Toxicology, histophysiological and nutritional changes in Apis mellifera (Hymenoptera: Apidae) submitted to limonene and natural pesticides in comparison to synthetic pesticides

Abstract

Apis mellifera has ecological, economic and social importance. Thus, this study aimed to compare, at a toxicological, physiological and nutritional level, the insecticidal activity of natural pesticides in comparison with synthetic ones, adding knowledge about the impacts of these products and verifying their safety for these animals. Toxicity bioassays were performed to obtain the LC50 (lethal concentration) of the products (Azamax®, Limonene, Karate® and Roundup®) through Probit analysis. The concentrations and toxicity ratios (TR) obtained, in decreasing toxicity level, were Karate® (0.0134 mL/100 mL, 53,156 times) > Limonene (1.44 mL/100 mL, 494.64 times) > Roundup® (712 .29 mL/100 mL). It was not possible to obtain the LC50 for Azamax®, as concentrations above 250 mL/100 mL caused repellency and below there was no mortality. LC50 and Azamax® concentrations were used as a treatment in histological, histochemical and biochemical analyses. Although the herbicide Roundup® has shown low toxicity by ingestion, it and the Limonene were the substances that most interfered with nutritional biochemical parameters, in addition to causing histopathological changes in midgut cells. The insecticide Karate® also led to histopathological changes in cells and a reduction in important macromolecules used in biochemical functions. Despite the repellency observed in the insecticide Azamax®, A. mellifera presented morphological alterations in the digestive cells and in the absorption of nutrients. It is concluded that natural pesticides can be as harmful to A. mellifera bees as synthetic ones, and they can cause deleterious effects on the digestive physiology of these insects, which may reflect on their reproduction.