Abstract
4-Nonylphenol (NP) is a compound that causes endocrine disruption and affects sperm quality of mammals and fish. However, the effects of NP on the sperm and fertilization rate of amphibians remain unknown. This study investigates the in vivoand in vitro effects of NP on the sperm dynamic parameters and fertilization rate ofBufo raddei during the period of amplexus and fertilization, and proposes the induction of these effects. In in vivo assay, male B. raddei were exposed to 3 concentrations of NP (50, 200, or 400 µg/l) or alcohol (0.04‰, control) for 1-3 days. The results suggested that effects on NP on the sperm dynamic parameters, sperm integrity and fertilization rate were not significant (p>0.05). In in vitro assay, the sperm of B. raddei was directly exposed to NP. Based on the results, NP significantly affected the sperm dynamic parameters and integrity (p<0.05). Meanwhile, the sperm reactive oxygen species (ROS) level in the sperm increased significantly (p<0.05), and a negative correlation was recorded between sperm motility and its corresponding ROS level (R=−0.90). Besides, fertilization rate was significantly reduced compared with that of control (p<0.01). The sperm membrane was impaired as well. However, a risk that NP can disrupt the reproduction behavior of B. raddei exists, and the ROS induced by NP and NP itself would be associated with the reduction of fertilization. Key words: 4-Nonylphenol, Bufo raddei, sperm, morphology, fertilization.
Highlights
Previous studies have shown that habitat degradations such as water pollution might play an important role in the decline of amphibians (Houlahan et al, 2000). 4-Nonylphenol (NP) was one of the predominant organic pollutants in the Lanzhou Region of Yellow River (Northwest, China), and its concentration fluctuate from 0.065 to 83 μg/l at different sites (Wang et al, 2006)
This study demonstrates that NP (≤400 μg/l) exposure for 3 days would not significantly affect sperm motility, VSL, VAP, and its viability in the gonads of B. raddei (p>0.05)
If only the short period during amplexus and fertilization is considered, this study suggests that the key period in which NP can affect the sperm is the period of fertilization
Summary
Previous studies have shown that habitat degradations such as water pollution might play an important role in the decline of amphibians (Houlahan et al, 2000). 4-Nonylphenol (NP) was one of the predominant organic pollutants in the Lanzhou Region of Yellow River (Northwest, China), and its concentration fluctuate from 0.065 to 83 μg/l at different sites (Wang et al, 2006). 4-Nonylphenol (NP) was one of the predominant organic pollutants in the Lanzhou Region of Yellow River (Northwest, China), and its concentration fluctuate from 0.065 to 83 μg/l at different sites (Wang et al, 2006). Whether NP in aquatic environment in Lanzhou Region would affect the reproduction of amphibian like that of the native common. Sperm morphology and fertilization rate could serve as valid indexes to access the effects of pollutants on toad reproduction, and the information would be useful to access the decline of amphibian. NP is estrogenic to aquatic organisms (Servos, 1999), and studies concerning amphibians have mainly focused on its estrogenic effects. Whether or not the estrogen receptors are present on the sperms of amphibians or other aquatic organisms is still unclear
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