Intestinal stem cell proliferation as an indicator of honey bee (Apis Mellifera) health

The role of honey bees as honey producers and pollinators makes the decline of these bees not just an environmental matter but also an agricultural and economical problem. Exposure to xenobiotics, such as pesticides and antibiotic treatments, might cause physiological changes, contributing to bee health decline. The midgut functions as the first physical barrier after honey bees ingest xenobiotics and could serve as an important indicator of health. The midgut of adult Apis mellifera is maintained by intestinal stem cells (ISCs), which usually represent the only large somatic proliferative cell population in adult insects. Therefore, we investigated the effect of twelve relevant xenobiotics on ISC proliferation rate at relatively high concentrations. Three of these xenobiotics (methoxyfenozide, fluvalinate and oxytetracycline) had a significant effect on ISC proliferation rate and fluvalinate and oxytetracycine caused strongly increased mortality. Next, we aimed at detecting sub-lethal effects on ISC proliferation of these xenobiotics. Therefore, three lower concentrations of fluvalinate, oxytetracycline, methoxyfenozide and a potentially synergistic combination of coumaphous and fluvalinate were assessed. To include the possibility of long-term effects, ISC proliferation was measured in treatment and control groups at three different ages. Data collected to test our hypothesis that these xenobiotics will affect ISC proliferation at concentrations that do not significantly affect bee mortality will be presented. This will contribute to our understanding of sub-lethal effects of xenobiotics in a novel, health-relevant context and evaluate ISC proliferation as a honey bee health indicator.