African Clawed Frog (Xenopus laevis)
Possessing claws and lacking a tongue, this unique amphibian is often sold in aquarium stores as an “underwater frog.” It is completely aquatic, being flattened in shape and unable to “sit up” like other frogs can. A very hardy and entertaining pet, the clawed frog becomes quite responsive to its owner, feeding from the hand and living in excess of twenty years. The clawed frog is nearly always in motion, driven, in part, by a near insatiable appetite (be careful, they become obese quite easily in captivity). The body is lined with sensory glands in the manner of the lateral line of fish, and, in contrast to other frogs, they also locate food by scent.
African clawed frogs were used to detect pregnancy in the Hogben Test. Hormones in the urine of pregnant women cause the frogs to lay eggs within a matter of hours after being injected with the woman's urine. Millions were imported into the United States for this purpose in the 1950s.
African clawed frogs thrive in a wide range of water temperatures and conditions but do best at temperatures suited for tropical fish in general (77ºF, 25ºC). This adaptability has led to the establishment of feral populations in many countries, including the United States. They rapidly decimate local fish and amphibian populations and thus should never be released into foreign habitats. They have even been found, apparently healthy and content, in underground cisterns in English castles, where water temperatures do not rise above 59ºF (15ºC) and in pools sprayed by saltwater along the coast of England!
That being said, these frogs do require clean water, or they will be killed by ammonia poisoning. Due to their large appetites, the tank must be well filtered or given frequent water changes.
African clawed frogs will eat nearly any form of animal based foods and should be given a varied diet. The basis of the diet can consist of the commercially available food pellets formulated specifically for them (it is one of the few frog species to accept nonliving food). To this should be added crickets and other insects, earthworms, fish, and black worms. They can coexist with nonaggressive fish that are too large to be swallowed (they may try anyway, but they seem to learn their lesson quickly!). Allowing the water level to drop and then adding water 10 degrees cooler than that in which they are normally housed will often stimulate reproduction. The eggs are fertilized externally, and the parents should be removed because they favor nothing so much as frog eggs for dinner. The tadpoles are filter feeders. Commercially prepared diets are available through biological supply houses, or the tadpoles can be reared on cool nettle tea. These frogs are amazingly good at finding even the tiniest spaces to escape from, so be particularly careful and tape up the areas around external filter tubes.
Two related frog species that are sometimes offered for sale are the dwarf African frog,
African clawed frogs are often sold as auxiliary animals to be placed in fish tanks and expected to thrive on fish flakes as a diet. While they can be kept with certain fish, they have specific requirements that must be met if they are to thrive. Be aware that females reach 5½ inches in length and can consume fish nearly that long.
The Surinam toad is a live-food specialist that prefers fish and earthworms. The eggs are incubated on the males' back, covered with skin that breaks down when the newly developed frogs are ready to emerge (the entire tadpole stage is passed within the skin of the male's back). Breeding for these and dwarf frogs is similar to that described for African clawed frogs. Surinam toads require a deep tank if they are to reproduce, as the egg laying process involves a circular swimming motion that positions the male below the falling eggs.