Raising Tadpoles through Adulthood
Stage 1 to Stage 43
After fertilization, embryos are kept in 150 mm Petri dishes, in approx. 75 100 ml 1/9 X Modified Ringers solution. Gentamicin is added at a dose of 100 micrograms/ml to retard bacterial growth. We keep a gentamicin 1000x stock at 4ºC. Keep plenty of fluid in the dish as evaporation can be a problem.
The number of embryos in a dish is critical to survival. We often have an overwhelming desire to save thousands of embryos even if we just need a few. However, in our experience, this is a mistake as it often leads to severe embryo death due to overcrowding. Typically we keep 100-200 embryos per 150 mm petri dish. In 90 mm petri dishes, we keep no more than 100. Looking into the dish, the smaller trop embryos look almost non-existent, but over-crowding will kill embryos. Simply keeping the embryos sparse and the use of prophylactic antibiotics will make the culturing of embryos simple and routine.
A light treatment of 2-3% cysteine will partially remove the jelly coat from the embryos and cause them to dissociate slightly. Usually we cysteine in a 250 ml erlenmeyer flask with vigorous swirlng for 30s-1min or until the embryos separate and are no longer in a big clump. Much of the jelly coat will remain, but the partial de-jelly will make sorting and cileaning the embryos much easier. If you do wish to completely remove the jelly coat, then the embryos must be raised on agarose coated dishes. Otherwise, embryos without any jelly coat often fail to gastrulate normally. Once gastrulation is completed they can be raised on standard glass/plastic Petri dishes.
Note: If a high degree of non-viability is expected (from poor fertilization, gamma irradiation or other mutagenesis), maintaining the jelly coat can be an advantage. The healthy embryos develop well protected from the dying ones. The jelly coat also helps keep the toxic residue of dying embryos from harming the viable embryos. When the embryos do hatch, they can be easily scooped up and transferred to another dish while the dead embryos remain in a clump. This can be a big timesaver if early stage embryos are not needed, and there is an otherwise high amount of mortality.
It is important to remove the dead and dying embryos from the dish to prevent the growth of bacteria, especially if the embryos have been treated with cysteine. This is done one to two times a day until the larvae are moved from the dish to a tadpole rearing tank. The embryos are kept at 25-28ºC, depending on the desired rate of development, and hatch at Stage 24 to 26. Embryos can also be raised at 22ºC, but we have noticed that at this lower temperature a protozoan often grows to high concentration in three - four days, and the embryos do poorly. We recommend changing the 1/9xMR+Gent daily as well. Usually when the embryos are at low numbers in a dish, the water looks clear, but they do seem to do better if you change the solution daily regardless.
At Stage 43, typically after 60 hours at 27-28ºC, the larvae are free swimming. They are placed in a tadpole transfer dish containing approximately 200 cc 1/20x Modified Ringers solution without gentamicin. They are brought to our tadpole nursery at this point.
Stage 41 to Stage 63
In general, raising embryos from fertilization to Stage 41 (Day 2 to 3 at 27ºC) is straightforward. The key is to keep the embryos at low density perform daily media changes with gentamicin. We have been quite successful at these stages, provided dead and dying embryos are removed. However, the transition to free-swimming tadpoles has been much more problematic. The first two weeks are an extremely fragile time for tadpoles, and they require great attention. Sudden, even minor, changes in the quality of the water can lead to widespread death.
Currently, our greatest success in this critical period utilizes the AHAB system as a nursery. Once the tadpoles become free swimming (st. 41), they can be introduced into AHAB. At stages earlier than this, the tadpoles seem to do poorly. Additionally, an initial trial comparing sudden introduction into the AHAB environment (pouring the tads straight into a full tank) versus slowly introducing them to the water at this stage did not seem to make much difference (Grammer, TC unpublished observation). The tadpoles seem to really thrive.
