Exposure To Endocrine Disrupting Pesticides And Impacts On Parasitic Infection In The Monarch Butterfly, Danaus plexippus

Victoria M. Pocius, Bridget E. Hilbig


I investigated sublethal effects of commercial herbicides on monarch butterfly development and success. Macek et alOphryocystis elektroscirrha. My study currently examines monarchs exposed to atrazine (ATZ), or the known endocrine disruptor estradiol (ESD) from early instars through emerging adults. Laboratory reared caterpillars (Rose Franklin, State College PA) were maintained on freshly collected Asclepias spp. leaves which were stringently cleaned to reduce proliferation of OE until eclosion. Initially 1st-3rd instars were maintained individually (n=50 per treatment) and exposed either to spring water (CTRL), 50 ppb ATZ or 50 ppb ESD daily. Ages were evenly distributed across treatment groups. Larval mortality was 14-26% in treated larvae compared to 24% in controls, but well below the 30-50% evident in the previous study. Duration of larval period was ~ 30 days for all treatment groups, 5 days longer than for those measured in 2009. All emerged adults were sampled for the parasite Ophryocystis elektroscirrha (OE) prior to tagging and release. OE infection rate was dramatically reduced to 9% compared to 90% in last year’s study, with appreciably lower severity of parasite load. Surviving adults exhibited sex ratio skewed toward females in control and estradiol treatments, but surprising skewed toward males in atrazine treatments. While standard wing dimensions were comparable among treatments, animals were slightly more robust in biomass among treated monarchs (3.4% to 8.4%). We continue to examine data for ways in which incidence of OE infection is related to other measures of monarch success.


Monarch Butterfly, Pesticides, Ophryocystis elektroscirrha

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