How does the greater white-toothed shrew, Crocidura russula,
responds to long-term heavy metal contamination? — A case study
Carla Cristina Marquesa,⁎, Alejandro Sánchez-Chardib, Sofia Isabel Gabriela,
Jacint Nadalb, Ana Maria Viegas-Crespoa, Maria da Luz Mathiasa
aCentro de Biologia Ambiental, Departamento Biologia Animal, Faculdade de Ciências, Universidade Lisboa,
Campo Grande, 1749-016 Lisboa, Portugal
bDepartament Biologia Animal (Vertebrats), Facultat de Biologia, Universitat Barcelona, Av. Diagonal 645, 08028 Barcelona, Spain
Received 7 April 2006; received in revised form 15 December 2006; accepted 5 January 2007
Available online 23 February 2007
Heavy metals accumulation in parallel with the evaluation of physiological and biochemical effects resulting from continued
metal exposure were considered here using for the first time the great white-toothed shrew Crocidura russula as an in vivo model.
Shrews were originated from an abandoned lead/zinc mining area and from a reference area, both in Alentejo, southern Portugal.
Hepatic contents of nickel, copper, zinc, cadmium, mercury and lead were quantified by Inductively Coupled Plasma Mass
Spectrometer (ICP-MS). Haematological parameters (white blood cells, red blood cells, haemoglobin and haematocrit) were
obtained in a Coulter Counter Analyser and biochemical markers of the redox balance (glutathione S-transferase, glutathione
peroxidase, and glutathione reductase) activities were measured spectrophotometrically using a Duo-50 spectrophotometer.
Compared with control animals, significantly higher concentration of hepatic cadmium (9.29 vs. 1.18 μg/g dry weight) and nickel
(1.56 vs. 0.343 μg/g dry weight) were detected in the shrews collected in the mining area. However, no significant changes were
observed on haematological or enzymatic parameters in animals exposed to metal pollution. The obtained results show that shrews
are good bioaccumulators of toxic heavy metals, but very tolerant to their effects, revealing an interesting long-term adaptation to
polluted environments. In addition, this study provides reference values for haematological parameters and antioxidant enzymes
levels in C. russula, which may be relevant for comparative purposes in further studies.
© 2007 Elsevier B.V. All rights reserved.
Keywords: Crocidura russula; Abandoned mining area; Heavy metals; Haematological parameters; Antioxidant enzymes
Mining wastes remaining after the extractionof target
metals are referred as important sources of environmen-
tal contamination, reaching in some cases levels that
to human health. Portugal has a legacy of about 85 old
mines deactivated for economical reasons. Most of these
mines were deactivated without any previous environ-
mental recovery plan. As a consequence, tones of metal
Oliveira et al., 2002). Preguiça, a lead/zinc mine located
in Alentejo, southern Portugal was deactivated 40 years
ago, being a fine illustration of this reality. Over the last
decades, the area once occupied by the mine has been
covered by vegetation, hiding all the tailings and scoria
produced and accumulated in the soil.
Science of the Total Environment 376 (2007) 128–133
E-mail address: email@example.com (C.C. Marques).
0048-9697/$ - see front matter © 2007 Elsevier B.V. All rights reserved.
Several studies have confirmed that insectivores may
accumulate superior amounts of heavy metals in their
tissues, suggesting their major role as biomonitors (e.g.
Talmage and Walton, 1991; Ma et al., 1991; Ma, 1996;
Pankakoski et al., 1993, 1994; Komarnicki, 2000; Ma
and Talmage, 2001). The potential interest of ground-
living insectivores as in situ models, such as shrews, is
explained by their widespread occurrence; limited home
range; small body size; high metabolic rate; and inver-
tebrate-based diet, especially because invertebrates are
known to accumulate high levels of metals (Hunter and
Johnson, 1982; Scanlon, 1987; Ma et al., 1991; Shore,
1995). In the present study, the greater white-toothed
western and southern Europe, including Portugal (ICN/
CBA, 1999), is tested as a model of environmental long-
term mining contamination.
Ecotoxicological surveys usually focus on bioaccu-
mulation but rarely determine biological effects of long-
term exposure to mining residues. So, only a few studies
report morphological, biochemical, haematological, or
genetic alterations for metal-exposed insectivores (e.g.
Ma, 1989; Dodds-Smith et al., 1992; Hendricks et al.,
1995) or other small mammals (Nunes et al., 2001;
Viegas-Crespo et al., 2003). In this study, in addition to
hepatic heavy metal accumulation, haematological and
biochemical effects are investigated in C. russula inhab-
iting an abandoned mine area. Haematological values
(white and red blood cells, haemoglobin and haemato-
crit) can be indicative of the physiological status of
wild animals (Marques et al., 2006). Biochemical
parameters, such as antioxidant enzyme activities
(glutathione S-transferase, glutathione peroxidase and
glutathione reductase) are often used as markers of
oxidative stress, considering the active role they play in
the detoxification of deleterious compounds produced
by several metals and other environmental pollutants
(Cnubben et al., 2001).