Pour the 1/9X MR + gent containing the tadpoles into a plastic dish containing 1/20X MR for a total volume about 200 ml. This will help transition the tadpoles from the 1/9 X MR to the water in AHAB. The tadpoles are then simply poured into an empty, clean 2.75 liter tank and 10 cc of a solution of Sera Micron tadpole food (Pondside Herp Supply) is added to the tank. The Sera Micron tadpole food solution is made by suspending 1 tsp Sera Micron in 250 ml AHAB system water. Add just enough solution to color the water light green, and monitor the tank. One feeding should be sufficient for the first day. Overfeeding can be dangerous, and we find the tadpoles do fine with a small amount of food on the first day, until the tank fills up and the water begins circulating. Note: Dry, unsuspended Sera Micron added directly to the tank does not disperse as well.
Usually we split a clutch (tadpoles generated from a single mating [siblings]) into 2-3 2.75 liter tanks. That way if anything happens in one tank the others are still available and an entire clutch is not lost. We do get sudden and unexplained deaths in an entire tank when a neighboring tank with the same clutch of tadpoles is fine. So raising a single clutch in multiple tanks is certainly worthwhile especially during the first few weeks of life when the tadpoles are particularly fragile. Tadpoles are initially raised at 20-50 tadpoles per 2.75 liter tank.
In the AHAB system, the inlet is set to a drip rate of about 1 drop every 4-5 seconds. The tank will fill up slowly, allowing for a gradual transition from 1/20xMR to purely AHAB water. After the tank is full and begins to overflow, the slow drip provides a continuous exchange of water but without a high flow (tads grow up in ponds and not rivers!). The inflow hoses and valves must be frequently monitored, as we have found the drips are prone to stop at this low flow rate.
Another reason to keep the drip rate slow initially is small tads can be sucked out the back of the tank through the baffle if the drip rate is too high. Special baffles with mesh are available through AHAB to reduce the loss of tadpoles. We are currently testing these baffles.
The drip rate is gradually increased over time. By the time hindlimbs appear, the drip rate is quite rapid, about 1-2 per second. The drip rate needs to be monitored so it is fast enough to clear the water, but not so fast the tadpoles appear to be suffering ill effects, such as floating and loss of equilibrium. The drip rate is gradually increased as the tadpoles grow to keep the water clean and prevent decay of debris sitting in the tank. If the water seems murky and stagnant, or the surface is covered with bubbles, increase the drip rate gradually, until the water is clean. Increasing the drip incrementally prevents shocking the tadpoles.
We routinely stop the drip to the tadpole tanks for about 2 hours after feeding to allow them to eat the food, which would otherwise be removed by the water flow.
It is not necessary to clear the baffles on the tadpole tanks for about the first week of life. Except for these feeding intervals, the drips are continuously flowing. Over time, uneaten food and debris will accumulate on the bottom of the tank. We find that this is not detrimental to the tadpoles as long as the drips are kept flowing to provide a continuous exchange of water to maintain the consistency of the pH and ammonia levels in the tanks. In fact, the tadpoles are often observed hiding, with their heads completely covered under the muck. (Maura Lane, observation)
Overall, as a nursery, the AHAB system has been very successful. It has allowed us to raise very large numbers of tads with less labor than other methods. The main time investment is in keeping the baffles clear of debris daily, and constantly monitoring the tadpoles for changes in behavior which might signal a problem with water quality, lack of food, too much food, or a variety of other problems. Constant vigilance and immediate troubleshooting is required when a problem arises, as all the tadpoles in a tank can die very quickly under unfavorable conditions.
We routinely split clutches up into two or three tanks, rather than trying to raise them all in one tank. If there is a problem with one tank, and the tadpoles die, we still have one or two tanks left. This procedure has saved us from losing entire clutches countless times.
NOTE: Our AHAB system has bubblers to maximally oxygenate the water and circulate it within the sumps and biofilters. We believe these bubblers led to a high percentage of death in older, metamorphosing tadpoles. The tadpoles would become bloated with air, float at the surface of the water, and die shortly thereafter. The gas disease completely resolved after we turned the bubbler off. Shortly after this incident, we expanded the AHAB facility to include 4 more racks, for a total of 6 racks. This included 2 more sumps, which greatly increased the amount of water re-circulating in the system. As we began transferring new tadpoles to this larger system without bubblers, the tads suffered complete die-offs within 24 hours of transfer. At this point, we tried turning the bubblers back on. The young tadpoles began surviving immediately, and the older tadpoles did not seem to be experiencing the bloat. We surmised the number of bubblers in our initial set-up was too great for the amount of water. If you have a smaller AHAB system, consider using fewer bubblers than come with the system, and monitor your metamorphosing tadpoles for signs of gas problems.
