Grainger Lab X. tropicalis Adult Husbandry Protocol
Updated June 1, 2001
Basic Care for Adults
All post-metamorphic animals are considered adults and receive essentially the same care, with certain significant differences to accommodate very young froglets. Animals are kept in 120 liter black, fiberglass tanks (see Grainger/Keller Frog Facilities document) filled with approximately 100 liters of well water. Animals are fed and cleaned three times weekly and are checked every day.
Three critical parameters that we have found to have a significant effect on growth rate, egg quality, and general health are: diet, density, and temperature.
Feeding should be done 3 to 4 hours before the tanks are to be cleaned. This interval gives the animals a chance to digest their food. Cleaning too soon after feeding can result in the animals regurgitating a large amount of what they have eaten.
We feed all of our frogs post-metamorph size #5 NASCO pellets (NASCO: 1-920-568-5565) in amounts relative to the number and size of frogs in a given tank. As a general rule of thumb, feed an amount of food that can be almost completely consumed by the frogs in 2 to 3 hours. This will obviously require some experimentation and will vary from tank to tank. We use the post-metamorph size for all frogs because it is easily ingested by even the smallest froglets and the small pellets go down the drain more readily.
We have experimented with several alternative foods and feeding schedules to determine their effects on growth rate. Our greatest success has come by combining pellets with live California blackworms and feeding 6 times a week. Using this regimen we have obtained frogs that are sexually mature at 31/2 months of age. The worms are purchased in bulk (5lbs. or more) from Aquatic Foods (Fresno, CA 1-559-291-0623) or they can usually be obtained in smaller quantities from a local pet store. Although we are aware of the arguments against using live food, we find no apparent increase in disease or ill health in these frogs while the increase in their rate of growth is substantial.
We have also tried freeze-dried bloodworms (Aquatic Ecosystems, 800-422-3939) and Repto-Min pellets (Tetra Inc., 800-526-0650), but the frogs don't seem to like them and won't eat them unless they are starved of other foods.
Crowded tanks clearly have an adverse effect on the growth rate of young froglets, and density experiments are ongoing. As a general rule of thumb, the less crowded a tank is the faster the animals will grow. Since our facility is already crowded, only animals that are important to ongoing experiments are placed in low-density tanks. For mature animals, we try to maintain a density between 1 and 2 frogs per liter.
Froglets and adults are kept in 24-25°C water. The air temperature in the rooms is set 1 to 2°C above the desired water temperature to offset the effects of evaporative cooling. This temperature appears to be optimal for good egg quality in females, particularly for applications such as transgenesis.
Exposure of adult animals to temperatures below 22°C for several months may cause an increased susceptibility to disease and should be avoided, although short-term exposure (i.e. taking animals up to the lab for egg collection) appears harmless.
All frog tanks are cleaned 3 times per week (usually Tu, Th, Sat). Tanks are drained, leaving an inch or two of water in the bottom, and uneaten food is swept down the drain. The tank walls and floor are gently scrubbed and rinsed down and then the tank is refilled. The tank scrubbers are treated with ethanol and rinsed between each tank. We use drain covers with 1/4" holes in adult tanks and 1/8" holes in froglet tanks. When draining tanks containing young (< 2 month) froglets, we place a metal colander upside-down over the drain to prevent froglets from being injured by the strong suction.
We are not currently using salt or phosphate to supplement the well water in our frog facility, although we will supplement tanks containing sick animals. Healthy animals seem to be fine in unbuffered well water (pH about 5.8). The recipe for salt/phosphate buffering solution follows. For sick or injured animals, the final concentration of salt in each tank should be 1 g/L. The water is buffered with phosphate to pH 6.5-7.2 (~1.89mM).
For 2 (100 liter) tanks:
210g rock salt (we use the type made for water softeners)
56.4g dibasic sodium phosphate
in 3600 ml distilled, deionized water
Add 1800 ml of the above solution to each tank.