LECTURE 19 - Amphibians Flashcards
Describe the transition from water to land.
IN THE WATER
- Buoyancy
- Low oxygen
- High specific heat
- Usually in thermal equilibrium
IN THE AIR
- No buoyancy (need more bones for support)
- Abundant oxygen (switch from gills to lungs)
- Low specific heat
- Usually need to thermoregulate
What do tetrapod split into in the phylogenetic tree of decent?
- Amphibians
- Amniota
- Synapsida (mammalia)
- Reptiles
Describe the amphibian and reptile skulls
- Temporal openings (fenestrae) in the skull are an important character for distinguishing between major groups of tetrapods
- Sit behind the eye orbit on the lateral surface of the skull
- Provide an attachment site for jaw muscles and can allow for greater bite force
- Lighten the skull without compromising strength
anapsids: no openings (amphibians and turtles)
synapsids: one opening (mammals)
diapsids: two openings (birds and reptiles other than turtles)
(IN TETRAPODA) What are Amphibians?
- Anamniotes (no extra-embryonic membranes in the egg)
- Ectothermic
- Glandular skin with mucous and granular glands
- 3-chambered heart
Describe thermoregulation in amphibians
- Temperature regulation in ectotherms is primarily controlled by behaviour
- Physiological processes proceed at optimal rates when organisms are at preferred body temperature
Describe thermoregulation in amphibians
- Temperature regulation in ectotherms is primarily controlled by behaviour
- Physiological processes proceed at optimal rates when organisms are at preferred body temperature
What does body temperature affect?
- Performance
- Jumping performance in frogs
- Signalling
- when they croak
Describe the skin of Amphibians
- Vascular, respiratory
- Environmental substances can enter bloodstream through skin
- Chromatophores produce pigment
- Dermal glands
- Mucous (preserve moisture)
- Granular (secrete toxins)
Describe the skeletal system of Amphibians
- Four limbs except for caecilians
- Hollow, lightweight bones
- Fully ossified bones with interlocking vertebrae
- Pelvic girdle supported by muscle
- Forward sloping ilium
Describe the circulatory system of Amphibians.
- Circulatory systems of juveniles and adults differ
- Juveniles have two chambered hearts similar to fish
- Adults have three chambered hearts with two atria
(IN AMPHIBIA) What are Gymnophiona?
- Caecilians
- ~200 species
- Tropical distribution (South and Central America, Africa, Southern Asia)
- Lack any limbs
- Diet not well known but probably consists of small subterranean species
- Exclusive internal insemination
- Most caecilians are fossorial
- highly limited vision (basic light-dark adaptation)
- strong skull with fused bones and a pointed snout used to force through mud or soil
- skeleton and muscles act as a piston
- chemosensory tentacles provide olfactory capabilities
(IN AMPHIBIA) What are Urodela?
- Salamanders
- ~650 species
- Distributed mainly in the northern hemisphere
- Overt similarities in body form to some ancient amphibians but possess ribs and have no middle ear
- Rarely more than 4 toes on front legs and five on rear legs
- Permeable skin: must stay in damp habitats to avoid water loss
- Opportunistic predators of organisms of any reasonable size
- Capable of tissue regeneration
What is so special about Salamanders’ feeding methods?
they have a tongue protractor muscle
when they stick their tongue out, the tongue skeleton can completely leave the mouth while still being anchored by the retractor muscles
What are the salamander’s mating behaviour?
- Sexually monomorphic and not vocal, so olfactory and tactile cues used to identify mates
- 90% of species use internal fertilization via a spermatophore
- Once inside the cloaca, spermatozoa move to the spermatheca and are sometimes stored for long periods of time before egg laying
(IN AMPHIBIA) What are Anura?
- Frogs and toads
- Fold limbs underneath body, no tail (in adults)
- ~85% of amphibian species
- Carnivores
- Urostyle formed of fused vertebrae, shorter forelimbs than hind limbs
- Most abundant of all tetrapods
- ~4,800 species
- Worldwide distribution