We have tried repeatedly to raise young tadpoles in our homemade drip system by attempting to reproduce the AHAB conditions, with very poor results. Currently, we think our facility water lacks adequate salts/buffering for these young tads and continuously shocks them.
Depending on weather conditions and other factors beyond our control, the pH of the facility water can fluctuate from 5.5-9. However in the AHAB system, we are able to maintain the pH between 7- 8 by monitoring the reservoir and adding sodium bicarbonate as necessary.
We have also raised young tads in small static tanks in 1/20xMR without antibiotics. In this system, we did four or five 1/5 volume water exchanges with fresh 1/20xMR during the day, so there was an overall entire water change daily. This is an extremely laborious task if you are trying to raise hundreds to thousands of tadpoles. We did not try to make 1/20xMR in our reservoir tanks and then have this drip into our tanks with young tads. Perhaps this would be an adequate salt/buffer for these young tads and eliminate the great amount of labor to do manual water changes. Unfortunately, we were required to remove our reservoir system due to building codes.
Sera Micron (Pondside Herp Supply)
For the first two weeks of life in AHAB, the tadpoles are fed Sera Micron Solution (1 tsp. dry Sera Micron/ 250 ml. AHAB water). For the first day, 10 cc is added to the tank, the drip is carefully monitored. One feeding should be sufficient for the first day. Overfeeding can be dangerous, and we find the tadpoles do fine with a small amount of food on the first day, until the tank fills up and the water begins circulating. Note: Dry, unsuspended Sera Micron added directly to the tank does not disperse as well.
Feeding amount is increased to 30 ml. once or twice a day for the second and third day, as long as the tadpoles seem healthy and water conditions are good. Feeding frequency can be increased to 3 or 4 times a day (or more) if the water is cleared quickly. If the water flow stops and the water becomes fouled, we increase the drip rate, and don’t feed again until the water is cleared.
After the third day of life in AHAB, feeding amount is increased to 50 ml. one to two times per day. We do not begin to turn the drip off after feeding until the fourth day, as we find the very young tadpoleas are very susceptible to any water fouling which may result from lack of water flow.
We have tried other types of food including Nasco Tadpole Diet and ground rabbit chow. However in comparisons, we found that these two foods led to a much higher mortality and so the trials were stopped. We have since settled on Sera Micron (Trott, KA and Grammer TC unpublished observations).
Feeding frequency and amount will also need to be increased as the tadpoles grow in size and consume more food. Generally, we increase the amount to 6 T (Tablespoons) of the Sera Micron Solution twice a day or more often if necessary, by 3 weeks of age (for a 2.75 L tank). If you are keeping tadpoles in a 9 liter tank, start with 8 T, increasing to 10 T or more as necessary by 3 to 4 weeks of age. As you begin to remove metamorphosing froglets from the tank, you may need to begin decreasing the amount of Sera Micron you are adding.
At 14 days of age, we begin adding a mixture we call Sifted Tadpole Diet, in addition to Sera Micron. We had originally been feeding only Sera Micron up to metamorphosis. We began feeding the Sifted diet because many of our tadpoles were looking weak and lying on the bottom of the tank. The tads seemed to become stronger after starting this diet. They swam actively and no longer laid on the bottom. The supplemented diet introduces a higher protein content and solid food for metamorphosing tadpoles and young froglets. This alleviates the need to remove froglets from the tank and saves on housing space. As the tadpoles increase in size, the amount of powder can be increased.
