IACUC Learning Module - Xenopus laevis | Previous Next |
AMPHIBIANS are intermediates between fish and reptiles and have moist, glandular skin with toes devoid of claws. If scales are present, they are hidden in the skin. Development follows the well known "frog-spawn-tadpole-froglet" transition in which eggs are laid in water and pass through an aquatic, larval stage before they metamorphose into adults.
The three orders that belong to the class Amphibia include:
Anurans do not drink, they absorb water through a highly permeable, specialized area of skin in the pelvic region. Anuran skin needs to be kept moist for carbon dioxide and water exchange. The skin is largely responsible for respiration via its outer surface. Adult anuran lungs have only enough lung vesicles as are necessary to carry out gaseous exchange. Because frogs lack ribs, air must be pumped into the lungs by the suprahyoid muscles (in the floor of the mouth). Larval stages use gills to extract oxygen from water via three branches of capillaries in the gills. These capillaries degenerate after metamorphosis.
In anurans, the tongue is important for securing prey. It is usually muscular, flexible, projectible and can be sticky with mucus. (Xenopus are an exception with the tongue completely attached to the floor of the mouth instead of being attached at the front of the mouth and folded back.)General Information on Xenopus laevis
Pipidae is a primitive family of the order, Anura that consists of 3 genera in Africa and one genera in South America. Pipidae have tongues completely attached to the floor of the mouth (not projectible). All species are entirely aquatic and are easily maintained in aquaria with lids.
Xenopus laevis, the African Clawed Frog, is the largest and most widely distributed of its genus. They are originally from Africa south of the Sahara. They have character traits in common with frogs and toads, and are commonly referred to either way. The natural habitat in Africa for these frogs is murky ponds. Xenopus laevis have been known to migrate overland from one pond to another during Africa's rainy season.
The African Clawed Frog is stout bodied and big footed like other members of the family Pipidae. The common name comes from the presence of small, black curved claws on the inner three toes of the hind feet. Xenopus laevis are pale to dark grey or green dorsally with an off white underside. Their average size is 8-15 cm. Their skin is smooth and VERY slippery due to a protective mucous covering. The hindlimbs are large and well adapted to a totally aquatic environment. The much smaller forelegs are used to push food into the mouth. Normal behavior is for these frogs to spend most of their time lying motionless below the surface of the water.
Interesting Link - Natural History Of The Upland Clawed Frog
Xenopus tadpoles are quite large compared to other species, and may need to be separated and re-accommodated several times before they metamorphose. Xenopus tadpoles have two long tentacles or antennae on their heads to differentiate them from Hymenochirus c. (dwarf clawed frog). Slightly smaller species, Xenopus mulleri, Xenopus borealis and others are often available and require identical care to Xenopus laevis.
A significant population of escaped Xenopus exists in Arizona and California. These animals should NEVER be released into local ponds or rivers because they are extremely hardy and will outcompete the native aquatic wildlife. For this reason, the purchase of Xenopus laevis by California and Arizona residents is restricted by permit.
Xenopus cannot leave the University of Arizona research labs unless they are transported/sold to another licensed facility. They may NOT be taken home as pets! Any research project using animals covered under State or Federal regulations may not proceed unless the investigator obtains valid permits for collection, purchasing, transporting and holding of these animals.
The investigator is responsible for obtaining and maintaining valid permits. If you have questions, please call the IACUC Protocol Coordinator at 621-9305.Sources
Adult or tadpoles of Xenopus laevis can be purchased as "lab bred" or "lab reared" animals from Nasco or Xenopus I. All animal orders must be placed through UAC and depend upon having an approved protocol, appropriate housing and animals being available from the vendor.Thermoregulation
Amphibians are ectotherms and cannot raise their body temperature by producing metabolic heat. They must rely on external heat sources. All species have a preferred body temperature range (PBT) at which they optimally function. Tadpoles prefer slightly warmer temperatures.
Enclosures should provide temperature gradients (via heat tape, heating pads, heat lamps, etc.) rather than constant uniform temperatures. This allows the animals to move within the gradient and behaviorally regulate their body temperatures as needed. Uniform constant temperature causes excessive adrenal secretions and may compromise the immune system. As anurans approach their thermal critical maximum (roughly 40o C), they begin to pant to try to reduce body temperature.
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Updated
01/02/2008 gea
