Amphibians of Pakistan: Threats and Conservation Action Plan

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What are Amphibians?

Amphibians are a group of small animals belonging to Phylum Chordata, sub-phylum Craniata or Vertebrata, Super class Tetrapoda and Class Amphibia. Being tetrapods, the amphibians are provided with two pairs of pentadactyle limbs which may be modified, reduced or absent in some adult forms.

Origin and Evolution of Amphibians

During the later part of Devonian Period, a population of Osteolepid fishes (Order Crossopterygia and sub-order Rhipidistia) Eusthenopteron were living in fresh water. Some of these fishes were crawling from pool to pool and then spending more time on land, gave rise to amphibia.

Amphibians are the first vertebrates to become adapted to life on land. As the class name “Amphibia” indicates, many members of this class have double mode of life i.e. they spend the early stages of their life cycles in water as gill breathing tadpoles. Later the larva transforms into lung breathing terrestrial adults through metamorphosis. There are however, some amphibians that never leave water and remain permanently in the larval stage e.g. Necturus while others never enter water at any stage of their life cycle e.g. Salamandara.

In both structure and function, amphibians stand between fishes and reptile.

Characters of Amphibians

Following are some of the characters that differentiate amphibians from other groups of vertebrates.

  1. These are cold blooded (Poikilotherms) animals i.e. they cannot change their body temperature according to the changing environment. Therefore, hibernate during winter to avoid extremes of temperatures.
  2. Skin is moist, glandular and scale less except in some burrowing apoda e.g. Ichthyophis that bear small dermal scales.
  3. Two nostrils connected to mouth cavity;mouth with fine teeth, protru slide tongue.
  4. Two pairs of limbs basically pentadectyle although the number of toes reduced to four or fewer. No limbs on Apoda: no hind limbs in Siren (a urodela).
  5. Skeleton is lagerly boney; the skull is moveable attached to the vertebral column by two occipital condyles; ribs when present are not attached to the sternum; the interclavicle serves to brace (to give firmness) the two halves of the pectoral girdle: pelvic girdle is attached to the vertebral column by a single sacral vertebra.
  6. The jaws suspension is autostylic (i.e. upper jaw is attached to the skull with a bone called Quadrate) the free hyomandibular is modified into columella auris which lies in the upper part of the spiracle between the inner ear and the tympanic membrane. In all but a few of the early forms, there is an opening called fenestra ovalis on the side of the ear capsule and through this opening columella auris conveys sound vibrations to inner ear.
  7. They breathe by gills in the larval stage and by the lungs in the adult. The gills are retained by the adults of some urodeles.
  8. Brain with the 10 pairs of cranial nerves.
  9. Heart comprises two auricles, one undivided ventricle, one cinus venosus and one conus arteriosus.
  10. Red blood cells are oval and nucleated.
  11. Fertilizationn is external in most amphibians, mostly oviparous and eggs with some youlk and enclosed in jelatinous covering; cleavage holloblastic but unequal; with an aquatic larval stage which metamorphosis in to adults.

Classification of Amphibians

Class Amphibia is divided into three orders,

  • Order Urodela or Caudata
  • Order Anura or Salientia
  • Order Apoda or Gymnophiona or Caecilia

Order Urodela or Caudata (Salamanders)

  1. Elongated scale less body consists of head, trunk and well developed tail; the tail is retained throughout the life.
  2. 2. Two pairs of small equal sized limbs are present in most species with the exceptions of siren which has no hind limbs; there are usually four digits in the fore limbs and five digits in the hind limbs.
  3. The eyes are small without eyelids. In the cave dwelling prsteus, the eyes are hidden under the integument.
  4. Excoskeleton is absent except the claws in anychodactylus (onycho=nail).
  5. The tongue is usually fixed and immovable in most urodeles.
  6. Vocal cord, tympanums are absent (so they cannot make any sound).
  7. The teeth are present in both the jaws.
  8. In lower urodeles e.g. ambystoma, the vertebrae are amphicoelus, but in higher urodeles e.g salamandra, the vertebrae are opisthocoelus.
  9. External gills are present in larval state which is lost in adults caducibranchiates. But in some while the gills are lost but gill slits persists as for example, Amphiuma, cryptobranchus, Megolobatrachus. While in other caducibranchiates, all traces of gill clefts disappear as for example, Ambystoma, Salamandra, Triton and Triturus.
  10. In perennibranchiates, gills are retained throughout life as for example Necturus, Proteus, Siren etc.
  11. Kidney is opisthonephros.
  12. Usually oviparous, most undergo complete metamorphosis (Triton, Triturus are oviparous).