At 14 days of age, we feed each 2.75 liter tank of tadpoles about 1/2 cc (1/8 teaspoon) Sifted Tadpole Diet twice a day for 5 days in addition to the Sera Micron solution. After 5 days of feeding, we increase the amount to 1 cc (1/4 teaspoon)/2.75 liter tank once or twice a day. Food consumption is monitored and the amount of feeding is adjusted as necessary to ensure we are not over- or underfeeding. Again, water flow is turned off for several hours after feeding. When the tadpoles reach stage 62-63 (essentially “frogs with tails”), we stop feeding Sera Micron, and feed the Sifted Tadpole Diet alone until stage 66 (complete metamorphosis).
To make the Sifted Tadpole Diet, sift Nasco Tadpole diet to separate the fine powder from the small granules. (Reserve the granules for later, as they can be useful to transition froglets to the larger size Nasco post-metamorphic pellets.) Next, grind up some fish flake food almost into powder, leaving some larger flakes in the mix. The fish flakes should be ground up enough to be about 60% fine powder, and 40% small flakes. This can easily be done with your fingers in a dish or cup. We have been using a tropical fish type flake (TetraMin Tropical Flakes, Tetra, Pet Express or Petco), which seems to work fine. Mix approximately 1 part fine Nasco powder with 1 part fish flake and mix well. Larger tadpoles eat the powdered portion of the mix, and small froglets eat the flakes. Feed only a very small amount of the diet at a time (1/16 tsp per 2.75 liter and 1/4 tsp per 9 liter) in the beginning, and do not feed more if the last feeding is uneaten. This amount may need to be adjusted, depending on the numbers of tadpoles in your tank. These amounts assume 15-20 tadpoles/2.75 liter tank.
As the tadpoles increase in size, the amount can be increased. By the time the tadpoles are ready to metamorphose, we are feeding 1/4 tsp. per 2.75 liter tank and 1/2 tsp. per 9 liter tank two to three times a day. This diet can be alternated with feedings of Sera Micron, if time permits. Otherwise, we have had success with feeding them both together, as long as care is taken not to overfeed.
Do repeat feedings only if the last feeding has been eaten. Uneaten food will remain on the bottom and foul the water. You can see the food build up on the bottom as a yellow layer, and often the surface of the water will have bubbles on it and look scummy. Sometimes the tadpoles are simply still in the tank, not swimming in search of food. In this case, we often change the tank altogether and reduce the feeding amount by half. This will eliminate the excess food, and also any other contaminants, which may be adversely affecting the tadpoles. A tank in which all the food has been eaten will have a clean bottom, clear water, and often the tadpoles will be actively skimming the bottom in search of food. These tadpoles need refeeding.
We are currently testing Sera Micron alone until metamorphosis, vs seraMicron + Nasco Tadpole diet, vs seraMicron + Sifted Tadpole diet. Preliminary results show Sera Micron alone results in lower weight at metamorphosis, as well as weaker froglets. The Sifted Diet (consisting of Nasco Tadpole diet and fish flakes) results in heavier, more vigorous froglets than the Nasco Tadpole diet alone.
We then tested seraMicron + Sifted Tadpole diet vs seraMicron + Fish Flake alone. We did this because the fish flakes cause less water fouling. We found negligible difference between the two regimens.
The drawback of using fish flake alone is higher cost. 5 pounds of Nasco Tadpole Diet costs $16.00, or $3.20/pound. Flake feeds we researched range from $4.40 to $9.50/pound. We feel using Nasco + Flakes or Nasco Tadpole Diet alone would depend on whether cost of feed or tank cleanliness is more important.
We also tested seraMicron + Finfish Starter diet (Zeigler). This diet is designed for fish, so we are not sure if the formulation is adequate for frog growth. It has a protein content of 55%, and a fat content of 15%. It comes in very small granule sizes(55-15, #1 and #2). We tested the #1 size on the tadpoles. We found the diet is not ideal for young tadpoles. They do not seem to ingest it as readily as powdered food. The excess food tends to settle on the bottom of the tank in a foul-smelling layer, which is unpleasant to clean. We also found white mold-like filaments forms on the surface of the water and edges of the tank.
We did find the Finfish Starter Diet #2 ideal to feed to new metamorphs, however. The small size is just the right size for them to eat, and they seem to find it highly palatable. We are planning to test it as a sole diet in post-metamorphic froglets to determine if the diet is adequate for growth and development.
