Ecotoxicological Evaluation of Parallelomorphus laevigatus (Coleoptera, Carabidae) as a Useful Bioindicator of Soil Metal Pollution

Abstract

Among soil invertebrates, the carabid beetles are predators considered useful ecological indicators [1][2][3][4][5][6][7]. This is because they play a key role in clarifying the route of contaminants in food webs; in fact, they are both predators of small invertebrates and prey for amphibians, reptiles, birds and small mammals [8].This taxon is generally considered as poor accumulator of trace elements [9,10]; this is probably due to a series of detoxification enzymes [9,11] of which it is endowed. However, a few studies have shown that physiology of carabid beetles [5,11,12] as well as their susceptibility to additional stressors [13] can be affected by the accumulation of heavy metals.Among these beetles, Parallelomorphus laevigatus (Fabricius) (homotypic synonym of Scarites (Parallelomorphus) laevigatus Fabricius, 1792) (Figure 1) did reserve a relative few interest from ecological point of view while has never been studied for an ecotoxicological analyses. It is a ground beetle widespread on the Atlantic coasts of the Mediterranean and Morocco and along the Mediterranean basin and the western coast of the Black Sea [14]. This species, living on sandy beaches, occurs in relatively dense populations in Sicily from April to October, while no specimens are visible during winter season. It has a highly precise orientation capacity; if it accidentally falls into the water, caused by waves or wind action (and this can occur whether by day or by night), it is able to float and swim on the sea surface using an effective swimming technique [15] and quickly lands by using a path perpendicular to the shoreline. During daytime, it uses the solar azimuth as an orientation cue (it carries out the chronometric compensation of the apparent motion of the sun using the photoperiod known as "Zeitgeber" [16]. Nocturnal tests have also discovered it has a lunar orientation [17] and is sensitive to the magnetic field [18]. P. laevigatus is particularly active on surface in the evening and in the night in summer [19] peaking after sunset. Conversely, it spends the daylight hours in an individual burrow in the sand near the shoreline. When active, the beetle uses its time hunting mainly Talitrus saltator [19,20].The progressive depletion of the population size due to human impacts [21] and the narrow habitat have made this species an excellent ecological indicator for sandy coastal environments [22].The presence of one of largest refining and petrochemicals industries in Western Europe and the Mount Etna (the tallest active volcano in Europe) in the southern part of the Ionian coast of Sicily stimulated to investigate on the bioaccumulation capacity of trace elements in this species. For this investigation, 16 target metals, 11 of which are essential elements for living organisms (Co, Cr, Cu, Fe, Mn, Mo, Ni, Se, Sn, V and Zn) and four of which are toxic (As, Cd, Hg and Pb) were analyzed in adult specimens from four Sicilian locality (Figure 2). The sites were selected according a gradient of trace metal pollution and considering the...

Recent Advances in Evaluating Insects as Bioindicators of Heavy Metal Pollution

“…Ground beetles as efficient bioindicator are commonly used by researchers because they show response to ecological variation as a consequence of anthropogenic activities including overgrazing, soil and land pollution [37]. In relation to their cosmopolitan distribution in land, Carabid beetles are commonly utilized to assess the heavy metal pollution in soil [38]. Previously, it was discovered the significant bioaccumulation factor range of mercury and arsenic in a research of Carabus lefebvri indicating that beetles were favorable for assessing mercury and arsenic in the environment [39].…”

“…Furthermore, Soliman and El-Shazly (2017) studied the average concentration of cadmium, lead, zinc, chromium, nickel and iron in grasshopper species [46]. Several researches have been conducted on heavy metal analysis in grasshopper, plants and soils having metal concentration higher in region closest to polluted areas [38,47]. Guria et al [4] described the reduction of grasshopper fitness to environment due to toxicity of arsenic and lead thus vulnerable to predation and infection [4].…”