Chapter 19-Amphibians

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Chapter 19-Amphibians

• Amphibian- Double Life
• - Water and land

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Amphibian Characteristics

• 1st true tetrapod vertebrates
• Bony skeletons with four limbs
• Exceptions Caecilians (limbless) and Sirens
  (forelimbs only)
• Many w/webbed feet
• Thin moist skin no scales
• Breathe w/ lungs (Internal, bag-like organ that
  exchanges oxygen and carbon dioxide with the air
  and blood)
• Exception Lungless salamanders
• Larvae- gills
• Cutaneous respiration- Skin breathing
• Supplement oxygen intake w/ moist skin
• Limited by body size

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Double-Loop Circulation
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Amphibian Characteristics

• Partially divided heart
• Atrium separated into left and right sides by
  septum, ventricle is not
• Right side sends oxygen-poor blood to lungs
• Left side send oxygen-rich blood to organs
• Double-loop circulation
• Two large veins (pulmonary veins) return
  oxygen-rich blood from lungs to heart
• Blood pumped to tissues at higher pressure than
  fish
• Systemic circulation- Blood flow to the body

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Class Amphibia

• Order Anura- Frogs and toads
• Order Urodela (Caudata) Salamanders, sirens,
  newts, waterdogs, mudpuppies
• Order Gymnophiona (Apoda)- Caecilians

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Class Amphibia
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Order Anura- Frogs and Toads

• Anura- without a tail
• Adult carnivores
• Skin with mucus and some with poison glands
• Sticky tongue, hinged at the front, attaches to
  prey
• Vomerine teeth- two small nobs help hold in prey
• Hind legs adapted for jumping
• Frogs are smooth w/ longer legs
• Toads are rough w/shorter legs

• Most frogs depend on water for life cycle
• Females lay eggs in water
• Males fertilize them
• Larvae are tadpoles
• Gills
• Feed on algae
• Incomplete metamorphosis
• Develop into adult frogs
• Rate depends on species and food

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Leopard Frog and Fowlers Toad
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Goliath Frog- Conraua goliath
- Largest frog in world - Found in Cameroon
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Poison-Dart Frogs- Family Dendrobatidae
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Frog Characteristics

• Tympanic membrane- thin membrane that detects
  vibration (eardrum)
• Eustachian tubes- equalize pressure on eardrums
• Skin has mucus glands
• Mucus is poisonous or foul tasting in most
• Nictitating membrane- transparent eyelid
• Two teeth in roof of mouth
• Swallow food whole

• Cloaca- Chamber opening to outside of body
• Serves as exit for wastes and gametes
• Oviduct- carries eggs to cloaca
• Vocal Sacs- Expandable membranes that collect air
  after passing over vocal cords for louder croaking

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Amplexus
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Order Urodela (Caudata- with a tail)
Salamanders

• 369 species of salamanders, newts, sirens,
  amphiuma, waterdogs, and mudpuppies
• Elongated bodies w/long tails
• Smooth, moist skin Require moisture
• External fertilization in water or moist area
• Internal fertilization- females insert sperm
  packet into cloaca
• Larvae gilled, carnivorous, smaller version of
  adult
• Some retain gills as adults (neoteny- never lose
  larval characteristics)

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Axolotl

• Salamander that never loses its gills
• Neoteny
• Found in N. america

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Other Urodela (Caudata)
Newt
Water dog
Amphiuma
Mud puppy
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Order Caudata- Sirens

• Aquatic salamanders
• Have only front extremities
• Maintain gills throughout life
• Some can vocalize
• Most likely external fertilization

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Order Apoda- Caecilians

• Apoda- without legs
• Tropical, burrowing amphibians
• Small, bony scales embedded in skin
• Legless
• Carnivorous
• Male deposits sperm directly into female
• Females may have live young or lay eggs