Análise morfológica e histoquímica do corpo gorduroso e dos túbulos de Malpighi de operárias adultas de Scaptotrigona postica (Latreille, 1807) (Hymenoptera, Apidae) tratadas com fipronil e ácido bórico

Abstract

Bees help to maintain the plant species in the ecological niche where they live. Some chemicals found in pesticides used in agriculture (fipronil), or thrown in the ambient with industrial waste (boric acid) are toxic to bees. The objective was to evaluate the toxic activity of these compounds at sublethal doses, as well as analyze the morphological (cytoplasmic and nuclear) of the fat body and Malpighian tubules. In the experimental groups, the compounds were added to the diet (Candi). The concentration of fipronil used in the experiment was 0.1 g/kg of candi and the concentration of boric acid was 0.75% (m/m). Statistical analysis for the experiment conducted with fipronil and boric acid profiles showed that the survival of bees that ingested the contaminated diet were significantly different to the profile of survival made by the control group (p <0.0001). Morphologically, in control group, changes found in Malpighian tubules of bees treated with boric acid and fipronil were subtle, showing apparent release of cellular material into the lumen, some pyknotic nuclei and, in some cases, brush border blocking the lumen organ, in some cells we observed morphological features of degeneration. Morphological changes are evident in the fat body of bees treated with fipronil and boric acid compared to control group. Among these changes, stand out intense activity of vacuolar coalescence, pyknotic nuclei and some nuclei of trophocytes with apparent branching. Histochemically, the cells of the Malpighian tubules showed, by the reaction of Bromophenol Blue, proteic activity more apparent in the treated groups compared to controls. The reaction of the PAS-Alcian Blue revealed the presence of glycoproteins in the apical portion of the cells of the Malpighian tubules of the treated groups. For the Feulgen reaction, we observed a high degree of chromatin compaction. The proteic activity in fat body, measured by reaction of Bromophenol Blue, there appeared differentiated between both groups. Tests for glycoproteins, by the reaction of the PAS-Alcian Blue, showed a greater amount of these substances in the treated groups. For the Feulgen reaction, the fat body cells showed higher degree of chromatin compaction. Ultrastructurally, the cells of the Malpighian tubules showed intense vacuolation in the treated groups, as well as the presence of mineralized granules, cytoplasmic concretions, evagination of the nuclear envelope, expansion of the apical portion (microvilli), release secretions into the lumen, altered mitochondrial cristae , rough endoplasmic reticulum with dilated cisterns and intense release of ribosomes to the cytoplasm, but in treated group and control group, the basal lamina and plasma membrane were shown to be intact. In fat body, among the changes highlighted in the treated groups compared to control group, we highlight the intense vacuolation, vacuolar coalescence, rough endoplasmic reticulum with intense release of ribosomes into the cytoplasm, and ferritin accumulation in cisterns. As in the Malpighian tubules, the basal lamina and plasma membrane of the fat body cells proved to be intact. The results showed that the dose of fipronil and boric acid are sub-lethal to bees, since there was a relatively high survival rate for an extended period of time, leading thus to chronic effects.