Primitive Breeding in an Ancient Indian Frog Genus Indirana

The Western Ghats biodiversity hotspot is rich in herpetofauna and harbours numerous endemic species. Unfortunately, many of these understudied species are threatened due to habitat loss, pollution, infectious diseases and climate change. Indirana (family Ranixalidae) is an ancient frog genus, endemic to the Western Ghats of India. Unlike most amphibians, it lays terrestrial eggs and has semi-terrestrial tadpoles. We barely have any knowledge about their development, life history, mating systems and reproductive ecology. Such information is crucial to design and implement successful conservation programmes. Hence, we studied the courtship, spawning behaviour and reproductive mode of an Indirana sp. from Amboli Reserve Forest located in the northern Western Ghats, Maharashtra, India. This species showcases a primitive type of inguinal amplexus and exhibits pronounced sexual size dimorphism, where females are significantly larger than the males. Average clutch size was 226 ± 41.5 eggs, with an egg diameter of 3.25 ± 0.32 mm. Fertilization rate was 87% with 100% hatching success. Additionally, this frog has evolved terrestrial eggs without the dependent traits like parental care and large egg size/small clutch size witnessed in other terrestrially egg-laying anurans (frogs and toads). This frog has reproductive mode 19, with its characteristic semi-terrestrial tadpoles. This genus represents the extreme of the trend (from obligatory aquatic to completely terrestrial) that amphibians show towards terrestriality.