Xenopus I, Inc.

Care And Feeding of Xenopus laevis

Kelly Evans has been the CFO of
Xenopus I for thirty years.

Thirty years among the Xenopus lead me to believe, we have made life with this frog way to complicated. I would like to share with you what we at Xenopus I Inc. feel will keep in your lab or Animal resource department a healthy research model. I think this is applicable to the most sophisticated systems or a single rubber tub.

There has been an enormous interest in tadpoles the last few years, so I shall start with them. We first inject both the male and female adult xenopus with 1000 units of Human Chorionic Gonadotrophin, HCG. This is one injection on the same day and the same time, usually in the morning. The opaque tanks are 10 inches high, and are half filled with 70-72 degrees well water since their normal breeding time is spring and at night. We cover their tanks to keep them dark and prevent escape. The following morning we remove the breeders from the tank leaving the many fertilized eggs. Air stones are put in the tanks with gentle bubbles.

Tadpole water must not only be de-chlorinated but chloramines have to be removed. We have well water, which is ideal, but if you must deal with the city water systems, use a product called Amquel + just follow the directions on the label. It works immediately. Letting your water sit for 24 hours does not work, it does not remove the chloramines. If you use distilled or de-ionized water you must add salts back or your tadpoles will die.

We do not de-jelly our eggs, as you would do in your labs, as we are only concerned with an abundant collection of tadpoles. Leaving the embryos undisturbed we wait for them to become free swimming, usually four to five days, before they have their first feeding. To introduce food into the tank before is useless since they can’t feed and the eggs will become covered with fungus and die.

After experimenting, over the years with many tadpole foods we have found, Nelsons Scientific Mash, has given us greater growth and less death than any other feed. The food is in powder form and must be blended. We recommend the following way to prepare the food for a twenty-gallon tank holding ten gallons of de-chlorinated water. Mix 1 tablespoon of powder in a household size blender with 4 cups de-chlorinated water on high for 1 to 2 minutes. Add enough to the tadpoles to make a light cloud in the water. When the water is clear they are hungry again. Do not over feed you can always add more, but its hard to adjust if you feed to much. Feed several times a day for maximum growth. You must blend the food before each use and keep leftovers in a cold room or refrigerator. We believe all artificial food should be kept in the freezer or cold room and thrown out after 3 months. We clean our tadpoles every day, scrapping the bottom of the tank with a squeegee and sucking it out with a simple siphon. We then replace at least one half the water with clean, trying to keep the temperature the same. If you are going to err it is better to be colder, adding warmer water can cause hemorrhage, especially in albinos. Continue this regiment till metamorphoses, which should be in 6 to 8 weeks.

We have a static system for both our tadpoles and frogs preventing cross contamination if a problem should arise.

Most labs are housing adult xenopus. There are 3 main factors to keep a healthy frog. They are water quality, diet and tank cleaning. Our well water comes in at 15 degrees centigrade and never warms past 17 degrees during the day. This temperature keeps the females oocyte firm and perfect for microinjection. The warmer you water is the softer the oocyte becomes making it mushy and hard to inject. Letting the water set for 24 hours does not work, the chlorine may go but the chloramines, which are more dangerous, to the frog stay, again use AmQuel© +.

There are several formulated feeds for frogs most are similar and most are good. We use Zeigler #2 Crumble for juveniles and 1.5 MM Finfish starter for adults. It’s how much and how often to feed that seems to be the quandary. Xenopus are going to eat their fill within a few minutes. We recommend putting a small amount into the tank to start. If they eat it all in 2 or 3 minutes they are probably still hungry. If there is food left you fed them too much. The problem with too much is the food will have to stay in the tank 6 to 8 hours before cleaning. Xenopus will regurgitate the food if not left undisturbed for that amount of time. We feed our frogs at the end of each workday and clean them first thing in the morning. We do a complete water change. Females should be fed at least 3 times a week or they will start to reabsorb their oocytes for nourishment. Males do not eat as much. The smaller your tank, as in rat cage, the more often it should be cleaned. Though ideal to clean every day as we do, many labs find this not possible. Be sure they are always cleaned the day after feeding. Food should be in a cold room, and not kept over 3 months. Older food sometimes grows a mold you can’t see or smell and could kill your frog.

After we remove all the frogs from a tank it must be cleaned before a new group goes in. We never use detergent on our tanks or other objects that would come in contact with them. We scrub them, bleach them, and finally spray them with 70% ethyl alcohol. When new frogs go in the tanks we are careful not to over crowd, especially females. They tend to decrease their production of acolytes, possibly as a birth control measure.

I am not discussing disease because I feel the above suggestions should provide a healthy and productive research model.

I have presented very simplistic methods of caring for this frog. They work.

Kelly Evans

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Xenopus I, Inc.

Kelly Evans has been the CFO of Xenopus I for thirty years.

Kelly Evans has been the CFO of
Xenopus I for thirty years.