The obtained results will also allow i) to assess the
role of the white-toothed shrew as a bioindicator of
heavy metal pollution, ii) to determine haematological
and biochemical reference values for this species and at
last iii) to confirm the potential environmental risk of
2. Materials and methods
2.1. Study areas
This study was carried out in a riparian area in the
surroundings of an old lead/zinc mine (Preguiça mine),
located in Alentejo, southern Portugal (38°02′15″N;
07°17′01″W). This mining area is included in the
Iberian Magnetitic–Zinciferous Belt, characterized by
the presence of lead and zinc oxides in soils, as well as
several other metals, present in trace amounts (Vairinho
and Fonseca, 1989) (Table 1). The climate in this region
is characterized by hot dry summers and mild winters.
The average annual temperature and precipitation are
approximately 17 °C and 600 mm, respectively. The
vegetation of this riparian area is dominated by trees and
shrub species (Quercus rotundifolia, Cistus ladanifer,
Rubus ulmifolius and Nerium oleander). Herbaceous
species (Echium plantagineum, Bromus rigidus, Vulpia
myunos and Phleum phleoides) were also present.
For comparative purposes, an area without known
exogenous sources of heavy metals and located 30 Km
northwest from Preguiça mine (38°11′18″N; 07°24′34″
W) was chosen as reference. Both sites have similar
climate, vegetation and relief.
2.2. Animal and tissue collections
8 females; Preguiça area: 7 males, 9 females) were live-
trapped using Longworth® and Sherman® traps baited
with a mixture of sardine, oil and wheat flour. The
captures were performed in 3-night trapping sessions,
using 150 traps along 800 m transects.
±0.1 g) and transported to the laboratory. Blood samples
were collected by cardiac punction using heparinized
syringes. Liver was promptly removed, weighed and
separated in two fractions, one for the immediate deter-
minationofantioxidant enzymeactivities,while the other
was stored at −20 °C for later quantification of heavy
metal contents. All methodologies were conducted in
strict accordance with the directive 86/609/EEC on the
protection of laboratory animals.
2.3. Metal analyses
Liver fractions were dried (60 °C) till constant weight
(dry weight: dw). For each specimen, 80 to 100 μg of
Soil elemental composition in the Preguiça area [Adapted from the
Vairinho and Fonseca (1989)]
129C.C. Marques et al. / Science of the Total Environment 376 (2007) 128–133
liver tissue was digested in Teflon vessels (120 °C, 12 h)
with 2.0 ml 70% nitric acid (Baker Instra Analysed) and
1.0 ml 30% hydrogen peroxide (Baker Instra Analysed).
Nickel (Ni), copper (Cu), zinc (Zn), cadmium (Cd),
mercury (Hg) and lead (Pb) were quantified by a Perkin
Elmer ELAN-6000 Inductively Coupled Plasma Mass
Spectrometer (ICP-MS). Two replicate subsamples and
a standard reference material (Bovine Liver SRM-
1577a) certified by the National Bureau of Standards
(NBS) were included in the analyses. The mean values
from twenty-six blanks were subtracted from each
sample. Method detection limits (in ppb) were 0.20 for
nickel, 0.10 for copper, 0.50 for zinc, 0.05 for cadmium,
0.20 for mercury, and 0.05 for lead.
2.4. Haematological and enzyme analyses
A Coulter Counter Analyser (Beckman Coulter,
USA) was used to determine blood parameters: white
blood cell count (WBC, ×103mm−3), red blood cell
count (RBC, ×106mm−3), haemoglobin concentration
(HGB, g dl−1) and haematocrit (HCT, %).
