Questions regarding proper food, housing, lighting, temperature, etc. are constantly encountered not only on USENET's rec.pets.herp discussion group but also in other herpetocultural fora as well. Hopefully, this sheet will be able to clarify the African Clawed Frog's basic requirements so that owners will finally be able to feel confident their charges are receiving the best possible care.

Background

The African Clawed Frog exemplifies the notion that nature is loathe to mess with a successful adaptation. Well-preserved fossils of Xenopi have been found from the Cretaceous, and the laevis is nowhere endangered even today. On the contrary, human commerce has served to establish viable colonies of these anurans in a number of areas well outside their home range, such as southern California and Arizona. For the ostensible purpose of stopping their uncontrolled spread, legislation prohibiting their possession is in effect in these and numerous other regions. Thus, local ordinances should be consulted before a decision is made to accommodate Xenopi, and they should never be released into the wild anywhere or under any circumstances.

Xenopi are grouped in Family Pipidae, all of whose members are wholly aquatic and tongueless. In addition, all Pipids embody a number of other exceptional characteristics: a wedge-shaped body which is dorsoventrally flattened, small, upward-gazing eyes, no visible eardrums, unique vocalizing apparatus requiring no inflatable sacs, no teeth, very slippery integument, etc. Xenopus laevis is perhaps the best known of the 14 species in Genus Xenopus. All are native only to sub-Saharan Africa, where they are commonly known as Platannas. The term "Xenopus" is Latin for "peculiar foot," an apt description of the enormous webbed, five-toed, three-clawed rear feet typical of the group. "Laevis" means "smooth." Other Pipids include the so-called Surinam Toad (Genus Pipa) of Central and South America, perhaps one of the world's strangest looking anurans, as well as the diminutive West African Hymenochirus and Pseudohymenochirus.

To obtain a feeling for Xenopus husbandry, one must understand how they live in the wild. The Clawed Frog is preeminently a creature of stagnant pools and backwaters arising on a substrate of deep mud. Its highly-developed lungs enable it to obtain practically all necessary oxygen at the surface; indeed, without constant access to air it will quickly succumb. Thus, Xenopi patrol a markedly turbid fluid environment often choked with rotting organic matter. Their incredibly sensitive fingertips, four on each hand, and sophisticated lateral line systems allow them to locate living prey easily, even when it is concealed in mud and detritus. Given these inhospitable conditions, however, they have also evolved the ability to locate by smell and efficiently consume nonliving food items--a rare adaptation in anurans and one which often gives the Xenopus a significant advantage when inadvertently transplanted to other parts of the globe.

Because the Clawed Frog's niche precludes holding physical territory as more terrestrial counterparts do, this anuran customarily utilizes survival strategies which minimize competition with adult conspecifics. For example, females tend to quietly reconnoiter areas above the water's surface for prospective meals, while males often prefer actively searching for food across the bottom.

When the Clawed Frog's shallow haunts dry out, as they frequently do during long hot summers, it burrows up to one foot into the mud to aestivate, carefully arranging the tunnel so an air hole remains open. Xenopi can spend up to ten months in this inactive state. Captive Clawed Frogs can live 15 years, but typical life spans for wild and feral Xenopi, including those which aestivate, have not been ascertained.

While Clawed Frogs are not known to be toxic to any animal, they possess chemical defenses which give protection against both predators and diseases. The mildly fishy smell they exude repels many vertebrate predators, especially those found outside of the Xenopus' native range. In addition, they generate organic compounds called magainins which have powerful antibiotic, antifungal, antiparasitic, and antiviral actions. Ongoing research on magainins and other substances produced by Clawed Frogs has already given rise to some useful pharmaceuticals, with many more in the offing.

The Xenopus laevis was the first vertebrate to be successfully cloned and has traveled aboard the Space Shuttle on several occasions.

General Husbandry of Juvenile & Adult Clawed Frogs

The African Clawed Frog's ideal captive environment is one which mimics as closely as possible the natural conditions under which it is normally found. The following should be employed as basic guidelines:

Housing

These are strictly aquatic anurans. At least 1 gallon of water per animal, with the depth no more than 12 inches and no less than six. Do not use distilled water. Bottles of tap water should stand open for at least 1 day before being poured into the tank to outgas chlorine and related chemicals. Alternatively, 2 tiny (1 mm cube) crystals of sodium thiosulfate can be added to each gallon bottle at least 1 day prior to use.

