IACUC Learning Module - Xenopus aevis

IACUC Learning Module - Xenopus laevis

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Housing

Xenopus are easily housed in a pan with 4-5 inches of chlorine and chloramine free water. Standard UAC polycarbonate rat pans (48x27x20 cm) with a wire lid hold approximately 10 liters of water when filled to a depth of 4-5 inches. The maximum number of adult Xenopus that can be housed in 5-10 liters of water is four. It is preferable to house less than four animals per pan (particularly if all four are females, which tend to be much larger than adult males). Animals must be segregated by size to prevent cannibalism. They should be segregated by sex unless breeding is desired and is part of the protocol.

Water temperature

Xenopus should be in the range of 20-23^o C (68-75^o F), but breeding may decline at warmer temperatures, particularly in the summer. If the water temperature is suboptimal, frogs will not eat and their metabolism and immune systems will be depressed. Xenopus are sensitive to temperature changes within the room as well as the temperature changes of water. Water for cage changing must be kept constant within 1^o C (2^o F), since greater variations can induce shock or even death in frogs.

Water quality

An issue of great concern for aquatic anurans. Frogs have very permeable skin and are therefore very sensitive to toxic substances. Personnel changing the water or handling animals should always wear gloves. Traces of hand lotions, colognes and medicated ointments which remain on the hands of personnel may kill these frogs! Water quality can be affected by geographical location, water source, quantity, method of transport, type of food fed to the frogs, and the amount of waste released back into the water. Water that is over saturated with dissolved gases (fresh out of the tap) will cause bubbles under the skin and in the toe webs of frogs. Water pH above or below the range of 6.5-8.5 (very acidic or very alkaline) can cause sudden death of an entire colony.

The following water quality standards for fish should also be applied to anurans:

Alkalinity and hardness as CaCO₃	150-250 mg/liter
Ammonia	< 0.2 mg/liter
Nitrates	< 0.3 mg/liter
Dissolved gases/carbon dioxide	< 5 mg CO₂/liter
Chlorine/chloramine	< 3.8 mg/liter
Fluorides	< 1.5 mg/liter
Heavy metals (Zinc, Copper, Mercury, Lead)	0
Oxygen content: for warm water fish	>5 mg/liter for cold water fish > 8 mg/liter
pH	6.5-8.5
Polychlorinated biphenyl (PCB's) and plastic toxicant	0
Toxicant (from insecticides, etc.)	0

Pipes for aquatic systems should be made of black iron or high density polyethylene, polypropylene or nylon. Avoid galvanized or copper water lines! Zinc can be leached from galvanized pipes. Copper leaches from copper or brass pipes and can be toxic to gill breathers. Furthermore, municipal water departments may add copper sulfate to the water supply to control algal growth. Copper sulfate inhibits tadpole growth. It can be removed by adding versene (EDTA) at 50 mg/liter of water.

The University of Arizona is served by well water and NOT Central Arizona Project (CAP) water at this time. It is therefore not necessary to go to the expense of water filtration to remove chlorine and chloramines from University of Arizona tap water. University of Arizona's well water is within all recommended limits for fish or other aquatic species. However, it is necessary to let the tap water sit for at least 2-4 hours to allow dissolved gases and some chlorine to dissipate before the water is used. This also allows time for the water to adjust to the current room temperature to avoid temperature shock on the animals.

Water quality should be monitored periodically with local water quality experts.

Lighting and photoperiod

Important concerns for breeding Xenopus laevis. Lab facilities should keep Xenopus in a room with no windows or block all outdoor lighting cues. Lights should simulate outdoor sunlight with UV in order to maintain proper Vitamin D levels and correct calcium/phosphorous balance. This can be accomplished with fluorescent Vita Lights and "BL" black lights. The photoperiod should be set with automatic timers to 12 hours on:12 hours off.

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Updated 01/02/2008 gea