For enzymatic determinations, liver was rinsed in an
ice-cold 0.154 mm KCl solution, for immediate deter-
mination of glutathione S-transferase (GST), selenium
dependent glutathione peroxidase (Se-GPx) and gluta-
thione reductase (GR) activities. Liver homogenates
(1:10 w/v) were prepared with approximately 0.3 g of
fresh liver and ice-cold 0.25 M potassium phosphate
buffer (pH=7.0), using a Potter–Helvehjem homoge-
nizer (B.Braun Melsungen, Germany), and immediately
centrifuged at 1000 g for 15 min at 4 °C. Then the
supernatant was collected and further diluted with
0.25 M potassium phosphate buffer, according to each
enzyme's specific protocol. Enzyme activities were
measured spectrophotometrically using a Duo-50 spec-
trophotometer (Beckman Instruments, USA). Assays
were performed in triplicate and average values were
of Habig et al. (1974), by following the change in the
absorbance of the substrate 1-cloro-2,4-dinitrobenzene
(CDNB), conjugated with GSH, at 340 nm and ex-
pressed as μmol of product/min/mg protein. Se-GPx
activity was determined according to the method devel-
oped by Paglia and Valentine (1967) and expressed as
μmol NADPH oxidized/min/mg protein. GR activity
was determined using the method described by Carlberg
and Mannervik (1985) and expressed as μmol NADPH
oxidized/min/mg protein. Total protein contents were
determined in triplicate according to the biuret method
(Gornall et al., 1949) in liver homogenates using Bovine
Serum Albumin (Sigma, Spain) as standard.
2.5. Statistical analyses
Statistical analyses were performed by SPSS 11.0 for
Windows (SPSS Inc., 1999). Most variables did not ex-
hibit normal distribution and/or variances homogeneity,
so all variables were compared using Mann–Whitney's
U-test. Results are shown as median and range values
(Minimum–Maximum). Differences were considered
statistically significant at pb0.05.
3.1. Metal concentrations
Significantly higher concentrations of cadmium and
nickel were detected in shrews collected in the mining
area comparing with the reference area (pb0.05 and
Hepatic concentrations (μg/g dw) of heavy metals in C. russula in
Metals Reference area Preguiça area
(⁎) (⁎⁎) Significantly different from the reference area (Mann–
n: number of animals.
n.d.: not detectable.
Haematological parameters in C. russula in study areas
Haematology Reference areaPreguiça area
Median Range Median Range
WBC (× 103mm−3)
RBC (× 106mm−3)
WBC, white blood cells; RBC, red blood cells; HGB, haemoglobin;
n: number of animals.
130C.C. Marques et al. / Science of the Total Environment 376 (2007) 128–133
pb0.01, respectively) (Table 2). Concerning the hepatic
values of other metals (copper, zinc, mercury and lead),
no statistically differences were observed between study
areas. Additionally, for most metals, hepatic levels re-
vealed a wider range in Preguiça when compared with
the unpolluted area (Table 2).
3.2. Haematological parameters and enzyme activities
No statistical differences between study areas were
reported for any haematological parameter (Table 3),
although median values were always higher in shrews
Hepatic activities of GST, Se-GPx and GR were
unaltered in C. russula from the mining area, although
GST activity revealed a higher median and larger dis-
persion of values, when compared with reference area
the role of C. russula as a bioindicator of environmental
pollution in an abandoned mining area.
Results showed that in reference shrews, metal levels
were similar or lower than those obtained in other in-
sectivores species from unpolluted sites (revision in
Talmage and Walton, 1991, Pankakoski et al., 1993,
Preguiça mine, revealed significantly high concentra-
tions of hepatic cadmium and nickel. Cadmium is a non-
essential metal that usually accompanies most ores of
lead and zinc. Mainly due to anthropogenic activities,
this metal has been widely distributed throughout the
food chains (Hunter and Johnson, 1982; Andrews et al.,
1984; Torres and Johnson, 2001). Considered highly
toxic to mammals (e.g. Talmage and Walton, 1991),
laboratory studies have shown that cadmium exposure
might contribute to its hazardous toxicity and carcino-
genicity (Karmakar and Chatterjee, 1998). Shrews
inhabiting the mining area showed, on average, a 7-
fold cadmium increased compared with the low accu-
mulation detected in shrews collected in the reference
area (9.29 and 1.18 μg/g dw, respectively). This result
points towards a contamination through direct ingestion
of soil particles and/or via transfer through the food web
(Torres and Johnson, 2001). In liver, ingested cadmium
forms very stable complexes with sulfhydryl rich pro-
several years (Scheuhammer, 1991; Wlostowski et al.,
2000, 2003). These complexes protect host tissues from
cadmium damage (Goering and Klaassen, 1983; Klaas-
sen et al., 1999). Generally, in mammals, the critical
renal lesions havebeenreported incommonshrew Sorex
araneus with cadmium concentrations over 253 μg/g dw
(Ma and Talmage, 2001). In Preguiça mine 31% of the
individuals of C. russula showed cadmium concentra-
tions in liver above the critical level reported by Nogawa
et al. (1986).
