3 orders of amphibians
- urodela (salamanders)
- anurans (frogs)
- gymnophiona (caecilians)
urodela
“conspicuous tail”
salamanders
anurans
“without tails”
frogs
gymnophiona
“naked snake”
caecilians
general body shape of urodela
elongated body shape with 4 functional limbs
amphibian synapomorphies
- moist permeable skin - evaporates/absorbs water quickly
- cutaneous gas exchange
- skin glands - mucus and poison glands
- carnivorous
- 2 middle ear bones (operculum-columella complex)
- green rod cells in the retina - increased sensitivity to violet/blue light
how many species of urodela are there
~700
what happens to urodela when they go through metamorphosis?
go thru an aquatic larvae stage and lose gills during metamorphosis
where are urodela found?
almost entirely limited to the northern hemisphere
what are examples of paedomorphosis in urodela
paedomorphosis is widespread amongst salamanders
larval tooth and both patters, absence of eyelid, functional lateral line system and external gills
paedomorphosis
retention of larval or embryonic characters later in life
lungless urodela species
plethodontidae
where are anura found?
all continents except antarctica
what is special about the anura’s skeletal structure
built and adapted for jumping
what are physical features of the gymnophiona
legless, burrowing or aquatic amphibians of the tropics
have no or greatly reduced eyes
skeletal adaptations of the anura
- elongated hindlimbs
- fused tibia and fibula
- elongated ilium
- urostyle fused vertebrae
- few presacral vertebrae
- strong flexible pectoral girdle
- large eyes with binocular vision (eyes in front)
how do most amphibians reproduce? how does this method vary?
- most lay eggs (in water or on land or carry eggs)
- eggs may hatch into aquatic larvae or mini adults
- others retain eggs internally and give birth to metamorphosed young
how much parental care do amphibians provide
varies
what does breeding season look like for amphibians
short:
- only a few days due to transient aquatic habitats
- males and females arrive at the same time
- “explosive breeding”: females lay all the eggs and then male fertilizes them by spraying sperm all over them
long:
- can be several months
- males arrive at the breeding site first and defend territory
what is a unique feature of anuran reproduction
advertisement calls!
(vocalizations) are a characteristic of anuran breeding
- calls are diverse and typically specie specific
- costs: energy and exposure to predators
females respond when eggs are ready to be laid
tadpoles - anurans
many anurans have tadpole stage in life
very diff from adults, filter feeders - can exploit ephemeral (short) food resources not available to adults
anuran metamorphosis from tadpole to adult
transition in body from from larva to adult
stimulated by hormone thyroxine
caecilian reproduction
internal fertilization
males have penis like organ that protrudes from cloaca
caecilians exhibit oviparity and viviparity
how do amphibians respire?
amphibian skin is permeable to gases and water
significant portion of gas exchange is cutaneous - remaining is pulmonary respiration
anurans rely more on lungs for oxygen uptake as temperature and their activity increases
