External structure, Locomotion, Excretion And Digestive system of amphibians

1. Presented by:
17371506-010 AREEJ TARIQ
17371506-016 KHADIJA KARIM
AMPHIBIANS
EXTERNAL STRUCTURE,
LOCOMOTION,
NUTRITION
AND
DIGESTIVE SYSTEM

2. AMPHIBIANS
General Characters
Smooth skin with mucoid secretions
Lack epidermal scales, feathers or hairs
Aquatic larva
During metamorphosis, gills get reabsorbed and convert into lungs
Two atrial chambers in the heart
One cervical and one sacral vertebrae
3 orders
 Order Caudata
 Order Gymnophiona
 Order Anura
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3. Caudata
Gymnophiona
Anura
Order
-In moist forest floors or caves,
-Long tail, Two pairs of limbs
-Aquatic larva
-Lack middle ear
-e.g. Salamanders, newts
-Elongate, limbless, tail short and pointed
-Burrow
-Worm like
-Segmented by annular grooves
-Nearly blind
-e.g. Caecilians
-In moist environment, few in dry
environment
-Tadpole aquatic
-Tailless
-Elongate hind limbs for jumping
and swimming
-Urostyle
-Tympanum and larynx well
developed
-e.g. Frogs and toads
AMPHIBIANS
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4. 4
SALAMENDER
CAECILIAN

5. 5
FROG
TOAD

6. Protects from U.V radiations, desiccation and mechanical injury.
Gas exchange, temperature regulation, and water absorption.
Lacks scales, feathers, or hair.
Highly glandular, secretions aid in protection.
Produce sticky secretions that help a male cling to a female during mating.
Produce toxic chemicals that discourage potential predators.
Warts, claws, or sandpapery textures; keratin deposits
Chromatophores in the epidermis of the skin
Cryptic coloration, aposematic coloration, and mimicry
Skin
EXTERNAL STRUCTURE
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7. Support and Movement
Small, flattened and light weight skull, fewer bony elements
Changes in jaw structure and musculature
Modification of the vertebral column
Acts like the arch of a suspension bridge by supporting the weight of the body
Zygapophyses; supportive processes on each vertebra
Unlike fishes, amphibians have a neck.
The first vertebra is a cervical vertebra, moves against the back of the skull,
allows the head to nod vertically.
LOCOMOTION
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8. Cont..
The last trunk vertebra is a sacral vertebra
Anchors the pelvic girdle to the vertebral column to provide increased support.
A ventral plate of bone; sternum is present in the anterior ventral trunk region
Supports the forelimbs and protects internal organs.
It is reduced or absent in the Anura.
Joints at the shoulder, hip, elbow, knee, wrist, and ankle allow freedom of
movement and better contact with the substrate.
LOCOMOTION
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9. The pelvic girdle consists of three bones (the ilium, ischium, and pubis)
that firmly attach pelvic appendages to the vertebral column; support
Depend more on appendages for locomotion.
Thus, body-wall musculature is reduced, and appendicular musculature
predominates.
Salamanders employ a relatively unspecialized form of locomotion like the
unadulatory waves that pass along the body of a fish.
LOCOMOTION
Cont..
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10. Terrestrial salamanders also move by a pattern of limb and body movements
Caecilians have an accordion-like movement
The long hind limbs and the pelvic girdle of anurans are modified for jumping.
The dorsal bone of the pelvis extends anteriorly
securely attaches to the vertebral column
the urostyle extends posteriorly and attaches to the pelvis
LOCOMOTION
Cont..
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11. These skeletal modifications stiffen the posterior half of the anuran.
Long hind limbs and powerful muscles form an efficient lever system for
jumping.
Elastic connective tissues and muscles attach the pectoral girdle to the skull and
vertebral column, and function as shock absorbers for landing on the forelimbs.
LOCOMOTION
Cont..
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12. Most adult amphibians are carnivores that feed on a wide variety of invertebrates.
E.g. a bullfrog (anuran) prey on small mammals, birds, and other anurans.
prey size and availability are main factors
Most larvae are herbivorous and feed on algae and other plant matter.
Amphibians often locate their prey by sight and simply wait for prey to pass by.
Olfaction plays an important role in prey detection by aquatic salamanders and caecilians.
Many salamanders are relatively unspecialized in their feeding methods, using only their
jaws to capture prey
A true tongue 12
NUTRITION AND THE DIGESTIVE SYSTEM

13. Use their tongue and jaws in a flip-and-grab feeding mechanism .
Tongue attaches at the anterior margin of the jaw and folds back over the floor of the
mouth.
Mucous and buccal glands on the tip of the tongue
When prey comes within range, an amphibian moves forward and flicks out its
tongue.
The tongue turns over, and the lower jaw is depressed.
The head tilts which helps aim the strike.
NUTRITION AND THE DIGESTIVE SYSTEM
Cont..
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14. The tip of the tongue entraps the prey, and the tongue and prey
are flicked back inside the mouth.
Press it against teeth on the roof of the mouth
The eyes sink downward and push the food towards the
esophagus.
Takes only 0.05 to 0.15 second!
Cont..
NUTRITION AND THE DIGESTIVE SYSTEM
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