Comparative Anatomy: Female Reproductive Systems in Birds, Rabbits, and Reptiles
Explore the female reproductive system of birds, rabbits, and reptiles. Detailed comparison of reproductive structures in pigeons, garden lizards, and rabbits.

The reproductive systems of birds, rabbits, and reptiles exhibit significant anatomical differences, reflective of their unique evolutionary pathways. A closer examination of these systems in Calotes (garden lizard), Columba (pigeon), and Oryctolagus (rabbit) provides insight into the diversity of reproductive structures across species.
Ovaries
In Calotes, the reproductive system includes two asymmetrical ovaries located on either side of the body. These ovaries are irregular in shape and are suspended from the dorsal wall of the body cavity by mesovaria. Notably, the right ovary is positioned slightly ahead of the left. Similarly, in Oryctolagus, there are two small, compact ovaries on both sides of the body, located just behind the kidneys and attached to the dorsal abdominal wall by mesovaria. In contrast, Columba (pigeon) has only one functional ovary—the left one—while the right ovary exists only as a vestigial structure.
Oviducts
The oviducts, responsible for transporting eggs from the ovaries, also vary considerably among these species. In Calotes and Oryctolagus, paired oviducts are present, while in Columba, only the left oviduct is developed, with a vestige of the right oviduct sometimes present. The oviducts in Calotes are notable for their striated appearance, extending well ahead of the ovaries and following a straight course. By contrast, the oviducts in Columba and Oryctolagus do not display striations and follow a more convoluted path.
The oviducal funnel, which helps guide the egg into the oviduct, also differs between species. In Calotes, the funnel is large with externally directed ostia, while in Columba, the single left oviducal funnel is very large, membranous, and features fimbricated margins. In Oryctolagus, the oviducal funnels are smaller with internally directed ostia.
Uterus and Vagina
The structure of the uterus and vagina is another area of distinction. In Calotes, the oviduct dilates to form an oval shell gland, and the oviducts enlarge into small ovisacs. The animal has two vaginae that open into the urodaeum. In Columba, the oviduct is divided into several parts: the magnum, which secretes albumen; the isthmus, responsible for secreting the shell membrane; and the uterus, which produces a calcareous shell. The vagina in pigeons is thick-walled and muscular. In rabbits (Oryctolagus), the reproductive system includes a pair of uteri, which are widened and muscular, leading into a median chamber known as the vagina. This chamber is associated with the urethra to form the urino-genital canal or vestibule.
External Openings and Associated Glands
The external reproductive openings also differ. In Calotes and Columba, the urodaeum opens to the outside via a transverse cloacal aperture. In rabbits, the urino-genital canal opens externally through the vulva, which is located in front of the anus and features a small structure called the clitoris. Additionally, while Calotes and Columba lack special glands associated with the reproductive system, Oryctolagus has Cowper’s and perineal glands.
Fertilization and Milk Glands
Fertilization is internal across all three species, but their reproductive modes differ. Calotes and Columba are oviparous, meaning they lay eggs, while Oryctolagus is viviparous, giving birth to live young. Finally, only rabbits have functional milk glands, with 4-5 pairs located on the ventral surface of the trunk. Neither Calotes nor Columba possess milk glands.
Reproductive System in Female Calotes (Garden Lizard) | Reproductive System in Female Columba (Pigeon) | Reproductive System in Female Oryctolagus (Rabbit) |
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On the right and left sides, two ovaries are present. | Only the left ovary is present. A vestige of the right ovary may occur. | A pair of ovaries are present on the left and right sides. They are small and compact bodies. |
Ovaries are irregular bodies situated asymmetrically and hanging from the dorsal wall of the body cavity by mesovaria. | The single left ovary is attached to the anterior lobe of the left kidney by mesovarium. | The ovaries lie behind the kidneys and are attached to the dorsal wall of the abdominal cavity by mesovaria. |
The right ovary is a little anterior to the left one. | The right ovary is absent. | The right and left ovaries are at the same level. |
Oviducts are paired. | Only the left oviduct is developed. A vestige of the right oviduct is often seen. | Oviducts are paired. |
Oviducts give a striated appearance over the greater part of their length. | The oviduct does not give a striated appearance. | Striated appearance is absent. |
Oviducts extend well ahead of the ovaries and follow a straight course. | The oviduct starts just behind the ovary and follows a convoluted course. | Oviducts start just outside the ovaries and follow a convoluted course. |
Oviducal funnels are large and have externally directed ostia with the entire margin. | The single left oviducal funnel is very large and membranous. It has fimbricated margins and lies close to the ovary with its ostium. | Oviducal funnels are small and have internally directed ostia with a fimbricated margin. |
Each oviduct dilates to form an oval shell gland along the ventral surface of the kidney. Uteri are not demarcated. Oviducts are enlarged into small ovisacs. There are two vaginae, which open into the urodaeum. | The oviduct is divided into an anterior oviducal funnel, followed by the magnum which is thick-walled and secretes albumen. Below the magnum is the isthmus, which secretes the shell membrane, and the succeeding part is the uterus. The uterus is thin-walled and secretes a calcareous shell and albumen. The posterior-most part is the thick-walled and muscular vagina. | The oviducal funnel leads distally into a long, narrow, and convoluted tube—the Fallopian tube. Its walls are lined with ciliated epithelium. The posterior-most parts of the two oviducts form uteri, which are widened, muscular, and vascular structures. The paired uteri open into a median and highly muscular chamber—the vagina. Associated with the urethra, the vagina forms the urinogenital canal or vestibule. |
The urodaeum opens outside by a transverse cloacal aperture. | The urodaeum opens outside by a transverse cloacal aperture. | The urinogenital canal opens outside by a longitudinal aperture—the vulva, located in front of the anus. The vulva has a 'clitoris.' |
There are no special glands associated with the female reproductive system. | Same as in Calotes. | Cowper's and perineal glands are associated with the female reproductive system. |
Milk glands are absent. | Milk glands are absent. | On the ventral surface of the trunk region, 4 or 5 pairs of milk glands open through their teats. |
Fertilization is internal. Oviparous animal. | Same as in Calotes. Oviparous animal. | Same as in Calotes and Columba. Viviparous animal. |
Reference(s)
- R.L. Kotpal. Modern Text Book Of Zoology: Vertebrates. Rastogi Publications. 5thEdition. 1 January 2022. ISBN: 9788193887561.
- Stephen Miller and John Harley. Zoology. McGraw-Hill Professional. 8thEdition. 16 October 2009. ISBN: 9780070164833.
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- Posted by Dayyal Dg.