In contrast to cadmium, information about nickel's
hepatic concentrationinbiotaisscarce andinconclusive,
polluted areas by Pankakoski et al. (1993, 1994) in
common shrew (0.00–0.64 μg/g dw), pygmy shrew
Sorex minutus (3.39 μg/g dw), and mole Talpa europaea
(0.13–0.25μg/g dw) are consistent with ourdata.Nickel
is a ubiquitous element easily transferred throughout the
food chain (Torres and Johnson, 2001; Punshon et al.,
2003), although some studies reported a low increase or
even a decrease of this metal in small mammals inhab-
iting nickel contaminated areas (Cloutier et al., 1986;
Fendick et al., 1989; Talmage and Walton, 1991;
Punshon et al., 2003). Nickel is known to be carcinogen,
teratogenic, genotoxic and hepatotoxic (Pandey and
Srivastava, 2000; Punshon et al., 2003), and concern
should be taken on the accumulation of this element in
the body (Kasprzak et al., 2003). Although, data on
critical nickel residues in whole body and target organs
associated with acute or chronic effects for terrestrial
wildlife are lacking (Torres and Johnson, 2001).
elements between study areas. However, shrews from
Preguiça showed hepatic levels of mercury and lead
slightly higher when compared with the reference
shrews. This tendency might indicate either present-
Enzymes activities (μmol/min/mg protein) in the liver of C. russula in
Enzymes Reference area Preguiça area
Median RangeMedian Range
GST — Glutathione S-transferase; Se-GPx — Selenium-dependent
glutathione peroxidase; GR — Glutathione reductase.
n: number of animals.
131C.C. Marques et al. / Science of the Total Environment 376 (2007) 128–133
day reduced levels of these elements in the environment
and/or its non-homogeneous distribution (Torres and
Johnson, 2001). Lead and mercury levels detected in C.
with liver pathologies or metal pollution in wild mam-
and 1.1 μg/g wet weight for mercury (Eisler, 1987).
It is well known that soils from lead/zinc mines con-
tain high amounts of copper and zinc (Andrews et al.,
1984; Santos Oliveira et al., 2002), but the bioaccumula-
tion of these two elements was not verified in C. russula.
As previously reported, the uptake of copper and zinc is
correlated with their amount in the gastrointestinal tract
(Torres and Johnson, 2001). Nevertheless, their absorp-
tion is generally regulated by an effective homeostatic
mechanism (e.g. induction of metallothionein) and does
not correlate with soil contents (Talmage and Walton,
1991; Mertens et al., 2001; Milton et al., 2003).
In this study, the physiological and biochemical re-
negligible, suggesting that the potential deleterious
effects of metal contamination are compensated by ad-
ditional detoxification pathways. In vertebrates, metal
binding metallothioneins are thought to be one of the
major routes for metal detoxification. Besides, exposure
to increased levels of metals over many generations may
impose a selective pressure on C. russula populations,
that adapt to low quality environments (Holloman et al.,
2000; Viegas-Crespo et al., 2003).
Despite no significant differences were found in the
contaminated area, the collected shrews show a greater
data dispersion both on haematological values and bio-
response of shrews inhabiting a low quality environ-
ment, as earlier reported in Algerian mice (Nunes et al.,
2001; Viegas-Crespo et al., 2003). Furthermore, it is
and GR, play an important role in the detoxification of
oxidant compounds, including lipoperoxides, which can
be partly produced by metal pollutants. However, ac-
cording to Wlostowski et al. (2000), high concentrations
of cadmium in bank vole's diet, produced histophatolo-
but paradoxically reduced the hepatic levels of lipoper-
oxides. The authors explain this result based on the
observed decreased of hepatic levels of iron and copper
in voles. In fact, these elements are essential compo-
nents of several proteins and enzymes involved in the
mithocondrial respiratory chain, possibly leading to
some disturbances in the ATP production (the main
endogenous source of free radicals) and consequently to
lipid peroxidation. So, a similar response may explain
the non-significant changes in antioxidant enzyme activ-
ities in cadmium contaminated shrews from the Preguiça
The results of the present study have illustrated the
relevance of C. russula as a bioindicator species in
environmental quality assessment. Besides, abandoned
mines, such as Preguiça mine, may constitute unpredict-
able long-term sources of heavy metal contamination.
Considering the position of shrews in food webs, we can
speculate about the accumulation of heavy metals in
higher trophic levels and assume an important biomag-
nification scenario of potentially toxic elements. So, it
cannot be disregarded the potential health risk of old
negative environmental impact.
This work was partly supported by FEDER funds
through Fundação para a Ciência e a Tecnologia-
(research project POCTI/BSE/39917/2001) and by Min-
isterio de Educación y Ciencia (ACI/2004HP-00026).
CCM was supported by a PhD fellowship (FCT/SFRH/
BD/5018/2001) and ASC was supported by a BE grant
from Generalitat de Catalunya (2002BEAI00182).
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