Earthworm presentation

The Anatomy and Physiology of a metamerically segmented annelida is discussed. Images are self explanatory

1. Anatomy and Physiology of Earthworm by Balogun Wasiu Gbolahan

2. Anatomy and Physiology of Earthworm General overview External anatomy Nervous system Digestive system Circulatory system Excretory system Respiratory system Reproductive system Muscular system Skeletal system Special senses Why Study Earthworm?

3. General overview Phylum: Annelida Shape: tube-shaped Body structure: metamerically segmented Habitat: inside the earthworm or moist places Feed: live or dead organic matter

4. External Anatomy

5. Nervous system

6. Nervous system The Peripheral nervous system a. Eight to ten nerves arise from the cerebral ganglia to supply the prostomium , buccal chamber and pharynx. b. Three pairs of nerves arise from the sub- pharyangeal ganglia to supply the 2nd, 3rd and 4th segment. c. Three pairs of nerves extend from each segmental ganglia to supply various structures of the segment. The sympathetic nervous system consists of nerve plexuses in the epidermis and alimentary canal.

7. Digestive system

8. Circulatory system The earthworm has a closed circulatory system. An earthworm circulates blood exclusively through vessels. Presence of haemoglobin

9. Excretory system The excretory system contains a pair of nephridia in every segment, except for the first three and the last ones. The three types of nephridia are: 1. The integumentary nephridia lie attached to the inner side of the body wall in all segments except the first two. 2. The septal nephridia are attached to both sides of the septa behind the 15th segment. 3. The pharyngeal nephridia are attached to fourth, fifth and sixth segments.

10. Respiratory system There is no formalized respiratory system in earthworms; exchange of oxygen and carbon dioxide takes place through the moist cuticle. Respiration normally occurs in air but earthworms can exist in water for long periods of time (e.g. for six months) if the water is oxygenated.

11. Reproductive system

12. Copulation and Fertilisation

13. Muscular system Useful Movement Digestion of food

14. Skeletal system They lack either an internal skeleton or exoskeleton, but maintain their structure with fluid-filled coelom chambers that function as a hydrostatic skeleton.

15. Special senses The Epidermal Receptors: These are found all over the epidermis but are more numerous on the lateral and ventral surface of the body. Earthworms are very sensitive to touch and to vibrations transmitted through solid objects. Buccal Receptors: They are found in large numbers in the epithelium of buccal cavity. These are olfactoreceptors and gustatoreceptors . Thus the earthworms can recognize different types of leaves that can be used as food. Photoreceptors: They are found in the inner parts of the epidermis. The photoreceptors are restricted to the dorsal surface and are more numerous on the prostomium and first segment. The photoreceptors enable the worm to detect changes in the intensity of light.

16. Photoreceptor cells in Prostomium

17. Why Study Earthworm? Understanding of animals for our own education and management purposes. Choose appropriate animals models to study disease. Add to human cultural base. Studying soil pollution. Vermicomposting . Bait for fishing.

18. Links for further reading http://www.sas.upenn.edu/~rlenet/Earthworms.html http://www.northallegheny.org/Page/19944 http://ibis.geog.ubc.ca/biodiversity/efauna/EarthwormsIntroduction.html http://cronodon.com/BioTech/Earthworm_NS.html http://passscience.blogspot.my/2010/09/reproductive-system-of-earthworm.html

19. Thank you for your time