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(181) Hormonal and Reproductive Effects of the Endocrine Modulating Bisacylhydrazine Insecticides on a Meiobenthic Copepod.
Block, David*,1, Monroe, Emily1, Chandler, George1, 1 University of South Carolina, Columbia, SC, USA
ABSTRACT- One of the newest classes of Insect Growth Regulating (IGR) compounds are the bisacylhydrazine insecticides which affect target pest species by mimicking the insect molting hormone, 20-hydroxyecdysone (20HE) - an essential endocrine signaling molecule for insect development and reproduction. Due to their selectivity for lepidopteran pests, the bisacylhydrazines are assumed to possess low toxicity to non-target organisms, however, limited research has been conducted evaluating adverse effects to aquatic crustacean species despite the high degree of homology between their respective endocrine systems. Subsequently, a 96-well microplate life-cycle screening bioassay was conducted utilizing the meiobenthic copepod Amphiascus tenuiremis to evaluate potential endocrine modulating effects of tebufenozide. Initially, 48 Stage-I copepodites were exposed in solutions containing 0, 50, 500, and 2000 g/L tebufenozide and monitored daily for development of secondary sexual characteristics and time, in days, to reproductive adult. Following adult emergence, individual males and females within each treatment were mated, with 20HE, vitellin, reproductive success and offspring measured for each pair. Control organisms exhibited a male:female sex ratio of 57:43 compared to ratios of 43:57, 44:56, and 44:56 for the 50, 500, 2000 g/L treatments, respectively. In addition, significant developmental delays were observed with copepodites requiring 10.1 ± 1.1 days (500 g/L) and 9.8 ± 1.0 days (2000 g/L) to reach adult maturity compared to 8.9 ± 1.1 days in control organisms. Tebufenozide caused no significant mating or reproductive effects, however, offspring production was reduced by up to 28 percent.
Key words: Crustacean, Endocrine, Reproduction, Life-Cycle
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