Corresponding author: Ruslan Olegovitch Butovsky (
Academic editor: R. Vermeulen
Carabid beetles (
Because of the increasing impacts of chemicals on terrestrial and soil ecosystems, assessment of environmental quality by bioindicators is of particular interest.
Carabid beetles are traditionally used as bioindicators of anthropogenic stresses for a number of reasons. They inhabit most terrestrial ecosystems. The ecology and systematics of the group are well studied. Sampling methods are simple and universal. And the data collected by different researchers are comparable.
In soil trophic webs, carabid beetles play an extremely important role as non-specialized predators and 2nd order consumers.
There are numerous publications demonstrating structural changes in carabid communities due to different anthropogenic impacts caused by motorways, metallurgic smelters, and recreation (see review by
This paper reviews the literature data on heavy metal (HM) impacts on carabid beetle communities and also considers the use of carabids as indicators of HM accumulation.
The mean HM content in carabids decreased in the following sequence Fe > Zn > Cu > Mn > Pb > Cd (
The concentration ratios of Cd : Pb : Mn : Cu : Zn : Fe in an average carabid beetle were 1 : 2.5 : 7 : 17 : 29.5 : 93. In other words, an average carabid beetle may contain 93 times more Fe than Cd and 37 times more Fe than Pb (
Variation coefficients of HM in carabids were variable and dependent on the carabid genus and type of HM (
The analysis of 14 HMs in 28 carabid species revealed that the variability of HM in
Inter-generic variability in HM contents (ppm) in carabid beetles (by different authors after
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3 | 0.1* | 15.9 | N/A | N/A | 3.1 |
62.8 |
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2 | 0 | 25.8 |
532.3 | 24.3 | 4.9 |
95.0 |
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4 | 1.0 |
57.2 |
58.7 |
29.1 |
6.7 |
89.2 |
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9 | 0.1 |
16.9 |
333.9 | N/A | 4.3 |
96.1 |
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1 | 0 | 23.3 | N/A | N/A | 0 | 130 |
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2 | 2.9 |
30.1 | N/A | N/A | 7.8 | 118.6 |
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1 | N/A | N/A | N/A | N/A | 1.9 | N/A |
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2 | 1.7 |
27.5 |
117.1 |
29.2 |
1.7 |
77.9 |
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2 | 0.1 |
16.3 | N/A | N/A | 4.2 |
118.7 |
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1 | 0 | 17.3 |
461.2 | N/A | 3.0 |
92.3 |
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5 | 0 | 29.5 |
436.3 |
N/A | 2.9 |
116.2 |
A positive correlation between body mass and Pb content was found in beetles of the genus
I subdivided the collected carabids into three groups: (1) with body mass (B) less than 15 mg (genera
Mean HM content (at least for Zn, Pb and Mn) was not dependent on the mass/size of carabid beetles. Medium-sized species contained more Fe compared to small-sized species and small species contained more Cd and Cu compared to medium-sized and large species.
Heavy metal content (
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Cd | 1.4 |
0.5 |
0.1 |
Cu | 35.1 |
20.5 |
16.9 |
Fe | 236.0 |
448.7 |
333.9 |
Mn | 26.7 |
29.1 | - |
Pb | 4.6 |
2.6 |
4.3 |
Zn | 95.2 |
104.0 |
96.1 |
In most studies no clear pattern of HM contents in males or females of carabid species were observed (
In some species, males contained more metals (Pb, Zn, Cd, Cu, Mn, Fe, Co, Ni, Sr, Cr, Al) than females (
Sex-specific differences were found in six carabid species (
Microelement (Na, Mg, K, Ca) concentrations were higher in females compared to males in populations of
No regular pattern was found in studies of HM contents in dozens of carabid species published by numerous authors (reviewed by
Omnivorous species (
The effects of feeding ecologies were evident only for the essential elements: carnivores (
Seasonal differences in abundance, species composition, and age structure of invertebrates may lead to high variability in HM contents in carabid beetles, and the highest variability can be expected at highly polluted sites (
Seasonal changes in Cd contents were not found for
I found a decrease of Zn and Cu contents in the dominant species
In roadside populations of
In ten carabid species, Zn and Cu contents during the spring were higher than in autumn. The authors speculated that in the period of increased feeding activity (spring), the elements were stored in body fat, while during sexual activity and wintering they were mobilized and excreted. The composition of a population with regards to the fraction of juvenile specimens, active feeders, or reproducing individuals may have a considerable effect on the seasonal dynamics of the metals (
Carabids are relatively poor accumulators of heavy metals, particularly the most toxic ones, such as cadmium or lead (
In contrast, the highest concentrations of non-essential metals (Cd and Pb) were found in carnivorous carabid beetles together with earthworms and oribatid mites in the vicinity of a metallurgic smelter (
In putative trophic chains, carabids as non-specialized predators accumulated less copper and zinc (
As in other holometabolic insects, carabid beetles possess various detoxification systems, which can segregate metals and turn it into inactive forms (
Compared to other groups of soil invertebrates, carabid beetles are characterized by low accumulation and high excretion rates of cadmium (
The concentrations of Pb differed between the exoskeleton and the soft tissues in the carabid body. Up to 63–82% of Pb was accumulated in the exoskeleton (
Females from contaminated sites have elevated activities of some enzymes (glutathione-S-transferase and carboxyl-esterase), but males do not (
The fat concentration in carabids collected from polluted sites was lower when compared to reference sites. Presumably, HM excretion requires energy, thus restricting the accumulation of fat (Lindqvist and Block, 2001).
Adaptation (in terms of HM accumulation and excretion) did not occur in carabids inhabiting chronically polluted sites and obviously had no genetic basis (
Cd “accumulators” and “disseminators” in soil invertebrate communities (van Straalen and van Wensem 1986;
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Carabid beetles constitute one of the most appropriate invertebrate groups for the study of “ecological” effects of different anthropogenic stressors of soil communities, and the changes in carabid community dominance, diversity, abundance, sex ratio etc. have been used as bioindicators in numerous studies (
On the other hand, carabids are relatively poor HM accumulators (being both holometabolic insects and predators). They may contain elevated amounts of HM in polluted sites compared to referent sites, but results are variable and no accurate assessments of contamination levels can be made.
Our extensive research in roadside ecosystems showed that HM contents in carabids did not correlate with their relative abundance or distance from the motorway (Butovsky 1995) or a metallurgic smelter (van Straalen et al. 2001).
More research is obviously needed on HM stress on carabids, e.g. detoxification, genetic resistance, physiology and demography.