Purple Frog, Pignose Frog
Species Description: Biju SD, and Bossuyt F. 2003. New frog family from India reveals an ancient biogeographical link with the Seychelles. Nature. London 425: 711–714.
© 2017 Sandeep Das (1 of 6)
The skeletal structure of N. sahyadrensis is characteristic of a burrowing frog, with a strongly ossified skull and well-calcified bones. Due to the species' unique appearance, as well as specific osteological differences, Biju and Bossuyt (2003) placed N. sahyadrensis in a new anuran family, named Nasikabatrachidae. Although some traits are shared with the sister group, Sooglossidae, the authors concluded the lack of toe discs and much larger size, as well as other characters, significantly separate N. sahyadrensis from Sooglossidae (Biju and Bossuyt 2003).
N. sahyadrensis tadpoles have a wide, flattened, wedge shaped snout. The nostrils are located on top of the head, closer to the eyes than the snout tip. Eyes are small and located dorsolaterally. The oral disc is suctorial and ventrally located. Body is wide and flattened. The tail is low relative to the body, dorsal and ventral fins are about the same height. The tail is about two thirds of the total length. The dorsum is dark brown, while the ventral surface is a silvery cream color. The eyes are black. The tail is light brown, with dark brown patches throughout (Raj et al. 2012).
Distribution and Habitat
As of 2012, the species ranges from Camel's Hump Hill Range in the north to the northern reaches of the Agasthyamalai Hill Range in the south, in the Western Ghats of India. It inhabits an elevational range of 60-1100 meters above sea level (Zachariah et al. 2012).
Life History, Abundance, Activity, and Special Behaviors
N. sahyadrensis is an explosive breeder, laying large numbers of eggs during the earliest rains of the pre-monsoon season. Additionally, the tadpoles are lentic, inhabiting fast flowing seasonal streams. The unique timing of reproduction and tadpole habitat significantly reduces competition (from other anuran larvae) and predation. The eggs are laid so early that there has not been time for predators to significantly establish themselves in the stream, and by the time other organisms have settled in, the tadpoles have moved to fast flowing waters over sheer rock, where there is little threat from predators (Zachariah et al. 2012).
Eggs are laid in rocky crevices at the edges of second-order streambeds. During amplexus, the male grasps the female's spine (as there are no adhesive glands present and the male is very small relative to the female). The female then carries the male to suitable oviposition sites, where he pushes the eggs out of the female with his hindlimbs and fertilizes them. The eggs are deposited in arrays or clumps. One mating pair deposited about 3600 eggs in one night (Zachariah et al. 2012).
N. sahyadrensis tadpoles are known to feed out of the water at night, using their strengthened abdominal muscles to move onto surfaces with extremely shallow water flow (Zachariah et al. 2012). Tadpoles take about 100 days from hatching to metamorphose (Raj et al. 2012).
N. sahyadrensis is fossorial and comes to the surface only for a few weeks a year to breed (Biju 2004). Sightings are more likely at the beginning of monsoon season, in July (Radhakrishnan et al. 2007). A captured specimen was reported to be able to dig itself into loose soil within 3-5 minutes. When placed on a pebbled gravel surface within an open, dry streambed, the frog tried to escape with stretching movements (not hopping). The pointed snout is touch-sensitive. In captivity, the frog used its hindlimbs for burrowing, with Radhakrishnan et al. (2007) providing a detailed description of the burrowing process. During five months of captivity, the frog did not emerge from the soil, even at night, although it moved about underneath the soil. Given the hard-knobbed snout and small ventral mouth, this species is likely to be a completely underground feeder specializing in termites (Dutta et al. 2004; Radhakrishnan et al. 2007).
Other frogs with similar lifestyles and morphology include those of the genus Rhinophrynus and Hemisus (Radhakrishnan et al. 2007).
Trends and Threats
Relation to Humans
Thomas and Biju (Salamandra 2015) extensively documented tadpole consumption in Nasikabatrachus sahyadrensis. At a single study site in the Western Ghats of India, thousands of tadpoles were harvested per year, as well as adults. While potentially sustainable, the combination of heavy exploitation with annual variation in monsoon rains likely have a long-term negative impact on this threatened and biologically unique species.
