Leeches are segmented worms that belong to the phylum Annelida and class Clitellata. There are over 700 known leech species, with the majority being aquatic and living in freshwater or marine environments. Leeches have cylindrical bodies, suckers at both ends used for locomotion and attachment, and internal organ systems like a digestive system, circulatory system that circulates hemoglobin-rich fluid, and nervous and excretory systems. Leeches reproduce sexually and are often used in medicine due to anticoagulant properties in their saliva that prevent clotting when feeding and have therapeutic effects.

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

11. CONTINUE

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

14. CONTINUE

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 22nd 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 22nd segment of body and runs forward
2 vas deferens runs on either side of nerve cord
Epididymis
At 10th 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 10th 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 11th segment
Each ovisac has a ribbon shaped ovary
Pair of oviducts
Each ovisac opens to a narrow oviduct
Common oviduct
Ovisac unite in 11th segment to form a single common oviduct
Posterior end is curved to opens into vagina

24. CONTINUE
Vagina
It is pear shaped
Present in 11th 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

25. CONTINUE

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
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