Poor geotaxis correlated with hematoporphyrin-induced peroxidation of brain lipids as a predictor of medfly longevity reduction

Abstract

Under illumination conditions, porphyrins generate cytotoxic radicals in cells. Our study evaluated the effects of haematoporphyrin IX (HP IX) in a laboratory population of male Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) during exposure to a low fluence rate (39 lE m 2 s 1) of light. We found that exposing flies to HP IX for at least 5 days was sufficient to cause irreversible damage that led to anticipated death, as also provoked by chronic exposure to the same concentration. To identify early indicators of the accelerated senescence, we analysed both in vitro and in vivo parameters. The thiobarbituric acid reactive substances content in the heads of treated flies revealed a significant increase in lipid hydroperoxides at day 10, whereas this occurred several days later in controls. In addition, a significant decrease in glycogen content was observed at 15 days of age, 5 days before the reduction observed in the control group. This decrease has been associated with a decline in locomotor activity. Differences in the distribution of flies in the rearing flasks were observed, reflecting an impairment of the motility and climbing capacity of HP IX-treated flies. This finding was also corroborated by a geotactic response assay (a rapid iterative negative geotaxis or RING assay). The results presented here demonstrate that low-lethal oxidative stress can anticipate the senescence of flies, which can be predicted using a simple and fast behavioural test, such as the RING assay.