Transcript ALAT Chapter 27 - AZ Branch AALAS Homepage

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)
AXOLOTL
(larval form of the Tiger Salamander)
Mudpuppies
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.
Frog’s head will then face handler’s wrist.
 Axolotls can be injured if restrained in a net.
A two-handed lift is preferred restraint.
(Image) Frogs
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.
Dorsal lymph sac injection
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.
Xenopus
(Image) Frog
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.
Husbandry
 Require covers atop cages, hiding places,
natural-spectrum lights, proper temp & humidity.
 Dry / wet composition of cage important; semiaquatic, 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 > importance.
 Small amount of detergents or disinfectants left in
tank could poison.
 Manual cleaning followed by heat sterilization &
rinsing is suggested when cleaning.
(Images) Frogs
Environmental Conditions
 Maintaining clean, chlorine-free water is critical.
Thin, porous skin susceptible to poisons & bacteria.
Too many changes stressful; > chance of injury.
 Solution = house fewer animals together.
< accumulation of fecal material, < # 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.
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 > susceptible to disease
(Image) Frog
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.
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.
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 & 25°C,
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 welladapted for survival.
(Image) Tadpoles
Environmental Conditions VI
 Little known about requirements for light.
 Natural photoperiod is probably best if no other
requirements are known.
 For Xenopus, a 14:10 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
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 brewer’s 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.
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.
(Image) Frog
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.
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.
(Image) Crickets
Additional Reading
DeNardo, D. “Amphibians as Laboratory Animals.” ILAR
Journal, 37(4):173–181, 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.