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Class: Amphibia
Order: Apoda
Family: Caeciliae (not studied much)
Order: Caudata
Family: Ambystomatidae
Genus: Ambystoma
species: mexicanum - axolotl
tigrinum - tiger salamander
Family: Salamandidrae
Genus: Notophthalamus
species: viridescens - red-spotted newt
Family: Proteidae
Genus: Necturus
species: maculosus - mud puppy
Order: Anura
Family: Ranidae
Genus: Rana
species: pipiens - leopard frog (mostly used in research)
catesbeiana - bull frog (second in use in res.)
grylio - pig frog
clamitans - bronze frog
palustris - pickerel frog
sylvatica - wood frog
Family: Pipidae
Genus: Xenopus
species: laevis - African clawed frog
Amphibians date from the early Devonian era from lobed-finned fishes. Amphibians, especially frogs, were studied in early Greece. Galvani used frogs to demonstrate the discharge obtained from rubbing two pieces of metal together.
Axolotls on the other hand date back to a shipment from Mexico to Paris in 1864.
Amphibians have moist, glandular skins and their toes are devoid of claws. Young pass through a larval, usually aquatic stage before they metamorphose into adults. External scales are not present. Fertilization is external or internal. Eggs are laid in moist surroundings or in water and have a yolk or gelatinous envelope. Respiration is through simple lungs, gills, skin or buccopharyngeal membranes. The heart is three-chambered, and there are 10 pair of cranial nerves.
The skin is moist and in many species is used as a respiratory organ. Water can pass through in either direction; therefore, the animal must be protected from water loss and uptake of toxins.
Gills are found only in larval forms and in those adults which do not metamorphose. In those species which metamorphose, the lungs are considered the first true lungs on the evolutionary tree. All amphibia still practice cutaneous respiration.
The heart is 3-chambered having 2 atria and 1 ventricle.
Dentition is weakly developed; the lips in many species are cornified to form horny rim.
There is a general reduction in the number of bones over fish, and the skeleton has been modified for a different mode of transportation.
occurs in all metamorphosing animals. It depends on external and internal factors, and the slough is usually eaten.
3 areas of change: regression of larval structures, transformation into adult forms, and development into new forms. It cannot be a protracted process since each stage may exist in a state not suitable for the next stage.
A feature found in some salamanders.
Fertilization is generally internal. Seasonal breeders with many extrinsic factors governing the cycle. Eggs are laid in flowing water and are temperature dependent for hatching. Larvae are not much differentiated from adults and larval stages tend to be long. In certain environmental conditions larval features may persist into sexual maturity called as NEOTENY. The mud puppy of eastern USA and axolotls of Mexico are the common species that exhibit neoteny. By adding 2-3 ppm iodine to the water metamorphosis will be induced and neoteny will be terminated.
Fertilization is external and involves an aquatic environment. Extrinsic factors control the breeding which usually occurs in a "home" pond. Length of the larval stage varies depending on environment. Laboratory breeding programs not common.
General:
Since most amphibians are aquatic in the larval stage and then become terrestrial, they need dual environments. Sanitation and waste disposal are critical in the aquatic environment, especially during metamorphosis, and there is a need to maintain strict water standards. Larval amphibians are vegetarians while adults are carnivores. Most frogs and salamanders are cannibalistic, so young must be separated from adults. Some species will continue to feed in aquatic environments as adults, some become terrestrial feeders, and some will feed in either environment. Optimum environmental conditions are needed at metamorphosis due to the rapid physiological changes occurring.
Caudata
Housing:
Glass aquaria are good for terrestrial forms provided a high humidity is maintained. For semi-aquatic species, some access to water is advisable. Aquatic salamanders can be housed in standard fish aquaria that have been adapted to their natural habitat.
Diet:
Most are specialized insect and invertebrate eaters, but earthworms and slugs can be substituted. Other foods which might be acceptable include crayfish, shrimp, fish chow, shrimp, aphids, flies, and fruit flies.
