AMPHIBIANS

1

• AMPHIBIANS

2

• Amphibians
• Amphibians are tetrapods (four foot)! The name is
  derived from the presence of four muscular limbs
  and feet with digits!

3

• Amphibians occur on all continents except
  Antarctica!
• Modern amphibians belong to three orders!

4

• Order Caudata salamanders
• Order Anura - frogs and toads
• Order Gymnophiona caecilians

5

• Order Caudata
• They posses a tail throughout life!

6

• Most terrestrial salamanders live in moist forest
  floor litter and have aquatic larva! A number
  live in caves!

7

• Members of the family Salamandridae are commonly
  called newts! They spend their lives in water and
  often have a caudal fin! Range in size from a few
  centimeters to 1.5 meters (Andias japonicus)!

8
(No Transcript)
9
(No Transcript)
10

• The largest in North America is the hellbender
  (Cryptobranchus alleganiensis) which grows to
  about 65 cm!

11
(No Transcript)
12
(No Transcript)
13
(No Transcript)
14

• Most salamanders have internal fertilization!
  Males produce a spermatophore which they deposit
  onto a leaf! The female picks it up and places it
  in a special pouch called a spermatheca and
  fertilization happens!

15
(No Transcript)
16

• Larva are similar to adults only smaller! Many
  salamanders undergo incomplete metamorphosis and
  are paedomorphic! (They become sexually mature
  while still showing larval characteristics!)

17

• Order Gymnophiona caecilians
• Wormlike burrowers that feed on invertebrates in
  the soil! They appear segmented because of folds
  in the skin that cover the separations between
  muscle bundles!

18
(No Transcript)
19
(No Transcript)
20
(No Transcript)
21
(No Transcript)
22

• Fertilization is internal in caecilians!
• Order Anura
• Includes about 3,500 species of frogs and toads!

23

• Adults lack tails and caudal vertebra fuse into a
  rodlike structure called a urostyle!
• Hindlimbs are long and muscular and end in webbed
  feet!

24

• Fertilization is almost always external and eggs
  usually are aquatic!
• Larval stages called tadpoles have well developed
  tails!

25

• Unlike adults, the larva are herbivores and
  posses a beaklike structure used in feeding!

26

• The term toads usually refers to anurans with
  relatively dry and warty skin that are more
  terrestrial than other members of the order!
• True toads belong to the family Bufonidea!

27

• External Structure And Locomotion!
• Their skin is designed to protect against
  infective microorganisms, ultraviolet light,
  desication, and injury!

28

• It also functions in gas exchange, temperature
  regulation, and the absorption and storage of
  water!
• Amphibians have no scales, feathers, or hair!

29

• The skin is highly glandular and its secretions
  aid in protection! They help keep the skin moist!
• They produce toxic chemicals that discourage
  potential predators!

30

• The skin is mostly smooth but some have warts,
  usually as the result of keratin deposits!

31

• Chromatophores are specialized cells in the skin
  that are responsible for skin color and color
  changes!

32
(No Transcript)
33

• Compared to fish, the amphibian skull is
  flattened, smaller, and have fewer bony elements!
• Changes in the jaws and jaw muscles allow
  terrestrial vertebrates to crush prey held in the
  mouth!

34

• The backbone of amphibians is modified to provide
  support and flexibility on land!
• Unlike fish, amphibians have a neck!

35

• The first vertebra is the cervical vertebra which
  moves against the back of the skull and allows
  the head to nod vertically!
• The last trunk vertebra is the sacral vertebra!

36

• It anchors the pelvic girdle to the vertebral
  column to provide increases support!
• A ventral plate of bone called the sternum
  supports the forelimbs and internal organs. It is
  reduced or absent in frogs and toads!

37

• The pelvic girdle of amphibians consists of three
  bones (the ilium, ischium, and pubis) that attach
  pelvic appendages to the vertebral column!

38

• Long hindlimbs and powerful muscles form an
  efficient lever system for jumping in anurans!

39

• Nutrition and the Digestive System!
• An adult bullfrog will prey on small mammals,
  birds and other anurans!
• Most larva are herbivorous and feed on algae and
  other plant matter!

40

• Most salamanders use only their jaws to capture
  prey but anurans use their tongue and jaws to
  capture prey. Amphibians are the first animals we
  have studied to have a tongue!

41
(No Transcript)
42
(No Transcript)
43

• Gas Exchange
• Terrestrial animals spend much less energy moving
  air across gas exchange surfaces than do aquatic
  organisms because air contains 20 times more
  oxygen than water!

44

• Amphibian skin is moist and richly supplied with
  capillary beds! These two factors permit the skin
  to function as a respiratory organ! Gas exchange
  across the skin is called cutaneous respiration!

45

• This can occur on land or in water!
• In salamanders 30 90 of respiration can occur
  across the skin!
• Gas exchange can also occur across the surface of
  the mouth and pharynx!

