Earthworm Male and Female Reproductive System

In this earthworm male and female earthworm reproductive system post we have briefly explained about male earthworm reproductive system and female earthworm reproductive system anatomy of earthworm.

Earthworm Reproductive System

Earthworms are hermaphrodites or monoecious, meaning they have both male earthworm reproductive system and female earthworm reproductive system. In earthworms, cross-fertilization is the most common method of reproduction. On the 9th to 15th segments, reproductive organs can be found.

Reproductive System

Reproductive System of an Earthworm, image Source: www.studyandscore.com

Earthworm Male and Female Reproductive System

Male Earthworm

Male earthworm reproductive system consist of testes, testis sacs, seminal vesicles, vasa deferentia, prostate glands, and accessory glands.

1. Testes

The testes of earthworm reproductive system are divided into two pairs. One pair is located in the tenth segment, while the other pair is located in the eleventh segment. These are located beneath the stomach, ventrally. Each pair is contained within that segment’s testis sac. They emerge from the anterior wall of the respective testis sac’s inner surface. Testes are small digitate bodies with four to eight digitate processes and a small base. They are formed by the parietal coelomic epithelium. They are responsible for the production of spermatogonia, also known as sperm mother cells.

2. Testes Sacs

The testes are surrounded by fluid-filled sacs of earthworm reproductive system known as testes sacs. One testes sac is found in the tenth segment and the other in the eleventh segment. The testis sac of the 10th segment is small and encloses the segment’s testes and spermiducal funnels, whereas the testis sac of the 11th segment is relatively large and encloses the segment’s testes, spermiducal funnels, and seminal vesicle. A small duct connects the testis sac to a seminal vesicle on each side.

3. Seminal Vesicle

Seminal vesicles of earthworm reproductive system come in two pairs. One pair is on the 11th segment, while the other is on the 12th. The testes sac connects with each seminal vesicle. Spermatogonia are transferred from the testes to the testes sacs, and then to the seminal vesicles, where they mature into sperms. The mature sperms return to the testes sac and pass through the seminal funnel.

4. Spermiducal Funnel

The spermiducal funnel of earthworm reproductive system comes in two pairs. One pair is found in the tenth section, while the other is found in the eleventh segment. They’re ciliated and reside beneath the testes. The margins of each funnel are fimbriated and ciliated.

5. Vasa differentia

From the 12th segment to the 17th segment, there are four tubes that run. They join the duct of the prostate gland in the 17th segment to form the combined prostatic and spermatic duct. Internally, the vasa deferentia are lined with ciliated epithelium all the way up to where they intersect the common prostatic duct.

6. Prostate gland

There are two prostate glands in the male body. They’re bigger, a little more uneven, flat, and wide. They run from the 16th or 17th segment to the 20th or 21st. Each prostate gland contains a short curved duct that connects to spermatic ducts and exits through the 18th segment of the male genital aperture.

7. Accessory gland

The auxiliary glands of earthworm reproductive system come in two pairs. One pair is in the 17th section, while the other is in the 19th segment. They have a tiny, spherical shape. They have tiny ductules that open through the papillae of the genital tract.

8. Genital papillae

There are two pairs of copulatory or genital papillae on the ventral side of the 17th and 19th segments, one pair in each segment. The spermatogonia generated in the testes are shed into the testis-sac cavities and then into the seminal vesicles. In the seminal vesicles, the spermatogonia mature into spermatozoa. The mature sperm return to the testes sacs and exit through the spermiducal funnels, passing through the vas differentia and male genital apertures.

Female Earthworm

The female earthworm reproductive system in Pheretima consists of the following parts, ovaries, oviducts, and spermathecae.

1. Ovaries

A pair of ovaries of earthworm reproductive system hangs from the septum between the 12th and 13th segments at the 13th segment. Each ovary includes projections that look like fingers and hold ova in a series. Immature ova are found towards the base of the lobules of the ovary, while mature ova are found near the end.

2. Oviducal Funnel

The oviducal funnel of earthworm reproductive system is a pair of funnel-like structures situated below the ovary on the 13th segment with a ciliated mouth. Each funnel leads to an oviduct, a short conical tube. At the 14th segment, two oviducts join and open to the outside through the female genital aperture.

3. Spermathecae

There are four spermathecae in all. Each pair is found between the segments 5-6, 6-7, 7-8, and 8-9. Each spermatheca resembles a flask. The ampulla is the main body of the spermatheca, and the diverticulum is a tiny lobe attached to its side. Sperm are stored in them.

Reproduction Process

Copulation

Two earthworms copulate at night during the rainy season. During copulation, two earthworms attach to each other through their ventral surfaces, with their anterior ends pointing in opposing directions. The male genital aperture is erected and inserted into each other’s spermathecal pore. Sperms are exchanged during the procedure. After about an hour, they part. Spermathecae receive the sperm and store them in their diverticula. Earthworms fertilise themselves from the outside, in their cocoons.

Cocoon formation

Membrane secreting glands secrete a membrane surrounding the clitellum after copulation. The membrane begins to move towards the earthworm’s anterior end, while the worm begins to recede backward. The membrane receives ova from the female genital aperture and sperm from the spermathecal pores during the process. The membrane is then spread out on the ground. The membrane’s elastomeric opening closes. The structure is referred to as a cocoon. One of the sperm fertilises the ovum within the cocoon to generate a zygote, and a baby worm develops within the cocoon. After around 2-3 weeks, the juvenile worm emerges from the cocoon. After each conjugant copulates, a dozen cocoons are created.

Development

Reproductive System

Reproduction Process

Only one embryo develops from the fertilised eggs in the cocoon. Other eggs that serve as nurse cells are being grown at the expense of others. Albuminous substances secreted by the clitellum glands for the embryo’s nourishment are also found in the cocoon. There are no larval stages in direct development in the cocoon.

The zygote undergoes holoblastic and a modified spiral cleavage resulting in a hollow ball of cells, the blastula, enclosed in a vitelline membrane. The lower cells of the blastula are endodermal and those of the upper cells are ectodermal. Gastrulation occurs by the invagination of endodermal cells into ectodermal cells to form a cylindrical gastrula with an archenteron cavity. A blastopore narrows to form the mouth. Mesoderm develops from 2 large cells of blastula, called mesoblasts. Mesoblasts divided to form 2 mesoblastic bands which later give rise to the coelomic epithelial lining. Young worm, when fully grown, crawls out of the cocoon in about 2 or 3 weeks to lead an independent life.

Further Readings

Reference

  1. https://kullabs.com/class-11/biology11/earthworm-1/reproductive-system-of-earthworm
  2. https://biomedres.us/pdfs/BJSTR.MS.ID.002015.pdf