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

[摘要] English: The African Clawed Frog, Xenopus laevis has been used extensively in medical andscientific research. For almost a full century this pipid frog has been exported around theworld by thousands.The present study is an attempt to investigate how to manage this important resource ofX. laevis that will allow this species to remain a commercially viable resource. Theapproach in this study was as follows:1. Market research concerning the use of X laevis to various end-users, conductedlocally and overseas, indicated that the oocytes of X. laevis is used to study themolecular aspects of development In South Africa X laevis is in high demand asbait for angling, but lacks a regular organised supply. The use of X laevis in teachingat South African universities has declined over the last decade. The sale of X. laevisas pets is limited and is mostly confined to the United States.2. The tadpoles of X laevis collected throughout the Free State province and togetherwith specimens from the Southern African Frog Atlas Project collection werestaged to determi ne their development and measured. A size-stage graph wasobtained that can be used to compare the development of X laevis from otherrainfall regions or even captive-raised tadpoles to their natural development in theFree State.3. Mark and recapture studies were performed on wild X. laevis populations in andaround Bloemfontein to investigate their population dynamics Factors thatdetermine the size of a population are: size of the habitat and permanency of thewater habitat (semi-permanent or permanent). Regulation of population size bypredatory birds becomes significant in semi-permanent habitats when water level islow. It can be concluded that uncontrolled harvesting from natural X laevis sourcescan easily cause a marked reduction in population size.Experiments on tadpoles and sub-adults were conducted to determine the optimumprocedures for rearing X laevis in captivity The volume of water available totadpoles beyond a density of two tadpoles per litre has an inhibitory effect ondevelopment. Factors that further effect tadpole growth rate are: type of enclosure,temperature of environment and tadpole diet. The best growth for sub-adult frogswas obtained by feeding with either Sinking Frog Food (a commercial brand of frogpellets), liver or pet's mince.5. X. laevis were maintained in captivity for Il months and parasite infections andabundance monitored. The cestode, Cephalochlamys namaquensis was the onlyparasite to experience a reduction in infection levels, while the only parasite toexperience 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 affordablemethod to control parasite infections.7. It was concluded that to exploit X laevis as a commercial resource on a sustainablebasis, efforts should be made to culture the frog following optimum breeding andrearing procedures. The collection method used for frogs from natural sources has toallow for the continued productivity of these populations

[发布机构] University of the Free State