Abstract
Sub-chronic toxicity of environmentally relevant atrazine concentrations on exposed tadpoles and adult male African clawed frogs (Xenopus laevis) was evaluated in a quality controlled laboratory for 90 days. The aim of this study was to determine the effects of atrazine on the survival, growth and gonad development of African clawed frogs. After exposure of tadpoles to atrazine concentrations of 0 (control), 0.01, 200 and 500 μg L−1 in water, mortality rates of 0, 0, 3.3 and 70% respectively were recorded for the 90 day exposure period. Morphometry showed significantly reduced tadpole mass in the 500 μg L−1 atrazine exposed tadpoles (p < 0.05). Light microscopy on testes of adult frogs exposed to the same atrazine concentrations using hematoxylin and eosin (H&E) and Van Gieson staining techniques revealed gonadal atrophy, disruption of germ cell lines, seminiferous tubule structure damage and formation of extensive connective tissue around seminiferous tubules of frogs exposed to 200 μg L−1 and 500 μg L−1 atrazine concentrations. Ultrastructural analysis of the cellular organelles using transmission electron microscopy (TEM) revealed significant amounts of damaged mitochondria in testosterone producing Leydig cells as well as Sertoli cells. Biochemical analysis revealed reduced serum testosterone levels in adult frogs at all exposure levels as well as presence of six atrazine metabolites in frog serum and liver. The results indicate that atrazine concentrations greater than the calculated LC50 of 343.7 μg L−1 cause significant mortality in tadpoles, while concentrations ≥200 μg L−1 adversely affect reproductive health of adult frogs and development of tadpoles sub-chronically exposed to atrazine.
| Original language | English |
|---|---|
| Pages (from-to) | 1-11 |
| Number of pages | 11 |
| Journal | Aquatic Toxicology |
| Volume | 199 |
| Early online date | 23 Mar 2018 |
| DOIs | |
| Publication status | Published - Jun 2018 |
Funding
This work was made possible by the collaboration between the University of the Witwatersrand School of Anatomical Sciences and School of Chemistry, as well as Vrije Universiteit Department of Environment and Health. The authors acknowledge the financial contributions from the South African Department of Water and Sanitation Bursary programme which paid for the independent TEM analytical services provided by Jan van Weering (Vrije Universiteit VU/VUmc EM facility), including production of high resolution images, identification of organelles and quantitative analysis of cell organelles. The authors also wish to thank the University of the Witwatersrand Microscopy and Microanalysis unit where preliminary qualitative TEM analysis was conducted by Mr. Rimayi. The authors also wish to thank Professor Amadi Ihunwo for the valuable assistance with the frog dissection, Rein Dekker, Lynette Sena, Jaclyn Asouzu, Hasiena Ali and Alison Mortimer for their significant contributions towards this work, the University of the Witwatersrand CAS for assistance with the frog husbandry and the University of the Witwatersrand Animal Ethics Screening Committee for helpful comments on the experimental design. The authors acknowledge the National Research Foundation for the travelling grant (grant numbers KICI5091018149662 and 98818 ) that allowed Mr. Rimayi to spend time in The Netherlands. Appendix A
| Funders | Funder number |
|---|---|
| National Research Foundation | 98818, KICI5091018149662 |
| National Research Foundation of Korea |
Keywords
- Atrazine
- Atrazine metabolites
- Leydig cells
- Seminiferous tubule
- Sertoli cells
- Testosterone
- Xenopus laevis
