The sustainable utilisation of the African clawed frog, Xenopus laevis (Daudin)

English: The African Clawed Frog, Xenopus laevis has been used extensively in medical and scientific research. For almost a full century this pipid frog has been exported around the world by thousands. The present study is an attempt to investigate how to manage this important resource of X. laevis that will allow this species to remain a commercially viable resource. The approach in this study was as follows: 1. Market research concerning the use of X laevis to various end-users, conducted locally and overseas, indicated that the oocytes of X. laevis is used to study the molecular aspects of development In South Africa X laevis is in high demand as bait for angling, but lacks a regular organised supply. The use of X laevis in teaching at South African universities has declined over the last decade. The sale of X. laevis as pets is limited and is mostly confined to the United States. 2. The tadpoles of X laevis collected throughout the Free State province and together with specimens from the Southern African Frog Atlas Project collection were staged to determi ne their development and measured. A size-stage graph was obtained that can be used to compare the development of X laevis from other rainfall regions or even captive-raised tadpoles to their natural development in the Free State. 3. Mark and recapture studies were performed on wild X. laevis populations in and around Bloemfontein to investigate their population dynamics Factors that determine the size of a population are: size of the habitat and permanency of the water habitat (semi-permanent or permanent). Regulation of population size by predatory birds becomes significant in semi-permanent habitats when water level is low. It can be concluded that uncontrolled harvesting from natural X laevis sources can easily cause a marked reduction in population size. Experiments on tadpoles and sub-adults were conducted to determine the optimum procedures for rearing X laevis in captivity The volume of water available to tadpoles beyond a density of two tadpoles per litre has an inhibitory effect on development. Factors that further effect tadpole growth rate are: type of enclosure, temperature of environment and tadpole diet. The best growth for sub-adult frogs was obtained by feeding with either Sinking Frog Food (a commercial brand of frog pellets), liver or pet's mince. 5. X. laevis were maintained in captivity for Il months and parasite infections and abundance monitored. The cestode, Cephalochlamys namaquensis was the only parasite to experience a reduction in infection levels, while the only parasite to experience an increase in both prevalence and mean intensity was the mite, Xenopacarus africamts. 6. Various commercial anthelmintics were tested for the elimination of parasites of X. laevis. The delivery technique proved to be as important as the choice of drug itself. The use of drugs to eliminate parasites in X laevis is an effective and affordable method to control parasite infections. 7. It was concluded that to exploit X laevis as a commercial resource on a sustainable basis, efforts should be made to culture the frog following optimum breeding and rearing procedures. The collection method used for frogs from natural sources has to allow for the continued productivity of these populations