Earthworms have a cylindrical shaped, reddish-brown segmented body which is divided into small segments. Dorsal side is characterized by a dark line of blood vessels and ventral side is characterized by the genital openings.The body consists of S-shaped setae helps this worm in locomotion.
Reproductive System of Earthworm
Earthworms are cross-fertilization hermaphrodites. Although not all earthworms use this reproductive strategy, the best-known species, Lumbricus Terrestris, is a cross-fertilization hermaphrodite and this strategy seems to be the most widespread in the earthworm.
The Earthworm is hermaphroditic, it has both male and female reproductive organs. The seminal vesicles which store sperm are three pairs of white sac-shaped with esophagus on each side of them. The seminal receptacles, which receive sperm during mating, are two pairs of small, white, round structures near the vesicles. Testes, which produce sperm, and ovaries, eggs, lie under the seminal vesicles.
Male Reproductive System
- There are two pairs of testes. One pair is situated at 10th segment and another pair at the 11th segment.
- Each testis consists of 4 to 8 digits.
- Function – They Testes produce sperm.
- Testes are enclosed by fluid filled sacs called testes sacs.
- One testes sac is found at 10th segment and other is at 11th segment
- Two testes sacs communicate each other.
- Function – Testes sacs lateral become saccular as they develop from the body cavity as a small outgrowth.
- There are two pairs of seminal vesicles.
- One pair is situated at 11th and other at the 12th segment.
- Each seminal vesicle communicates with testes sac.
- The spermatogonia are passed from testes into testes sacs and then they are passed into seminal vesicles where they develop into sperms.
- The mature sperms again go back into testes sac and pass into the seminal funnel.
- Function – Spermatozoa or sperm is formed after Spermatogonia undergo maturation division. Maturation of sperm takes place in seminal vesicles.
- There are two pairs of the seminal funnel.
- One pair is found in the 10th segment and another pair in 11th segment.
- They are ciliated and found below tests.
- Function- Mature sperms from seminal vesicles move back to the testes sac and pass through the spermicidal funnel into vasa differentia.
Female Reproductive Organ
Ovaries: There is a pair of ovary situated at the 13th segment hanging on septum between 12th and 13th segment. Each ovary has finger like projections, which contained ova in series. The mature ova are found toward the end and immature ova are found on the base of the lobules of the ovary.
Oviducal Funnel: One pair funnel like structures at 13th segment found below ovary with ciliated mouth called oviductal funnel. Each funnel opens into a short conical tube called oviduct. Two oviducts fuse together at the 14th segment and open outside through female genital aperture.
Spermatheca: There are four pairs of spermatheca. Each pair is found between 5-6, 6-7, 7-8, and 8-9th segment. Each spermatheca is flask shaped. The main body of spermatheca is called ampulla and short small lobe found attached at its side is called diverticulum. They store sperms.
Earthworms are simultaneous hermaphrodites, and reproduction usually occurs through copulation and cross-fertilization, A seminal groove, carry sperm as droplets from the male pore to the clitellar region, where it collects, and eventually enters the spermathecae of the partner earthworm with the aid of the Tubercula pubertal.
After which each of the mated individuals produces cocoons containing variable numbers of fertilized ova.The resistant cocoons are usually deposited near the soil surface, except in dry weather when they are laid in deeper layers. Earthworms are iteroparous animals and display indeterminate growth, continuing to grow in size after completing their sexual development.
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