The first publication that provided systematic descriptions of Indian amphibians was "The Reptiles of British India" by Albert Gunther (1864) who reported of 37 anurans and 2 gymnophionans. But most of the taxonomic information on the amphibian fauna of India is available in the outstanding contributions of George Boulenger (1890) in the "Fauna of British India" series which includes 124 anurans, one salamander and five gymnophionans.
Even today, identifications are mostly done by consulting this account. Nelson Annandale published a series of papers from 1905-1924 on amphibian systematics and described several species from the Indian region. C.R.N. Rao (1937) also described 20 new species from South India. Thereafter, R.S. Pillai (1973-1990) described 14 new species from Southern India, S.K. Chanda (1986-1990) described five new species from Northern India and Pranjalendu Ray (1992) four new species from Northern India. Recently, Indraneil Das (1995-1999) and Sushil Dutta (1997-2000) added six and three new species respectively from different parts of India.
However, considerable nomenclatural changes have occurred subsequently in amphibian systematics throughout the world at both the generic and species level. Due to lack of taxonomic revisions, such nomenclatural changes have not been carried out for Indian amphibians, since their types are scattered in different museums throughout the world and therefore not readily accessible to most Indian workers. But taking into account the recent taxonomic revisions, Indian amphibia comprises of 219 species. This species number is mainly based on the recent checklist of Indian amphibia prepared by Das and Dutta (1998).
Rana tigerina, (Ranidae)
Distribution
The amphibian species are not evenly distributed throughout India. Table –1 (on page 13) clearly shows that the highest concentrations of species are found in the Western Peninsula followed by the North-East. Interestingly, all the three living orders of Amphibia, viz., Gymnophiona (limbless amphibians), Caudata (tailed amphibians) and Anura (tailless amphibians) are distributed in North-East India. The Western Peninsula has Gymnophiona and Anura while the remaining geographical regions of India harbour only Anura.
The order Gymnophiona include worm-like fossorial limbless amphibians living a subterranean mode of life. These are very rare and secretive, as a result of which very little is known about their habits and life history. Twenty species occur in India under two families – Ichthyophiidae and Caeciliidae, each containing two genera. The family Ichthyophiidae contains the genera – Ichthyophis with ten species and Uraeothyphlus with five species. The family Caeciliidae contains the genera – Gegeneo-phis with four species and Indotyphlus with the monothypic species, Indotyphlus battersbyi.
The only repre-sentative of the order Caudata in india is the Himalayan salamander. Tylototrition verrucosus. It is semi-aquatic and found in the hilly lakes of Sikkim, Northern West Bengal, Khasi hills of Meghalaya, Lohit district of Arunachal Pradesh and Manipur between altitudes of 1330-2220 metres. But its population is dwindling.
The Anurans (frogs and toads) show the highest diversity among Indian amphibians inhabiting all types of habitats – aquatic, semi-aquatic, fossorial, terrestrial, semi-arboreal and arboreal. They are at present represented by 33 genera and 198 species under six families. Of these, the Ranids with 90 species are the most diverse, living both on land and in water and some species being common throughout the country. The Rhacophorids with 58 species are tree-dwellers and mostly restricted to the Western Peninsula and the North-East. The terrestrial Bufonids (toads) are also more or less common throughout India while the fossorial Microhylids are mostly restricted to South India. The Megophryids are found in the hill streams of the Himalayas. Their tadpoles have suckers for clinging onto the rocks. The single Hylid species in India, Hyla annectans is found in the moist evergreen forests of Meghalaya.
Endemicity
Out of the 219 amphibian species in India, 134 species (i.e. 61%) are endemic to the country, as detailed in Table-2 (on page 13). From the Table it is evident that six genera are also endemic to India. Out of these only one, Indotyphlus belongs to Gymnophiona and the remaining five to Anura. The Western Peninsula harbours highest number of endemic species (92) followed by the North-East (29). Besides these, Andaman & Nicobar Islands have five endemic species while the North has three, Deccan Plateau three and the Gangetic Plains two. All the 20 species of Gymnophionans reported from India are endemic while among Anurans, 114 species out of 198 (i.e., 57.5%) are endemic.
