Introduction to Amphibians

I. Characteristics
    A. Lack amnion and allantosis
    B.  Presence of Gills
    C.  Glandular skin
    D.  Most have lungs
    E.  Many have poison glands in skin
    F.  All adults are Carnivorous
    G.  Two condyles

II. Evolution
    A. 408 million yrs ago in Devonian
    B.  sarcopterygian fishes (lobe fined fishes)
    C. osteolepiforms had a dorsoventral flexion allowing for cranial kinesis
    D. Ichthyostega  was the earliest tetrapod (appeared at end of Devonian)
    E. Big gap between osteolepiform fishes and Ichthyostega   (40 million yrs)
    F. Fish Characters of Ichthyostega
            1. scales
            2. tail fin supported by fin rays
    G. Amphibian Characters of Ichthyostega
            1. limbs
            2. pelvic girdles
            3. ribs
    H. Skull Connection
            1. osteolepiformes used fusion of auditory capsules
    I. Polyphyletic ?
    J. Current Theory Temnospondyl lineage

III.. Reproduction
    A. Remarkable Variety of modes of Reproduction and Parental Care
    B. Most are egg layers -  aquatic or terrestrial  (require moisture)
    C. Eggs usually hatch as aquatic larvae or miniature adults
    D. Oviparous, viviparous and ovoviviparous
 

Salamanders (urodela or caudata)

    A.  Four functional limbs (most)
    B.  Swim as fish with sine wave motion
    C. Gape limited Predators
    D. Sound detection is through legs
    E.  Paedomorphic forms are common
    F.  larval characteristics include
            1. larval tooth and bone patterns
            2. absence of eyelids
            3. retention of functional lateral line
            4. retention of external gills (such as in cryptobranchidae and necturus)
    G. Troglodyty forms are not uncommon
    H.  Plethodontid Salamanders (lungless)
            1.  most advanced
            2.  nasolabial grooves :
            3.  tongue protrusion
            4.  Binocular vision
    I. Reproduction
            1. Most have internal fertilization
            2. Transfer of sperm packet (spermatophore)
            3.  Typical Courtship
                  - Male nudges female around cloaca region
                  - If female is receptive , male climbs on top
                  - Male rubs female head with  his chin
                  - hedonic glands secrete unknown stimulating substance
                  - female follows male  -  tail wagging
                  - female nudges male cloaca
                  - male drops spermataphore
                  - female picks up spermatphore with cloacal lips
            4. Behavior is species specific
            5. Aquatic breeders tend to lay eggs in water
            6. Terrestrial breeders tend to lay eggs on land
            7. Many Plethodontids are terrestrial breeders (no aquatic phase)
            8. Some salamanders give birth to live young

 Frogs & Toads (Anurans = without tail)

    A.  Fusion and bone reduction to create catapult
    B.  Binocular vision
    C.  Flip out sticky tongue
    D.  Adaptations of  Aquatic Groups
            1. webbing
            2. lateral line system
            3. sensory structures at tips of fingers
    E. Jumping species are ambush predators
    F. Hopping species are wide ranging hunters stalking behavior
    G. explosive breeders
    H. prolonged breeders
    I. Types of males at breeding ponds
            1. territorial singers and / or advertisers
            2. large individuals  = lower frequency voice = more matings
            3. satellite males = hang out in water around territorial males and don't advertise attempt to intercept females or steal
                territory
            4. patrolling males  = males outside perimeter of pond trying to intercept arriving females
    J. Calls
            1. advertisement
            2. aggressive
            3. release
            4. alert
    K. Amplexus
    L. External Fertilization
    M. Parental Care
            1. egg carrying
            2. egg guarding
            3. feeding
            4. tadpole carrying
            5. nests
 

Caecilians (Gymnophiona)

    A.   Legless
    B   Covered eyes
    C.   Aquatic or burrowing
    D.  Pronounced Segmentation
    E.  Peristalsis
    F.  Little is known about their Ecology
    G.  Internal fertilization
    H.  Oviparous and viviparous species
    I.  Young scrape uterus -  produces creamy substance called uterine milk