Chapter Twenty-Seven

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Chapter Twenty-Seven

• Amphibians

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Amphibians

• Scaleless, smooth-skinned, ectothermic
  vertebrates
• Begin life in water as aquatic gill-breathing
  larvae.
• Some aquatic entire life, many metamorphose into
  air-breathing adults w/ lungs appendages.
• Spend varying amounts of time in both aquatic
  terrestrial environments.
• Laboratory use frogs, toads salamanders
• Used for genetic, physiological neurology /
  endocrine studies.
• bullfrogs, leopard frogs, African clawed frog
  tiger salamander (axolotl)

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AXOLOTL(larval form of the Tiger Salamander)
Mudpuppies
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Handling Restraint

• Slimy skin secretion a protective covering
• Handling w/ dry hands causes covering to rub off,
  allowing entrance of bacteria.
• Handle frogs salamanders only as necessary.
• Pick up with wet gloves.
• Do not adapt well to handling will struggle.
• Place fingers on each side between legs to pick
  up frogs.
• Frogs head will then face handlers wrist.
• Axolotls can be injured if restrained in a net.
• A two-handed lift is preferred restraint.

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(Image) Frogs
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Handling Restraint II

• Marine toad tropical frogs secrete toxic
  substances from skin glands.
• Wear protective gloves when handling.
• Handle amphibians gently carefully to avoid
  injuring skin delicate gills.
• All handling introduces a degree of stress.
• Separate newly arrived from established colonies.
• Rinse thoroughly with dechlorinated water as they
  are removed from shipping crates to
• remove feces accumulated in transit.

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Dorsal lymph sac injection
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Sexing Breeding

• Most wild-caught or bred reared by suppliers.
• Only way to determine sex is observe courtship.
• Males vocal sacs become prominent during breeding
  season.
• Bullfrogs - external tympanic membrane caudal to
  each eye.
• Same diameter as eye in female.
• In males, this membrane is twice as large as eye.
• Males also have heavy thumb pads.
• Xenopus female has larger ventral flaps body.
• Male Xenopus have black surfaces on inner
  forelimbs, larger digits during breeding season.

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Xenopus
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(Image) Frog
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Behavior

• Skin more porous than most terrestrial vertebrate
• Sensitive to toxic substances in water.
• Temp change cause behavioral abnormalities,
  lethargy loss of appetite, can trigger
  illnesses.
• Sensitive to sudden temp change of more than a
  few degrees at a time.
• Providing appropriate food may not be sufficient
  to ensure feeding.
• May stop eating starve from stress.
• Feeding indicates acceptance of environment.
• Housing in low density providing w/ adequate
  food can reduce or eliminate cannibalism.

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Husbandry

• Require covers atop cages, hiding places,
  natural-spectrum lights, proper temp humidity.
• Dry / wet composition of cage important
  semi-aquatic, such as common leopard frogs, need
  to to leave water.
• Tank materials should not contain toxins that
  leach into water.
• Cleanliness of water housing unit gt importance.
  
• Small amount of detergents or disinfectants left
  in tank could poison.
• Manual cleaning followed by heat sterilization
  rinsing is suggested when cleaning.

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(Images) Frogs
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Environmental Conditions

• Maintaining clean, chlorine-free water is
  critical.
• Thin, porous skin susceptible to poisons
  bacteria.
• Too many changes stressful gt chance of injury.
• Solution house fewer animals together.
• lt accumulation of fecal material, lt water
  changes
• Rinse cages after fed to eliminate uneaten food.

• Limit of frogs / cage to that allows all in
  or out of water without being on top of, or
  frequently bumping into one another.

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Environmental Conditions II

• Vary with species stage of life cycle.
• Eliminate toxic materials or keep at safe levels.
• Water hardness levels less than 250 ppm, or mg/l
• Water CO2 greater than 5 mg/l
• pH between 6.5 - 8.5
• Adjust new water temp. to old water temp. before
  placing the animals in it.
• sudden change can animals gt susceptible to
  disease

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(Image) Frog
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Environmental Conditions III

• Bullfrogs leopard frogs, spend greater time
  submerged.
• Untreated tap water in most locations may be
  used.
• Low levels of chlorine (under 4 mg/l) may help
  inhibit bacteria growth.
• Chlorine levels vary with seasons region.
• Harmful or lethal in excessive amounts.
• Check chlorine level before placing in tap water.
• Dissipate water in open containers for 24 hours
  or add sodium thiosulfate to water.
• Chloramine cannot be removed by aging 24 hrs.
• Check water for this before contact.

