Nasikabatrachus sahyadrensis

Nasikabatrachus Sahyadrensis is an unusual species of purple frog found in the mountainous Western Ghats region of southern India. Only loosely related to other kinds of frog, it is the only species of its family, Nasikabatrachidae. It was discovered in October of 2003 by Franky Bossuyt of the Free Univerity of Brussels, and S.D. Biju of the Tropical Botanic Garden and Reseach Institute in Kerala.

Nasikabatrachus is a significant and unique find in several distinct ways. For one, the discovery of N. Sahyadrensis, in the Indian state of Maharashtra, is the first find of a new family of frog since 1926, bringing the count to 29, and will probably be the last one for a long time. It is unique because most new species found (around 70 per year) are closely related to other known species. This frog, however, is a lone wolf; its closest relatives are the Sooglossidae frogs of the Seychelles, 3,000 kilometers to the southwest, and it bears little resemblance even to them. Genetic comparisons show that the Nasikabatrachidae and Sooglossidae families diverged around 100 million years ago, when India was part of the continent Gondwana. Like the Coelacanth and the Crocodile, this frog is a living fossil, giving scientists hope that it will help to both paint a better picture of frog evolution and lend further insight into the breakup of Gondwana.

N. Sahyadrensis's mouthful of a name is a multilingual hodgepodge of Sanskrit and Greek. "Nasika" is Sanskrit for "nose", while "Batrachus" is the Greek word for "frog." "Sahyadrensis" comes from the Sanskrit "Sahyadri", the name of the remote mountain range in which the frog was found.

Aesthetically, this frog is no Kermit. Its skin is purple and has a rubbery appearance, almost like a squishy toy. The most remarkable feature is its head, which inspired the scientists to call it a "nose-frog" ; it looks as though its head was chopped off, and then, like some twisted salamander, it tried to regenerate but failed part way, leaving it neckless and with its eyes on its shoulders, tapering off on the end. My favorite description by far likens it to "a bloated doughnut with stubby legs and a pointy snout"¹. It is rightly nicknamed the "Pignose Frog."

Due to pressures put on its habitat by agriculture, the tropical forest in which it makes its home now covers only ten percent of its former area, severely limiting Sahyadrensis' range and prompting the IUCN Red List to classify it as an endangered species in 2006.²

Photos of Nasikabatrachus can be found here. To see Sooglossidae, go here

¹http://news.nationalgeographic.com/news/2003/10/1015_031015_purplefrog.html ²http://en.wikipedia.org/wiki/Nasikabatrachidae

The Nasikabatrachus sahyadrensis, more commonly known as the purple frog, pig-nosed frog, Jurassic frog, or the coelacanth of frogs was first officially discovered in 2003. It is the first new frog species to be named to a new family since 1926. The new family, Nasikabatrachidae, joins the other 28 known families.

The species name Nasikabatrachus sahyadrensis comes from various words in Sanskrit, a classical language of India. “Nasika” means “nose”, “batrachus” meaning “frog” and "Sahyadri” meaning Western Ghats, which is the mountain range in India where the frog is located.

Distribution

The purple frog is endemic to the Western Ghats mountain range in southern India. As of 2006 it is known from only two locations, both in Idukki District in the Cardomom Hills in Kerala; Kattapana and near Idukki town.

Habitat

Purple frogs have been found in secondary forest contiguous with montane evergreen forest. The altitudinal range it is found in is 850-1,000 meters above sea level. It has been found in subtropical/tropical moist lowland and montane, inland wetlands such as marshes and pools, as well as canals and ditches. It requires fairly loose, damp, well-aerated soil, preferably in close proximity to termite colonies, to burrow into. The Western Ghats mountains where the purple frog is found is considered by conservationists to be a biodiversity hotspot; a rich but threatened reservoir of unique plant and animal life

Physical Description

The type specimen for the physical description of the purple frog was an adult female collected in 2000 by S. D. Biju. The purple frog is a relatively large frog with a generally bloated appearance. An adult purple frog will reach about 7 cm in length, but females tend to be larger than males. Its skin is smooth, yet thick and has a blackish purple coloration. The head is short and small in comparison to the rest of its body and is pointed. The snout is tapered to a knob-like white protuberance, which is the reason for one of its common names – pig-nosed frog. The eyes of the frog are small with a black iris and rounded, horizontal pupil. It has prominent upper eyelids, but the lower eyelids are merely integumentary folds. The mouth is small and ventral, with a narrow gape and contains a small, basally attached and fluted tongue. The fore limbs are short and end in rudimentarily webbed feet with the tips of the fingers being rounded without disks. The hind limbs are small and short, with the toes being three-quarters webbed and rounded at the tips without disks. Each hind foot also possesses a large, elongated, white shovel-like inner metatarsal tubercle, which is used for digging.

The skeleton of the purple frog is characteristic of a burrowing frog and displays bones with a “well-calcified cortical area, a skull with strongly ossified neurocranial and dermal elements, a short tibiale and fibulare, strong and short tibiofibular bones, and a well developed and highly calcified prehallux”¹.

Reproduction

The purple frog only breeds a few weeks a year during the monsoon season. During mating they have a repetitive loud call consisting of single notes of ‘rraaak’. The frogs can be heard calling from 3 to 4 cm beneath the ground and emerge during the night to breed. They often breed in ponds that are close to streams, as well as temporary and permanent ponds and ditches. During mating, the purple frog shows inguinal amplexus, which is where the male clasps the female from behind just above the legs. The bloated shape of both male and female purple frogs, and the smaller size of the male, may mean that males partially glue themselves onto females using sticky skin secretions. The eggs are laid in water, often ponds close to streams, and hatch into tadpoles.

