Frog: Reproductive System

Sexual dimorphism

    • They show sexual dimorphism.
    • Male frogs produce sound sounds during mating.
    • Hence, they possess sound producing vocal sacs.
    • They also have a copulatory pad (nuptial pad) on the first digit of the fore limbs.
    • Both these are absent in female frogs.

Male reproductive organ

  • The male reproductive system is composed of a pair of testes, a long duct called vas effertia, urinogenital duct and a cloacal opening.

  • Testis
    • The testis is yellow in color and ovoid in shape.
    • Each testis is found attached to the upper part of the kidney by a doubly folded peritoneum known as mesorchium
  • Vas efferentia
    • A group (10 – 12 in number) of ducts called vas efferentia arises from the testis.
    • They enter into the kidneys, and then open into Bidder’s canal.
  • The duct then continues to join the urinogenital duct that comes out of the kidneys and opens into the cloaca.
  • The cloaca is a small, common chamber that is used to pass faecal matter, urine and sperms to the exterior.

Female reproductive organ

The female reproductive consists of a pair of ovaries, oviducts, ostia, ovisacs and a cloacal opening.


  • A pair of ovaries is present near the kidneys.
  • They are attached to the kidneys by means of folds of peritoneum called mesovarium.
  • But they do not have any functional connection with kidneys.


  • A pair of coiled oviducts arising from the ovaries lies on the side of the kidneys.
  • Each oviduct opens into the body cavity through a funnel-shaped opening called ostia.


  • At the posterior end, oviduct dilates to form ovisacs.
  • The ovisacs store eggs temporarily before they are released through cloaca.

Fertilization & Development

Fertilization is external and takes place in water. Both eggs and sperms are released to the water during spawning.

Development involves a larval stage called tadpole. They are hatched from eggs within a few days after fertilization.

Tadpole undergoes metamorphosis to form the adult.

  • For a newly hatched tadpole, the first source of food is the yolk stored in its body.
  • They gradually grow larger and develop three pairs of gills.
  • After metamorphosis, the tadpoles get transformed into an air – breathing carnivorous adult frog
  • Legs grow from the body, and the tail and gills disappear.
  • The mouth broadens, developing teeth and jaws, and the lungs become functional.


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