Anurans
Housing:
The object is to provide a suitable environment for each particular life stage. For aquatic forms, factors to consider are water quality, temperature, oxygenation, and toxins. Terrestrial forms need the proper temperature, high humidity, adequate sunlight (for vitamin D), and most important, avoid overcrowding.
Diet:
This group eats a highly varied diet but the more common foods include insects, crickets, etc. Live food is necessary as a frog will not strike non-moving food. Force feeding is possible.
Chemical restraint:
This is not usually necessary for routine handling or examination. However, it is sometimes used in research. Agents are readily absorbed across the skin. The more common are:
- Tricaine menthanesulfonate (MS-222) 0.1 -.5%
- Methoxyflurane 3.0%
- Ethanol 10.0%
- Etorphine 0.25 mg/animal
- Ether
In general, two methods are followed
Embryo - finger bowls or shallow dishes Larvae - continuous water flow size dependent on species Juveniles - place to emerge from water static water can be used Adults - aquatic or terrestrial depending on the species need hibernation quarters adequate temperature adequate oxygen levels light adjustments place to submerge in water minimize agitation of animals
Gases and anesthetic agents in solution readily absorbed across the skin. Can be administered by sitting the animal in moist atmosphere or by wrapping animal in anesthetic-soaked cloth.
Some agents used are:
Ether - to effect
11.6.1.1 Red Leg Disease: (very common in frogs).
The most reported causative organism is Aeromonas hydrophilia. Clinical signs are a red flesh on the ventral thigh and abdomen, anorexia, unresponsiveness, slumped posture. However, entire groups may be found dead with no clinical signs. Gross lesions are hemorrhages in skeletal muscle and intestinal tract, ulcerations in the skin, subcutaneous edema, and ascites. Microscopically, there is focal necrosis of many organs. The recommended treatment is oral tetracyclines at a dose of 3 mg/30 g of body weight once a day for 1 week. Stress is thought to be the inducer of the disease, should be avoided.
11.6.1.2 Mycobacterial infections:
- Mycobacterium ranae and M. xenopi
11.6.1.3 Salmonellosis:
- S. reading, S. anatum, S. wetteureden, S. newport, and
- S. enteriditis serovar enteriditis.
11.6.1.4 Aeromonas liquifaciens infection:
Clinical signs - see ulceration and necrosis of rostrum, destruction of mucus gland and edema.
11.6.1.5 Edwardsiella tarda infection:
Common in African clawed frogs. Clinical signs - see gas-filled subdermal lymph spaces mostly in the rear legs.
11.6.2.1 Lucke's Herpes Virus (LHV):
- The causative agent of Lucke's renal adenocarcinoma. Occurs naturally in Rana pipiens with strain differentiation between northern and southern strains. Clinical signs are abdominal enlargement, edema, and slow wasting away. Grossly, there is a nodular appearance to the kidney. Histologically, the tumor has the typical appearance of an adenocarcinoma. No treatment is advocated, euthanatize.
11.6.2.2 Other Viral Diseases Found in Frogs:
- a. Amphibian Polyhedral Cytoplasmic Deoxyribovirus - (Frog virus -3)
- b. Lymphosarcoma virus of Xenopus
11.6.3.1 Saprolegnia parasitica
Causes deep ulceration of the skin, subcutis, muscle down to the bone. Dip infected frogs in 0.5% copper sulfate solution for a few minutes for five to seven days.
11.6.3.2 Basidiobdus ranarum:
11.6.3.3 Fonsecaea pedrosoi:
Causes Chromomycosis
Papular or ulcerative skin lesions develop with the destruction of underlying soft tissue and bone. Treat with tincture of iodine for seven to ten days.
This is an important criterion to find suppliers whose animals are reliable. Many species are available either from the other research investigators or only on a seasonal basis. Investigators should know seasonal characteristics of animals, resources of suppliers and reliability, whether supplier is a collector or obtains, animals from a primary supplier.
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