The active biological process by which an organism produces its own kind of individual is called reproduction.
Frog is an unisexual animal and shows sexual dimorphism. It reproduces only sexually and having external fertilization.
Its reproductive system can be studied under two headings:-
The male reproductive system of frog is also called urinogenital system because its reproductive system and excretory system (Urinary system) remain fused together.
The male frog can be recognized by the presence of copulatory pads in fore limbs, vocal sac, deep colour, slim body and comparatively more muscular fore limb.
The male reproductive system consists of following structure:-
A testis is an elongated (1.25 Cm long) or, ovoid, light yellow body.
It remains attached with antereo – ventral surface of each kidney by a double fold of peritoneum, called mesorchium. Near the anterior end of testis arise several branched finger like fat bodies which provide reserve food used to nourish developing spermatozoa and during hibernation.
A large number of seminiferous tubules are present in bed of loose connective tissue. Connective tissue contains a large number of blood vessels and a group of cells called interstitial cells. Interstitial cells are endocrine gland which secretes male sex hormone which helps in spermatogenesis (The process of formation of male gametes.) and develops secondary sexual characters.
Each seminiferous tubules is lined by single layer of germinal epithelial cells. The cells of germinal epithelium forming spermatogonia produce spermatozoa by spermatogenesis. Spermatozoa are found in group (Spermatophore) and having a head contains acrosome and nucleus, middle piece with centriole and mitochondria and tail with an axial filament.
B. & C) Vasa – efferentia, Bidder’s canal and collecting tubules present in kidney:-
Seminiferous tubules of each testis are connected to narrow tubes (10 to 12 in number), called vasa – efferentia. These leave from inner margin of tests, run through mesorchium and enter the inner margin of kidney to open into the Bidder’s cxanal. The latter is connected to the ureter through collecting tubules of kidney.
The longitudinal collecting tubule is extended backward as urinogenital duct. The duct serves for the passage of both male gametes and urine so it is called urinogenital duct. The ducts of both sides open into the roof of cloaca separately on urinogenital papillae.
From cloaca gametes are given outside through cloacal aperture.