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I.                
Amphibians

Amphibians
are transitional in different ways between the plenary aquatic and fishes
amniotes. But, they are not simply transitional in their morphology, life
history, ecology, and comportment. In the prosperous procurement of
independence from water and colonization of land, amphibians have undergone a
remarkable adaptive radiation, and the living groups reveal a countless
diversity of modes of life history than any other group of vertebrates (Duellman,
1994).

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Figure 1: Amphibians

 

Their
shell-less eggs have been studies extensively by developmental biologists, and
much of the basic understanding of vertebrate embryology is predicated on
amphibians. The metamorphosis from aquatic larvae to terrestrial adults has
been the subject of intensive studies, and much of what is kenned about the
action of thyroid and pituitary hormones has originated from endocrinology
studies on amphibians. Likewise, the facileness of breeding amphibians in the
laboratory and their relatively simple chromosomes complements have provided
bases for consequential advances in studies of hybridization and
specialization. The vocalizations of frogs have provided an expedient for
studying acoustic communication and, together with other aspects of courtship
and mating, have presented and evolutionary biologist with a wealth of material
for studies on sexual cull. These are a few culled examples of the exhilarating
ways in which studies of amphibians are contributing to erudition of biology
and out understanding of biological phenomena (Duellman, 1994).

The
term amphibian can be interpreted in two ways-either as an animal spending part
of its life in water and then transmuting to an aquatic adult, or as an animal
that alternates life in and out of water, such as pond frogs.

According
to Duellman, W. (1994), amphibians can be defining as quadrupedal vertebrates having
two occipital condyles on the skull and no more than one sacral vertebra. The
skin is glandular and lacks the epidermal structures (scales, feathers, hair) features
of other groups of tetrapod’s. Yet, some Paleozoic amphibians were large,
plated quadrupeds, most living amphibians are small. The most astronomically
immense salamander procures a total length of about 1500mm, whereas the most
immensely colossal frog is about 300mm. caecilians reach a length of about
1500mm. Caecilians and some salamanders lack limbs and girdles, and in some
other salamanders these structures are reduced. In frogs the post sacral
vertebrae are fused into a single rod like element, the coccyx, the tail is
absent, and the hind limbs are elongated and modified for jumping. Albeit
epidermal scales are absent in amphibians, dermal scales are present in the
skin of most caecilians. A highly glandular skin contains both mucous and
granular glands. True claws are absent, but horny tips are present on the toes
of some frogs and salamanders.

Within,
the structure of living amphibians is intermediate between that of fishes and
amniotes. The heart has to atria, a single ventricle, and a distinct conus
arteriosus with numerous valves. The aortic arches are proportioned. Usually,
amphibians have two lungs, but the lungs are reduced in some salamanders and
absent in one entire family. The left lung is greatly reduced in most of the
elongate caecilians. Living amphibians also have some distinctive characters.
They all have pedicellate teeth and specialized papillae in the inner ear, and
salamanders and anurans have green rods in the retina of the eye.

The
life histories of amphibians are highly diversified. Most species of frogs have
external fertilization, where internal fertilization occurs in the bulk of
salamanders and probably in all caecilians. The classic amphibian life history
of aquatic eggs and larvae, where typically of many frogs and some salamanders,
is only one of the many modes of reproduction, which consist of direct
development of terrestrial eggs, ovoviviparity, and even viviparity. All
amphibian eggs must develop in moist situations, for although they have several
protective mucoid capsules, these capsules are highly permeable. The eggs lack
a shell and the embryonic membranes of higher vertebrates. In those amphibians
that have aquatic larvae, the larvae undergo metamorphosis into the adult form;
this is an especially dramatic change in frogs (Duellman, 1994).

 

a.    
Amphibian
Names

People
used three variants of names when verbalizing about amphibians, and all
describe the animal to one degree or another. Colloquial designations are names
utilized by people within categorical areas of the country for an individual
species or group of amphibians, but these have little or no apperception beyond
the area or immediate use. In the South, the terms “spring lizard,” for
example, is often used to refer to salamanders that are utilized as allurement,
regardless of the species involved, or whether “the lizard” is not a reptile at
all, but an amphibian. Other colloquial names include waterdog, puppy canine,
hop toad, and tree toad. In herpetology, reptiles customarily receive the more
colorful colloquial denominations (Dodd, 2004).

 

 

Figure 2: Spring Lizard

 

Prevalent
denominations are utilized by the general public and biologists kindred to
identify species. Some common names are often used incorrectly, sometimes to
differentiate frogs from toads or salamanders from nets. Prevalent names often
are descriptive of the animal, such as “Spotted Salamander” for the salamander
Ambystoma maculatum. This species has harge, bright orange, yellow or red spots
on its dark back, thus making the common name very opportune. Sometimes
colloquial designations, such as mudpuppy, can even become accepted common
designations.

 

 

Figure 3: Spotted
Salamander in Orange Spot

 

 

Figure 4: Spotted
Salamander in Yellow Spot

 

Moreover,
Dodd, K. (2004), explained the terms Urodela and Apoda are sometimes used instead
of Caudata and Gymnophiona for salamanders and caecilians. However, in some
literature Salientia is utilized interchangeably with Anura for frogs. Even common
English names become obscure. It is not (‘unusual’, ‘eccentric’, ‘unorthodox’,
‘unwonted’) in the literature to find “salamanders and newts” or “frogs and
toads.” Newts are aquatic members of the family Salamandridae, and are
salamanders. Similarly, at least in the narrow sense, toads are members of the
family Bufonidae, and are frogs in the broad sense. Thus, all newts are
salamanders, but not all salamanders are newts, and all toads are frogs, but not
all frogs are toads. To avoid misperception, the terms new and toad are
utilized in their narrow sense; in referring to all frogs and toads, the
ordinal derivative anuran is utilized.

