Impact of a lambda-cyhalothrin formulation residues on larval Apis mellifera: Examining midgut and fat body morphological response to insecticide chronic exposure.

Abstract

Pollination by honey bees (Apis mellifera) is crucial for maintaining biodiversity and crop yields. However, the widespread use of pesticides may threaten bees' survival by contaminating their resources. Lambda-cyhalothrin, a neurotoxic insecticide commonly used in agricultural pest control, poses particular risks. In insects, the midgut and fat body serve as primary barriers against xenobiotics, and exposure to these chemicals during larval development can impact adult bees. This study aimed to assess whether the residual concentration of lambda-cyhalothrin in pollen grains affects the midgut and fat body of larval A. mellifera workers after chronic exposure. The midgut epithelium of larvae exposed to a lambda-cyhalothrin-based insecticide exhibited autophagic vacuoles, apical cell protrusions, apocrine secretion, nuclear pyknosis, and high levels of polysaccharides and glycoconjugates in the cytoplasm, with smaller amounts in the brush border. Histochemical analysis revealed areas of vacuolation and damage to cell integrity in the midgut. In fat body cells, the insecticide increased polysaccharide storage and decreased lipid droplet diameter. Despite the histopathological damages, no effects were found in the larval development and adult emergence. These findings suggest the occurrence of apoptosis and autophagy in midgut cells and alterations in nutrient storage in the fat body of A. mellifera larvae exposed to the lambda-cyhalothrin-based insecticide, potentially impacting the physiology and development of this pollinator with possible effects on adult workers.