Effects of chronic exposure to toxic metals on haematological parameters in free-ranging small mammals

Blood circulates through the vascular system to carry oxygen, nutrients and metabolites to and away from tissues, and as such is a key-component of animal physiology. The impacts of metal pollution on blood, however, are poorly documented in free-ranging vertebrates. While the counteracting effect of selenium on mercury toxicity is well known in marine mammals, its potential role against the toxicity of other metals is less studied, especially on terrestrial wildlife. We explored the consequences of chronic exposure to two non-essential metals (cadmium and lead) along a pollution gradient in Northern France, on eleven haematological parameters in two free ranging small mammals, the wood mouse Apodemus sylvaticus and the bank vole Myodes glareolus. We hypothesized that haematology was related to metal concentrations in tissues, and that selenium might exert modulating effects. Concentrations of cadmium and lead in the tissues indicated an increased chronic exposure to and accumulation of metals along the gradient. Some haematological parameters were not explained by any measured variables while some others varied only with gender or age. Red blood cells, red blood cells distribution width, and blood iron concentration, however, decreased with increasing cadmium in the tissues in wood mice. Red blood cells and haemoglobin decreased with increasing renal lead and hepatic cadmium, respectively, in bank voles. Red blood cells distribution width in wood mice increased with cadmium concentrations in the liver but this was counteracted by high selenium levels in the same organ. An interaction of selenium and lead on red blood cells was also observed in bank voles. Further, selenium concentrations were associated with an increase of monocytes in wood mice. The present results show that toxic metals were related to haematology changes, particularly erythrocyte indicators, and that some essential elements like selenium should be measured as well since they may counteract toxic effects

Can Body Condition and Somatic Indices be Used to Evaluate Metal-Induced Stress in Wild Small Mammals?

Wildlife is exposed to natural (e.g., food availability and quality, parasitism) and anthropogenic stressors (e.g., habitat fragmentation, toxicants). Individual variables (e.g., age, gender) affect behaviour and physiology of animals. Together, these parameters can create both great inter-individual variations in health indicators and interpretation difficulties. We investigated the relevance of body condition and somatic indices (liver, kidneys) as indicators of health status in wood mice (Apodemus sylvaticus, n = 560) captured along a metal pollution gradient in four landscape types (30 sampling squares 500-m sided). The indices were calculated using a recently proposed standard major axis regression instead of an ordinary least square regression. After considering age and gender for the body condition index, no landscape type influence was detected in the indices. However, important index variability was observed between sampling squares; this effect was included as a random effect in linear models. After integrating all individual and environmental variables that may affect the indices, cadmium (Cd) concentrations in both the liver and kidneys were negatively related to body condition and liver indices only for individuals from highly contaminated sites. Lead in the liver was negatively related to the liver index, and Cd in kidneys was positively linked to the kidney index, potentially suggesting metal-induced stress. However, interpretation of these indices as a wildlife ecotoxicology tool should be performed with caution due to the sensitivity of potentially confounding variables (e.g., individual factors and environmental parameters)

Évolution des effets non intentionnels de la lutte chimique contre le campagnol terrestre sur la faune sauvage et domestique

International audienceThe use of bromadiolone to combat water vole outbreaks can result in the accidental poisoning of non-target fauna (e.g., raptors, foxes, and wild boars). Available data indicate that switching from a curative approach (applied post outbreak) to a preventative approach (applied before outbreaks occur) can limit these unintended secondary effects. In May 2014, a joint ministerial order was issued that established how bromadiolone (an anticoagulant) could be employed in agricultural settings and that promoted integrated control practices. Efforts related to these new regulations include 1) the development of a decision-making tool that can help prevent the accidental poisoning of non-target species and 2) the establishment of a new standardised monitoring regime to quantify bromadiolone’s unintended secondary effects and the pesticide’s accumulation in the tissues of non-target fauna.L’utilisation de bromadiolone pour lutter contre les pullulations de campagnols terrestres est responsable d’intoxications de la faune noncible (rapaces, renards, sangliers...). Les indicateurs disponibles montrent que le passage d’une logique de lutte curative à celle d’unelutte préventive a permis de limiter les effets non intentionnels de la bromadiolone. Un arrêté interministériel encadrant l’emploi de cetanticoagulant en plein champ et favorisant les principes de la lutte raisonnée a été promulgué en mai 2014. Les enjeux liés à cetteréglementation concernent la validation d’un outil d’aide à la décision développé pour prévenir les intoxications d’espèces non-cibles etla mise en place d’une surveillance standardisée de l’imprégnation de la faune par la bromadiolone et de ses effets non intentionnels

Study site localisation, Cd contamination (µg/g DM) in soils and landscape types.

<p>Study site located around the former Metaleurop Nord smelter (Nord-Pas de Calais, France); maps present the landscape types in each square and the Cd concentrations in the study area soils. Selected squares for wood mice sampling are bolded in both maps.</p

Predicted relationships between indices and metal concentrations in organs (µg/g DM).

<p>Predictions between indices and TM concentrations are performed on wood mice from the former Metaleurop Nord smelter; (a) between SMI and [Cd]_liver; (b) between SMI and [Cd]_kidneys; (c) between SLI and [Cd]_liver; (d) between SLI and [Cd]_kidneys; (e) between SLI and [Pb]_liver; and (f) between SKI and [Cd]_kidneys. For all figures, the age of individuals was fixed (7 mg of crystalline lens mass, which corresponds to adulthood). For graphical representation, the “highly polluted” class was subdivided into two classes of contamination, “highly polluted” (10≤ [Cd]_soil ≥20 µg/g DM) and “extremely polluted” (20≤ [Cd]_soil ≥70 µg/g DM) in figures (a) to (d). For figures (a) and (b), predicted relationships are shown only for males. For figures (a) to (d), relationships between indices and TM concentrations are represented at different levels of soil contamination (lightly, moderately, highly and extremely polluted). Because interactions between concentrations in organs and soil were not significant in figures (e) and (f), predicted relationships are drawn for all contaminations levels.</p

For each soil contamination level, concentrations of Cd and Pb (minimum, mean, and maximum values, µg/g DM) in the liver and kidneys and number and percentage (in brackets) of wood mice at risk for metal-induced stress from the surroundings of the former Metaleurop Nord smelter.

<p>Individuals are considered at risk for metal-induced stress when TM concentrations were above the thresholds defined by Shore and Douben <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0066399#pone.0066399-Shore1" target="_blank">[22]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0066399#pone.0066399-Shore2" target="_blank">[23]</a>.</p

Field mixtures of currently used pesticides in agricultural soil pose a risk to soil invertebrates

International audienc

Model outputs presenting partial R_LR² and <i>p</i>-values in brackets (F-statistics) for each variable and for the entire model.

<p>Models were constructed as follows: Index ∼ age+gender+[TM]soil+landscape+[TM]organ+age:gender+age:[TM]organ+gender:[TM]organ+[TM]soil:[TM]organ+landscape:[TM]organ. Because landscape and two-way interactions between [TMs] in organs and age or gender were not significantly related to the studied indices in all tested models (LRT, p>0.050), these variables were not included in the table. When a two-way interaction was significant, all terms (even not significant ones) included in this interaction are presented in the table.</p

Pollution level, median Cd and Pb soil concentrations (µg/g DM), and the number of sampling squares for each landscape type studied.

<p>Pollution level, median Cd and Pb soil concentrations (µg/g DM), and the number of sampling squares for each landscape type studied.</p