BackgroundFor thousands of years, Tunisian geothermal water has been used in bathing. Indeed, thermal baths “Hammam” were recommended in the treatment of different type of illnesses as, for instance, for relaxing joints and soothing. The ability of microalgae to sustain at the high temperature makes them potential producers of high value thermostable bio-products. This study aimed to explore the therapeutic potential of the aqueous extracellular polysaccharides (AEPS) of the Tunisian thermophilic microalgae Graesiella sp. and to evaluate its physico-chemical characteristics.MethodsDifferent parameters were used to characterize the AEPS. The dry weight, volatile dry weight, elemental analysis, monosaccharide composition and IR-spectroscopy analysis. Carbohydrate, uronic acid, ester sulfate and protein concentrations were also determined using colorimetric assay. AEPS was analyzed for its antioxidant propriety by means of total antioxidant capacity, DPPH radicals scavenging assay, ferrous chelating ability and hydroxyl and superoxide radical scavenging activity. The antiproliferative activity of AEPS was evaluated for HepG2 and Caco-2 cells using the MTT assay.ResultsThe Graesiella sp. AEPS is found to be a hetero-sulfated-anionic polysaccharides that contain carbohydrate (52 %), uronic acids (23 %), ester sulfate (11 %) and protein (12 %). The carbohydrate fraction was formed by eight neutral sugars glucose, galactose, mannose, fucose, rhamnose, xylose, arabinose and ribose. The FT-IR revealed the presence of carboxyl, hydroxyl, amine and sulfate groups. AEPS showed high activity as reducing agent, high ferrous chelating capacity and caused a significant decrease in a concentration-dependent manner of hydroxyl radical. A moderate DPPH scavenging activity and a poor superoxide radical scavenging ability were also observed. AEPS treatment (from 0.01 to 2.5 mg/ml) caused also a clear decrease of cell viabilities in a dose-dependent manner. The IC50 values obtained in HepG2 and Caco-2 cells were 1.06 mg/ml and 0.3 mg/ml respectively.ConclusionsThis study evidenced that the Graesiella sp. AEPS exhibits antioxidant and antiproliferative activities. The biological activities of this extract depend on its fine structural features. Further work will identify and purify the active polysaccharides to enhance our understanding of their complete structure and relationships with its function.

Genetic diversity of loggerhead turtles, Caretta caretta, nesting on the Kuriat Islands, the most important Tunisian nesting beach (central Mediterranean), was investigated using both nuclear and mitochondrial markers. Allozyme electrophoresis of 63 hatchlings from four different clutches showed a low genetic diversity. The genotypic composition of two clutches did not match Mendelian expectations suggesting the occurrence of multiple paternity. The analysis of 380 bp of the mitochondrial DNA control region revealed no genetic variability. Only one haplotype was described in our sample (N ¼ 16), which corresponds to the sequence of the most common haplotype found on the Mediterranean nesting beaches (CC-A2). The low genetic diversity detected by both mitochondrial and allozyme markers is discussed taking into account available data about past and present situations of loggerhead nesting activity in this site. Adequate conservation measures should be urgently taken to protect the nesting population in this area. 4olfa chaieb et al.

Understanding the dispersal pattern and mechanisms affecting the mixing of Endangered loggerhead sea turtles Caretta caretta is a key issue for establishing sound conservation strategies. Loggerhead turtles are commonly encountered all along the Tunisian coast and particularly in the Gulf of Gabès, which is one of the most important foraging habitats for this species in the Mediterranean Sea. We conducted extensive sampling of 175 juvenile and adult loggerhead turtles that were stranded or incidentally captured in the areas along the northern (NTC), eastern (Gulf of Hammamet, GHAM) and southern (Gulf of Gabès, GGAB) Tunisian coast over a 6 yr period (2004 to 2009). A 380 bp fragment of the mitochondrial DNA control region was sequenced and analysed. Seven haplotypes were revealed, and a gradual variation in haplotype frequencies was observed among the studied areas. The extreme samples (NTC and GGAB) differed genetically from each other, while both were similar to the central sample (GHAM). This finding was confirmed by mixed stock analysis estimates, which suggested that the proportions of Atlantic turtles were very high in the NTC and decreased southward, while the proportions of Mediterranean contributions were higher in the GGAB and decreased in the opposite direction. The observed pattern of genetic variation and turtle distribution, which is probably related to differences in geomorphology and sea surface currents among these coastal areas, should be considered in future management plans.KEY WORDS: Loggerhead sea turtle · Mitochondrial DNA · Foraging · Dispersal · Mixed stock analysis Resale or republication not permitted without written consent of the publisher Editorial responsibility: Paolo Casale,

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