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The freshwater mussel Unio durieui is a rare bivalve endemic to North African watersheds. Although this is an important species from an ecological and conservation perspective, information on its genetic diversity and population structure is lacking. Here, we combine geometric morphometric and molecular genetic analyses to characterize and evaluate the status of populations of this endangered species from four Tunisian watershed basins (Cap Bon, Ichkeul, northwest and Mejerda River basins). By using a multiparameter approach, we sought to test the hypothesis that populations from these geographic regions could be considered as distinct management units. Shell outline shapes were assessed using elliptic Fourier analysis followed by linear discriminant analysis of principal components. Multivariate analysis applied on normalized Fourier coefficients showed highly significant differences in shell shape among the populations. Population genetic analysis based on inter-simple sequence repeats revealed low levels of diversity and high differentiation between the populations studied. Two groups of populations are clearly evident, thus separating samples from the Northwest from those from the other watersheds. Although there is no evidence for isolation by distance patterns, genetic and phenotypic diversity appeared significantly correlated with climatic variables. These findings suggest isolation by environment and the nominal species U. durieui may constitute two biological species. Conservation programme actions should consider this substructure in establishing effective recovery strategies for this endangered species. [ABSTRACT FROM AUTHOR]

We determined the condition factor and relative growth patterns of the newly established invasive Atlantic blue crab Callinectes sapidus in the Ghar El Melh Lagoon, northern Tunisia, central Mediterranean Sea using two biometric relationships: carapace width-weight and carapace length-weight. Crabs were sampled during winter and summer 2020. Growth coefficient (slope b) for width-weight relationship ranged from 2.037 to 3.008 according to sex and seasons, indicating an isometry to negative allometry growth patterns. Length-weight relationship, however, demonstrated isometry growth patterns, with the exception of the summer sample, which displayed a positive allometry. The allometry seems to be not affected by seasons, but sex demonstrated a strong effect for the width-weight relationship, as indicated by ANCOVA. The Fulton's condition factor, however, showed significant variation between seasons, but not between sexes. [ABSTRACT FROM AUTHOR]

Ten monoclonal microalgal cultures were obtained from several Tunisian inland water bodies, and their dichloromethane and methanolic extracts were screened for antibacterial, antileishmanial, and antioxidant properties, as well as phycobiliprotein production capacity. Cylindrospermopsis raciborskii has been shown to synthesize high levels of phycocyanin and may be an effective alternative source to other sources used for commercial production of phycocyanin. Chroococcus sp. and Leptolyngbya sp1. exhibited the strongest radical scavenging activity against DPPH (IC50 = 212.15 and 263.91 μg ml−1, respectively), indicating their promising potential for use as new effective and non-toxic antioxidants. Furthermore, Dunaliella sp. showed an interesting antileishmanial activity against the pathogens Leishmania infantum and Leishmania major (IC50 = 151 and 284 μg ml−1, respectively), thus representing a good candidate for use against cutaneous and visceral leishmaniasis in Tunisia, a country endemic to these diseases where thousands of new cases are registered every year. These results suggest that the strains of microalgae featured in this work have the potential to serve as natural alternative, safe and sustainable sources of high value-added products that could be used to improve the final biomass value. [ABSTRACT FROM AUTHOR]

We determined the condition factor and relative growth patterns of the newly established invasive Atlantic blue crab Callinectes sapidus in the Ghar El Melh Lagoon, northern Tunisia, central Mediterranean Sea using two biometric relationships: carapace width-weight and carapace length-weight. Crabs were sampled during winter and summer 2020. Growth coefficient (slope b) for width-weight relationship ranged from 2.037 to 3.008 according to sex and seasons, indicating an isometry to negative allometry growth patterns. Length-weight relationship, however, demonstrated isometry growth patterns, with the exception of the summer sample, which displayed a positive allometry. The allometry seems to be not affected by seasons, but sex demonstrated a strong effect for the width-weight relationship, as indicated by ANCOVA. The Fulton's condition factor, however, showed significant variation between seasons, but not between sexes. [ABSTRACT FROM AUTHOR]

To understand patterns of genetic and morphological variability, population structure and dispersal dynamics of the invasive bivalve Pinctada imbricata radiata (Leach, 1814) in Tunisian waters, we studied 200 individuals from five different sites (natural, polluted and/or subjected to environmental and anthropogenic pressures) using 10 enzymatic systems and six shell measurements. In this study, we attempt to elucidate the relationship between the spreading ability and the adaptive potential of the species under various environmental stresses. Fourteen putative enzyme-coding loci were resolved, six of which were polymorphic at the level of 99%. P. imbricata radiata maintains a relatively consistent level of polymorphism at the genetic markers studied, since 10% of individuals were heterozygous. The mean FIS value was positive and significant in two samples. However, the remaining samples collected from the disturbed marine sites (polluted, urban and lagoon areas) were at Hardy–Weinberg equilibrium. Highly significant genetic (mean FST = 0.022, P < 0.001) and morphological (Wilks' lambda = 0.0814, approximate F20, 627 = 35.484, P < 0.001) differentiations between samples were observed, with no evidence of isolation caused by geographic distance. However, the Mantel test performed between genetic and morphological distances revealed a significant correlation. Our results indicate that natural selection seems to have a greater influence on genetic differentiation in P. imbricata radiata than genetic drift. The combination of genetic and morphological data provided important theoretical information for determining the invasion mechanisms of the species. [ABSTRACT FROM AUTHOR]

