We will discuss here about the structure of toad. The toad has an oval shaped fat body covered with moist skin. A full grown toad may be five inches long.
The females are larger than the males. The dorsal surface or back of a toad is darker in color with patches while the ventral surface or the abdominal side is devoid of such patch. The skin is warty and moist. The body of an adult toad is bilaterally symmetrical. The body can be divided into two parts; these are head and trunk. It does not have any tail.
(i) Head: The head is triangular in shape with a blunt snout (nose). The roof of the head is flat. Behind the snout there are two small pores; these are external nostrils. Toad has two large eyes at two sides of its head. Each eye has two eye lids one upper and one lower. It has an extra transparent eye membrane, known as nictitating membrane. Behind each eye, a circular light-colored thin membranous patch is found. It is known as tympanum, commonly called as eardrum.
(ii) Trunk: The body part behind the head is called trunk. The back portion of the trunk is rough and darker but it is smoother and paler towards the belly. Behind each tympanum, a little towards the back, there is an elevated region with larger warts; it is called parotid gland. This gland produces a sticky poisonous secretion, which helps them in defence.
The trunk has two pairs of limbs emerging ventrolaterally. The fore limbs are shorter and each bears four almost equal sized fingers. During breeding season male toads develop a cushion like pad at the base of each thumb, which is called thumb pad. The hind limbs are longer and strongly built. Each bears five unequal fingers of which middle one is the longest. These fingers are partly joined by thin skin folds. This type of foot is known as webbed foot, which helps in jumping and swimming as well. At the posterior end of the trunk, in between the bases of the hind limbs, a round aperture is present, which is called the vent or cloacal aperture.