Wednesday, 10 September 2014

Indian Purple Frog (Pignosed Frog)

Indian Purple Frog (Nasikabatrachus sahyadrensis)
Indian Purple Frog
Credit: Karthickbala at ta.wikipedia (CC-BY-SA-3.0)
via Wikimedia Commons
Kingdom: Animalia
Phylum: Chordata
Class: Amphibia
Order: Anura
Family: Sooglossidae
Genus: Nasikabatrachus
Species: Nasikabatrachus sahyadrensis
Conservation Status: Endagered
Common name(s):  Indian purple frog, Pignosed frog, Indian purple frog

Meet the Indian puple frog, an endangered and odd-looking species of frog from the mountains of India’s Western Ghats.

The species was formally described only in 2003, although there was a lot of anecdotal evidence surrounding its existence. Other than its weird spherical looks, the pignosed frog also has a very unique and unusual burrowing lifestyle which is covered down below.

Distribution & Habitat
Initially believed to be restricted to the south of the Palghat Gap in the Western Ghats, additional research has revealed that the species distribution extends further north of the gap. Today, the pig-nosed frog is known to be distributed in the Western Ghats, ranging from the Camel's Hump Hill Range in the north, all the way to the northernmost portions of the Agasthyamalai Hill Range in the south.

MapP showing the distribution of the purple frog (Nasikabatrachus sahyadrensis)
Purple frog distribution map
(click to enlarge)

Adults have a plump, round body with a pointed, pig-like snout. The head is conical and very small compared to the rest of the body. The eyes are small and rounded, with a horizontal pupil. The skin is smooth and has a dark purple coloration that fades into grey along the stomach.

Adults are about 7 cm (~2.7 in.) long, with males being about one third the size of females.

The fore and hindlimbs are short but strong, allowing it to dig as far as 3.7 m (12 ft) below ground. The limbs end in partially webbed feet with rounded toes. ╬Ľach hind foot possesses a large, white wart-like growth, probably used for digging purposes.

The purple frog has a skeletal structure that is characteristic of most burrowing frogs, with a strongly ossified skull and well-calcified bones.

Dorsolateral and frontal view of a male purple frog
Dorsolateral (left) and frontal (right) views of a calling male that was removed from under
the soil at the entrance of the tunnel from which it had been calling. The male was induced
to call above ground after brief exposure to a female.
Credit: Ashish Thomas [2]

Behavior & Reproduction
Pignosed frogs spend most of the year underground, coming out in the surface only for about two weeks each year, to reproduce. This is why the species had gone unnoticed for so long by biologists, until 2003 when it was officially described.

Mating occurs during the pre-monsoon rains, primarily in May. Males use strange calls to attract females, from burrows beside headwater streams. Once approached by females, they mount them in the amplexus position. While in amplexus in the pectoral position, the male tightly holds the vertebral column of the female. The pair then enters a crevice in a rock pool amid a flowing stream and the female lays the eggs in a clutch comprised of more than 3000 eggs. The hatchlings are tadpoles and metamorphose after about 100 days.

Male frog calling from above ground

Contrary to most other burrowing frogs that emerge and feed above the ground, the purple frog forages exclusively underground, feeding primarily on termites using the tongue and a special buccal groove. It occasionally also feeds on ants and small worms. It is presumed to use its smell to forage due to the lack of light and its poor vision.

N. sahyadrensis has a narrow mouth with a small gape that prevents it from catching and consuming larger prey items.

Conservation Status
This strange animal is listed by the IUCN as an endangered species, because its known distribution area covers less than 5,000 km2, with all individuals occurring in fewer than five locations. The IUCN also notes the continuing decline in the extent and quality of its habitat in the Cardamom Hills.

Their main threat is forest loss due to expanding cultivation (of coffee, cardamom, ginger and other crops). The purple frog has not been reported in any protected areas, making the protection of its known habitat an urgent priority.

Other Interesting Facts about the purple frog
- N. sahyadrensis tadpoles were first described in 1918, without specimens of adults. The species was tentatively assigned to the family Cystignathidae.
- The pignosed frog used to be considered the only extant member of an ancient amphibian family called Nasikabatrachidae. However, in 2006 the family was incorporated into the Sooglossidae
- Only 135 specimens have so far been observed or collected. Only three of them were females.

You may also like
  • Turtle Frog: A bizarre frog with a turtle-shaped body.

References & Further Reading
-  Biju SD, & Bossuyt F (2003). New frog family from India reveals an ancient biogeographical link with the Seychelles. Nature, 425 (6959), 711-4 PMID: 14562102
- Thomas A, Suyesh R, Biju SD, & Bee MA (2014). Vocal behavior of the elusive purple frog of India (Nasikabatrachus sahyadrensis), a fossorial species endemic to the Western Ghats. PloS one, 9 (2) PMID: 24516517
- C. Radhakrishnan, K. C. Gopi and Muhamed Jafer Palot (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):213-216
- Das, K. S. Anoop 2006 Record of Nasikabatrachus from the Northern Western Ghats. Zoos' Print Journal 21(9):2410
- Zachariah, A; RK Abraham; S. Das; KC Jayan & R Altig (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
- Nasikabatrachus sahyadrensis. In: IUCN 2006. 2006 IUCN Red List of Threatened Species. . 

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