African Clawed frogs are specifically adapted for stagnant water conditions. Although aesthetically pleasing to the keeper mechanical and/or electrical filtration invariably produces adverse long-term effects on the frogs. Constant water movement no matter how slight is sensed through the highly developed lateral-line system and results in severe stress. The effect is insidious and can be compared to what would happen to a human if (s)he were compelled to live where sandblasters and jackhammers were in use 24 hours a day.

99 % of the water should be changed by bailing, siphon, and/or spigots every 3-4 days, or whenever it becomes extremely cloudy. When in doubt about changing the water, try to err on the side of cleanliness, though extreme fastidiousness is unnecessary. At every water change use a towel to remove any algae and accumulated exudate which form on the tank walls, but do not use any type of algae-inhibiting or water-purifying chemicals other than the minuscule amount of sodium thiosulfate mentioned above.

Metal ions are toxic to Xenopi, lowering their resistance to infection. Make absolutely certain there is no metal of any kind in or on the tank or upon which water can splash and drip back into the tank, e.g. from a screen or light fixture. Never clean the tank with soaps or caustics or allow such compounds to come in contact with the water. Do not use pest-strips or insecticides in the vicinity of the tank.

The Clawed Frog is quite comfortable in ascetic surroundings, provided they are suitably spacious. Do not use a substrate of small stones, as these can be accidentally ingested. Avoid living plants, as the frogs uproot them quickly. A few sterilized medium-to-large rocks are sufficient to break up the physical monotony of a plain tank.

Adult Xenopi may be gently handled, although they're notoriously slippery. They must never be netted, however, because their thin fingers may be inadvertently entangled and amputated by even the finest mesh. Since they desiccate easily they must never be kept in a dry situation for more than a few minutes.

Lighting & Temperature

Avoid extremes. In particular, do not expose the tank to any direct sunlight, very bright artificial light, or temperatures above 90 degrees or below 40 degrees F. The frogs are most comfortable with indirect lighting during regular daylight hours and a temperature range of from 60 to 80 degrees F., i.e. customary indoor temperature. As a rule of thumb, if you're comfortable in the environment where the tank is located, Xenopi will be too. Clawed frogs have no special ultraviolet lighting requirements.

Food

Xenopi should be fed once a day with as much food as they will consume in 15 minutes. Avoid overfeeding; it only clouds the water. Content African Frogs will often take food from their keeper's fingers. They'll nibble the keeper too, but their toothless mouths can't do any damage. In the wild, Clawed Frogs are happy to dine on living, dead, and dying arthropods, bits of organic garbage, and loose material from putrefying corpses of miscellaneous vertebrates. For captive specimens, Reptomin (tm) sticks are excellent basic fare as are many other heavily proteinaceous foods compounded primarily for aquatic turtles.

There are several biological supply houses (e.g. Three Rivers Amphibian, Carolina Biological, etc.) which offer balanced food formulated specifically for this anuran. Pieces of lean raw beef, insects and larvae, cat and dog food, shrimp, worms, etc. may be offered. Supplementation with calcium or vitamins is unnecessary if professionally balanced formula foods are used as a dietary staple.

Tadpoles

The broad, shallow aquatic expanses which are home to the Xenopus assure minimal contact between healthy frog larvae and adults. But in captive situations the two must be kept completely separate; even freshly metamorphosed Xenopi will quickly make a meal of sibling tads if given the chance.

Clawed frog tadpoles have catfish-like barbels and swim in a head-down position. They have somewhat different requirements than their metamorphosed conspecifics. In particular, they are exclusively filter-feeders with no rasping mouthparts. Thus, unless food circulates freely in their water as micron-sized particles it cannot be utilized. To assure the proper degree of fluid circulation around each tad, their tails vibrate continuously in a manner reminiscent of a gray flame burning beneath the water.

No matter how large or small the tank there should be no less than 1 pint of water per tadpole. Powdered egg is an ideal food, but goldfish flakes ground extremely fine with mortar and pestle may be used as an alternative. Each tad should receive only enough powder per day to lightly cover a 14-point capital letter O. Overfeeding tads poses a real danger to the animals, as their gills cannot process needed oxygen when the water is clogged with particulate food. 98% of tadpole water must be changed once a day, even if it appears to be perfectly clear. Clawed Frog tads are extremely delicate and should not be touched or netted. Their beating hearts and coiled silvery intestines are clearly visible through transparent skin. Xenopi often produce a high percentage of genetically defective offspring.

Mating

Xenopi are sexually mature at 10 months to 1 year. At that time sexing is easy. Males vocalize frequently during evening hours, have a smooth rump, are 1/2 the size of females, relatively skinny, and develop dark mating pads on the undersides of their hands and forearms. Females are chubby, almost entirely silent, and possess a cloacal extension; they range between 3 and 6 inches snout-to-vent. Mating via inguinal amplexus can take place at any time but is more common during the spring; up to four matings per year have been reported for compatible couples.

