The effects of pesticide and salinity on early life stages of the green tree frog (<i>Hyla cinerea</i>)

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Wilder, Anneke E
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Increased salinity in freshwater habitats can result from anthropogenic factors such as climate change and sea level rise, use of road salts, over-irrigation and groundwater depletion. This emerging threat can affect freshwater species in both coastal and inland environments. Pesticides have also been found in freshwater environments around the globe, and can be harmful to many different aquatic organisms. Amphibians are highly sensitive to changes in their surroundings, making them good indicators of environmental quality, especially in freshwater habitats. This study examined the effects of increased salinity and a common insecticide, carbaryl, on early life history stages of the green tree frog (<i>Hyla cinerea</i>). To test effects of salinity on sperm activity, we subjected <i>H. cinerea</i> sperm to levels of salinity ranging from freshwater to moderately brackish and analyzed activity using computer assisted sperm analysis (CASA). Effects of carbaryl on sperm activity were measured in a similar fashion, using concentrations ranging from zero to a dose that is beyond the expected field concentration. We also examined female oviposition site selection in response to salinity and the presence of carbaryl in artificial pools. Mean sperm motility and velocity were both found to decrease as salinity concentration increased, butcarbaryl had no significant effect on sperm activity. Females tended to avoid ovipositing in pools with increased salinity. Although no significant difference was observed in oviposition between pools with and without carbaryl, pools received no oviposition when freshly dosed with carbaryl. These findings suggest that increased salinity may negatively affect reproductive success in <i>H. cinerea</i>, but that females may be able to avoid these effects through depositing eggs in freshwater sites. Selective oviposition may increase the ability of amphibian populations to persist in degraded habitats.
pesticide, amphibian, oviposition, salinity