Comparison of whole-body and hemolymph protein composition through development in the German cockroach, Blattella germanica.

Protein composition was studied across the various life stages in a multi-insecticide-resistant field strain and an insecticide-susceptible laboratory strain of Blattella germanica. Whole-body and hemolymph samples were collected and analyzed to understand the variation of protein expression through development. Developmental categories included large nymphal instars, small nymphal instars, adult males, virgin adult females and gravid adult females. To ensure age homogeneity among nymphs, each sample was composed of a cohort hatched from a single ootheca. Each cohort was raised until late in the instar for which it was processed. Based on the assumption that nymphal weight is strongly correlating to its instar stage, average weights were determined to verify sample uniformity. Insects from the lower and upper end of the weight spectrum were separated from those that were to be processed and were allowed to molt until adulthood. If the insects on both ends of the weight spectrum were at the same stage at the point of sampling, the entire sample was assumed to be homogenous. Collected protein samples were run on SDS-PAGE gels and yielded a variety of data. Nymphal instars, gravid females and virgin females all prominently expressed hexamerin storage proteins. Nymphal instars were remarkably similar in general protein expression. Gravid females also showed high expression of proteins associated with ootheca production and maintenance. By understanding the composition of proteins for Blattella germanica, we can better understand insecticide susceptibility and potentially develop novel insecticides that target Blattella germanica at specific life stages.