Development of Embryo in Rabbit
0
Medically Reviewed
Zoology

Development of Embryo in Rabbit

Explore the captivating journey of embryo development in rabbits, from fertilization to birth. Learn about this marvel of nature's design.

By Dayyal Dg.
Published:
Print this Page Email this Article
BS
Login to get unlimited free access
Be the first to comment!
Development of Embryo in Rabbit.
Development of Embryo in Rabbit.

Embryo development in rabbits is a fascinating journey through the intricate stages of life, showcasing the marvels of nature's design. In this comprehensive exploration, we will delve into the remarkable process of embryo development in rabbits, from fertilization to the formation of a fully developed fetus. Understanding these stages is not only essential for breeders but also provides valuable insights into the wonders of reproduction in this species.

Fertilization: The Commencement of Life

The journey of embryo development in rabbits begins with the magical moment of fertilization. When a male rabbit, or buck, successfully mates with a female rabbit, known as a doe, a crucial event unfolds within her reproductive tract.

In the doe's ovaries, multiple tiny eggs, or ova, are housed within structures called follicles. During the act of mating, the buck delivers sperm into the doe's reproductive tract. These sperm embark on a quest to find and penetrate one of the waiting eggs. When a sperm successfully penetrates an egg, fertilization occurs.

  1. After ovulation, a secondary oocyte is taken into the fallopian tube (oviduct) where it fuses with a sperm received during copulation.
  2. Thus fertilization is internal.
  3. An unusual feature is that an entire sperm enters the cytoplasm of the oocyte.
  4. The tail of sperm, however, soon disintegrates.
  5. The haploid male and female pronuclei then become fused to form a diploid zygote nucleus.

Egg Structure of Rabbit

  1. The egg of the rabbit is 0.1 mm in diameter and is a secondary oocyte.
  2. When shed from the Graafian follicle of the ovary, it is surrounded by a striated secondary membrane, the zona pellucida secreted by the follicle cells.
  3. Around the zona pellucida are some follicle cells forming a corona radiata which is soon dissolved away.
  4. The egg is alecithal with almost no yolk. The nucleus lies in the upper half or animal hemisphere, but the lower half, or vegetal hemisphere has some particles of yolk distributed evenly in the cytoplasm.
  5. The egg is fertilized in the upper part of the oviduct and it immediately undergoes a second maturation division to become a mature ovum.
  6. Two polar bodies lie within the zona pellucida near the animal pole.
  7. In mammals, the entire spermatozoan penetrates the egg but the tail soon degenerates, penetration of sperm into an egg is brought by an enzyme hyaluronidase present in the semen.
  8. The zygote passes down the oviduct and is covered by a coat of dense albumen.

Cleavage and Blastocyst Formation

Following fertilization, the newly formed zygote, which is the union of the egg and sperm, undergoes a series of rapid divisions known as cleavage. These divisions result in the formation of a multicellular structure known as the morula. The morula further develops into a blastocyst.

The blastocyst is a spherical structure with two distinct cell types: the inner cell mass and the outer trophoblast cells. The inner cell mass will eventually give rise to the embryo, while the trophoblast cells play a crucial role in implantation.

  1. The development of rabbits starts with a diploid zygote or egg.
  2. The embryo develops within a specialized part of the oviduct called the uterus.
  3. The embryo establishes intimate contact with it, and the young are born alive so that the eutherian mammals (rabbit) are viviparous.

Cleavage

  1. Cleavage is holoblastic but unequal.
  2. The first cleavage furrow is vertical dividing the zygote completely into two unequal blastomeres, one being smaller and more opaque than the other.
  3. The second cleavage is also vertical and at a right angle to the first, so that the zygote is divided into four unequal cells called blastomeres.
  4. The third cleavage is horizontal and slightly above the equator. After this, cleavages are irregular.

Morula

  • Cleavage results in the formation of a more or less spherical solid mass or ball of cells called morula.
  • A fully formed morula shows an outer or superficial layer of cells, the trophoderm or trophoblast.
  • The morula stage passes down the oviduct to enter the uterus.
  • It makes contact with the uterus of the mother and absorbs liquid food.

Blastocyst

  1. The embryo swells rapidly and the liquid food collects in a cavity that separates an outer layer of smaller trophoblast cells from a solid inner cell mass.
  2. The embryo is now called a blastocyst which appears like a blastula but is not comparable to it.
  3. Those trophoblast cells which lie above the inner cell mass are called cells of Rauber.
  4. As the blastocyst grows the inner cell mass becomes a knob-like thickening at one pole and it is called an embryonal knob because all parts of the embryo will be derived from it.
  5. The trophoblast cells opposite the embryonal knob form small papillae of trophoblastic villi which penetrate into depressions or crypts in the uterine wall.
  6. The blastocyst becomes attached or implanted in the uterus of the mother.
  7. The villi absorb food from the uterus.

Implantation: Nurturing the Embryo

Implantation is a pivotal step in embryo development, where the blastocyst attaches itself to the lining of the doe's uterus, known as the endometrium. This process is critical for the embryo to receive nutrients and support from the mother's body.

In rabbits, implantation occurs approximately six to eight days after fertilization. The trophoblast cells of the blastocyst invade the endometrial tissue, establishing a connection with the maternal blood supply. This connection allows for the exchange of oxygen, nutrients, and waste products between the developing embryo and the mother.

