Characteristics of Amphibians
- Created by: ValentineDevil
- Created on: 08-03-19 15:17
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- Characteristics of Amphibians
- Major group of tetrapods (limbed verts)
- General characteristics
- Often with ears specialised for detecting ground or airborne vibrations
- Often broad and abbreviated skulls with large openings and slender bones, and incompletely ossified; ossified vertebrae
- Wet skins
- Size varying from a little over half a centimetre to nearly two metres
- 3-chambered hearts, ureotelic and ammoniotelic; gill and lung (and skin) breathers; four-stroke breathing mechanism
- Ectothermic vertebrates w/ terrestrial, aquatic, arboreal and fossorial habits
- Low metabolic rates and limited food and energy requirements
- All amphibians possess smooth skins packed with glands, even though several species may superficially appear to have a "rough" skin
- Glands
- Mucous: aid in skin respiration, tbermoregulation, defense and reproduction
- Two kinds
- Granular: aid in defence as they secrete toxic or noxious chemical compounds
- e.g. Parotoid glands ('next to the ear'); neurotoxin-secreting skins in lissamphibians
- Caecilians
- Scales embedded in skin
- Stacks of closely packed scales lodged in connective pouches situated below the skin annulations (appearing as folds)
- Scales embedded in skin
- Simple skull bone configuration
- Broad palatal vacuities delimited by palatines
- Two condyles for neck ariculation
- Frogs: Frontals and parietals fused into paired frontoparietals
- Salamanders: otic notch and tympanum lost: impedance-matching ear reduced; maxilla does not connect posteriorly with the cheek, resulting in a gap in the skull margin
- Caecilian: otic notch and impedance matching ear lost; endochondral elements of the neurocranium fused into an os basale. bones of the jaw fuse into a pseudodentary and pseudoangular; behind the jaw articulation, a large process provides leverage for jaw-closing muscles that originate on the brachial skeleton
- Frogs generally don't have ribs
- Salamander generally have extremely short ribs (same with caecilians) (note: double-pronged processes of the vertebrae to which ribs articulate)
- Four or fewer fingers in anterior limb when present
- Levator bulbi muscle: thin, floor of orbit, innervated by 5th cranial nerve
- Causes eye to bulge outward leading to enlarged buccal cavity (used in breathing/ feeding)
- Frogs, salamanders and reduced form in caecilians
- Intermaxillary gland: system of alveoli and tubules in the anterior part of the mouth (between nasal capsules)
- Operculum-Columella complex (note circular tympanum)
- Sits in an embayment at the back of the skull
- Note the wide squamosal embayment for the tympanum
- Two bones in middle ear that transmit sound to inner ear via oval window
- Dual high/low frequency system
- HF: >1000Hz (columella vibration-air)
- frogs- vocalisation
- LF: < 1000Hz (operculum and columella vibration- ground) transmitted by leg bones plus scapula (activated by opercularis muscle)
- predator/prey detection in frogs and salamanders
- HF: >1000Hz (columella vibration-air)
- Inner ear
- Basilar papillae
- hair cell system for HFs
- Amphibian papillae
- hair cell system for LFs
- Basilar papillae
- Sits in an embayment at the back of the skull
- Green rods in retina
- Detection of blue light, and hue discrimination in dimness
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