Q.Briefly describe external fertilisation as it occurs in the frog, including the role of amplexus.

In the male frog, paired testes attached to the kidneys by the mesorchium release sperm via vasa efferentia into the kidney, and thence via a shared urinogenital duct to the cloaca; there is no separate penis. In the female, paired sac-like ovaries, greatly distended with pigmented eggs by the breeding season, release eggs into the body cavity, from where they enter coiled oviducts (which coat each egg in protective jelly) opening into the cloaca. Frogs are markedly seasonal breeders, with breeding in West Bengal triggered by the onset of the monsoon. Males call using vocal sacs to attract females, then clasp a female in amplexus usi …