The multifaceted effects of fluoranthene and polystyrene on the taxonomic composition and associated functional traits of marine meiofauna, by using single and mixture applications.

The current experiment measured the multifaceted effects of polystyrene and fluoranthene, acting alone or in a mixture on marine meiofauna, but with a special focus on nematodes' morphological and functional traits. The results showed changes in the abundances for all tested concentrations of both compounds. The nematode communities exposed to the highest concentrations of fluoranthene (30 ng.g-1 Dry Weight (DW)) and polystyrene (100 mg.kg-1 DW) alone or in a mixture, were significantly less diverse compared to control and were associated with significant changes in the percentage of taxonomic composition and feeding-guilds. The most sensitive taxa to fluoranthene comprised epistratum feeders, whereas the nematodes mostly affected by polystyrene were omnivores-carnivores. A new functional tool, the Index of Sensitivity (IOS), proved to be reliable in depicting the changes that occurred in the taxonomic and functional features of the nematofauna.

Artificial wetlands as tools for frog conservation: stability and variability of reproduction characteristics in Sahara frog populations in Tunisian man-made lakes.

Amphibian populations are in decline principally due to climate change, environmental contaminants, and the reduction in wetlands. Even though data concerning current population trends are scarce, artificial wetlands appear to play a vital role in amphibian conservation. This study concerns the reproductive biology of the Sahara frog over a 2-year period in four Tunisian man-made lakes. Each month, gonad state (parameters: K, GSI, LCI), fecundity, and fertility of females (using 1227 clutches) were evaluated in the field under controlled conditions. Clutches were present for 110-130 days at two of the sites, but only for 60-80 days at the other two. Maximum egg laying occurred in May, corresponding to the highest point in the gonad somatic index. Clutch densities were higher in the smaller lakes. Female fecundity was in relation to body size; mean clutch fecundity attained 1416 eggs, with no differences observed according to site. Egg fertility varied over a 1-year period, with a maximum in May followed by a decrease when water temperature was at its highest. Eggs were smaller at the beginning of spawning; maximum size was in May, which might explain the higher fertility, but no maternal influence was detected. Embryonic development was strictly dependent on temperature. The population at each site appeared as a small patch within a metapopulation in overall good health, as shown by the relative temporal stability in reproduction variables. Constructed wetlands may therefore play an important role in the conservation of amphibians, especially in semi-arid zones.

Alexandrium pacificum Litaker sp. nov (Group IV): Resting cyst distribution and toxin profile of vegetative cells in Bizerte Lagoon (Tunisia, Southern Mediterranean Sea).

A high spatial resolution sampling of Alexandrium pacificum cysts, along with sediment characteristics (% H2O, % organic matter (OM), granulometry), vegetative cell abundance and environmental factors were investigated at 123 study stations in Bizerte Lagoon (Tunisia). Morphological examination and ribotyping of cells obtained from a culture called ABZ1 obtained from a cyst isolated in lagoon sediment confirmed that the species was A. pacificum. The toxin profile from the ABZ1 culture harvested during exponential growth phase was simple and composed of the N-sulfocarbamoyl toxins C1 (9.82pgtoxincell-1), the GTX6 (3.26pgtoxincell-1) and the carbamoyl toxin Neo-STX (0.38pgtoxincell-1). The latter represented only 2.8% of the total toxins in this strain. High abundance of A. pacificum cysts correlated with enhanced percentages of water and organic matter in the sediment. In addition, sediment fractions of less than 63µm were examined as a favorable potential seedbed for initiation of future blooms and outbreaks of A. pacificum in the lagoon. A significant difference in the cyst distribution pattern was recorded among the lagoon's different zones, with the higher cyst abundance occurring in the inner waters. Also, no correlation due to the specific hydrodynamics of the lagoon was observed in the spatial distribution of A. pacificum cysts and vegetative cells.

Effects of temperature, density and food quality on larval growth and metamorphosis in the north African green frog Pelophylax saharicus.

The ectodermic status of Amphibians explains their heavy dependence at ambient temperatures and thus their sensitivity to global warming. Temperature is likely the main factor regulating their physiology by acting on the endocrine system, with consequences on development, growth and size at metamorphosis. All these parameters control survival in the wild and performances in raniculture. This study is, to our knowledge, the first report on the effects of temperature, density and protein level in food on the rearing of the North African green Frog Pelophylax saharicus. Results show that a temperature of 26 °C is optimal for maximum weight gain. The maximum metamorphosis rate is obtained between 24 and 26 °C. The highest yields occur at low densities from 1 to 10 tadpolesl(-1). The best survival rate and accelerated metamorphosis are obtained at a level of 35% protein in food whose impact on food intake and weight gain is low. The maximum weight attained by tadpoles at metamorphosis, however, is obtained with a level of 40% protein. These results justify examination of this species in the light of climate change and suggest new techniques for aquaculture.