We tested the usefulness of exuviae as an environmentally friendly method for exploring the variability of the trace element contents of protected insect populations without killing specimens. It is a notable characteristic of dragonflies that they are good ecological indicators for both aquatic and terrestrial habitat quality. Thus, we investigated the trace element accumulation in different stages of dragonflies: larva, exuvia, and adult. Using microwave plasma atomic emission spectrometry (MP-AES), we analysed the concentrations of Al, Ba, Cr, Cu, Fe, Mn, Pb, Sr and Zn. We found that the trace element contents of exuviae are a good proxy of the trace element contents of both the larvae and the adults. We conclude that exuvia is useful for assessing the environmental health of aquatic ecosystems. It is an environmentally friendly method and it can be used even in the case of protected dragonfly species. 2 of 10 their larvae stage in aquatic habitats and use a wide range of terrestrial habitats as adults, and they are important predators in aquatic and terrestrial ecosystems [19][20][21][22].Aquatic insects can accumulate elements such as Al, Cd, Cr, Cu, Fe, Mg, Mn and Zn from sediment and from food [23]. In aquatic insects, the concentrations of Hg, Cd, Ni, Cr, As, Pb, Cu, Ti, Zn and Mn change with size, life cycle stages and different bioaccumulation patterns [24]. There are only a few reports dealing with the changes in trace element concentration during different developmental stages [25]. Among these stages, dragonfly adults increase their bioaccumulation potential because they feed on other invertebrates [21]. Larvae and exuviae are also useful to detect accumulation and element bioavailability [24].Accumulated trace metals can be detoxified and excreted in aquatic invertebrates [26]. Trace elements become associated with the calcium in the exoskeleton matrix. They may be absorbed on the surface of the exoskeleton or bind to the inner exoskeleton matrix after uptake [27,28]. During metamorphosis, the protein and lipid content alter; stored resources and decomposing cellular structures are metabolized. Metamorphosis influences metal concentration by metal excretion; thus, the concentration of these metals decreases in the body. Mechanisms of contaminant loss include the exoskeleton as exuvia; the importance of this pathway also depends on the contaminant [21,29,30]. The decontamination process under conditions of an intensive intake of trace elements to an organism is the production of excrement [27].Earlier studies demonstrated that the river clubtail (Gomphus flavipes (Stylurus flavipes)) (Odonata: Gomphidae; Linnaeus, 1758) is a sensitive indicator of pollution [31,32]. This species is a characteristic of large lowland rivers in Europe [33,34] and in Hungary [35]; thus, this species was chosen for our study. The aim of our study was to investigate the trace element accumulation in different stages of the dragonfly to test whether the exuviae may be used as a tool for contamination level assessment. We an...

In the nature, larvae living in watercourses are exposed to a complex system of environmental influences. It is known that different watercourse types (creeks, brooks, streams, little rivers and medial rivers) provide different conditions for larval development (water depth, flow rate, temperature, oxygen content, substrate type, nutrient supply, etc.). These conditions can vary significantly between watercourse types, but be very similar within types. In this work, we examined the body sizes and wing morphometric characteristics of males of Calopteryx splendens reared from different watercourse types (brook, stream, creek, little river, medial river). Although there were no significant differences in body size among watercourse types, we found significant differences in the wing features. We found the most differences between the individuals reared from streams and creeks and between the individuals reared from stream and medial river. Our results show that the individuals reared from different watercourse types were clearly separated on the two wings. The results also suggest that there are significant differences in the number and pattern of allometric features on the wings of individuals reared from different watercourse types.