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Environmental Conditions IV

• O2 enters at air-water interface.
• Maintain a large surface to volume ratio.
• Shallow tank has greater water surface / liter
  than a deep tank of volume.
• Surface site of CO2 dissipation
• greater surface area volume surface area
  animal ratios minimize amount of CO2 retained in
  water.
• Bubbling filtered air through water stirs
  surface.
• Increases direct O2 contact with the water.
• Helps maintain proper levels of O2 CO2 in tanks
  with greater population density.

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Environmental Conditions V

• Slight aeration for newly hatched tadpoles
• Tadpole populations vary between 50 / liter of
  water when hatched to 5 / liter when
  metamorphosis begins.
• Adults of most species kept between 20 25C,
  thrive better at cooler end of range.
• Rapid temperature change harmful for small
  larvae, eggs or embryos.
• Cooler temperature prevents early metamorphosis.
• At higher temperature, metamorphosis occurs more
  quickly, but adults may be smaller less
  well-adapted for survival.

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(Image) Tadpoles
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Environmental Conditions VI

• Little known about requirements for light.
• Natural photoperiod is probably best if no other
  requirements are known.
• For Xenopus, a 1410 lighting cycle is
  recommended for optimum oocyte production.
• To identify individuals, the system of choice
  would be one that allows identification of
  individual animals at all stages of development.
• tattooing, toe clipping use of drawings
  photographs to record unique markings

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Diet

• Larval amphibians are omnivorous, in nature
  consume algae or soft vegetable matter.
• Replace in captivity w/ boiled lettuce or canned
  low salt spinach, ground dog chow, rabbit
  pellets, liver or brewers yeast.
• Tadpoles of African clawed frog fed ground peas
  or split pea soup powder.
• Avoid overfeeding and remove uneaten food.
• Adults become carnivores, feed on insects.
• Terrestrial adults rely on movement to detect
  prey to stimulate feeding response.
• Leave area once feeding is observed.

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Diet II

• Some do not feed if below a certain temperature.
• Gradually raising temperature a few degrees
  before feeding may increase feeding activity.
• Diet of laboratory raised insects is preferable,
  likely to be cleaner than wild-caught.
• Crickets available from biological supply houses.
• easy to maintain can be dusted prior to feeding
  w/ calcium / vitamin supplement powder
• Mealworms (beetle larvae) readily eaten by most.
• Feed to satiation, 1 - 3x / week.
• Programmed to eat all the prey they can get, in
  captivity limits must be set.

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(Image) Frog
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Diet III

• Sometimes a salamander does not metamorphose,
  remains in larval form w/ gills.
• neoteny
• Aquatic adult, larval neotenic salamanders feed
  on aquatic invertebrates, such as isopods or
  crustaceans, small fish.
• In captivity, eat brine shrimp.
• Live prey used with reluctant eaters.
• Salamanders toads thrive on crickets,
  earthworms, insect larvae non-flying insects
• Live mouse neonates minnows will vary diet of
  larger salamanders.

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Diet IV

• Frogs eat live insects, worms, crickets slugs,
  but generally prefer flying insects.
• Leopard frogs bullfrogs eat such a large amount
  that insect diet is impractical.
• Feed small mice, mouse neonates, crayfish or
  small fish.
• Xenopus will eat raw liver chunks or commercial
  frog food.
• Force-feeding done at risk of injury trauma of
  handling often harms more than food benefits.
• It is extremely difficult to sustain an amphibian
  by force-feeding can actually discourage
  natural feeding behavior.

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(Image) Crickets
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Additional Reading

• DeNardo, D. Amphibians as Laboratory Animals.
  ILAR Journal, 37(4)173181, 1995.
• Duellman, W.E., and T. Trube. Biology of
  Amphibians. McGraw-Hill Book Company, New York,
  NY. 1985.
• Fowler, M.E. Zoo and Wild Animal Medicine. W.B.
  Saunders Company, Philadelphia, PA. 1986.
• Rollin, Bernard E., and M. Lynne Kesel (ed.).
  The Experimental Animal in Biomedical Research.
  Volume II Care, Husbandry and Well-Being An
  Overview By Species. CRC Press, Boca Raton, FL.
  1992.