46

• This is called buccopharyngeal respiration and
  account for about 7 of respiration!
• The amount of gas exchange in these two methods
  cannot be increased when metabolic rate increases!

47
(No Transcript)
48

• Temperature Regulation
• Amphibians are ectothermic (cold blooded)! They
  depend on external heat sources to maintain body
  temperature!
• Animals in water loose heat very quickly!

49

• When amphibians are in water they take on the
  temperature of the water they are in! On land
  they can regulate their temperature more easily!

50

• Temperature regulation is mainly behavioral!
• Many are nocturnal!
• Some warm themselves by basking in the sun,
  especially after eating because it speeds up
  digestion!

51
(No Transcript)
52

• Nervous And Sensory Functions
• similar to other vertebrates!
• The brain is divided into three regions
  forebrain, midbrain, hindbrain!

53

• Forebrain contains the olfactory centers and
  the regions that regulate color changes!
• Midbrain assimilates sensory information and
  initiate motor responses!

54

• The hindbrain functions in motor coordination and
  in regulating heart rate and respiration!
• Olfaction is used in mate recognition as well as
  in detecting food and chemicals!

55

• Vision is one of the most important senses in
  amphibians because they are primarily sight
  feeders often responding to the movement of their
  prey!

56

• The lower eyelid is moveable and it cleans and
  protects the eye! Most of it is transparent and
  is called the nictitating membrane! When the
  eyeball retracts into its socket the nictitating
  membrane is drawn up over the cornea!

57

• There are receptors called rods and cones in the
  retina! Because cones are associated with color
  vision in some vertebrates they can probably see
  some wavelengths of light!

58

• The ears of aunurans consists of a tympanic
  membrane, a middle ear, and an inner ear! The
  tympanic membrane receives airborne vibrations
  and transmits them to the middle ear!

59

• Next to the tympanic membrane is a bone called a
  stapes or columella which transmits the
  vibrations of the tympanic membrane into the
  inner ear!

60
(No Transcript)
61

• Excretion and Osmoregulation
• The nitrogenous waste products that amphibians
  excrete is either ammonia or urea!
• They produce large amounts of very dilute urine!

62

• Adult amphibians do not replace water by
  drinking, instead they limit water loss by
  behavior that prevents desiccation! Many are
  nocturnal, or burrow, or live in areas of high
  humidity!

63

• Some make a protective cocoon from the outer
  layers of the skin that detaches and becomes
  paper-like!

64
(No Transcript)
65

• REPRODUCTION, DEVELOPMENT, and METAMORPHOSIS!
• Amphibians are dioecious!

66

• Fertilization is usually external and because the
  developing eggs lack any resistant covering
  development must occur in water!

67

• In a few species larval stages occur in the egg
  and the babies emerge looking like miniature
  adults!

68

• All others produce spermatophores and
  fertilization is internal!

69

• Amphibian tadpoles often differ from the adults
  in the way they breath, how they move, and what
  they eat! These differences reduce competition
  between adults and larvae!

70
(No Transcript)
71

• VOCALIZATION
• Sound production is primarily a reproductive
  function of the males!
• They produce advertising calls, reciprocation
  calls, release calls, and distress calls!

72

• The sound production apparatus of frogs consists
  of the larynx and vocal cords. The males also
  have a vocal sac!

73

• Air from the lungs is forced over the vocal cords
  and cartilages of the larynx causing them to
  vibrate. Muscles control the tension of the vocal
  cords and regulate the frequency of the sound!

74

• Vocal sacs act as resonating structures and
  increase the volume of the sound!

75
(No Transcript)
76

• PARENTAL CARE
• The most common form of parental care in
  amphibians is the attendance of the egg clutch by
  either parent!

77

• METAMORPHOSIS Metamorphosis is a series abrupt
  structural, physiological, and behavioral changes
  that transform a larva into an adult!

78

• Metamorphosis is under the control of
  neurosecretions of the hypothalamus, the
  pituitary gland, and the thyroid gland!

79
(No Transcript)
80

• AMPHIBIANS in PERIL
• Frogs and salamanders are disappearing very
  quickly. One reason is loss of habitat by cutting
  forests, mining, industrial development and
  agriculture.

81

• An increase in U.V rays in the 280 320 nm range
  has killed many embryos .
• Amphibians are especially susceptible to changes
  in the pH of water. A pH lower than 5 will kill
  them. This is caused by acid rain.

82

• Pollutants that contribute to acid rain and the
  depletion of the ozone shield of the earth may be
  partly responsible for the disturbing reduction
  in amphibian populations.

83

• Chytrid, a fungus, first seen in the 1980s has
  been detected on at least 385 species of
  amphibians from 36 countries and is likely
  responsible for over 100 species extinctions.