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BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.

In order to provide a better characterization and understanding of the brine shrimp Artemia salina life-cycle, different ecological and biological parameters were taken out monthly during two periods from Sabkhet El Adhibet (south-east Tunisia). Variation of water temperature, salinity, pH, dissolved oxygen, nutrients (orthophosphate, nitrites, nitrates and ammonium) and phytoplankton density were monitored. The Artemia population was also surveyed. Artemia were present in the site with salinity between 32.2 and 281.7 g l 21 and water temperature between 12.1 and 25.48C. The pH ranged from 7.6 to 9 and dissolved oxygen concentration from 3.4 to 17.5 mg l 21 . Minimum and maximum values of phytoplankton density were 0.19 and 14.59 10 6 cell l 21 . In addition, the nutrient analysis registered showed that nitrate and ammonium represent the major nutrient. The Artemia population density fluctuated between 0.22 and 38.57 individuals per litre. The male:female ratio was dominated by the males. Artemia from Sabkhet El Adhibet showed variability in fecundity (total offspring and brood size) as well as in the ratio encystment/oviviparity. The individual fecundity fluctuates between 29.4 and 70.2 cysts and 17.8 and 69.8 nauplii. Finally, the influence of physical and chemical parameters as well as phytoplankton density over the Artemia population was noticed.

Artemia salina is an extremophile species that tolerates a wide range of salinity, especially hypertonic media considered lethal for the majority of other aquatic species. In this study, A. salina cysts were hatched in the laboratory and nauplii were acclimated at three different salinities (60, 139 and 212 ppt). Once in the adult phase, their hemolymph osmolality was measured. The animals were strong hypoosmoregulators in the entire range of tested salinities, with up to 10 fold lower hemolymph osmolalities than their surrounding environment. Immunostaining of Na+/K+-ATPase was done on sections and on whole body mounts of adults in order to localize the ionocytes in different organs. An intense Na+/K+-ATPase immunostaining throughout the cells was observed in the epithelium of the ten pairs of metepipodites. A positive immunoreactivity for Na+/K+-ATPase was also detected in the maxillary glands, in the epithelium of the efferent tubule and of the excretory canal, as well as in the anterior digestive tract. This study confirms the strong hypo-osmotic capacity of this species and affords an overview of the different organs involved in osmoregulation in A. salina adults. Abbreviations.

In the present study, decapsulated cysts from eleven Tunisian Artemia salina populations were analysed for their fatty acid profile. Results showed that palmitic (16:0), palmitoleic (16:1n-7), stearic (18:0), cis-vaccenic (18:1n-7), oleic (18:1n-9), linoleic (18:2n-6), linolenic (18:3n-3) and eicosapentaenoic (20:5n-3) were the major fatty acids. The ratio of C16:0/C16:1 fatty acids fluctuated between 0.8 and 3.8. Docosahexaenoic acid (22:6n-3) was absent or found in trace (<0.2%) and arachidonic acids (20:4n-6) was found in higher quantity in all marine-type cysts than in freshwater-type cysts samples. Furthermore, based on the fatty acid profile of the studied Artemia salina populations, we can concluded that Sijoumi, Sahline, Bekalta, Mcheguig and El Adhibet strains could be ascribed to marine-type Artemia, whereas the population from Moknine, Sidi El Hani, Sfax, El Melah, Zarzis and Mhabeul could be categorized as freshwater-type. Principal components analysis showed that palmitoleic acid, linolenic acid, eicosapentaenoic acid, arachidonic acid and C16:0/C16:1 ratio are the most important fatty acids variable between cysts samples, with a total contribution of 68.73% relatively to the first component, whereas, for the second component, palmitic acid, cis-vaccenic acid and oleic acid, are the most important variables, with a total contribution of 56.25%. Moreover, palmitoleic acid, linolenic acid, eicosapentaenoic acid, arachidonic acid and C16:0/C16:1 ratio are the most important fatty acids which contribute to the discrimination between freshwater and marine-type Artemia; while palmitic acid, cis-vaccenic acid and oleic acids represent the major fatty acids permitting differentiation between strains from the same Artemia type, especially for freshwater-type Artemia.

This study was aimed to examine in greater detail the influence of selected environmental factors on the life cycle and morphological characteristics of the brine shrimp Artemia salina (Linnaeus, 1758). During this follow-up, from November 2005 to April 2006 and from November 2006 to April 2007, Sabkhet El Adhibet (southeast Tunisia: 33°07'7.58"N, 11°24'8.69"E) was surveyed monthly to determine the impact of water salinity, temperature, pH, dissolved oxygen, and phytoplankton density and community structure on Artemia density, population structure, reproductive mode, and total offspring. Strong correlations were found between physicochemical parameters of water and Artemia reproduction characteristics. In contrast, no significant relationship was detected between physicochemical variables and Artemia population structure and density. Further, there were no correlations between phytoplankton density and the Artemia life cycle. Moreover, we observed relationships between physicochemical parameters and all morphological characteristics, especially between the width of 3 rd abdominal segment and salinity (r xy = 0.96), temperature (r xy = 0.73), pH (r xy = -0.77) and oxygen (r xy = -0.92) for male specimens, and between the length of the furca and both salinity (r xy = -0.76) and dissolved oxygen (r xy = 0.74), and between the maximal diameter of compound eyes and temperature (r xy = -0.56) for female specimens. Principal component analysis (PCA) shows that male and female specimens collected at different environmental conditions converge, which explains the morphological similarity between them according to salinity, temperature, and dissolved oxygen concentration as well as total phytoplankton, diatom, cryptophyte, and dinophyte density.