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.