We conducted a trial raising and feeding brine shrimp to the tadpoles and froglets. We were hoping to supplement their diet, causing faster growth and bigger tadpoles. We used BRINE SHRIMP DIRECT brand, Grade A (80% hatch rate) and shrimp in hatchers we ordered from Aquatic Ecosystems (see catalog). We raised brine shrimp for 48 hours, then harvested and rinsed the shrimp well to remove the salts. The shrimp were mixed in a squirt bottle with AHAB water and administered to the older (34 weeks) tadpole tanks. The results were disappointing. The tadpoles only seemed to eat the shrimp accidentally, and would immediately spit them out.
The shrimp raised for 48 hours were too small for the froglets to notice. So we raised batches of shrimp for 2 weeks, adding sera micron as a food source for the shrimp. After two weeks, the shrimp were large enough for the froglets to see and eat. They ate the shrimp vigorously, however there were several problems with this arrangement. We only have two hatchers, so the froglets can be fed shrimp at most only every week with the hatchers set-up on a rotating schedule. The amount of shrimp harvested from each hatcher is small. After about a week, the food in the hatcher began to smell unpleasantly. We concluded the amount of effort required to produce a small amount of shrimp for once a week feeding outweighed the advantages of supplementing the diet. Perhaps a system with more hatchers or a higher grade shrimp (which has a higher hatch percentage) might improve the situation.
We have been turning the water supply to the tanks off for 2 hours after any feeding during the day to prevent food from being swept out under the baffle. The water is turned back on to allow the debris and waste to be cleared from the tanks. The tadpoles and froglets seem to be thriving under this regimen. Concurrent with this change in flow, we began feeding a Sifted Tadpole Diet (see Sifted Tadpole Diet Section). We are not sure if one or both of these changes have been factors in improving the health of the tadpoles. We are planning to perform controlled studies to determine this.
NOTE: The AHAB system is equipped with valves to allow shutting off water to individual tanks, whole shelves, or entire racks at a time. Which valve you use depends on whether or not individual tanks on a particular shelf or rack need constant water supply. For instance, brand new tadpole tanks, which are just having AHAB water introduced should be allowed to fill, to prevent the small amount of MR in the tank from fouling.
Currently, the tadpole density is about 10 tadpoles per liter. We are conducting experiments to determine the best density for raising frogs to reach sexual maturity in the shortest time. We have observed that despite an initial density of anywhere from 20 to 150 tadpoles in a 2.75 liter tank, the tadpoles consistently seem to self-limit their numbers to a final density of 12 - 20 tadpoles/2.75 liter tank at about 3 weeks of age. We therefore initially put 25 or so in a 2.75 liter tank. Having several tanks of the same clutch ensures survival of some tadpoles if there is a disaster and an entire tank dies. Around two weeks of age, the largest 12 to 15 tadpoles in each tank are kept and the rest removed or transferred to more tanks. This lower density (3 to 5 tadpoles/liter) often results in faster growth and metamorphosis (M. Lane, unpublished results).
We are conducting ongoing experiments to determine the best density for raising frogs to reach sexual maturity in the shortest time. Preliminary results show tadpoles raised at a density of 5 per 3 liters(1.6 per liter) began to reach metamorphosis faster than those raised at a density of 15 per 3 liters(5/liter). Additionally, tadpoles raised at a density of 5/ liter in a 1 liter tank took longer to metamorph than either of the other two groups. This suggests that volume of water is as important to growth rate as density of tadpoles.
It is important to avoid sudden changes to the tadpole's environment. This includes rapid changes in pH, ammonia, temperature, and amount of debris in the tank. The temperature in the tadpole tanks is maintained between 27 and 28 degrees Celsius, and the pH around 77.5. We have found a sudden change in temperature or pH can be more detrimental to survival than a consistently low/high temperature or pH. Additionally, the tadpoles seem to do fine in water quite high in ammonia. In our experience, attempting to quickly lower ammonia levels with water changes or increased drip rates may result in tadpole death. Siphoning more than a quarter of the buildup of food and fecal debris from the tank bottom has also led to negative results. In general, be sure to perform any changes gradually.
