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(Millbrook, NY) Insect repellents containing picaridin can be lethal to salamanders. So reports in a new study published today in Biology Letters That investigated how to exposure to two common insect repellents influenced the survival of aquatic salamander and mosquito larvae.
Insect repellents are a defense against mosquito bites and mosquito-borne diseases like dengue, chikungunya, Zika, and West Nile viruses. Salamanders provide natural mosquito control. During their aquatic juvenile phase, they are drilling on mosquito larvae, keeping populations of these nuisance insects in check.
Emma Rosi, a freshwater ecologist at the Cary Institute of Ecosystem Studies and co-author on the paper explains, "Use of insect Chemicals in repellents in aquatic ecosystems through sewage and effluents in water and wastewater are two of the most important examples of water pollution in the world (19659002 The most popular repellents
The research team tested the effects of two of the most widely used insect repellents – DEET (Repel 100 Insect Repellent) and Picaridin ( Sawyer Premium Insect Repellent) – on larval salamanders and mosquitoes. In a lab, they exposed mosquito larvae and just-hatched spotted salamander larvae to three environmentally relevant concentrations of these chemicals,
Rosi notes, "The concentrations in our experiments are conservative; unadulterated commercial formulations, not concentrations of pure active compounds. "
Mosquito larvae were not impacted by any of the treatments and matured unhindered. After a few days of exposure to picaridin, salamanders in all of the treatment groups. By day 25, 45-65% of picaridin-exposed salamander larvae died.
Co-author Barbara Han, a Cary Institute PhD, explains, "Our findings demonstrate that larval salamanders Relevant concentrations of repellent containing the active ingredient picaridin. "
Adding, "The expediency of salamander mortality is disconcerting." When studying the effects of a chemical on an amphibian, we usually look for a result of abnormalities. 19659002] How toxic is toxic?
LC50 tests are used to define a chemical's environmental toxicity. These standard tests, based on a single life stage of a single species, measure how long it takes for a test of a test population to increase its chemical exposure.
Co-author Alexander Reisinger, an Assistant Professor at the University of Florida, Gainesville
says, "We're seeing heavy salamander mortality with picaridin, but not until after the fourth day of exposure." By the LC50 measure, picaridin would be The 'safe', but clearly, this is not the case. "
Results may underestimate the problem [19659002] Lethal in a controlled setting, picaridin may cause greater mortality in a natural context, where organisms are exposed to numerous stressors. Rosi notes, "Animals do not exist in isolation." In nature, competition, predation, resource limitation, and social interactions make it difficult for an organization to tolerate the stress of exposure to a harmful substance, even in small amounts. 19659002] Timing – of both repellent and amphibian reproduction – is also key. Many amphibians breed in a single seasonal pulse, putting all their eggs in one basket, so to speak. Mosquitoes have an extended breeding season, and reproduce multiple times.
Lead author Rafael Almeida, a postdoctoral researcher at Cornell University, conducted the research as a PhD student at the Cary Institute. He explains, "The amount of repellents entering waterways peaks seasonally." If amphibians are exposed during a sensitive life stage, then they would continue to reproduce. It suggests a negative feedback loop. "
Additional study
Future work is needed to explore the relationship among mosquito repellents, amphibians, and other ecological factors, and to better badess the severity of repellents' impact in the wild. 19659002] Almeida concludes, "The effects of repellents containing DEET and picaridin need to be studied to determine the extent to which these chemicals may be disrupted aquatic ecosystems and potentially increase mosquito-borne disease risk worldwide."
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