Differential susceptibility of a few members of the nasuta-albomicans complex of Drosophila to paraquat-induced lethality and oxidative stress.

The evolution of karyotypically stabilized short-lived (SL) and long-lived (LL) cytoraces in the laboratory have been established and validated through our previous lifespan studies. In the present investigation, we examined the possible reason(s) for the differential longevity among selected members of SL and LL cytoraces, employing the well known paraquat (PQ) resistance bioassay. Exposure of these races to varying concentrations of PQ revealed relatively higher resistance among LL cytoraces than SL cytoraces, as evident by the lower incidence of mortality. Biochemical analysis for endogenous markers of oxidative stress revealed that LL-2 cytorace exhibited lower reactive oxygen species (ROS) and lipid peroxidation (LPO) levels, higher activity levels of superoxide dismutase (SOD), and coupled with higher levels of reduced glutathione (GSH) compared with the levels found in SL-2 cytorace. These findings suggest that the higher susceptibility of SL cytoraces to PQ challenge may be, at least in part, related to the higher endogenous levels of oxidative stress markers. Although the precise mechanisms responsible for the longer longevity among LL cytoraces of the nasuta-albomicans complex of Drosophila merits further investigation, our data suggest that the relatively longer lifespan may be related to the status of endogenous markers that renders them more resistant towards oxidative-stress-mediated lethality, as evident in the PQ assay.