The tadpoles we raise take four to eight weeks to reach metamorphosis. Metamorphosis is a delicate stage. The froglets can die by drowning or exhaustion as they try to reach and stay at the surface to breathe. The frogs eat less during metamorphosis, as their digestive system is undergoing significant changes. Ensuring the tadpoles are well fed prior to metamorphosis seems to result in healthier, more vigorous froglets, which begin to eat sooner and have a lower mortality rate.
Once a tadpole has completely metamorphosed (st. 66), we refer to it as a froglet. When froglets begin to appear in the tank, we begin to add HBH Frog and Tadpole Bites (HBH, purchased from Pondside Herp Supply) to the Sifted Tadpole Diet (see below). HBH is high in fat and an ideal size and consistency for froglets. We feed 3 to 5 pellets per froglet once or twice a day. This amount is gradually increased as the froglets grow. We generally increase the amount of food when we find the first feeding is consumed within 30 minutes.
Recently, we have not been transferring froglets out of the tadpole tank, and the froglets seem to do well. We believe this is due to the fact that the tadpoles are so well fed and healthy. So depending on the health of your metamorphs, the froglet transfer may or may not be necessary.
Squares of floating plastic mesh can also used in the juvenile tank. The froglets cling to these pads, which allow them to rest at the surface to breathe.
When all tadpoles have metamorphosed, the flow rate in the tank is turned up to a small steady stream to clear out uneaten solid food. Approximately one week after metamorphosis, the froglets are transferred to a 9 liter tank (Aquatic Habitats) to decrease their density. At lower densities, the froglets grow faster and at a more even rate (M. Lane, unpublished data). We have found keeping more than 10 12 froglets in a 9 liter tank may stunt growth of some juvenile frogs. With a lower density, the froglets seem to get bigger faster, and grow at a more even rate. In addition, froglets in overcrowded tanks are able to jump out of the tank more easily by climbing on the backs of their many siblings and launching themselves out.
The juveniles are generally kept in the 9 liter tanks through adulthood. Adults are kept at a density of 1-2 frogs per liter. Some are moved to our holding water system after 4 to 5 months of age, and seem to do fine with the switch. Others are moved to individual 1 liter tanks, alone or with a mate.
When froglets begin to appear in the tank, we begin to add HBH Frog and Tadpole Bites (purchased at Pondside Herp Supply) to the Sifted Powder. We find it to be highly palatable for the froglets, which begin to eat it almost immediately. It is a small moist pellet, which is easy for little froglets to eat. It is about three times higher in fat than Nasco diet, helping to grow fat, vigorous little froglets.
Previously, newly metamorphosed froglets would show minimal interest in feeding for weeks. However, with the HBH Frog Bites, froglets are feeding aggressively during/after metamorphosis. In fact, tadpoles at stage 61 will try to eat HBH and by stage 63 are even successful. Having a number of froglets in the tank seems to encourage eating behavior also.
Generally, we feed new froglets 3 5 pellets per froglet once or twice a day. This amount is gradually increased as the froglets grow. We generally increase the amount of food when the froglets are eating the first feeding within half an hour or so. By one month of age, a 2.75 liter tank of 5-7 froglets can eat 1/4 tsp HBH once or twice a day. A 9 liter tank of 12- 15 froglets can easily eat 1/2 tsp of HBH once or twice a day.
After four months of age, frogs seem to do fine on HBH as a permanent diet, where we want maximum growth rate. In cases where we don’t need maximum growth, the frogs are weaned off of HBH onto the less expensive Nasco Post metamorphic Frog Brittle (Frog Brittle for Post-metamorphic Xenopus, Catalog #: SB29028(LM)M) when they are four months old. Simply mixing the Nasco with the HBH for a few days seems to do the trick. Currently we are testing whether older juveniles fed Nasco Frog Brittle alone or Nasco/HBH brings frogs to sexual maturity the fastest. We don’t feed Nasco Postmetamorphic Frog Brittle prior to four months of age because it often seems too big for the froglets to eat. We feed about 1cc (1/4 teaspoon) Nasco/ 10-12 frogs in a 9 liter tank. We feed a second time if the first feeding is eaten within 30 minutes.
