Search

Though halophytes are naturally adapted to salinity, their salt-tolerance limits are greatly influenced by their provenance and developmental stage. In the present study, physio-biochemical responses of two Tunisian ecotypes of the oilseed coastal halophyte Cakile maritima (Brassicaceae) to salinity (0–400 mM NaCl) were monitored during germination and vegetative growth stages. Tabarka and Jerba seeds were collected from humid or arid climatic areas, respectively. Plant response to salinity appeared to depend on the ecotype and salinity levels. Increasing salinity inhibited germination process. Jerba seeds were found to be more salt tolerant than the Tabarka ones. At the autotrophic stage of growth and under salt-free conditions, Jerba was less productive than Tabarka (in terms of dry matter accumulation), but plant biomass production and leaf expansion (area and number) of the former ecotype were progressively improved by 100 mM NaCl, as compared to the control. In contrast, at the same salt concentration, these parameters decreased under increasing salinity in Tabarka (salt sensitive). Leaf chlorophyll content was reduced at severe salinity, but this effect was more conspicuous in the sensitive Tabarka plants. Na+ contents in the Jerba and Tabarka leaves collected from the 400 mM NaCl-treated plants were 17- and 12-fold higher than in the respective controls. This effect was accompanied by a significant reduction in the leaf K+, Mg2+ and Ca2+ contents, especially in the salt-treated Tabarka. A significant accumulation of proline and soluble carbohydrates in leaves was found during the period of intensive leaf growth. These organic compounds likely play a role in leaf osmotic adjustment and in protection of membrane stability at severe salinity.

Ecological and biogeographical characteristics of 14 species of Tenebrionids (Coleoptera Heteromera) so far known for the Djerba Island (Tunisia, Gulf of Gabes) are illustrated for the first time. Basing on distribution we may recognize South-Western Mediterranean species; 3 centro-southern Mediterranean; 1 extended to the shores of Mediterranean Basin; 1 Western-Mediterranean element; 2 limited to South Mediterranean coast east of Morocco; 1 extended from Morocco (Atlantic coast) to Iran and Northern Arabic Peninsula, 1 extended from Algeria to Iran; 1 endemic of Djerba (Stenohelops berettai Marcuzzi), 1 widely distributed (Mediterranean s. lato). The distribution if often of relict type, due probably to its age. Basing on ecology there are 2 psammophilous species, 4 steppic, 3 rather euryoikous. Most Djeba Tenebrionids can be considered steppic (litoral or continental). Beside an endemic, 3 species show a distribution limited to centro-southern part of Mediterranean; the other are Western Mediterranean or widely distributed species (Scleron armatum and still more Tentyriagrossa and Zophosis punctata. The Tenebrionid coenosis –as well as insect coenoses as a whole– are heavily menaced by the continuously increasing anthropization, with human density, agriculture, grazing and tourism. The former determines a pumping of water from pits, with a possible salification of the water table, harmful to both invertebrates and plants. The excavation of clay for handicraft is another menace to environment, here included landscape. Grazing is bringing about a reduction and sometimes disappearance of coastal dunes, because of destruction of local vegetation (especially Gramineae). Measures of conservation characteristics of landscape invoked due to the great ecological and biogeographical interest of Tenebrionid coenoses living on Djerba since Miocene, and due to the systematic status of some species, still discussed, in this as in many steppic and desertic North African localities.

A revised diagnosis of the genus Saldula Van Duzee based upon synapomorphic characters of male genitalia and hemelytral pigmentation patterns is given. According to this concept ca. 55% of the species World-wide currently assigned to Saldula will have to be transferred to other genera. Several new characters are employed in the definition of species and species groups. The species attributable to the pallipes species group are listed and supplemented by a brief overview of the taxonomic relationships of the Old World species. Saldula luteola sp. n. is described from coastal salt marshes on the Island of Djerba, Tunisia. It mainly appears in extremely depigmented morphs unparalleled elsewhere in the Saldidae and likely constitutes a sister-species of S. sardoa Filippi. The conspicuous intraspecific variation in body size and hemelytral pigmentation in S. palustris (Douglas), the closest relative of the former species, is depicted and briefly discussed. The descriptive accounts are accompanied by numerous photographic illustrations of somatic and genital characters.</p></div></section>

