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Earthworm Reproductive System Short Notes

In this article we will discuss about the earthworm reproductive system

Earthworm Reproductive System

Earthworms are hermaphrodites
They cannot fertilize their own eggs because of their relative position of male and female genital aperture and they are protrandous
Thus, cross fertilization occurs in earthworm.
Earthworm reproductive system comprises of male reproductive organs and female reproductive organs

Male Earthworm Reproductive System

Testes

Two pairs of testes located in 10th and 11th segment
Testis produce spermatogonia and each testis is located testis sac
Function: They produce sperm

Seminal vesicles

It has two pairs of seminal vesicles. They are located in 11th and 12th segments
They are also termed as septal pouches, as they develop as septal outgrowths.
Function: Maturation of sperm takes place in seminal vesicles

Spermiductal Funnels

Earthworms have two pairs of seminal funnels
These are located at the 10th and 11th segments.
Function: Passing on spermatozoa to the Vasa deferentia and onwards.

Vasa deferentia

It is thin, long, narrow, thread like tubular structure
Two pairs and each pair is located on the either side of the alimentary canal
They extends from 12th to 18th segment.
In 18th segment they join together with a thick prostatic duct and forms common prostatic duct
Function: They collect sperm from spermatic funnel and give to prostate gland

Prostate gland

Pairs of large, solid, and irregularly shaped glandular masses
Situated in the segments from 17th to 20th
Ventral side of 18th segment, prostatic duct opens via a male genital pore
Function: It produce prostatic fluid which is alkaline in nature. It activates sperms. And also it keeps sperm motile.

Accessory glands

These are two pair of whitish, spherical structures found one pair in each of the 17th and 19thsegment.
Function: Secretion of these gland helps in holding two worms during copulation.

Male genital pore

It is found in one pair located in 18th segment.
Function: It acts as male genital pore.

Female Earthworm Reproductive System

Ovaries

One pair of ovaries present on 13th segments
Each ovary consists of several finger like processes in which ova are arranged in a linear series in various stage of development
Function: they form ova

Oviducal funnel

Each oviducal or ovarian funnel arises from both ovaries
Oviducal funnels appear as large saucers consisting of ciliated margins
Function: ova enter through oviducal funnel and travel backward along the oviduct.

Oviduct

Each ovarian funnel continues into the oviduct.
Oviducts open on female genital pore in the 14th segment
Function: they collect ova from ovary and give to female genital pore.

Spermathecae

Spermathecae are 4 pairs – one pair each in the 6th, 7th, 8th, and 9th segments.
The spermatheca opens to the exterior via small ducts
Function: spermatheca is to receive and store spermatozoa from another earthworm during copulation

Female genital pore

It is a single unpaired small pore, lies in 14th segment.

Copulation

During copulation two earthworms come closer and are ventrally attached in opposite direction
Both worms remain united together by the secretion of accessory glands and also by mutual penetration of setae in each other’s body
Sperm and prostatic fluid of each worm are exchanged and released or stored in spermathecae through spermathecal pore
Copulation lasts for about an hour
Fertilization is thus external, taking place in the cocoons.

Cocoon Formation In Earthworm

Cocoon formation takes place after copulation, when ovaries mature.
The epidermis of clitellar region contain 3 kinds of gland
1. Mucous gland: produce mucus
2. Cocoon secreting gland: secrete wall of cocoon. Also secrete a gelatinous viscid and sticky substance
3. Albumen gland cell: produce albumen; serves for nourishment of the growing embryo
These gland secretion soon harden on exposure to the air, into a tough but elastic tube which is called cocoon or egg capsule.
Worm starts to wriggle behind so that the girdle slipped forward
Girdle pass over the female genital pore, it receives ova and when it passes over spermathecal, it receives sperm through spermathecal pores
The girdle is thrown off from the anterior end and soon the elasticity of its wall closes up two ends to form a cocoon or ootheca.

Fertilization

Fertilization takes place inside the cocoon, where each ovum is fertilized by sperm.
Albumen cells provide nutrition to the embryo
Young one hatch out after 2-2.5 months
Development is direct without any larval stage.

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