## 3 Results and Discussion
### Metal Analysis
When an organism's rate of absorption exceeds its rate of excretion, net accumulation develops. The size of the individual organism can also have an impact on metal bioaccumulation in crabs. For both freshwater and marine crabs, smaller animals do indeed accumulate more metals [50; 51]. Some work on the contamination of crab tissues by heavy metals has been reported in the literature. The values recorded in different regions of the world have been mentioned in Table 3. The concentrations of copper reported in our study in the gills of _P. segnis_ individuals from Ghannouch and Djerba are lower than those reported in the samples of crabs collected from the Bizerte Lagoon, the Monastir Coast, and Gargour in Sfax [52; 53]. The levels of the same element in the hepatopancreata of _P. segnis_ in the two studied sites (Ghannouch and Djerba) are also lower than those recorded in crab samples from Canada [54], Australia [35], and the United States [55]. However, the concentration in the hepatopancreas samples of individuals from Ghannouch is similar to the concentration found in crab samples from Brazil [56]. The zinc contents in the gills of crabs from Ghannouch and Djerba are lower than those reported in the samples of crabs collected from the Bizerte Lagoon, Monastir Coast and Gargour in Sfax [52]. The zinc concentrations in the hepatopancreata of _P. segnis_ from Ghannouch and Djerba are lower than those recorded in crab samples from Canada [54], Australia [35], and the United States [55]. However, the concentration of this element in the \begin{table}
\begin{tabular}{l l l l l l} \hline \hline
**Organism** & **Cu** & **Pb** & **Zn** & **Cd** & **References** \\ \hline Fish & - & 0.3 & - & 0.05 & [40] \\ Crustaceans & - & 0.5 & - & 0.5 & \\ Bivalves & - & 1.5 & - & 1 & \\ Fish & 50 & 0.5 & 150 & 0.1 & [39] \\ Crustaceans & 50 & 0.5 & 150 & 0.5 & \\ Bivalves & 50 & 1.0 & 150 & 1.0 & \\ Fish & 30 & 0.5 & 30 & 0.05 & [41] \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Data relating to some metal levels (mg/kg dw) in the tissues of aquatic organisms, according to standards [39; 40; 41]. hepatopancreas samples of crabs from the Ghannouch site was similar to the concentration found in crab samples from Brazil [56]. For cadmium, the values noted in the gills of _P. segnis_ from Ghannouch and Djerba are higher than those reported in the samples of crabs (_Carcinus maneas_) collected from the Lagoon of Bizerte, the Coast of Monastir, and Gargour in Sfax [52]. The cadmium content in the hepatopancreata of individuals from Ghannouch is higher than the values recorded in crabs from Canada [54], Australia [35], the United States [55], and Brazil [56], while its concentration in the hepatopancreata of the Djerba crabs is similar to that reported in samples from Canada [54], Australia [35], and the United States [55]. However, it is higher than in the samples from Brazil [56]. The concentrations of lead in the gills of crabs from the two sites Ghannouch and Djerba are lower than those observed in crab samples collected from the Bizerte Lagoon and Monastir Coast [52]. The content of this element in the gills of crabs from Djerba is close to that of crabs collected in the site of Gargour in Sfax [52]. In the hepatopancreata of Ghannouch individuals, the Pb contents are close to the concentrations reported in _C. maneas_ from the Bizerte lagoon. However, for the values observed in the hepatopancreata of _P. segnis_ individuals from both from Ghannouch and Djerba, the levels are higher than those obtained in the samples from the coast of Monastir and from Gargour in Sfax (Table 3). Regarding the data from the study by [PERSON] et al. [53] on _C. maneas_ captured from Bizerte lagoon, the Pb concentrations are higher than those in the gills and hepatopancreata except for the levels in the gills of individuals from the Sfax site (Table 3). Comparing our data with other studies in other localities, we notice that the Pb levels in our samples are higher.