthworm

Giant Gippsland Earthworm of Australia

External Anatomy

Internal Anatomy

Musculature  *Cuticle- thin external layer.  *Epidermis- outer cellular layer  Circular muscle layer  Longitudinal muscle layer

Digestive System  obtain food by eating through and taking nutrients from soil

 Mouth  Pharynx  Esophagus  Crop: storage compartment.  Crop: storage compartment.  Gizzard: soil ground up and churned  Intestine: digestion and absorption occur  Anus: Undigested material is voided

Earthworm Digestion Animation  m/Overview.html m/Overview.html m/Overview.html

Respiratory System  All annelids live in moist environments –most are aquatic. –most are aquatic.  earthworm can survive only in damp soil.  earthworm can survive only in damp soil. –Gas exchange occurs at body surface through diffusion –No lungs!

Circulatory System  closed system  five pairs of pseudohearts surround esophagus and pump blood  blood travels to dorsal vessel

Nervous System  Cerebral ganglia acts as “brain”  Prostomium: tongue-like lobe above mouth, allows earthworms to “feel” through soil

Reproductive System  Earthworms are hermaphrodites –male and female reproductive organs present in each individual –cross fertilize  mate by attaching at clitella, exchanging sperm, then seperating – sperm stored while clitellum secrete a mucous cocoon –cocoon slides along worm to collecting sperm and also eggs –slips off worm's head –embryos develop in cocoon.

What happens when an earthworm is cut in half?  Can it form two separate worms?  most organs are in anterior  can regenerate a new posterior  posterior end can not regenerate a new posterior  so, no you don't get two new worms.

Photographs, Images and text adapted from  /kentsimmons.uwinnipeg.ca/16cm05/16labm an05/lb6pg2_files/earthworm2.bmp&imgrefu rl= /16labman05/lb6pg2.htm&h=480&w=640&s z=901&hl=en&start=4&tbnid=Rvj5IZLbr72Dv M:&tbnh=103&tbnw=137&prev=/images%3 Fq%3Dearth%2Bworm%26gbv%3D2%26sv num%3D10%26hl%3Den%26sa%3DG