Based on length, weight, and age data, we examined allometry and growth parameters for common pandora, Pagellus erythrinus, commercially collected seasonally from northern and southern Tunisian coasts in 2007. A total of 370 specimens (14-27.5 cm in length) were used to assess the allometric variation at seasonal scales. The slope b values (regression coefficient) of the length-weight relationship varied between 2.494 to 3.237, indicating (roughly) an isometric to negative allometric growth pattern. The allometric relationship, as a proxy for fish condition, seems to be affected by seasons and sex in the northern population, while only seasons seem to have a strong effect in the southern population, as indicated by ANOVA. The von Bertalanffy growth parameters were identified at L∞ = 34.076 and 28.017 cm, k = 0.153 and 0.150/year, and t0 = -1.922 and -3.961 years for the northern and southern sample, respectively. [ABSTRACT FROM AUTHOR]

Many marine organisms have complex genetic patterns that cannot be easily resolved by data analysis on spatial distribution of variability usually applied in population genetic studies. We propose an analytical framework to evaluate the role of dispersal during early life stages that considers the actual hydrodynamic connectivity in the Mediterranean Sea, as a factor shaping the population structure of demersal fishes. To this purpose, and to test different scenarios of gene flow, genotypes of individuals of Pagellus erythrinus sampled at 12 sites in the central Mediterranean Sea were analyzed at ten microsatellite loci. The results show the lack of genetic structure in western Mediterranean basin and a pattern of gene flow that deviates from an isolation by distance model. The observed gene flow estimates appear to be scale-dependent. At local scale, it is likely the result of multifactorial components, whereas at a larger scale it is mainly driven by the sea currents, directly influencing dispersal of larvae between sites not reachable by adult movements. Our results stress the importance of a quantitative analysis of potential early life stage dispersal in any study focusing on the population structure of fishes with a long larval stage. [ABSTRACT FROM AUTHOR]

The common dentex, Dentex dentex, is a fish species which inhabits marine environments in the Mediterranean and Northeast Atlantic regions. This is an important species from an ecological, economic and conservation perspective, however critical information on its population genetic structure is lacking. Most samples were obtained from the Mediterranean Sea (17 sites) with an emphasis around Corsica (5 sites), plus one Atlantic Ocean site. This provided an opportunity to examine genetic structuring at local and broader scales to provide science based data for the management of fishing stocks in the region. Two mitochondrial regions were examined (D-loop and COI) along with eight microsatellite loci. The COI data was combined with publicly available sequences and demonstrated past misidentification of common dentex. All markers indicated the absence of population genetic structure from the Bay of Biscay to the eastern Mediterranean Sea. Bayesian approaches, as well as the statistical tests performed on the allelic frequencies from microsatellite loci, indicated low differentiation between samples; there was only a slight (p = 0.05) indication of isolation by distance. Common dentex is a marine fish species with a unique panmictic population in the Mediterranean and likely in the Atlantic Ocean as well. [ABSTRACT FROM AUTHOR]

The distribution of the genetic diversity and the population structure of Pagellus erythrinus were analysed using mitochondrial control region sequences and cytochrome b restriction profiles in a total of 128 and 508 individuals, respectively, that were collected from 15 sampling sites in the central Mediterranean Sea and from one site in the Atlantic Ocean. No population genetic structure was detected within the central Mediterranean and thus, the commonly recognized transition zones in the area do not seem to affect population connectivity. The comparison between the Mediterranean samples and the single Atlantic sample suggests weak differentiation between the two basins. Three mitochondrial lineages were identified, each including individuals from almost every sampling site. The haplotype and nucleotide diversity values, mismatch distribution and demographic parameters indicate that the sympatry of these lineages can be ascribed to a period of isolation followed by genetic divergence, population expansion and secondary contact, all of which are likely to be associated with climatic oscillations that occurred during the middle and late Pleistocene. [ABSTRACT FROM AUTHOR]

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Geographic and temporal genetic variation of allele frequencies at 21 isozyme loci were examined in two populations of common Pandora, Pagellus erythrinus (Linnaeus, 1758, Sparidae). Fishes were sampled from Western and Eastern Mediterranean basins off Tunisian coasts over one year at the beginning of each season. Analysis of genetic diversity showed a low level of heterozygosity for all populations (average He=0.052). Fixation indices reflected a significant departure from Hardy_Weinberg equilibrium with heterozygote deficiencies, slight spatial differentiation between both sampling localities (FST=0.003, P=0.017) and temporal genetic stability at seasonal and annual scales. Annual genetic variation was evaluated over a five-year period estimated indirectly from fish otoliths. Comparison of genetic diversity between year classes of both locations showed an increase of the He values concurrent with age, supporting the hypothesis of the high variance in individual reproductive success. Finally, our results suggest that the effective population size of Pagellus erythrinus is large and genetic drift is weak but variable, especially between successive adult year classes for both sampling locations. [ABSTRACT FROM AUTHOR]