Amphibians

1
Amphibians

• First Tetrapods on Land

2
Class Amphibia

• First truly tetrapod vertebrate
• Ectothermic
• All amphibians have bony skeletons
• Most have 4 limbs, except Caecilians (limbless)
• Many have webbed feet
• Typically the glandular skin is smooth, moist,
  and lacks scales
• Metamorphose from juvenile water breathing to
  adult air breathing
• Ecological indicators

3

• Order Anura (Salientia) Frogs and Toads
• Order Caudata (Urodela) Salamanders, Newts,
  Waterdogs, Mudpuppies, Sirens, and Amphiuma
• Order Gymnophiona (Apoda) Caecilians

4
Class Amphibia

• Gas exchange occurs through lungs, gills, and/or
  the skin
• Some salamanders have no lungs (secondarily lost)
• Adults have double circulation
• Both a pulmonary and a systemic circuit
• Heart has three chambers
• Two atria and one ventricle
• Some mixing of oxygenated and deoxygenated blood
  occurs in ventricle

5
Anamniotic egg
http//epod.usra.edu/archive/images/egg_mass.jpg

• Jellylike
• unshelled must develop in water
• Small-sized
• lack large membranes to nourish embryo and store
  waste

Amphibian egg mass
6
Amphibian development
http//www.mybitoftheplanet.com/2002/
http//www.herpnet.net/Iowa-Herpetology/
Newt
http//fwie.fw.vt.edu/VHS/
http//www.herpnet.net/Iowa-Herpetology/
Controlled by the hormone thyroxin