Status
The status of most of the species of Indian amphibians is unknown as no population studies have been properly conducted. In 1997, the amphibian experts of our country, under the guidelines of the IUCN met in Bhubaneshwar to assess the status of the Indian species. They concluded that out of the 207 amphibian species then known from India, nine were critically endangered, 42 endangered, 39 vulnerable, 74 in the lower risk category while for 43, the data was deficient for determining their status. However, only four species, the Garo Hills tree toad (Pedostibes kempi), the Malabar black narrow mouthed frog (Melanobartrachus indicus) and the Himalayan salamander (Tylototrition verrucosus) are protected under Schedule II of the Indian Wildlife (Protection) Act, 1972 and the frogs of the genus Rana under II Schedule IV of the Act.
Threats
Since amphibians must breed in water, their permeable skin and eggs are particularly sensitive to pollution and other changes in water quality. Therefore discharge of pesticides, fertilizers, detergents, domestic sewage and toxic industrial effluents into the water bodies take a heavy toll on the numbers of the amphibians. Besides, habitat destruction in the form of draining and filling up of wetlands, clearing of land for agriculture and felling of natural forests (canopy opening) has devastated the amphibian population of our country.
In the last few decades, a large number of frogs belonging to the species Hoplobatrachus tigerinus, H.crassus and Euphlyctis hexadactylus were captured and their limbs exported as part of the frog-leg industry to gain foreign exchange. However, this activity resulted in a tremendous increase in agricultural insects/ pests. Realizing this, the Government of India has banned the export of frog-legs since April 1986. Since then, the trade has declined but some illegal export still takes place through the neighbouring countries.
Table – 1 Distribution of Amphibians in different geographical regions |
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Region |
States included |
Orders |
Genera |
Species |
Northern India |
Jammu and Kashmir, Himachal Pradesh, Punjab, Haryana, Uttaranchal |
Anura |
10 |
22 |
Western India |
Gujarat, Rajasthan |
Anura |
10 |
15 |
Gangetic Plains |
Uttar Pradesh, Bihar, Orissa, West Bengal |
Anura |
12 |
19 |
Deccan Plateau |
Madhya Pradesh, Jharkhand, Chhattisgarh, Eastern Maharashtra, Andhra Pradesh, Tamil Nadu (Eastern Part) |
Anura |
12 |
27 |
Western Peninsula |
Tamil Nadu (Western Part) |
Anura Gymnophiona |
19 4 |
98 16 |
North-Eastern India |
Assam, Meghalaya, Arunachal Pradesh, Nagaland, Manipur, Mizoram, Tripura |
Anura Caudata Gymnophiona |
22 1 2 |
75 1 4 |
Andaman and Nicobar |
Andaman and Nicobar Islands |
Anura |
9 |
18 |
Table-2 Endemicity of Indian Amphibians (*mark indicates endemic genus) |
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Order |
Family |
Genera |
No. of Species |
Gymnophiona |
Ichthyophiidae |
Ichthyophis Uraeothyphlus |
10 5 |
Gegeneophis *Indotyphlus |
4 1 |
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Anura |
Megophryidae |
Megophrys Scutiger |
1 2 |
Bufonidae |
Ansonia Bufo *Bufoides Pedostibes |
3 7 1 2 |
|
Microhylidae |
*Melanobatrachus Microhyla Ramanella |
1 2 5 |
|
Ranidae |
Amolops *Indirana Limnonectes *Micrixalus *Nyctibatrachus Phrynoglossus Rana Tomopterna |
3 9 13 7 10 1 5 3 |
|
Rhacophoridae |
Chirixalus Philautus Polypedates Rhacophorus |
2 26 2 9 |
|
Total |
134 |
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Selected References