HERPETOLOGY

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HERPETOLOGY

• AN OVERVIEW

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Studies of amphibians, reptiles

• Have played key roles to understanding
• Developmental biology
• Frog development
• Ecology
• Diurnal activity patterns of lizards
• Physiology
• Freezing frogs
• Medicine
• Stress proteins first identified in salamanders

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The Most Important Reason to Study Herps
Pseudacris crucifer (Spring Peeper)
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Amphibian Diversity

• Lissamphibiamodern amphibians
• Smooth, scaleless skin
• 4,600 species
• Extant groups of amphibians
• Salamanders (Urodela)
• Frogs (Anura)
• Caecilians (Gymnophiona)

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Amphibian Characteristics

• Permeability of skin
• Gas exchange through skin.
• Dehydration occurs easily.
• Large impact on behavior.
• Hedonic glands in skin produce pheromones used in
  courtship.
• Granular glands in skin produce toxins used in
  defense.

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Urodela Salamanders

• Salamanders have elongate trunks and tails and
  usually 4 legs.

Marbled salamanderAmbystoma opacum
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Trend I Loss of Lungs

• Plethodontids
• How do Plethodontids breathe?

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Trend II Paedomorphosis

Larval characteristics found in
adults Aquatic Lateral line system External
gills Absence of eyelids Absence of adult teeth
Axolotl
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Anura Frogs Toads

• Frogs have short bodies, large heads, and 4
  limbs.
• Enormous variety of reproductive modes
• Aquatic larvae (tadpoles)
• Direct development
• Viviparity

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Tadpoles
Pacific tree frog
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Direct Development
R.W. van Devender
Eleutherodactylus (greenhouse frog) lays eggs in
leaf litter. Froglets develop directly from
eggs. Indiginous to Caribbean invasive species.
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Froglet in Egg
Eleutherodactylus mother cares for eggs and
froglets in this species which lives in caves.
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Viviparity in frogs
Froglets are born alive. Gastric brooding
frog. Frog swallows eggs and froglets Emerge from
stomach. Adult Turns off acid production
in stomach. Lived in Australia. Aquatic. Last
seen in 1995. Presumed to be extinct.
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Gymnophiona (Caecilians)

• Least known group of amphibians.
• Fossorial or aquatic.
• Tropical habitats.

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Reptiles

• Characteristics
• Scales
• 3-chambered heart except crocodilians.
• Groups
• Testudines (Turtles)
• Squamata (Lizards, Snakes)
• Crocodylia (Crocodilians)

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Testudines (Turtles)

• All have shell
• Aquatic
• Relatively flat shells
• Webbed feet
• Terrestrial
• High domed shells
• Stout limbs

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Which is which?
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Squamata (Lizards Snakes)

• Lizards usually are diurnal, brightly colored and
  conspicuous
• Snakes are often secretive, rely on scent, are
  less conspicuous.
• Legglessness is common. All snakes, some
  lizards.
• Many live on ground or are arboreal.

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Leglessness

Bipes
Glass lizard
Speckled worm lizard Amphisbaenian)
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Crocodylia (Crocodilians)

• Only 21 species alive most endangered or
  threatened.
• Provide parental care.
• Diversity
• Alligators
• Crocodiles
• Gharials

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Crocodylia
Gharial
Crocodile
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Rhynchocephalia (Sphenodontida or Tuatara)

• Lizard-like in appearance.
• Live on islands near New Zealand.
• Very endangered.

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Shared Characteristics of Amphibians/Reptiles

• Ectothermy
• Mammals, birds are endothermic.
• Body temp is maintained at most efficient level
  for maximum performance.
• Body size, shape

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Ectothermic Amphibians, Reptiles

• Control body temp within narrow limits during
  active periods.
• Warms up from direct sunlight (basking), sitting
  on warm substrate
• Cools in shade

Thermoregulation of desert iguana
Night 20oC Day up to 42oC
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Advantages of Ectothermy

• Uses less energy to maintain same body temp as
  squirrel of same size.
• Drop in body temp at night conserves energy even
  more.
• Less active than endotherm even less use of
  energy.
• Requires less food.

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Metabolic Rates of Ectotherms/Endotherms
Mass-specific energy use MR of endotherms is
7-10x that of ectotherms.
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Effect of Body Temp on Activities of Ectotherms
Disadvantages of ecto? Escape? Vulnerability at
night? Activities in winter?
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Impact of Ectothermy and Endothermy on Ecosystem

• Study of Hubbard Brook experimental forest in NH
• Salamanders consumed food worth 46,000kJ/hectare
• Birds consumed 209,000kJ/hectare.
• Conversion efficiency of salamanders is 60
  birds lt 2. Sal. provide much more energy to food
  chain than birds.
• Small salamanders eat small prey that is not
  available to larger endotherms.