Phloxine B affects glycogen metabolism in larval stages of Ceratitis capitata (Diptera: Tephritidae)

Xanthene dyes have been tested as photoinsecticides on different dipteran species. Phloxine B ingested by Ceratitis capitata larvae showed low toxicity under dark conditions and acute light-dependent toxicity when the insects were exposed to light during the dispersion stage before pupariation. In this study we show that sub-lethal concentrations of Phloxine B generated subtle changes in weight gain and in the accurately regulated jumping behavior of metamorphosing larvae. These changes are correlated with a strong accumulation of glycogen in fat body, intestine and muscles, as well as with an inhibition of the glycogen phosphorylase activity. These results suggest that some of the non-phototoxic effects of Phloxine B might be caused by an alteration of the glycogen catabolism, which can eventually affect the viability of the flies.