Urodela and Caecilian

Created by: ValentineDevil
Created on: 21-03-19 15:05

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Amphibian Diversity and Biology
- Gymnophiona (Caecilians
  - Superficially earthworm-like, limb-less, tail-less and fossorial amphibians
  - Diagnostics
    - No tail; terminal or subterminal cloaca
    - No limbs or girdles
    - Small, sometimes protrusible eyes or none
      - Otic notch and impedance-matching ear lost
        Endochondral elements of the neurocranium are fused into an os basale (HEAVILY OSSIFIED SKULL); bones of the jaw fused into pseudodentary and pseudoangular
        
        Behind jaw articulation a large process gives leverage for jaw-closing muscles that originate on the branchial skeleton
    - Internally fertilizing
    - Sensory tentacle (paired) between eye and nostril
    - Oviparous or viviparous
    - Two sets of jaw-closing muscles
      - STRONG JAWS
    - Dermal scales; skin annulations (concentric rings called annuli)
      - BREATHABLE
  - Reproduction
    - Internal insemination only
    - Male: long, tube-like intromittent organ (phallodeum)
    - 25% oviparous
      - egg guarding
      - Some eggs, the young already metamorphosed, some hatch as larvae (not fully aquatic). Any larvae gills are lost with time
    - 75% viviparous
      - Foetus fed inside female with cells lining the oviduct, which they eat with scraping teeth
    - Dermatothrophy
      - Egg-laying species that feeds young by developing outer skin high in fat etc which young peel off with scraping teeth
- Urodela (Salamanders. Newts)
  - Elongate bodies, skin grooves along flanks, long tail, four equal/ subequal limbs where present
  - Diagnostics
    - Tail in Larvae/adults; two pairs equal limbs
    - NO otic notch or middle ear; stapes w/ short stylus and large footplate
      - Impedance-matching ear is reduced; maxilla does not connect posteriorly with the cheek, creating a gap in the skull margin
    - Gill slits/ external gills in aquatic larvae
    - No teeth on both jaws
    - Short, stumpy ribs borne on bicipital rib bearing processes
    - Small levator mandibulae posterior muscle
    - Most w/ intercostal grooves marking position of muscular septa in trunk
    - Dorsal origin for adductor mandibulae internus superficialis muscle
  - Diet/prey capture (generalist carnivores, primarily inverts)
    - Aquatic
      - Mouth gape
        Suction into oral cavity; working with one way flow of gills,
        
        Tongue: broad, flat immobile
    - Terrestrial
      - Thick, sticky tongue grabs prey
  - Senses
    - Aquatic
      - Vibrations- retain lateral line system
      - Taste chemicals
    - Terrestrial
      - Smell- Vomeronasal organ (nnon-volatile)
        Bigger in males
        
        Courtship/ identification
        
        Nasolabial grooves: non-ciliated grooves, upper lips to nares
        Sexually dimorphic (especially in repro season)
        
        Aids in collection/ delivery of chem cues (capillary action)
      - Vision- acute
      - Smell- Olfactory epithelium (volitile)
      - Hearing- limited (no eardrum); primarily ground vibrations.
  - Larvae
    - Stream
      - Depressed body profile, narrow tail fin (not onto trunk), short thread-like or curly gills and all four legs at hatching
    - Pond
      - High body profile, broad tail fin extending up to head, long, plume-like gills, only front legs at hatching
  - Defence mechanisms
    - Biting
    - Toxins
    - Posture
    - Tail autotomy
    - Case: poking poison glands on flanks with needle-like ribs
    - Unkenreflex
    - Rolling up and rolling away

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Urodela and Caecilian

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