The influence of age and sex on the bioaccumulation of heavy metals in Apodemus sylvaticus was studied in Merja Zerga lagoon in northern Morocco. Five trace metal elements (Zn, Pb, Cr, Cu and Fe) were quantitatively analyzed by Varian AA 240 atomic absorption spectroscopy with graphite furnace in three organs (Liver, Kidney and Heart) from animals of different age and sex. The maximum metal level of the analyzed samples was recorded in adults and was limited to 46.62 μg/g for Pb and 35.1 μg/g for Cu, while it reached 22.69 μg/g, 7.59 μg/g and 6.78 μg/g for Cr, Zn and Fe, respectively. Highly significant differences were found for bioaccumulation of heavy metals according to animal ages and no significant differences were observed between the two sexes among the studied animals. Our results revealed also the existence of a strong correlation (r > 0.65) between the majority of biometric parameters and the trace element concentrations. In general, we found that age is a critical factor in estimating the level of heavy metal pollution. Other characteristics such as habitat, feeding habits and anti-predator behavior of the species need to be studied.

Even though Gerbillinae rodents represent an important part of the mammalian fauna in North Africa, many gaps remain in our understanding of the distribution, ecology, evolution, and systematics of some lesser known species in this family. We present in this study the most recent findings on two of these species. The first species, Gerbillus simoni Lataste, 1881, is a short-tailed, small gerbil, endemic to North Africa. In Morocco, it is present only in a small area in the northeast, where it has not been caught since 1970. In 2014, we captured a small gerbil in this region that was identified as G. simoni based on morphology and molecular data (cytochrome b gene sequencing). This study represents the first genetic characterization of G. simoni in Morocco and the first one outside Tunisia. Populations from Morocco and Tunisia (mainland and Kerkennah Islands) show very little genetic differentiation. The second species, Gerbillus henleyi de Winton, 1903, is a long-tailed small gerbil that lives in the Sahel and North Africa with an extension to the Middle East. In Morocco, this species was only known in the southwest. Between 2014 and 2015, we have captured four gerbils in the northeast of the country, which were confirmed genetically and morphologically as belonging to this species. This represents an extension of its known distribution of about 370km to the northeast of the country. These new Moroccan specimens form a distinct lineage. High genetic diversity is observed throughout the geographic range of G. henleyi, suggesting the existence of several cryptic species.

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Many micromammals were shown to be vulnerable to metallic trace elements and are therefore suitable for biomonitoring. The objective of our research is to assess the exposure of a small rodent, Mus spretus, as a bioindicator of pollution to trace elements. We have determined the concentrations of Cu, Pb, Cr, Zn and Fe in the liver, kidneys and heart of 71 individuals of Mus spretus in north-west Morocco in two areas: Merja Zerga and Dayet Erroumi. Tissue metal concentrations in this species varied widely with age, sex, sites and organs. The concentration of Cu in the liver was the highest among all the metals and was recorded in adult females of Merja Zerga with a maximum of 60 µg / g ; at Dayet Erroumi, it was around 14 µg / g. At the same time, we found a similar trend for Fe, Pb, Cr and Zn in the three organs in males and females at the two sites. Highly significant differences between females at the two sites were recorded for the variables weight (W) and head to body length (TL) (t = -3.992; p < 0.001 and t = -2.242, p < 0.05), however, males obtained equal values ​​in the two sites. Spatiotemporal monitoring in small mammals must be studied, but requires the application of a non-lethal estimator.