Population-specific incidence of testicular ovarian follicles in Xenopus laevis from South Africa: a potential issue in endocrine testing.
The African clawed frog (Xenopus laevis) has been identified as an appropriate sentinel for testing endocrine activity of existing chemicals in North America and Europe. Some reports suggest that the herbicide, atrazine (CAS Number [1912-24-9]) causes ovarian follicles to form in the testes of this frog. X. laevis collected from North East (NE) sites in South Africa had testicular ovarian follicles, irrespective of exposure to atrazine, while frogs from Southwest Western (SW) Cape region sites had none. Phylogenetic analysis of mitochondrial and nuclear genes indicates that frogs from the SW Cape are evolutionarily divergent from those from NE South Africa and the rest of sub-Saharan Africa. These findings provide a possible explanation for why conflicting results have been reported concerning the impact of atrazine on amphibian sexual differentiation and highlight the importance of understanding taxonomic status of the experimental animal. Even in common laboratory animals, there is a need for their correct taxonomic characterization before their use in tests for endocrine disruption.
Du Preez
Louis H
LH
School of Environmental Sciences and Development, North-West University, Potchefstroom 2531, South Africa. Louis.DuPreez@nwu.ac.za
Kunene
Nisile
N
Hanner
Robert
R
Giesy
John P
JP
Solomon
Keith R
KR
Hosmer
Alan
A
Van Der Kraak
Glen J
GJ
D000818:Animals; D001280:Atrazine / Q000633:toxicity; D005260:Female; D006540:Herbicides / Q000633:toxicity; D015994:Incidence; D008297:Male; D006080:Ovarian Follicle / Q000473:pathology*; D010802:Phylogeny; D013019:South Africa; D013045:Species Specificity; D013737:Testis / Q000187:drug effects / Q000473:pathology*; D014982:Xenopus laevis / Q000033:anatomy & histology* / Q000145:classification* / Q000235:genetics
D006540:Herbicides; D001280:Atrazine