Imposex level and penis malformation in Hexaplex trunculus from the Tunisian coast

Volume: 24Start Page: 79End Page: 8

Shell alterations in Hexaplex trunculus collected in the vicinity of an impacted zone by industrial marine discharges (Gabès, Southern Mediterranean)

International audienceUsing the gastropod Hexaplex trunculus, a comparative study of the shell characteristics (morphometrics, microstructure and elemental composition) was carried out in the vicinity of Gabès city (Chatt Essalem, CE) which is known as seriously affected by industrial pollution, and two control zones (Ghanouche, GH and Teboulbou, TB). Gastropods from CE had larger, thicker and heavier shells, associated with bigger apertures and slighter soft bodies. Scanning electron microscope (SEM) revealed the presence of three shell layers having a crossed lamellar structure. The inner layer was thinner, while the median layer was thicker in snails from CE, suggestive of the ability of H. trunculus to remodel the shell microstructure accordingly. Moreover, the median and inner layers were marked by the presence of fibrous interbeds that were numerous and thicker in shells from CE. In this site, shell elemental alteration was also observed with a decrease in Ca, P, S, K and O contents against an increase in C, Cl and Mg compared to control sites. This investigation was in agreement with previous studies and further suggests the deleterious effect of coastal pollution generated by various industrial units implemented around Gabès city on marine organisms

Population Genomics Reveals the Underlying Structure of the Small Pelagic European Sardine and Suggests Low Connectivity within Macaronesia

The European sardine (Sardina pilchardus, Walbaum 1792) is indisputably a commercially important species. Previous studies using uneven sampling or a limited number of makers have presented sometimes conflicting evidence of the genetic structure of S. pilchardus populations. Here, we show that whole genome data from 108 individuals from 16 sampling areas across 5000 km of the species’ distribution range (from the Eastern Mediterranean to the archipelago of Azores) support at least three genetic clusters. One includes individuals from Azores and Madeira, with evidence of substructure separating these two archipelagos in the Atlantic. Another cluster broadly corresponds to the center of the distribution, including the sampling sites around Iberia, separated by the Almeria–Oran front from the third cluster that includes all of the Mediterranean samples, except those from the Alboran Sea. Individuals from the Canary Islands appear to belong to the Mediterranean cluster. This suggests at least two important geographical barriers to gene flow, even though these do not seem complete, with many individuals from around Iberia and the Mediterranean showing some patterns compatible with admixture with other genetic clusters. Genomic regions corresponding to the top outliers of genetic differentiation are located in areas of low recombination indicative that genetic architecture also has a role in shaping population structure. These regions include genes related to otolith formation, a calcium carbonate structure in the inner ear previously used to distinguish S. pilchardus populations. Our results provide a baseline for further characterization of physical and genetic barriers that divide European sardine populations, and information for transnational stock management of this highly exploited species towards sustainable fisheries