We have found the large scale feeding of worms is not economically feasible. In addition, the frogs may become “fixated” on the worms, and refuse to eat a prepared diet. We keep a small supply ( 1 lb) of California Blackworms to supplement the diet of skinny or otherwise unhealthy frogs/froglets two to three times weekly. (Aquatic Foods, email: firstname.lastname@example.org)
3133 N. Argyle, Fresno, CA 93727
(559) 291-0623 -Information
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Aquatic Foods has information on care of the worms. We feed about 1 worm per froglet. Often when the worms are first introduced into the tank, they entwine, making just a clump of worms. Shaking the ball of worms as you put them in the water helps separate them. This makes it more likely that each froglet will get one worm, instead of one froglet getting an entire ball of worms. Be sure to check for dead (grey colored) worms and rinse them before feeding. As the froglets get to be two months old, the feeding of worms is eliminated to prevent the chance of fixation on live food. After this point, worms are only fed to encourage eating in cases where an important frog is thin or not eating well.
After the juvenile frogs reach about 4 months of age, they are weaned from the HBH to Nasco Post metamorphic Frog Brittle (Frog Brittle for Post-metamorphic Xenopus, Catalog #: SB29028(LM)M). We simply mix the two diets for a few days, and the frogs seem to make the switch with little problem. Generally, we feed 1 cc (1/4 tsp.) Frog Brittle/ 10-12 frogs in a 9 liter tank, and feed again if the diet is eaten within 1/2 hour. Adults are fed 1/5 cc(~1/16 tsp.) frog brittle per frog every other day. As with the tadpole and juvenile frog tanks, we turn the water off for 2 hours after feeding to allow the frogs to eat.
We have been testing the Finfish 2mm size diet on our adult frogs. We like this diet because the frogs are unable to break up the pellets, resulting in a cleaner tank. They seem to like it much more than the Nasco diet. It is 40% protein and 10% fat, vs 44% protein and 6% fat for Nasco. The higher fat content may explain why the frogs find Finfish so palatable. The Finfish is designed for fish, so we are not sure if the formulation is adequate for frog growth.
Note: For adult frogs kept in individual 1 liter tanks, it is important to regulate the inflow on these tanks. Having a steady stream flow into the tank will sweep all the food to the baffle, which will block the outflow of water. Frogs can then easily reach the lid of the tank, and have gotten it open. We generally turn the water off for a few hours after feeding, and keep the front of the tanks propped up on the shelf. Switching to the Finfish diet has also helped to keep the tanks clean and prevent blockage because the frogs can’t break up these pellets, and generally eat them all.
From the age of 4 to 5 months on, the healthy adult frogs require very little care. We maintain a frog density of 1-2 frogs per liter. Our very important screening frogs are housed in the AHAB system and fed 1/16 tsp Finfish 2mm diet per frog every day. The tanks are changed about every 2 - 3 weeks, as they become dirty. The water flow keeps them fairly clean in the interim. Other adult frogs are housed in our holding water system, and are fed 1/8 tsp. Frog Brittle per frog twice a week. They seem to do fine on this regimen. The holding water tanks are cleaned every other day.
Recently, we noticed if the temperature of the water gets too high, the frogs become anorexic and produce poor quality eggs. We control the temperature in our AHAB system by controlling the ambient room temperature, and adjusting the incoming water temperature. The AHAB pumps and UV bulbs warm the water to temperatures higher than ambient, which requires daily monitoring. We keep our AHAB temperature at 28ºC, which the frogs seem to like. Temperatures above 31-32ºC cause the adult frogs to stop eating and become emaciated.
For information on treatment of sick frogs, please refer to the disease section.
Contributed by Maura Lane, K. Trott, Tim Grammer, and Mustafa Khokha
Many thanks to L. Zimmerman and N. Hirsch, and the Grainger web site for help with raising tads.