Ontogenetic systematic characterisation of an endemic frog Rhacophorus malabaricus Jerdon, 1870 (Anura: Rhacophoridae) from Western Ghats, Kerala, India

Abstract

In the present study, the complete description of the development and metamorphosis of an endemic frog Rhacophorus malabaricus, Jerdon, 1870, is documented in its natural habitat from the Southern part of Western Ghats (Peppara Wildlife Sanctuary, India). A brief illustration of each Gosner stage (fertilized egg to metamorphosed froglet) is given based on the direct monitoring and characterisation of morphological and morphometric variations. The identity of the tadpoles was confirmed by gene sequencing. Fertilisation and early development (cleavage, blastulation gastrulation and neurulation) take place inside the foam at 21.4 ± 0.1°C. The motile stage begins at 3rd day, after hatching and then eventually dropping into the water body. Hind limbs start differentiation first on the 15th day. The larva attains maximum size (TL 48.70 ± 0.22 mm) at Gosner stages 42. The morphometric measurements are significantly correlated with Gosner stages especially from 26 to 39. Oral disc features are described with LTRF of 7(3-7)/3 and KRF of 2:5+5/3. The morphological and morphometrical data of R. malabaricus larva is compared with other known Rhacophorus Kuhl & Van Hasselt, 1822 members. The present study shows that the relative lengths of TL, SVL, BH and TAL with stages are significant morphometric characters for taxonomy. Morphological features (limb bud development, pigmentation, oral disc features, etc.) are potentially useful characters for tadpole based anuran taxonomy at stage 26 or later.