Leech

Introduction of Leech

1. leech Scientific Name Hirudenea

2. leech

3. taxonomy Kingdom Animalia Phylum Annelida Class Clitillata Subclass Hirudinea

4. Introduction First leech fossils are found in Jurassic period around 150 millions years ago Leeches are blood sucking worm which belong to phylum Annelida 700 species of leeches are currently recognized 100 are marine, 90 terrestrial and the remainder freshwater. All leeches are carnivores means that mainly eat meat Some leeches are haemophagic this means they drink the blood of other animals Leeches are mostly found in marine water

5. General Characteristics Leeches have cylindrical bodies Leeches have 10 eyes, arranged in five pairs close to the anterior sucker Leeches look like segmented worms with suction cups at both ends All leeches have a posterior and anterior disc-shaped sucker Not all leeches are bloodsuckers. Beside their harmful effects they have been used for medical purpose No setae or parapodia

6. habitat Usually found in ; Fresh waters Marine waters Rivers Ponds One fifth of all leeches live in the sea Some are terrestrial means they are found on land

7. locomotion The anterior and posterior suckers serve as point of contact When the posterior suckers attach to the surface, the circular muscles contract beginning at the posterior end The leech thus elongates and the anterior end fastens to the surface When the posterior sucker is released a wave of contraction of the longitudinal muscle moves in a forward direction This completes one cycle. The coelom fluid act as a hydrostatic skeleton

8. Internal structure

9. Digestive system Consists of ; Alimentary Canal Extends from mouth to anus Divided into 3 parts Fore Gut Comprise of preoral chamber , buccal cavity and pharynx Lined with cuticle Mid Gut Comprise esophagus ,crop, stomach and intestine Having endodermal lining Hind Gut Consist of rectum and anus Lined with cuticle

10. continue Digestive Glands 2 types of digestive glands Salivary Glands Unicellular Present below the pharynx Opens in salivary papillae of jaw Saliva contain hirudin which prevents blood clotting of host Gland cells Scattered in epithelium of crop , stomach and intestine Secrete mucous in crop

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12. Circulatory system No true blood vessels Four (4) homoceolomic channel around alimentary canal Dorsal channel Ventral channel 2 lateral channels All channels are filled with homoceolomic fluid Haemoceolomic fluid tinged red with hemoglobin and amoeboid leucocytes No heart for pumping fluid Haemoceolomic fluid circulates through channel

13. continue Lateral channels perform pumping Dorsal and ventral act as distributing channels Lateral serve both as distributing and collecting Haemoceolomic fluid flows forward in dorsal and lateral Haemoceolomic fluid flows backward in ventral dorsal supplies alimentary canal and dorsal body wall Ventral supplies nephridia and ventral body wall Lateral supplies reproductive organ

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15. Gaseous exchange Gaseous exchange occurs through body wall They have Annelid like circulatory pattern Some have coelomic sinuses Respiratory pigments are absent

16. Nervous system Nervous system is alike Annelids Ventral nerve cords are not fused Supraesophageal and sub esophageal ganglia fuses to form nerve ring Nerve ring surrounds the pharynx Ganglia are fused

17. Excretory system Leeches have 10-17 pairs of metanephridia Each middle segments of body have one nephridium Metanephridia are highly modified Metanephridia have a capsule Capsule is involved in production of coelomic fluid

18. reproduction All leeches reproduce sexually They are monoecious Regeneration Is absent Single pair of ovaries They have to many testes Three body segment “clitellum” appears in spring (breeding season of leech)

19. Male reproductive organs It includes Testes-Sacs 11 pairs of testes sacs from 12 to 22 nd body segment Testes sacs present ventrally to alimentary canal Whitish in color Spherical in shape Sac cavity is filled with coelomic fluid Vasa Efferentia Each testes opens to a narrow vas efference

20. continue Vasa Differentia Eleven vasa efferentia opens to vas deferens Start from 22 nd segment of body and runs forward 2 vas deferens runs on either side of nerve cord Epididymis At 10 th segment each vas deferens becomes a compact mass called epididymis Ejaculatory Ducts Each epididymis give rise to muscular ejaculatory duct

21. continue Atrium Left and right ejaculatory duct opens to a sac called atrium It is pear shaped Present in 10 th segment Atrium have 2 parts Broad interior part It contain prostate gland Narrow posterior part It contain a thin penis

22. continue Sperm motor cells comes from inner wall of testes sacs and develop to spermatozoa Vasa differentia carries sperm to be stored in epididymis Sperm pass on to the base of atrium By secretions of prostate glands sperms become spermatophores Spermatophores are transferred to female during copulation

23. Female reproductive organs It includes Pair of ovisacs There is only one pair of ovisacs Present in 11 th segment Each ovisac has a ribbon shaped ovary Pair of oviducts Each ovisac opens to a narrow oviduct Common oviduct Ovisac unite in 11 th segment to form a single common oviduct Posterior end is curved to opens into vagina

24. continue Vagina It is pear shaped Present in 11 th segment Ova budded off from ovaries Ova is coated by albumen when pass through common oviduct into vagina Ova is stored in vagina in readiness for fertilization

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26. Economic importance Leeches are used for medicinal purposes in which Hirudo medicinalis (also called medicinal leech) are mostly used. Some of the uses are;   To treat nervous system abnormalities, dental problems, skin diseases, arthritis, hypertension, and infections. Live leeches attach to the target area and draw blood To prevent clotting Secretion of leeches helps in healing To remove bad blood from the disease

27. continue To relieve pressure and restore circulation Leech saliva used in antibiotics Mostly used in plastic surgery Can be used to treat cardiovascular diseases It is also used in the treatment of diabetes

28. The end Thanks