Examples:

  1. Cryptobranchus (commonly called Hell bender)
  2. Ambystome tigrinum (Tiger salamander) its larva is called Axolotl larva.
  3. Salamandra, (European fire salamander)
  4. Siren (Mud eel)
  5. Necturus (Mud puppy)

Order Apoda or Gymnophiona or Caecilia (Limbless Amphibians)

  1. They live in burrows in swampy damp places.
  2. Eyes are very small, function less, buried beneath the skin.
  3. The smooth slimy skin is transversely grooved and small calcified dermal scales are present in the groves.
  4. Tympanum and tympanic cavity are absent.
  5. Vertebrae are amphicoelus. Number of vertebraes is 200 or more usually up to 250. Ribs are long.
  6. No gills or gill slits in adults. Respiration is pulmonary (through lungs).
  7. Teeth on both jaws and also on palatine and vomers.
  8. Fertilization is internal. Several aquatic genera are viviparous in which there is no larval stage. Terrestrial species lay large yolky eggs and larval stage is passed within the egg envelopes.

Examples: Ichthyophis (Found in India, Ceylon and Malayisia), Caecilia (America), Dermorphis (Found in America and Africa).

Order Anura or Salientia (Frogs and Toads)

  1. Short, scale less, tail less, four legged body; head and trunk are fused and there is no neck region.
  2. Hind limbs are longer than the fore limb; the feet may be webbed for swimming or or long figures with suction pads for climbing as for example in hyla (tree frog, arborial).
  3. They have vocal cards, tympanum and tympanic cavity.
  4. Skin is smooth and slimy due to cutaneous glands (except in toads).
  5. Vertebral column is short with only 8-10 vertabrae and a urostyle; the ceutra are procoelus.
  6. Gills and gill slit are abscent in adults. Respiration is pulmonary.
  7. Kidney is mesonephros with mesonaphric duct.
  8. Fertilization is external eggs are laid in water except Nototrema.
  9. Anura is divided in to two sub orders on the basis or absence of tongue.

  1. Sub order Aglossa
  2. Sub order Phaneroglossa

1. Sub Order Aglossa

Tongue is absent and the Eustachian tubes are united and open by a median aperture in to the pharynx.

Examples: Pipa Americana, Xenopus.

2. Sub Order Phaneroglossa

Tongue is present. Eustachian tube opens separately into the pharynx.

Examples:  Bombinators (Fire Bellied toad), Alytes (mid wife toad), Hyla (tree frog), Rana

Amphibians of Pakistan

A total of 24 Amphibian Species, have so far been, reported in Pakistan (Khan 2006).

  1. Bufo olivaceus Blanford, 1874
  2. Bufo stomaticus Lütkin, 1862
  3. Duttaphrynus  himalayanus (Günther, 1864)
  4. Duttaphrynus melanostictus hazarensis (Khan, 2000)
  5. Pseudepidalea baturae (Stöck, Schmid, Steinlein and Grosse, 1999)
  6. Pseudepidalea latastii (Boulenger, 1882)
  7. Pseudepidalea pseudoraddei (Mertens, 1971)
  8. Pseudepidalea siachinensis (Khan,  1997)
  9. Pseudepidalea surda (Boulenger, 1891)
  10. Pseudepidalea zugmayeri (Eiselt and Schmidtler, 1973)
  11. Scutiger nyingchiensis Fei, 1977
  12. Microhyla ornata (Duméril and Bibron, 1841)
  13. Uperodon systoma (Schneider, 1799)
  14. Allopaa barmoachensis (Khan and Tasnim, 1989)
  15. Allopaa hazarensis (Dubois and Khan, 1979)
  16. Chrysopaa sternosignata (Murray, 1885)
  17. Euphlyctis cyanophlyctis cyanophlyctis (Schneider, 1799)
  18. Euphlyctis cyanophlyctis microspinulata Khan, 1997
  19. Euphlyctis cyanophlyctis seistanica (Nikolsky, 1900)
  20. Fejervarya limnocharis (Boie, 1834)
  21. Fejervarya syhadrensis (Annandale, 1919)
  22. Hoplobatrachus tigerinus (Daudin, 1802)
  23. Nanorana vicina (Stoliczka, 1872)
  24. Sphaeroteca breviceps (Schneider, 1799)