We studied the spring spatial distribution of the ciliate community coupled with environmental factors along the coast and in the open sea at 30 stations sampled (between 27 May and 9 June 2006) in the Gulf of Gabes (Tunisia, Eastern Mediterranean Sea). A total of 61 taxa belonging to 36 genera and 5 taxonomic classes were identified. The ciliate assemblage was numerically dominated by spirotrichs (86% of total ciliates). This group is largely dominated by the choreotrichs (92%) among which tintinnids represented 99%. The total ciliates abundance showed a gradual decrease from the coastal area to the open sea and an increase from the surface to the bottom. The maximum abundance (400 cells l-1) and biomass (6.29 µgC l-1) were found in station 27, close to Djerba Island. The tinitinnid Rhabdonella spiralis was cosmopolitan, being found almost at every station and at each depth, while other taxa may be exclusive to the neritic area, others to the open sea area. The distribution of species in the Gulf of Gabes seemed most likely influenced by the combined effects of hydrographic conditions, zooplankton predation and urban interferences.

Given the growing interest of consumers worldwide in safe, healthy and good quality olive oil, the present study aimed to investigate a number of Tunisian virgin olive oil varieties in an attempt to procure physico-chemical characteristics of interest to the local and global olive oil industry, particularly in terms of variety and area of cultivation. Eight samples collected from Chetoui, Chemlali, Zarrazi, and Zalmati Tunisian cultivars located at Sfax, Thibar, Zarzis, and Jerba were employed. Various physic-chemical parameters were investigated, including free acidity, peroxide value, UV absorption, pigment concentrations, oxidative stability, fatty acid composition, phenolic compounds and sterols. The findings revealed high heterogeneity within and between the varieties. The Chemlali Jerba" and Zarrazi oil samples showed high oleic acid and low linoleic acid concentrations, rich phenolic compounds, and high stability. The sterols fractions in Chemlali Sfax, Chemlali Jerba, and Zalmati olive oils displayed high levels of β-sitosterol, campesterol, and ∆-5-avenasterol. Overall, the olive oil from Chemlali Jerba presented higher levels of natural antioxidants and oxidative stability. Its chemical composition was also noted to be particularly interesting in terms of fatty acid contents, minor components, and antioxidants, namely sterols, tocopherols, carotenoids, and phenolic acids.

The mudsnail taxon Hydrobia s.l. plays a major role in numerous ecological and parasitological studies. Yet, its taxonomy is confusing and its biogeography is poorly understood. A principal problem is that taxa of Hydrobia s.l. belong to morphostatic radiations – widely allopatric species radiations with little or no habitat diversification and a low level of anatomical change. So far, three morphostatic radiations can be identified within Hydrobia s.l.: Hydrobia s.s., Peringia, and Ventrosia. These radiations are identical with the putative genera of Hydrobia s.l. The purpose of the paper is to infer phylogenetic relationships within one of these radiations, Hydrobia s.s. in the northern Atlantic and western Mediterranean. A total of 22 populations, including topotypical populations of five commonly used taxa, were studied genetically using partial sequences of the mitochondrial cytochrome c oxidase subunit I gene. Based on molecular data and the species concept we define, the following species and subspecies were identified: Hydrobia acuta acuta (Draparnaud, 1805) [=H. minoricensis (Paladilhe, 1875)], H. acuta neglecta Muus, 1963, and H. glyca (Servain, 1880) (=H. joossei van Aartsen, Menkhorst and Gittenberger, 1984). One population from Djerba, Tunisia (Hydrobia sp. A) and one population from Mallorca, Spain (Hydrobia sp. B) are genetically distinct from all other taxa studied here. Both populations potentially represent new species. Due to the fact that only one population each has been studied, and so the degree of variation within these two taxa cannot be assessed, a final decision regarding their species level cannot yet be made.