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    Earthworm Reproductive System Short Notes | Free Biology Notes

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    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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