ZOO 4910 Lecture Notes - Lecture 5: Salientia, Vocal Sac, Salamander
2 May 2018
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Department
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Professor
Eggs are not desiccation resistant
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Amphibious -may spend time on land, but must have water to breed
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Tetrapods (some are secondarily legless)
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Have pulmonary and cutaneous respiration
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Anura (Salientia) -frogs
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Urodela (Caudata) -salamanders
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Gymnophiona (Apoda) -caecilians
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Lissamphibia, has three orders:
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Amphibians:
Frog disparity: body size ranges from 7.7mm to 32cm
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May help bring about life history morphological
changes
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Delayed endochondral bone formation
!
Maintains cartilaginous skeleton until later in adult life
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Adaptation to facilitate larval metamorphosis
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Developmental adaptations:
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Fused radius-ulna
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Fused tibia-fibula
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Modified pelvic girdle (has urostyle bone)
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Have a greatly modified endoskeleton
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Female uniparental, biparental, male uniparental
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Nest or egg attendance
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Nest or egg guarding
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Males may carry eggs
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Females may carry tadpoles
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Carry froglet in pouches
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Tadpoles carried in male's vocal sac (Darwin's frog)
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Egg, larvae or hatchling transport
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Egg brooding
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Feeding of young
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Guarding or attending young
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Large diversity in parental care
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Toxin production
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Sexual dimorphism (extreme size disparity)
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Females compete more strongly for males, males
more selective
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Not supported, some studies demonstrate that male
and female competition is strong and females are
more selective than males
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There is support for parental quality selection
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Evidence for sexual role reversal
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Tropical or Sub-tropical Frogs:
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Cyroprotectant strategies
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Water shunting
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Can tolerate freezing due to an increase in glycogen
synthase activity (increase blood sugar glycogen
levels)
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Trade-offs
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North American Wood Frogs
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Life-History Strategies:
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Anura:
Climate change
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Contaminates
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Disease
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Competition
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Collecting amphibians
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Invasive species
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Predation
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Habitat destruction
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UVB radiation
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Factors that Contribute to Extinction:
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Historical (lay eggs in water)
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Evolutionary compromises (adaptations are the result of numerous
selection pressures)
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Not all evolution is adaptive (schooling increases likelihood of
transmitting disease; basking and laying eggs in shallow water
exposes amphibians to UBV)
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Evolution alters existing variation (amphibians have thin,
permeable skin and do not have protective hair/feathers)
○
*therefore, there is limited ability to adapt to extreme
changes
Evolution takes time (adaptations may not evolve if not given
enough time)
○
Constraints:
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Complexity of Amphibian Population Declines:
Arose during the Carboniferous
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Amnion -surrounds embryo
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Chorion -surrounds entire inner part of egg
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Allantois -respiration, disposal of wastes
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Embryo is surrounded by a series of membranes
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Egg shell is desiccation resistance and protective
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Origin of Amninota
There is a large controversy in understanding the origin of turtles
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Are they more closely related to Archosaurs (crocs/birds) or to
Reptiles
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Read: "The Troubles with Turtles"
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Ondontochelys (~220 mya) -contains bony plates on ventral side
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Ribs were internal within body cavity
!
Pappochelys (~240 mya) -contains bony scutes (plaston) on
ventral side
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*see slide
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Possible Origins:
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Buoyancy
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Movement in water
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Could had evolved to help with thermal regulation
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Fossilized sister clades of reptiles show dorsally-oriented and
flattened ribs
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Osteoderms are observed in dermal layer
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Palentological evidence suggests closer affinities to the reptile lineage
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Turtles
More desiccation-resistant eggs with extra membranes
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Keratinized skin (with scales/feathers/fur)
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Lipids in skin (water-proofing)
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Costal (rib) ventilation of lungs
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Amphibian: sprawling
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Primitive reptilian stance: semi-erect
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Saurian/avian/mammalian stance: erect
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Position of limbs
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Amniotes (vs. Amphibians)
Amphibian Diversity & Evolution of Eggs
Wednesday,+ September+ 20,+2017
12:26+PM
Document Summary
Amphibious - may spend time on land, but must have water to breed. Frog disparity: body size ranges from 7. 7mm to 32cm. May help bring about life history morphological changes. Maintains cartilaginous skeleton until later in adult life. Tadpoles carried in male"s vocal sac (darwin"s frog) Females compete more strongly for males, males more selective. Not supported, some studies demonstrate that male and female competition is strong and females are more selective than males. Can tolerate freezing due to an increase in glycogen synthase activity (increase blood sugar glycogen levels) Evolutionary compromises (adaptations are the result of numerous selection pressures) Not all evolution is adaptive (schooling increases likelihood of transmitting disease; basking and laying eggs in shallow water exposes amphibians to ubv) Evolution alters existing variation (amphibians have thin, permeable skin and do not have protective hair/feathers) Evolution takes time (adaptations may not evolve if not given enough time) *therefore, there is limited ability to adapt to extreme.
