Leech (Hirudinaria ) Reproductive system

 

Reproductive System in Leech:

 

The leech is monoecious or hermaphrodite, that is, both male and female reproductive organs are found in the same individual

 

Male reproductive organs consist of:

 1.     Testis-sacs,

2.     Vasa efferentia,

3.     Vasa deferentia,

4.     Epididymis,

5.     Ejaculatory ducts, and

6.     Atrium.

  

Testis-sacs:  

There are about eleven pairs of testis-sacs, one pair in each of the segments XII to XXII. These are situated ventral to the alimen­tary canal, between the nerve cord and the nephridia.  Each testis sac is rounded and  whitish in colour.   Its cavity is filled with coelomic fluid.

Function. Production of spermatozoa

 

Vas efferentia:

It is in the form of thin delicate duct arised from each testis-sac gives off  laterally narrow duct called vas efferens.

 Function – Carries sperm to vas deferens

 

Vasa deferentia:

All the eleven vasa efferentia of one side open into a long tube known as vas deferens. Running from either side of ventral nerve cord from  twenty-second segment up to the 10th segment.

 Function: transfere of sperm into epididymis

 

Epididymis.

In tenth segment vas deference  become coiled or convoluted to from a compact mass called epididymis.

Function: storage of sperm

Ejaculatory duct

It is short and  narrow duct arrsed from the anterior end of each epididymis. The right and left ejaculatory ducts lead inwards to open into a median sac called atrium.

Function : transfer of sperm into atrium

 

Atrium:

 It is a pear-shaped muscular organ lying anteriorly in the mid-ventral line of the tenth segment. It consist of two parts i.e anterior prostate chamber and posterior narrow penis sac. The sac encloses eversible penis.  

Function:  formation of sperm bundles or sperm pocket.

 

Male genital aperture : it is in the from of minute aperture opens in tenth segment mid-ventrally as male genital aperture.

 Function: Deposition of sperm into the female genital aperture of other leech.

 

 Female reproductive system.

 1.     Pair of ovisacs

2.     A pair of oviducts

3.     Common oviduct

4.     Vagina

 Pair of ovisacs

 In leech  only one pair of ovisacs situated in the eleventh segment.

Each ovisac is oval and rounded structure encloses the cavity called coelomic cavity filled with coelomic fluid. In coelomic fluid  a coiled ribbon-shaped ovary with dilated ends is floats. .

 

A pair of oviducts: from each ovisac arises a short and narrow delicate duct called oviduct. The

The base of each ovisac is continued as a short and narrow oviduct. The two oviducts unite in the mid-ventral line of the eleventh segment to form a common oviduct.

Common oviduct:

The two oviduct from either side unite together to from common oviduct. The common oviduct  turned  in to ‘S’ shaped  curve to open into the vagina. At the junction of common oviduct there is presence of whitish mass called albumen glands which open into it.

Vagina:

 It is a pear-shaped muscu­lar bag  like structure  in the posterior part of the eleventh segment.

 Its narrow neck leads into the female gonopore which is situated on the mid-ventral line of the eleventh segment. The ova are budded off from the ovaries. They receive a coating of albumen as they pass through the common oviduct into the vagina where they are stored in readi­ness for fertilization.

 Reproduction Organs of Hirudinaria in X to XIII segments

 

 

Copulation and FORMATION OF COCOON or Ootheca

 

After copulation leech will develop a ootheca around the clitellar zone. The completely formed cocoon is laid on moist soil. In this cocoon the zygotes will develop into young individuals.

 

Copulation:

In the months of March and April leeches will show copulatory process. Two mature leeches living near by will come together and meet on their ventral surfaces in opposite directions. The male genital opening of one leech lies opposite to the female genital opening of other leech. The penis of one leech will penetrate into the female into the genital opening of the other leech and deposit spermatophores in the vagina. Thus, both leeches will exchange their sperms during copulation. The entire process takes nearly one hour. It takes place on land or in water.

 

Cocoon or ootheca : In leeches the cocoon or ootheca will be formed after copulation. The formation of cocoon is very slow process. It takes nearly six hours’ time. Clitellum develops in leeches in the 9th to 11th segments region which is responsible for the formation of cocoon.

 

The clitellar glands will secrete a white girdle around clitellar region. In addition to this the clitellar glands will deposit albuminous fluid in the cocoon or ootheca. After the formation of ootheca the fertilized eggs are laid in the cocoon through the female genital openings present in the ventral side of the body in between 2nd and 3rd annulus of 11th segment. By rhythmic contractions of the body leech withdraws its body from the cocoon. Both ends of the cocoon will be closed by plugs. These plugs are secreted by the prostomial glands. Thus a box like ootheca or cocoon is formed. It is barrel shaped. It is laid on moist land. It is 25-30 mm in length and 12-15 mm in width. When it is exposed to air it gets hardened.

 Within the cocoon or ootheca the development of the zygote takes place. Development: The development of zygote takes place in the cocoon.

 1) This development takes nearly 15 days.

 2) The cleavage is unequal.

 3) The developing embryo absorbs albumen as its food.

 4) The development is direct and larval form is absent.

 One to twenty four leeches may come out of each cocoon. The young one resembles the adult.