Sulfoxaflor influences the biochemical and histological changes on honeybees (Apis mellifera L.)

Abstract

Pesticide application can have an adverse effect on pollinator honey bees, Apis mellifera L., ranging from mortality to sublethal effects. Therefore, it is necessary to understand any potential effects of pesticides. The present study reports the acute toxicity and adverse effects of sulfoxaflor insecticide on the biochemical activity and histological changes on A. mellifera. The results showed that after 48 h post-treatment, the LD₂₅ and LD₅₀ values were 0.078 and 0.162 µg/bee, respectively, of sulfoxaflor on A. mellifera. The detoxification enzyme activity shows an increase of glutathione-S-transferase (GST) enzyme on A. mellifera in response to sulfoxaflor at LD₅₀ value. Conversely, no significant differences were found in mixed-function oxidation (MFO) activity. In addition, after 4 h of sulfoxaflor exposure, the brains of treated bees showed nuclear pyknosis and degeneration in some cells, which evolved to mushroom shaped tissue losses, mainly neurons replaced by vacuoles after 48 h. There was a slight effect on secretory vesicles in the hypopharyngeal gland after 4 h of exposure. After 48 h, the vacuolar cytoplasm and basophilic pyknotic nuclei were lost in the atrophied acini. After exposure to sulfoxaflor, the midgut of A. mellifera workers showed histological changes in epithelial cells. These findings of the present study showed that sulfoxaflor could have an adverse effect on A. mellifera.

Keywords: Apis mellifera; GST; Histological effects; MFO; Sulfoxaflor; Toxicity.

Fig. 1

Light micrographs of the brain of Apis mellifera L. (H&E X160) A the control bees showing no histopathological alteration B Brain of treated bees administrated insecticide (sulfoxaflor) for 4 h. Showing nuclear pyknosis (pk) and degeneration in some few cells. C Brain of treated bees with administrated insecticide (sulfoxaflor) For 24 h. showing most of the neuronal cells have nuclear pyknosis and degeneration. (D) (x80) after 48 h. The mushroom shaped tissue showed loss of most neurons and replaced by vacuoles in magnification showing vacuolization replacing the damage neurons. Nb: mushroom body (Mb), calyx (Ca), kenyon cells (kc), pyknosis (pk), damage neurons(dn)

Fig. 2

Light micrographs of the hypopharyngeal gland of Apis mellifera L. (H&E X160). A the control bees showing cytoplasm of the secretory cell seen contain a variable number of secretory vesicles that are almost unstained. B hypopharyngeal gland of treated bees with administrated insecticide (sulfoxaflor) for 4 h, showing slightly effect in secretory vesicles (vs). C hypopharyngeal gland of treated bees with administrated insecticide (sulfoxaflor) for 24 h, showing atrophy with nuclear pyknosis (pk) in most of the cells showing loss of cytoplasmic fat vacuoles. (D) (X80) after 48 h. There were loss of the vacuolar cytoplasm and basophilic pyknotic nuclei in the atrophied acini

Fig. 3

Light micrographs of the midgut of Apis mellifera L. (H&E X160) A the control bees showing single layered epithelium with columnar cells containing spherical nucleus (N) and apical surface with peritrophic matrix layers (pm). B Midgut region of treated bees with administrated insecticide (sulfoxaflor) for 4 h. Showing vacuolar degeneration lumen (L) epithelium of villi (ev). C Midgut region of treated bees with Administrated Insecticide (sulfoxaflor) for 24 h. showing necrobiotic change was detected in the lining epithelial cells. (D) (x80) after 48 h. The mucosal lining epithelium showed necrosis with lose of the histological structure and replaced by pigmented material. Other’s areas of the mucosa had vacuolar degenerative changes