Threats to Amphibians in Pakistan

Frogs and toads are under great threat not only in Pakistan rather all over the world, because of the main threats from environmental changes, high temperature, dryness and problem of human increasing encroachment on habitat.

The riparian Indus Valley which once teamed with animals of several local species during monsoon rains, and their croaks proverbially echoed the valley for several days. Human encroachment has now quieten several localities across the valley, as their potential breeding areas have shrunk and disappeared, replaced by large industrial estates, colonies and agricultural tilled fields, with meandering web of roads, disturbing whole ecosystem. 

Humans’ encroachment has overwhelmed all spheres of amphibian’s normal life: toxic affluents from factories; sewerage, tanneries have polluted rivers, streams, ponds and puddles. Killing plant and animal life in wetlands; wash-down of pesticides  and chemical fertilizers have polluted soil where amphibian once hopped about in search of food (definitely they are now hopping on chemical fire!). Ponds and puddles where adults called, laid eggs and larvae develop, are now barren and death traps for amphibians and fish. Thus overall amphibian life is made perilous by human greed and short sightedness, and local amphibians are speedily loosing ground to man’s unabated onslaught.

Natural enemies of amphibians in Pakistan 

With soft juicy nutritious body amphibians occur in variety of sizes, their defencelessness, aggregations at adult, egg and tadpoles stage, invite host of predacious sympatric animals. They are included in the diet of aquatic insect larvae, conspecific adults, fishes, snails, water birds, lizards, turtles, snakes, mongoose, and otters etc., especially when food is scarce.

Echoing bleating cries in the dead of night indicate that some snake is in the act of devouring of an amphibian. The wetlands are regularly visited by different species of sympatric snakes: Ptyas mucosus, Amphiesma stolatum, Spalerosophis diadema, Xenochrophis piscator, Bungarus caeruleus, Naja naja, and varanids V. bengalensis and V. flavescens. Occasional injured frogs with broken legs tell the story of attacks of ferocious mongoose and predacious fishes (Khan 2006). Dry charred bodies at the bed of dried ponds and puddles, speak of the devastation done by draught.

Dead toads and frogs that line roads and highways during breeding season, illustrate how mechanization has affected our ecosystem (Khan 1990). 

Decline and Conservation of frogs and toads

Amphibians are in existence for over 300 million years, yet in just the last two decades there have been an alarming number of extinctions, nearly 168 species are believed to have gone extinct and at least 2,469 (43%) more have populations that are declining, indicating that the number of extinct and threatened species will probably continue to rise if no constructive measures are not taken as quick.

Why Are Amphibian Populations Declining?

Apparently factors leading to worldwide disappearance are multifarious, differing from situation to situation, which are summed below.

Habitat destruction, alteration and Fragmentation

Use of land for urbanization, felling, overgrazing and draining long- set wetlands, have destroyed balanced ecosystem. Blind use of agrochemicals, draining the industrial refuse into streams feeding the wetlands and rivers irrigating agricultural fields have unbalanced natural chemistry of the soil, thus affecting natural self regulatory mechanism in the ecosystem, resulting multifarious disaster causing effects on local flora and fauna. Roads, introduced species, or other factors separate remaining populations of amphibians from each other.

Introduced Species

Non-native species prey on or compete with native amphibians.

Over Exploitation

Amphibians are removed form the wild and sold internationally as food, pets, or for medicinal and biological supply markets

Climate Change

Amphibians are extremely sensitive to small changes in temperature and moisture. Changes in global weather patterns (e.g. El Niño events or global warming) can alter breeding behaviour, affect reproductive success, and decrease immune functions and increase amphibian sensitivity to chemical contaminants.

