Question

During breeding season, nuptial pad is found in the thumb of
A) Male frog
B) Female frog
C) Both of these
D) None of these

Answer 1

Hint:-A frog is any member of a diverse and tailless carnivorous group belonging to the order Anura and class Amphibia. The oldest fossil ‘proto-frog’ of the early Triassic age of Madagascar and molecular clock dating suggests their origin to the Permian age, about 265 million years ago.

Complete Answer:-
Frog exhibits sexual dimorphism and the male and female are distinguishable externally only during the breeding season when the male develops rough hypertrophied spiky epithelial swelling on their forearm and prepollex called nuptial pads on the bases of the thumb. Male anurans characteristically grasp the back region of a receptive female with the help of nuptial pads associated with forelimbs and release sperms. This clasping behavior of anuras is termed as amplexus and triggers the release of eggs from the female. Androgens are responsible for secondary sex characteristics such as nuptial pads. They also play a role in the initiation of amplexus. Studies suggest that the administration of androgens can activate amplexus in males while a peptide with female attractive properties has been isolated from the skin glands of male anuran.
Thus, the right option is A.

Note:- Amplexus is induced by AVT and antagonized by corticosterone. During amplexus, the male mounts over the female and attempts to rub his chin on the female’s nasal region to transfer pheromones that enhance the chances of spermatophore transfer. The female frog has paired ovaries and oviducts and a uterus that stores eggs until the eggs are released. However, gestation and fertilization occur outside in an external environment.