amphibian general characters

1. Amphibia- General characters
B.Ashok kumar
Lecturer in Zoology
KRK Govt Degree College
Addanki-523201
@9652929696,9441635264
ashokkumarzoology@gmail.com

2. Introduction
• Amphibians are cold blooded vertebrates.
• In the Devonian period of palaeozoic era they
were originated from fishes,
• In the carboniferous period, they increased
their number, hence that period is called ‘Age
of amphibians’

3. • According to Romer
– Dipnoi fishes are the “uncles of Amphibians”
• According to Newman
– “Dipnoi and amphibians had same grand father.”

4. General characters of Amphibians
• 1) Amphibians are cold blooded vertebrates
which can hue on land and in water.
• 2) Amphibians show four limbs with which they
can swim in water and jump or walk on the land,
(But In apoda limbs are absent.)
• 3) In Amphibians animals exoskeleton is absent.
But in apoda animals small cycloid scales are
present.
• 4) In Amphibians the adult animals lungs are
present. Gills are absent. But In some urodelans
the gills are present.

5. • 5)Amphibians Skin is a respiratory organ.
• 6) The Amphibians skull is dicondylic.
• 7) Amphibians Ribs are absent.
• 8)In Amphibians The body divisible into head
and trunk Tail is present in, urodela animals.
• 9)Amphibians Digestive system is well
developed. A well developed liver Is present

6. • 10) External ear is absent. Middle and inner
ears are present, the middle ear columella auris
Is present.
• 11)Amphibians Heart is 3 chambered with 2
auricles and 1 ventricle The blood contains
R.B.C. They are nucleated. They contain
hemoglobin.
• 12) Blood vascular system contain hepatic and
renal portal systems.
• 13) Amphibians Kidneys are mesonephric.
Urinary bladder is present. It stores urine.

7. • 14) Central nervous system is well developed.
The brain occupies completely the cranial
cavity. The brain is divided into fore, mid and
hind brains. Brain continuous as spinal cord.
• 15)10 pairs of cranial nerves will arise.
• 16) Sexes are separate.
• 17) Male and female can be indentified - Sexual
dimorphism.
• 18) In Amphibians the life history a larva stage
may be present.
• 19) Amphibian Eggs are telolecithal, Cleavage is
holoblastic unequal.

8. Classification of Amphibia
• J.Z.Young classified Amphibia into three sub
classes
– Labarynthodontia
– Lepospondyli
– Lissamphibia

9. Sub-class: Labyrinthodontia
• Folded teeth
• Extinct
• Enamel and dentine at the base of tooth was
folded
• Some had scales
• Others had dry leathery skin
• Includes three orders
– i. ichthyostegalia eg: Ichthyostega
– Ii. Temnospondyli eg: Eryops
– Iii.Anthracosauria eg: Seymouria

10. Sub-class: Lepospondyli
• Small salamander like extinct amphibians
• Eg: Diplocaulus

11. Sub- class: Lissamphibia
• Based on the characters of
present day (extant)
amphibians(Lissamphibia)
are classified Into 3 orders.
• Order I . Anura - (Frogs and
Toads).
• Order 2. Urodela -
(Salamanders).
• Order 3 Apoda - (Limbless
amphibians)

12. Order 1. Anura(Gr.An=Without, oura=tail) Salientia(L.saliens=leaping)
• This order Anura includes frogs and toads.
• They can live in water and on land.
• Inhabits tropical and temperate regions
• Body is short and broad with head and trunk
• The fore limbs are small, the hind limbs are long for leaping and swimming, feet are
webbed .
• In the adult stage tail is absent
• Skin is scaleless
• Vertebrae are procoelous and are fewer(generally 9)
• Caudal vertebrae fuse to form urostyle
• Ribs are reduced/ absent
• Teeth are on upper jaw or absent
• Gills and gill slits are absent in adults
• Vocal cards are present
• They show a pair of eyes. tympanic membranes.
• Their Life history includes a larval stage called tad-pole larva.
• Eg:1. Alytes . (Mid wife toad).
• 2. Cacopus (Burrowing frog).
• 3. Xenopus (Clawed Toad),
• 4. Bufo.

14. Order 2. Urodela / Caudata(Gr.Oura=Tail; Delos=visible;, L.Cauda=tail; ata=
bearing)
• This order includes Salamandars and newts. These urodelans are more in North
America. Hence North America is called Head Quarters of Urodeles
• The body is divisible into head, trunk and tail.
• The fore limbs and hind limbs are equal and weak.
• Scaleless
• Vertebrae opistocoelous(amphicoelous in some)and numerous
• Ribs are present
• Teeth on both the jaws
• Vocal cords are absent
• In some adults the gills are presents
• Middle ear is absent,
• Eyes are small and eyelids are present in some
• Copiulatory organ is absent, fertilisation is internal
• Some forms show neoteny and paedogenesis. In North India only one species is
available. Tilototriton venvcosa. In South India urodelan animals are absent.
• 1.Necturus
• 2. Proteus(Mud puppy).(Blind salamander)
• 3. Molge (Newt).
• 4. Amblystoma

16. Order 3. Apoda/ Gymnophiana
• These animals are limbless. Hence they me called Apoda.
• The body is long and snake like. Hence it Is called gymnophiona.
• The body is divisible into head and hunk. Tail is absent
• On the head two eyes are present. They covered by skin and scales.
Hence they are blind (Cecaelians).
• Vertebrae are amphicoelous and numerous
• Lungs are asymmetrical.
• The skin shows minute cycloid scales. in the male apoda animals
copulatory organs present.
• Fertilization is internal.
• 1. lchthyophis (Limbless amphibian).
• 2. Gegenophis (Limbless amphibian).
• 3. Ureotyphlus.