Widely used mos­quito re­pel­lent proves lethal to lar­val sala­man­ders: new study

Tehran Times - - SCIENCE -

In­sect re­pel­lents con­tain­ing pi­caridin can be lethal to sala­man­ders. So re­ports a new study pub­lished to­day in Bi­ol­ogy Let­ters that in­ves­ti­gated how 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 virus. Sala­man­ders pro­vide nat­u­ral mos­quito con­trol.

Dur­ing their aquatic ju­ve­nile phase, they for­age on mos­quito lar­vae, keep­ing pop­u­la­tions of these nui­sance in­sects in check.

Emma Rosi, a fresh­wa­ter ecol­o­gist at Cary In­sti­tute of Ecosys­tem Stud­ies and a co-au­thor on the pa­per ex­plains, “Use of in­sect re­pel­lents is on the rise glob­ally.

Chem­i­cals in re­pel­lents en­ter aquatic ecosys­tems through sewage ef­flu­ent and are now com­mon in sur­face wa­ters. We set out to un­der­stand the im­pact of re­pel­lent pol­lu­tion on both lar­val mosquitoes and the lar­val sala­man­ders that prey on them.”

The pa­per is the first to sug­gest that en­vi­ron­men­tally re­al­is­tic con­cen­tra­tions of pi­caridin-con­tain­ing re­pel­lents in sur­face wa­ters may in­crease the abun­dance of adult mosquitoes due to a de­crease in pre­da­tion pres­sure on mosquitoes at the lar­val stages.

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, as well as a con­trol treat­ment.

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