In this article we will discuss about the male and female reproductive organs in toad. This will also help you to draw the structure and diagram of reproductive system in toad.
The sexes are separate. Male and female toads are very much alike in external feature. During the breeding season, however, the female bulges out, being distended by her eggs, whereas the male remains slender.
The male, on the other hand, produces cushion like thumb-pads at the bases of his first two fingers. This thickening is used for grasping the female. Lastly, the male can croak loudly because it has a vocal sac under its throat.
The reproductive system consists of the gonads (gono = that which generates) which produce the germ cells, and the ducts through which the germ cells are let out. The function of this system is the perpetuation of the race.
Male Reproductive Organs (Fig. 34):
In a male toad the gonads are a pair of yellowish-white, elongated bodies called testes singular=testis). Each testis is attached to the ventral surface of the corresponding kidney by a fold of peritoneum called mesorchium.
Sometimes a testis may consist of two or three pieces joined end to end. Each testis is a collection of very fine tubes called seminiferous tubules which manufacture the male germ cells or spermatozoa. A spermatozoon is a highly specialised cell, with an oval head containing the nucleus, a short middle piece containing the centrosome, and a long wavy tail composed of cytoplasm.
The seminiferous tubules of a testis are connected to the collecting tubes of the kidney by several fine ducts called vasa efferentia which pass along the mesorchium. The sperms are expelled through the vasa efferentia into the ureter which, therefore, serves as the urinogenital duct. The sperms are finally let out through the cloacal aperture at the time of mating.
Attached to the anterior end of the kidney, and in front of the testis, is a small-rounded body called Bidder’s organ. It is an undeveloped female gonad and serves no useful function in the normal male.
In front of the gonads and in both the sexes, there are several yellowish outgrowth called fat bodies. These are the reservoirs of fatty substances which are utilised in the manufacture of germ cells. They also provide nourishment during hibernation, when no feeding is possible.
Female Reproductive Organs: (Fig. 37)
In a female toad the gonads are the two ovaries. Each ovary is a much-folded sac of irregular shape fixed to the ventral surface of the corresponding kidney by a fold of mesovarium. In the breeding season the ovaries are much enlarged and distended with eggs.
The eggs or ova (singular=ovum) are the female germ cells. Each ovum is a spherical cell with a blackish animal pole containing protoplasm, and a whitish vegetative pole full of yolk. The egg is surrounded by a thin vitelline membrane. The oviduct for each ovary is a long much-coiled tube situated laterally. The oviducts are not connected with the ovaries in any way.
The anterior end of each oviduct lies far forward near the base of the corresponding lung, and opens directly into the body cavity by a funnel-shaped ostium. The middle part of the oviduct is thick-walled, narrow, and convoluted, whereas the posterior part widens out to form a thin-walled ovisac or uterus.
The two uteri join to form a single median tube which opens into the dorsal wall of the cloaca, just anterior to the urinary opening. When mature, the eggs escape into the body cavity by rupturing the ovarian wall. They then find their way into the oviducts through the funnel- shaped ostia.
As the eggs are passing down the convoluted middle part of the oviducts, each egg receives a coating of jelly-like albumen. The eggs accumulate in the dilated ovisacs or uteri and are voided through the vent during mating. The process of reproduction will be described along with the life-history.