Many interesting and provocative techniques have been attempted to encourage mating, but the results remain controversial. One factor is clear, however: the frogs must be given substantially more room than usual. For 2 males and 2 females, 5 to 50 gallons of water at a depth of 8 to 9 inches is adequate. Water should be kept as clean as possible, and its temperature should be around 70 degrees F. Mating often takes place late at night when the frogs detect no other activity, so it is challenging to observe. Sticky eggs are cast loose singly, with hundreds extruded during a 3 to 4 hour period. Within obviously narrow limits, the speed of metamorphosis is directly proportional to the water temperature. The average interval from egg to froglet is about 6 to 8 weeks.

Metamorphosis is a critical event, since the entire circulatory, digestive, and nervous systems are reorganized in a short space of time. The keeper must be particularly concerned about the radical change in eating habits: while Clawed Frog tadpoles must filter-feed, the short gut of newly transformed juveniles (and subsequent adults) can only accommodate visible solid food. To insure only appropriate fare is offered, the following should be carefully observed. Massive morphological changes will be noted soon after the front limbs appear, and the tail's energetic vibrations will slow and finally stop. During this period, feeding with powdered food should continue as usual. However, when the tail clearly begins to degenerate the frog is deriving nourishment from it alone, and feeding is not necessary. In this very brief interim, lasting on the average of 4-5 days, when the animal is balanced on a developmental edge between tadpole and frog, no external nourishment can be absorbed. Soon, the tail shrinks to nothing but a small stump. At this point adult food should be offered. The newly metamorphosed frog's first regular meal should be particularly appetizing: a few small slivers of lean, raw beef are good. The period between formation of the front legs and first acceptance of solid food is around 10 days.

Xenopus froglets are fragile creatures small enough to fit on an average-sized postage stamp; tads are considerably longer. Their rear legs are so transparent the femurs can be seen clearly. Over the next few months the frog's natural coloration will appear, and their legs will become opaque. Simple vocalizations from males may be heard as soon as months after metamorphosis.

Final Notes

While the Clawed Frog may be commonly encountered in both laboratories and the pet trade, it is not a boring animal. A strikingly "social" and intelligent anuran, its lifestyle still holds many mysteries for those who have not lost the capacity to wonder at nature. For example, no one yet knows how many calls Xenopi utilize or the characteristics and purposes of such vocalizations.

A partial bibliography is appended to this sheet. While much information on the Xenopus is squirreled away in obscure academic literature, those with the time, energy, and fortitude to peruse it will encounter many fascinating intellectual treats. A long-time confirmed fan of the Xenopus laevis, the author has tried his best to do justice to basic Clawed Frog husbandry in a condensed format. To accomplish this he has drawn liberally from personal, testimonial, popular, and scientific sources. Still, if errors large or small have crept in, they are his responsibility alone and much regretted. Special thanks are due to Andy Broome, Tuomas Koivu, and Nathan Tenny for their valuable insights, observations, and scholarship.

Relevant additions, anecdotes, comments, corrections. and/or queries may be forwarded to me at the E-mail address below.

Happy herping!

SELECTED BIBLIOGRAPHY

Alper, Joseph. "Frog Factory" _Science 85_ May 1985 pp. 70-74 Anonymous. Frog care literature 1983 (Massapequa, NY: Three Rivers Amphibian, Inc.)

Behler, John L. & King, F. Wayne. _The Audubon Society Field Guide to North American Reptiles and Amphibians_ (New York: Alfred A. Knopf) 1979 pp. 423-424

Breen, John F. _Encyclopedia of Reptiles and Amphibians_ (Neptune City, NJ: TFH Publications) 1974 pp. 442-451

Frank, Norman. "Xenopus The African Clawed Frog" _Reptile & Amphibian Magazine_ Sept./Oct. 1990 pp. 34,36,60

Grenard, Steve. _Medical Herpetology_ (Pottsville, PA: NG Publishing) 1994 pp. 3-13

Halliday, Tim R. & Adler, Kraig eds. _The Encyclopedia of Reptiles and Amphibians_ (New York: Facts On File) 1986 pp. 43-44, 52

Mattison, Chris. _Frogs & Toads of the World_ (New York: Facts On File) 1987 pp. 64-65,152-153

Rose, Walter. _The Reptiles and Amphibians of Southern Africa_ (Cape Town: Maskew Miller) 1950 pp. 23-34

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