UV-B Radiation

Levels of UV-B radiation in the atmosphere have risen significantly over the past few decades. Researchers have found that UV-B radiation can kill amphibians directly, cause sublethal effects such as slowed growth rates and immune dysfunction, and work synergistically with contaminants, pathogens and climate change.

Chemical Contaminants

Chemical stressors (e.g., pesticides, heavy metals, acidification and nitrogen based fertilizers) can have lethal, sub lethal, direct or indirect effects on amphibians. These effects may include death, decreased growth rates, developmental and behavioral abnormalities, decreased reproductive success, weakened immune systems and/or hermaphroditism.

Disease

New diseases or higher susceptibility to existing diseases leads to deaths of adults and larvae

Deformities

There has been a recent and widespread increase of deformities (or malformations) in natural populations of amphibians; this is now perceived as a major environmental problem.

Synergisms

Multiple factors can act together to cause mortality or sub lethal effects. To explore this issue in detail visit following links for insight in various factors contributing to the amphibian decline and their possible ratification:

Amphibian Conservation Action Plan

Following solutions are suggested to reverse amphibian decline:

Captive Breeding

Captive breeding programs for endangered species are best carried out in zoos. Similar plans should be carried on in agricultural rural areas, motivating farmers etc.  

Reintroduction

Reintroduction programs to place juvenile amphibians back into wild habitats, so that new populations are established.

Use of amphibian friendly fertilizers

Researching for chemicals with no or minimal negative effect on amphibians, not polluting soil, pond and puddles. 

Researching to find chemicals

Neutralizing harmful effects of waste chemicals prior to dumping in rivers and streams.

Removal of non-native species

Non-native species threatening native species are removed.

Biological control of Agriculture Pests

Researching to find biological agents to control crop pests.

Creating amphibian friendly habitats

Save heaven areas in parks and farmlands or in the suburbs of towns and cities should be declared where artificial ponds and puddles, resting and hibernation sites and vegetation is provided for the local amphibian species.    

Captive /Breeding

Market demands for frog legs (tigerina, cyanophlyctis) and scientific experimentation in schools, colleges and universities, have depleted number of these species in nature. Several areas in Pakistan where once these species once abound are now almost devoid of them (Khan 2006). The story is not different in other Southeast Asian countries (Hung et al., 2006). To replenish damage done to the natural population, planned aquaculture of frogs is being carried in several Southeast Asian countries, where these species have now become potential source of food and export (Virkr et. al., 2004; Hung et al., 2006). In Vietnam aquaculture has now become common in urban areas with formers, in 2006 about 300 frog hatcheries were working successfully. 

Endemic Amphibian Species of Pakistan

According to Dr. Mohammad Sharif Khan (August, 2008), nine out of the 24 recorded amphibian species in Pakistan are endemic to Pakistan. It makes around 38 % of the amphibian fauna of the country.  A list of endemic amphibian species is given below.

  1. Duttaphrynus  hazarensis (Khan, 2000)
  2. Pseudepidalea baturae (Stöck, Schmid, Steinlein, and Grosse, 1999)
  3. Pseudepidalea pseudoraddei (Mertens, 1971)
  4. Pseudepidalea siachinensis (Khan,  1997)
  5. Pseudepidalea surda (Boulenger, 1891)
  6. Pseudepidalea zugmayeri (Eiselt and Schmidtler, 1973)
  7. Allopaa barmoachensis (Khan and Tasnim, 1989)
  8. Allopaa hazarensis (Dubois and Khan, 1979)
  9. Euphlyctis microspinulata Khan, 1997

Courtesy: Dr. Waseem Ahmad Khan

Naeem Javid Muhammad Hassani is working as Conservator of Forests in Balochistan Forest & Wildlife Department (BFWD). He is the CEO of Tech Urdu (techurdu.net) Forestrypedia (forestrypedia.com), All Pak Notifications (allpaknotifications.com), Essayspedia, etc & their YouTube Channels). He is an Environmentalist, Blogger, YouTuber, Developer & Vlogger.

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