# Bioaccumulation of Trace Elements along the Body Longitudinal Axis in Honey Bees
## 1 Introduction  
Honey bees, _Apis mellifera_[PERSON], 1758, primarily _Apis mellifera ligustica_([PERSON], 1806), are frequently used as bioindicators of the terrestrial environment quality--being very sensitive to environmental pollution caused by urbanisation, industrialisation, and agriculture--of all environmental compartments (i.e., air, soil, water, and vegetation) [1, 2, 3, 4, 5, 6, 7]. These pollinator insects are widespread in the territory due to the practice of beekeeping. Their colonies reside in a specific zone, usually frequenting a limited area of about 7 km\({}^{2}\) with a radius of about 1.5 km from the hive [7, 8]. The foraging bees of a single hive (about 10,000 specimens, a quarter of the total colony population) during the spring-summer period visit up to 10 million flowers per day [9, 10] and consequently intercept a large number of pollutants in all the environmental compartments during their large-scale foraging behaviour. Therefore, the level of contaminant bioaccumulation in their tissues and the hive products is an effective detector of environmental contamination [11, 12, 13]. Honey bees are susceptible to pesticides. Pesticide exposure effects can be acute and lethal (rapid and severe, quickly leading to death) or sub-acute and sub-lethal, not causing mortality. In the first case, the number of dead bees in front of the hive is the primary variable to be considered [2]. In the second case, the physiological or long-term behavioural effects [14, 15] must be considered. There has been much talk about colony collapse disorder (CCD) in recent years. This phenomenon, which consists of the deathof bees with the loss of entire colonies or depopulation of many apiaries, appeared in 2005/2006. According to some authors, one of the main responsible factors is the use of neonicotinoid pesticides [16; 17]. In addition, bees weakened by insecticide poisoning are more susceptible to pests and diseases [18; 19; 20; 21]. Contamination by metals can be distinguished from that by pesticides due to their different environmental fates. Metals do not decay in the environment and are characterised by peculiar latent toxicity [2]. Metals generally are accumulated in the honeybee tissues, thus making honeybees efficient bioindicators [11; 22; 23]. Therefore, honey bees can be exploited to monitor metal pollution, usually caused by anthropic activities, which allows highlighting of the areas of most significant environmental risk with repercussions not only for the health of ecosystems but also for human health [24]. In addition, due to the relatively short lifetime of these insects, it is possible to verify the validity of any environmental recovery strategies in use in the territory [12]. However, the relationship between the levels of the elements in the environment and biota is very complex. It is based on their bioavailability, which presupposes the elements' entry into the food chain and their assimilation by organisms into their tissues [25]. Organisms require essential elements, but excess amounts can cause the onset of diseases. Some elements are instead toxic at any concentration (i.e., As, Cd, Hg, and Pb) and not required for any metabolic function [26; 27; 28]. This study's main objective is to analyse the accumulation levels of trace elements along the body axis of honey bees. We hypothesise that the tagmata of the bee body should have a diversified level of accumulation of trace elements. In particular, the abdomen should show the highest concentrations because it contains the excretory system (Malpighian tubule system), which is connected to the intestine right in the area between the midgut and the hindgut, and the rectum, which is the place of storage and disposal of waste. In order to verify this hypothesis, we considered, as a case study, the bioaccumulation of trace elements in the tissues of honey bees collected at the artificial lake of Alviano (Central Italy).