Sublethal doses of imidacloprid decreased size of hypopharyngeal glands and respiratory rhythm of honeybees in vivo

Abstract

International audienceMost studies that have shown negative sublethal effects of the pesticide imidacloprid on honeybees concern behavioral effects; only a few concern physiological effects. Therefore, we investigated sublethal effects of imidacloprid on the development of the hypopharyngeal glands (HPGs) and respiratory rhythm in honeybees fed under laboratory conditions. We introduced newly emerged honeybees into wooden mesh-sided cages and provided sugar solution and pollen pastry ad libitum. Imidacloprid was administered in the food: 2 μg/kg in the sugar solution and 3 μg/kg in the pollen pastry. The acini, the lobes of the HPGs of imidacloprid-treated honeybees, were 14.5 % smaller in diameter in 9-day-old honeybees and 16.3 % smaller in 14-day-old honeybees than in the same-aged untreated honeybees; the difference was significant for both age groups. Imidacloprid also significantly affected the bursting pattern of abdominal ventilation movements (AVM) by causing a 59.4 % increase in the inter-burst interval and a 56.99 % decrease in the mean duration of AVM bursts. At the same time, the quantity of food consumed (sugar solution and pollen pastry) per honeybee per day was the same for both treated and untreated honeybees

The influence of sublethal doses of imidacloprid on protein content and proteolytic activity in honey bees (Apis mellifera L.)

“…It has recently been observed that sublethal doses of imidacloprid have a decreasing effect on hypopharyngeal glands (HPGs) of the nursing bees (Hatjina et al, 2013). The changes in the size of HPGs (which refers to the diameter of acini) constitute an indicator of the activity of HPGs.…”

“…Based on our results, we can conclude that pollen containing both doses of IMD decreases the level of the honey bee proteins and it suggests an intense negative effect of the pesticide on the activity of the honey bee's HPGs. The causes of this phenomenon presumably lie in a decrease in the size of HPG lobules (Hatjina et al, 2013). This leads to a disturbed protein synthesis in the glands, and in particular to a decrease in the production of royal jelly by nurse bees (Ohashi, Natori, & Kubo, 1997).…”

“…For example, it has been shown that sublethal doses of IMD have an adverse effect on the bee's sense of smell and memory (Decourtye, Devillers et al, 2004, Decourtye, Armengaud et al, 2004Kirchner, 1999;Williamson, Baker, & Wright, 2013), as well as on the insects' intensity of feeding (Schneider, Tautz, Gruenewald, & Fuchs, 2012;Yang, Chuang, Chen, & Chang, 2008), territorial disorientation (Hatjina, Papachristoforou, Charistos, Bouga, & Arnold, 2012;Henry et al, 2012), and neurophysiologic changes (Goulson, 2013;Guez, Suchail, Gauthier, Maleszka, & Belzunces, 2001a, 2001bLambin, Armengaud, Raymond, & Gauthier, 2001). In recent in vivo studies, it has also been shown that the sublethal doses of imidacloprid not only cause decrease in the size of HPGs but also in the respiratory rhythm of A. mellifera (Hatjina et al, 2013). Besides imidacloprid itself, its degradation products released as a result of its metabolism have a further effect on bees (Suchail et al, 2004;Simon-Delso et al, 2014) and the proteins showing enzymatic qualities constitute an interesting group of compounds involved in different biochemical processes in insects (Frączek, Ż ó łtowska, Lipiński, & Dmitryjuk, 2013;Shi, Dick, Ford, & Casida, 2009).…”

Combined effect of pollen quality and thiamethoxam on hypopharyngeal gland development and protein content in Apis mellifera

“…Pollen also represents one of the most frequent ways of exposure to pesticides (Krupke et al 2012;Mullin et al 2010), particularly relevant for nurse bees and larvae, which consume the highest amount of stored pollen (Rortais et al 2005). The residual concentrations of highly toxic pesticides, like neonicotinoids, are still able to induce adverse effects in bees, such as the lowered development of HPGs demonstrated in newly e m e rg e d b e e s c h r o n i c a l l y e x p o s e d t o imidacloprid (Hatjina et al 2013;Heylen et al 2011;Smodiš Škerl and Gregorc 2010).…”

“…Babendreier et al 2005;Hatjina et al 2013;Heylen et al 2011;Smodiš Škerl and Gregorc 2010), little is known about combination of stressors, which can occur in a field-realistic scenario. Here, we tested the hypothesis that low protein content in pollen combined with pesticide exposure has a significant impact on young-bee development.…”