Histological, histochemical and energy disorders caused by R-limonene on Aedes aegypti L. larvae (Diptera: Culicidae)

The study evaluated the effects of R-limonene, in sublethal concentration, on the histology, histochemistry, biochemistry, and carbohydrates and proteins levels in the third instar Aedes aegypti larvae. The R-limonene (LC50 of 27 ppm) and control groups were analyzed 12 and 24 h after the beginning of treatments. The midgut of the control larvae was composed of cylindrical and elongated cells with a spherical and central nucleus and regenerative cells with a pyramidal shape. After 12 h of treatment, columnar cells, protuberances, and cytoplasmic vacuolization were found. However, 24 h after treatment, complete disorganization of the epithelium was observed. There was a positive reaction in all treatments for the presence of glycogen. However, the midgut of larvae treated with R-limonene showed higher levels. For the total protein, positive marking occurred in all groups evaluated, with higher levels in treatments and the lowest in control 12 h. The levels of total protein and glycogen increased in the treated larvae compared to the 12 h control. Besides, a reduction in total sugar levels was observed in the treated larvae compared to controls 12 and 24 h, being more evident in the last one. Therefore, these results demonstrate that R-Limonene caused pathological changes in the epithelium of the A. aegypti midgut at histophysiological and biochemical levels.