 

b.    
Amphibian
Richness and Biogeography

According
to Dodd, K. (2004), throughout the world, there are approximately 4,700 species
of amphibians currently describe: more than 440 are salamanders, 165 are
caecilians, and the rest are frogs. More than 240 amphibian species are found
in North America. The greatest number of amphibian species occurs in the
tropics, particularly among the frogs of South America, Australia, South Asia,
and Africa, including Madagascar. There are no frog families that have their
centers of species richness within the southern mountains, and only a few
genera even have their greatest diversity within the southeastern Unites
States.  In many respects, frogs seem to
be peripheral lowland invaders of the high Appalachians. The region of
temperate North America with the greatest species richness of frogs is the
South Atlantic Coastal Plain.

The
very large salamander family Plethodontidae, on the other hand, has two centers
of species richness, one of which is in the Southern Appalachian region; the
other is in the highlands of southern Mexico to Panama. This family includes 67
percent of the world’s salamanders and, in the Appalachians, contains species
with a wide diversity of life histories. The remaining salamander families are
relatively small, often containing only a handful of species. The newts are
mostly Eurasian; the primitive hynobiids occur only in Asia; the torrent and
Pacific giant salamanders are found in the pacific Northwest; and two of the
three species of giant salamanders occur in temperate Asia. The remaining four
salamander families have their greatest diversity in eastern, temperature North
America, albeit not in the southern mountains. These families are the mole
salamanders, amphiumas, mudpuppies, and sirens. The newt cryptobranchid, mole
salamander, and mudpuppy families are all represented in the Smokies. A much
more detailed of the biogeography of North American amphibians is given by
Duellman and Sweet (1999).

 

Figure 5: Plethodontidae

 

Figure 6: Hynobiids

 

Figure 7: Newt Cryptobranchid

Figure 8: Mole Salamander

 

Figure 9: Mudpuppy

 

Figure 10: Mudpuppy

c.    
Species
Richness in the Smokies

There are 31 species of
salamanders and 13 species of frogs that have been reported historically from
the Great Smoky Mountains National Park. The Green Salamander may be extirpated
from the park and likely never was abundant. The Northern Cricket Frog was
reported from the park based on records from Chilhowee, Tennessee (Huheey and
Stupka 1967), but probably never happened within park boundaries. The Northern
Leopard Frog may be extirpated, though there was a possible sighting in 2000. More
historical information on these species is found in their respective species
accounts (Dodd, 2004).

 

Figure 11: Cricket Frog

 

The remaining 40
species are not distributed evenly throughout the Great Smokies. Some
salamanders customarily are found only in the higher elevations, although they
are not, perhaps, as exclusively confined to these habitats as previously
believed. Others are lowland species. A few salamanders (black-bellied
Salamander, Spring Salamander) span a great range of elevations. Likewise, a
few salamanders are found only in Tennessee, whereas others essentially are
found only in North Carolina (Three-lines Salamander). Some salamanders have
profoundly restricted distributions within the park, reflecting specialized
habitat requisites, whereas others are widespread and occur in many types of
habitats (Dodd, 2004).

 

Figure 12: Black-bellied
Salamander

 

 

Figure 13: Spring
Salamander

 

 

Figure 14: Three-lines
Salamander

          Undoubtedly, (Dodd, 2004) researches said that the recent
amphibian distribution patterns are the outcome of a complex interaction of
evolutionary divergence, historical biogeography, and specialized habitat
requirements, even without considering the influence of humans. The interplay
between evolution, geography, and ecology has resulted in a high species
richness of salamanders within the park, but the same is not true of frogs. Frogs
require aquatic breeding sites, and these are scarce in the mountains,
especially on the south and southwestern sides of the park. Hence, few species
of frogs are found in the Smokies relative to the Atlantic Coastal Plain or the
Tennessee Valley.

     There
are three non-human-related historical and biological factors that contribute
to the high species richness of salamanders within the plethodontids opted for
life and shallow flowing streams. Such habitats are still centers of salamander
diversity.

     Natural
selection probably favored lung loss by larval protoplethodontids, and the
evolution of narrow heads, in order to exploit Coastal Plain. The cool waters
of the leaks still permitted sufficient oxygen diffusion to compensate for the
lack of lungs, and terrestrial mating progressed as a method to facilitate
courting and sperm transfer. A combination of morphological, physiological, and
ecological changes allowed salamanders to exploit the specialized ravine. As the
Appalachians were subjected to regional up warps and faulting during the late
Cenozoic era and as erosion took its toll, these combined factors created the
present topography. During this time, early plethodontid salamanders were
isolated, which allowed genetic differentiation. As a result of this
differentiation, associated physical isolation, and changes in climate, the
plethodontid salamanders have undergone a steady process of speciation in the
southern mountains- a process that continues today. Consequently, there is a
high level of species richness in the Smokies and elsewhere in the Southern
Appalachians among the lungless salamanders. In addition, the evolution and
radiation of the lungless salamanders can be found in Ruben and Boucot (1989),
Regan and Verrell (1991), Beachy and Bruce (1992), Bruce et al (1993) and,
Meand (2000).

 

 

Figure 15: Lungless
Salamander

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