Wednesday, March 15, 2017

Earthworm: Reproductive System

Earthworms are hermaphrodite i.e. monoecious, an individual with both male and female reproductive organs.   
Male Reproductive Organs
The male reproductive organs are testes, testis sacs, seminal vesicles, spermiducal funnel, vasa defferentia, prostate glands and accessory glands.
·        Testes: Two pairs of testes, each pair ventrally beneath alimentary canal of 10th and 11th segment are present. Testes remain enclosed inside the testis sac of respective segments. Each testis is white coloured structure with narrow base and 4-6 digitate projections. The base remains attached with the under surface of roof of testis sac. Inside the digitate projections a number of round structures are present called as spermatogonia. These spermatogonia undergo the process of spermatogenesis to form sperms.
            The testis are found well-developed in young earthworms while remains degenerated in adult earthworm.




·        Testis Sacs: A pair of testis sacs, each in ventral surface of 10th and 11th segments below alimentary canal are present. They are general coelomic space cut off from body cavity. Each testis sac encloses a pair of testis and a pair of spermiducal funnels. The testis sac of 11th segment also encloses additional one pair seminal vesicles. Thus the testis sac of 11th segment is larger than that of 10th segment.
The testis sac of each segment remains connected with the seminal vesicles of succeeding segments.
·        Seminal Vesicles: Two pairs of seminal vesicles, each pair in 11th and 12th segments are present. They are also called as septal pouches as they are developed as outgrowth of spetum. The seminal vesicles of 11th segment remain enclosed inside the testis sac of that segment while that of 12th segment are free. Thus seminal vesicles of 12th segment are larger than that of 11th segments. Seminal vesicles of each segment remains connected with testis sacs of preceeding segments.
Inside seminal vesicles process of spermatogenesis takes place.
·        Spermiducal funnels: Two pairs of spermiducal funnels each pair in 10th and 11th segments are present. The spermiducal funnel remains enclosed inside the testis sac of respective segments. Each spermiducal funnel is funnel shaped structure with ciliated margin. Its function is to capture sperms.
·        Vasa defferentia :- from the posterior end of each-spermiducal finnel a fine internally ciliated duct arises called as vas deferens. The vasa defferentia of each side come in close contact and run parallely upto the middle of 18th segment. Its function is to carry sperms.
·        Prostate Glands :- A pair of prostate glands on ventrolateral position each on either side of alimentary canal and extends from 16th or 17th segment in front upto 20th segment in back. Each gland is multilobed structure of dirty white colour. The glandular part is of racemose gland while non-glandular part consists of a number of ductules which unite with each other to form a curved Prostatic duct at the middle of 18th segment. The prostatic duct come in association of vasa differentia of its own side to form common spermatic and prostatic duct. Thus each male genital pore consists of three openings, two of vasa defferentia and one of prostatic duct.
The prostate glands produce a type of fluid of unknown function.
·        Accessory glands:-            Two pairs of accessory glands – each pair in ventro – lateral position of 17th and 19th segments respectively. Each gland is white fluffy mass and opens outside by a number of openings present on genital papillae. It produces a type of sticky fluid which helps during copulation.
When the testes get matured spermatogonia are released in testis sac they pass into the seminal vesicle with which the testis sac remains connected. The process of spermatogenesis takes place inside the seminal vesicles and sperms are formed. The sperms again come back in the testis sac and are captured by spermiducal funnel. From funnel sperms pass into vasa defferentia. From vasa defferentia sperms pass down and are finally passed out through the male genital pore during copulation into the spermetheca of another Earthworm.

Female reproductive organs:
The female reproductive organs are ovaries, oviducal funnel, oviducts and spermetheca.
·        Ovaries: A pair of ovaries, each on either side of median line on ventral surface of 13th segment are present. Each ovary is white coloured structure and consists of narrow base and 4-6 digitate projections. The base remains attached with the undersurface of septum lying between 12th and 13th segments. Inside the digitate projections round structures are present which are called as oogonia. These oogonia undergo the process of oogenesis to form egg.

·        Oviducal funnel:  A pair of oviducal funnel are present on ventral surface of 13th segment each on either side of median line each behind each ovary. It is funnel shaped structure with ciliated margin and its function is to capture egg.
·        Oviducts:  A fine internally ciliated duct arises from the posterior end of each oviducal funnel and is called as oviduct. Its function is to carry eggs. Each oviduct moves towards posterior side and penetrate the septum lying between 13th and 14th segment and enters inside 14th segment. After entering in 14th segment each oviduct bends toward middle and meet with each other at the middle of 14 segment to form common oviduct which opens outside through female genital pore.
·        Spermetheca : Four pairs of spermetheca, each pair in ventro-lateral position of 6th, 7th, 8th  and 9th segments are present. Each spermetheca is sac like structure with narrow neck and main body, ampulla. From neck, a small outgrowth arises called as diverticulum. It stores sperms. Each spermetheca opens outside by spermethecal openings. Thus, 4 pairs of spermethecal opening, each pair in ventro-lateral position of intersegmental groove lying between 5/6, 6/7, 7/8 and 8/9 segments are present.


When the ovary gets matured, eggs are released in body cavity and are captured by oviducal funnel. From funnel eggs pass into oviduct and are finally passed out through the female genital pore inside the cocoon.