Lifestyle

The purple frog lives a very reclusive, fossorial (digging or burrowing) lifestyle. It spends most of its life 1.3-3.7m below the ground and only comes to the surface for a few weeks a year during the monsoon season to breed before it disappears again

Behavior

Digging is the primary behavior exhibited by the purple frog other than living underground almost full time. Purple frogs can dig themselves completely into the ground if the soil is right within 3 to 5 minutes. If the frog finds itself on an unsuitable surface for digging, such as hard ground, pebbled- or gravel-strewn soil, or areas with a thick mat of weeds, they will go in search of cover and a more effective place to burrow. To burrow downwards, the purple frog assumes a squatting position and uses it strong hind feet like spades to push the soil from underneath itself over to the back of its body. After digging they rest underground in a horizontal position with their limbs tucked under their body, but not for long. They do not remain idle underneath the soil for long periods of time, especially when they are foraging for prey.

Diet

The diet of the purple frog mainly consists of soil termites. Since it lives underground for the majority of its life, it is a fully capable underground forager. Due to the nature of the anatomy of its mouth, which is narrow with a small gape, it cannot catch and consume larger prey. But the anatomy of its head, a strong and pointed snout, allows it to penetrate underground termite nests. Other than termites, it mostly eats ants and small worms.

Conservation Status

The main threat to the purple frog is forest loss due to expanding cultivation of coffee, cardamom, ginger, and other crops. The forest coverage in the Western Ghats has been reduced to less than 10 percent of its original extent due to human pressure from agriculture. The remaining 10 percent is remote and fairly inaccessible which is one reason the frog has gone undiscovered for so long. Its IUCN Red List Status is endangered as of 2004 because its “Extent of Occurrence is less than 5,000 km2, all individuals are in fewer than five locations, and there is continuing decline in the extent and quality of its habitat in the Cardomom Hills”. The species is thought to be declining in numbers, but it is difficult to accurately determine how many exist since it is so hard to find. There have only been 135 specimens observed since it was first classified as a new species of frog and only three of them have been female. It has not yet been observed in any protected areas within its known habitat, such as the nearby Silent Valley National Park.

Interaction with humans

The purple frog does not have much interaction with or impact on humans. The only time humans have ever seen it is when it comes above ground during the monsoon season to breed. Humans are destroying its habitat, so if scientists are going to continue studying the purple frog, the protection of their forest habitat is an urgent priority.

How the species relates to ancient fossil forms

The purple frog is a true “living fossil” and is the only surviving member of the ancient amphibian family Nasikabatrachidae. Its closest living relatives are found in the Seychelles, near Madagascar 1,800 miles away, in the Sooglossidae family. India and the Seychelles were once a part of the same landmass, but were separated about 65 million years ago. From a phylogenetic analysis done by S. D. Biju and Franky Bossuyt, the discoverers of the purple frog, it is estimated that the origin of the Sooglossidae/Nasikabatrachidae lineage occurred around 182 million years ago. The relationship between the purple frog and the Sooglossidae in the Seychelles suggests that these frogs diverged from a common ancestor about 130 million years ago before the ancient landmass Gondwana broke apart. The two families of frogs are similar, yet they differ in both molecular genetics and morphology. It is estimated that both families became isolated from Neobatrachia (the “new” or “higher” frogs) during the Middle/Late Jurassic and Early Cretaceous periods, which is around the time that Gondwanaland broke up. The discovery of the purple frog has also revived the idea of there being a prehistoric land bridge between Africa and India that might have been a dispersal corridor for animals between the two countries. There are many ideas about how the Sooglossidae and Nasikabatrachidae got separated, but so far there is no definite explanation.

¹Biju, S. D. and Bossuyt, Franky.  “New frog family from India reveals an ancient biogeographical link with the Seychelles”.  2003, October 16.  Nature.  Vol. 425, p. 711-714.

Dutta, S. K. et al.  “Jurassic frogs and the evolution of amphibian endemism in the Western Ghats”.  2004, January 10.  Current Science.  Vol. 86, No. 1, p. 211-216.

Hedges, S. Blair.  “The Coelacanth of Frogs”.  2003, October 16.  Nature.  Vol. 425, p. 669-670.

“Nasikabatrachus sahyadrensis”. Global Amphibian Assessment.  2006.  IUCN, Conservation International, and NatureServe. <http://www.globalamphibians.org/servlet/GAA?searchName=Nasikabatrachus+sahyadrensis>

“Purple Frog (Nasikabatrachus sahyadrensis)”.  EDGE of Existence.  2006.  Zoological Society of London.  <http://www.edgeofexistence.org/amphibians/species_info.php?id=549>.

Radhakrishnan, C. et al.  “Extension of range of distribution of Nasikabatrachus sahyadrensis Biju & Bossuyt (Amphibia: Anura:  Nasikabatrachidae) along Western Ghats, with some insights into its bionomics”.  2007, January 25.  Current Science.  Vol. 92, No. 2, p. 213-216.

Reisman, Elizabeth.  “AmphibiaWeb - Nasikabatrachus sahyadrensis”.  2008.  AmphibiaWeb.  <http://amphibiaweb.org/>.

Roach, John.  “Frog Discovery Is “Once in a Century””.  National Geographic News.  2003, October 15.  National Geographic.  <http://news.nationalgeographic.com/news/2003/10/1015_031015_purplefrog.html>.

Ruder, Kate.  “Purple Frog Pops Up”.  2003, October 17.  Genome News Network.  <http://www.genomenewsnetwork.org/articles/10_03/purple_frog.shtml>.