amphibian natural history

Terms in this set (17)

synapomorphies of amphibia (frogs, salamanders, caelcilians)

soft, permeable skin with mucus (for moisture) and poison (granular) glands
moist skin allows for cutaneous gas and water exchanges as well as some waster

other shared trains of most amphibia

carnivorous as adults: mostly invertebrates, but also fish, tadpoles, other frogs, lizards, birds, rodents
dependence on water: thin, moist skin requires replenishment, aquatic larval stage

Order Gymnophonia or Apoda

(naked snake, without tail; caecilians 175sp in 6 families)
- burrowing or aquatic, pantropical
- feed on small or elongate prey
- some oviparous, other viviparous

autoapomorphies of order gymnophiona or apoda

- No legs (secondary loss)
- eyes reduced or absent (covered in skin/bone)
- body encircled in dermal rings like worms (annuli)
- some with dermal scales in pockets within annuli
- protrusible tentacles on face (uses former eye muscles & glands)
- sensory organ (replace eyes & detect chemicals like a tongue)
- Terrestrial species have elongate embryonic gills (derived)

reproductive pattern diversity in order gymnophiona or apoda

25% oviparous, eggs guarded by female
75% viviparous & matrotrophic (= mother provides nutrient to young), inc. maternal dermatophagy:Young have special dentition, feed on superficial skin layers of mother

Order urodela or caudata

(tail; salamanders)
elongate body with long tail, & usually 4 short limbs: most small, terrestrial & secretive, some aquatic

ancestral tetrapod gait: lateral fish-like undulating + limb motion
slow

no ribs: buccal pumping for ventilation
(use hyobrachial apparatus)

Great diversity of body form and size,
& reproductive patterns:

Some species blind, live in caves
Some mostly terrestrial (but aquatic larvae)

reproductive patterns of order urodela or caudata

Often elaborate courtship behavior (pheromone transfer)

Most spp. oviparous

A few are viviparous

Paedomorphosis common: adults with some/many larval traits (laterally compressed tail, larval teeth, no eyelids, gills); some entire species, some populations

Plethodontid success

1/2 of all salamander species!
rely wholly on cutaneous respiration (no lungs), thus ... need to be elongate for maximum surface area and need moist terrestrial habitats

absence of lung freed up space and hyobranchial muscles & apparatus elongated & light hyobranchial apparatus:TONGUE PROJECTION
- associated with enhanced prey detection
- frontal eye position, complex neuroanatomy for binocular vision & distance/direction processing
- nasolabial grooves for enhanced chemosensation
-direct development and parental care in many species

(without tail, frogs/toads 5400sp in 45 families)
body specialized for jumping
- no tail
- shortened rigid body (5-9 reinforced vertebrae)
- elongated hind limbs, tibia & fibula fused
- large rigid pelvis (elongated ilium, lower vertebrae fused into urostyle
- strong, short forelimbs with a flexible pectoral girdle (landing)
no ribs
large mouth w/ protruding tongue, eyes forward
powerful vocalizing abilities in males
all but two sp. have external fertilization

tailed frog
- most ancestral species (2 sp.)
- intromittent organ
- NA cold mountain streams; tadpoles

- 30 aquatic sp. from South America/Africa
- no tongue (suction feed)
- lateral line

true toads
- >500 sp., most of world
- dry skin (terrestrial) with well developed poison glands
- bulky, short legs, short hops
active foragers

tree frogs
- >800 sp., most of world
- most arboreal
- toes with expanded pads
- eyes forward

dart poison frogs
- 200 sp., C. & S. America, diurnal
- aposematic coloration (batrachotoxin)

"true" frogs
- >300 sp., worldwide, diverse

Reproduction in amphibians

almost as diverse as fish, despite 1/5th as many sp.

- external fertilization is ancestral
nearly all Anura & primitive salamanders

- internal fertilization has evolved in:
Gymnophiona: phallodeum (penis-like organ)
Caudata (most): spermatophore = capsule of spermatozoa transferred from male to female during copulation
Anurans: Ascaphidae (tailed frogs): male has "tail" (extension of cloaca), used as intromittent organ

Eggs and parental care of amphibians

primitive, like fish eggs
- two poles
- animal - becomes embryo
- vegetal - becomes yolk sac
- surrounded by jelly coat
- wastes (ammonia) diffuses into environment
- dependent on the presence of standing water
or saturated envtl. conditions

majority show no parental care but egg attendance not uncommon and some show offspring attendance

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