Earthworm Reproductive System Short Notes | Free Biology 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.