Possible reasons for amphibian decline
General habitat alteration and loss
N. sahyadrensis tadpoles were first described in Annandale (1918), without specimens of adults. It was tentatively assigned to the family Cystignathidae (Raj et al. 2012).
In Sanskrit, nasika means "nose" and batrachus means "frog," while Sahyadri refers to the location where this species is found (the Western Ghats, also known as the Sahyadri Mountains, a low-lying mountain range along the west coast of the Indian subcontinent).
As pointed out by Hedges (2003), most of the anuran families were named in the mid-nineteenth century; the last time the discovery of a new species led to the description of a new family was in 1926 (Frost 2003). Based on a phylogenetic analysis of mitochondrial genes, Biju and Bossuyt (2003) suggest that this species, endemic to India, is a sister taxon to the Sooglossidae, a family of frogs endemic to the Seychelles Islands. This has lent support to the idea of a possible land bridge between Africa and India, enabling faunal dispersal. The species Nasikabatrachus sahyadrensis is estimated to have originated in the Jurassic, 130-180 million years ago (Biju and Bossuyt 2003; Dutta et al. 2004) which is 50 to 100 million years earlier than any other known frog species in India (Aggarwal 2004), and predating the breakup of the ancient continent Gondwana (Radhakrishnan et al. 2007; Dutta et al. 2004).
Aggarwal, R. K. (2004). ''Ancient frog could spearhead conservation efforts.'' Nature, 428, 467.
Biju, S. D. and Bossuyt, F. (2003). ''New frog family from India reveals an ancient biogeographical link with the Seychelles.'' Nature, 425, 711-714.
Dutta, S. K., Vasudevan, K., Chaitra, M. S., Shanker, K. and Aggarwal, R. K. (2004). ''Jurassic frogs and the evolution of amphibian endemism in the Western Ghats.'' Current Science, 86, 211-216.
Frost, D. R. (2003). ''Amphibian Species of the World: An Online Reference.'' Electronic database available at http://research.amnh.org/herpetology/amphibia/index.html. American Museum of Natural History, New York, USA.
Hedges, S. B. (2003). ''The coelacanth of frogs.'' Nature, 425, 669-670.
Myers, N., Mittermeier, R. A., Mittermeier, C. G., Da Fonseca, G. A. B. and Kent, J. (2000). ''Biodiversity hotspots for conservation priorities.'' Nature, 403, 853-858.
Radhakrishnan, C., Gopi, K.C., and Palot, M.J. (2007). ''Extension of range of distribution of Nasikabatrachus sahyadrensis Biju & Bossuyt (Amphibia: Anura: Nasikabatrachidae) along Western Ghats, with some insights into its bionomics.'' Current Science, 92(2), 213.
Raj, P., Vasudevan, K., Vasudevan, D., Sharma, R., Singh, S., Aggarwal, R.K., and Dutta, S.K. (2012). ''Larval morphology and ontogeny of Nasikabatrachus sahyadrensis Biju & Bossuyt, 2003 (Anura, Nasikabatrachidae) from Western Ghats, India.'' Zootaxa, 3510, 65-76.
Thomas A and Biju SD (2015). "Tadpole consumption is a direct threat to the endangered purple frog, Nasikabatrachus sahyadrensis." Salamandra, 51(3), 252-258. [link]
Zachariah, A., Abraham, R.K., Das, S., Jayan, K.C., and Altig, R. (2012). ''A detailed account of the reproductive strategy and developmental stages of Nasikabatrachus sahyadrensis (Anura: Nasikabatrachidae), the only extant member of an archaic frog lineage.'' Zootaxa, 3510, 53-64.
Originally submitted by: Elizabeth Reisman, John Cavagnaro (first posted 2003-10-20)
Trends and threats by: Michelle S. Koo (updated 2021-11-05)
Relation to humans by: Michelle S. Koo (updated 2021-11-05)
Comments by: Michelle S. Koo (updated 2021-11-05)
Edited by: Kellie Whittaker, Michelle S. Koo (2021-11-05)
Species Account Citation: AmphibiaWeb 2021 Nasikabatrachus sahyadrensis: Purple Frog <https://amphibiaweb.org/species/6197> University of California, Berkeley, CA, USA. Accessed Dec 4, 2021.
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Citation: AmphibiaWeb. 2021. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 4 Dec 2021.
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