Gastrulation and Organ Formation

As embryo development progresses, the blastocyst undergoes gastrulation, a transformative process during which the three primary germ layers - ectoderm, mesoderm, and endoderm - are established. These germ layers give rise to different tissues and organs in the developing embryo.

The ectoderm forms the nervous system, skin, and hair, while the mesoderm contributes to muscles, bones, and the circulatory system. The endoderm develops into the digestive and respiratory organs. This intricate orchestration of cell differentiation sets the stage for the formation of a fully functional rabbit.

  1. Some cells separate from the lower surface of the embryonal knob.
  2. These cells migrate and form a new layer of cells, the endoderm.
  3. The blastocyst is now two cell layers thick like a gastrula. It encloses a fluid-filled yolk sac that contains no yolk.
  4. The embryonal knob enlarges and becomes flat to form an embryonal disc.
  5. It soon becomes exposed by the disintegration of the cells of Rauber and by the zona pellucida and albumen being dissolved away.
  6. This gastrulation is not comparable to that of Amphioxus or frog.
  7. In the center of the embryonal disc, cells collect to form a primitive streak.
  8. The movements of the cells of the primitive
  9. streak on both sides result in the separation of mesoderm cells.
  10. Cells move forward and the primitive knob forms a notochord.
  11. The formation of mesoderm and notochord is the same as in chick.
  12. The primitive streak retreats towards the hind end.
  13. After giving up the chordamesoderm cells of the notochord and mesoderm, the remaining cells of the embryonic disc form ectoderm.
  14. The ectoderm cells form a neural plate and neural folds which becomes a neural tube.

Gestation Period

  • The period of intrauterine development of the fetus in the mother is called the gestation period.
  • The uterine-endometrium (vascular cushion for the implantation of the embryo) is maintained by a hormone called progesterone.
  • The gestation period in mammals varies from species to species.
  • The gestation period of different mammals are:
    1. Opposum: 13 days.
    2. Rat: 21 days.
    3. Rabbit: 30 days.
    4. Cat and Dog: 60 days.
    5. Guinea Pig: 68 days.
    6. Goats and Sheep: 149 days.
    7. Cow: 280 days.
    8. Horse: 336 days.
    9. Whale: 360 days.
    10. Rhinoceros: 540 days.
    11. Elephant: 600 days.
    12. Human: 270 days.
  • The expulsion of the fully developed embryo in mammals is called parturition.

Placenta Formation: Sustaining Life

In rabbits, as in many mammals, the placenta is the vital link between the developing embryo and the mother. The placenta is formed by the trophoblast cells of the blastocyst, which undergo further differentiation into specialized structures called placental villi. These villi enable the exchange of nutrients, oxygen, and waste products between the maternal and fetal circulatory systems.

The development of a functional placenta is crucial for providing the growing embryo with the essential resources needed to thrive and develop.

Fetal Development: Growth and Maturation

As the embryo continues to develop, it transforms into a fetus. The fetal stage is marked by rapid growth and maturation of organs and systems. During this period, the fetus gains size and weight, and all major organs and structures continue to develop and mature.

The duration of rabbit pregnancy, also known as gestation, varies depending on the rabbit breed but typically ranges from 28 to 31 days. During this time, the fetus undergoes significant growth, preparing for the transition to the outside world.

Viviparity

  1. Animals that give birth to their young ones are called viviparous animals.
  2. In these animals, the development of the fertilized egg takes place in the uterus of the mother.
  3. The development of the embryo depends on the mother for both nourishment and shelter.
  4. This phenomenon of giving birth to young ones is called viviparity.
  5. Fertilization is internal in these groups of animals.
    E.g.: Snakes like vipers and all mammals except the egg-laying ones.

Birth: A New Beginning

After a remarkable journey of embryo development, the time for birth arrives. Female rabbits, or does, give birth to a litter of kits, typically ranging from one to over a dozen, depending on the rabbit breed. The process of birth, known as parturition, is a natural and instinctive event.

Once born, the kits are entirely dependent on their mother's care and nourishment. The mother doe exhibits remarkable maternal behaviors, providing warmth and sustenance to her offspring.

Conclusion: The Miracle of Life in Rabbits

The process of embryo development in rabbits is a testament to the intricacies of life's creation. From the moment of fertilization to the birth of the kits, every stage is marked by remarkable transformations and adaptations. Understanding this journey not only enhances our appreciation for the complexity of reproduction in rabbits but also provides valuable insights into the wonders of life itself. In the world of nature, the development of each rabbit embryo is a small miracle that continues to captivate and inspire.

Last Updated:

Cite this page:

Dayyal Dg.. “Development of Embryo in Rabbit.” BioScience. BioScience ISSN 2521-5760, 29 May 2017. <https://www.bioscience.com.pk/en/topics/zoology/embryo-development-of-rabbit>. Dayyal Dg.. (2017, May 29). “Development of Embryo in Rabbit.” BioScience. ISSN 2521-5760. Retrieved September 13, 2023 from https://www.bioscience.com.pk/en/topics/zoology/embryo-development-of-rabbit Dayyal Dg.. “Development of Embryo in Rabbit.” BioScience. ISSN 2521-5760. https://www.bioscience.com.pk/en/topics/zoology/embryo-development-of-rabbit (accessed September 13, 2023).
  • Comment
  • Posted by Dayyal Dg.
Start a Conversation
Add comment

Follow us on social media

End of the article