Solar Pond devices: free energy or bioreactors for<Emphasis Type="Italic"> Artemia</Emphasis> biomass production?

The recent exponential growth in industrial aquaculture has led to a huge increase in Artemia biomass production in order to meet increased fish production needs. The present study explores the potential use of salt gradient solar ponds (SGSPs) for production of Artemia nauplii. An SGSP is a basin of water where solar energy is trapped and collected via an artificially imposed gradient. Three zones can be identified in an SGSP: upper and lower zones, which are both convective, and a middle zone, which is intended to be non-convective. The latter acts as a transparent insulation layer and allows for storage of solar energy at the bottom, where it is available for use. The combination of salt, temperature and high transparency could make SGSPs promising bioreactors for the production of Artemia nauplii. Using particle image velocymetry (PIV) and Shadowgraph visualisation techniques, the behaviour of Artemia nauplii under critical cultivation parameters (namely, salinity, temperature and light) was monitored to determine movement velocity, and how movement of Artemia affects the salt gradient. It was observed that Artemia nauplii constantly follow light, irrespective of adverse salinity and/or temperature conditions. However, despite the substantial displacement of Artemia following the light source, the salt gradient is not disrupted. The suitability of SGSPs as bioreactors for Artemia biomass production was then tested. The results were disappointing, probably due to the lack of sufficient O₂ for Artemia survival and growth. Follow-up trials were conducted aimed at using the SGSP as a green and economically attractive energy source to induce faster hatching of cysts and improved Artemia nauplii growth. The results of these trials, and a case study of Artemia nauplii production using an SGSP, are presented. The authors constructed a Solar Pond device, which they suggest as a novel way of supplying thermal energy for Artemia biomass production in an aquaculture enterprise. Finally, the authors suggest a method of producing and collecting Artemia biomass, and of heating a fish larval tank, in an ‘ideal’ Solar Pond device, profiting from the low investment costs of using a decommissioned salt works.     

Characterization of brine shrimp Artemia from Cam Ranh Bay in Central Vietnam

Artemia cysts collected from inoculation experiments in Cam Ranh salterns are evaluated for their potential use in aquaculture. Cyst biometrics, hatching quality, naupliar fatty acid profile and naupliar growth were measured and compared to reference Artemia strains. Cyst characteristics reveal that the parthenogenetic strain (PR China) used in inoculations, was eliminated from the environment and that the remaining brine shrimp are likely to be composed of Macau and Great Salt Lake Artemia strains, and of their cross-breds. Differences in cyst diapause deactivation characteristics between Macau and Great Salt Lake Artemia may have resulted in the disappearance of Macau Artemia during the rainy season and the persistence of Great Salt Lake Artemia during the following dry season.     

Genetic variation in sympatric populations of diploid and polyploid brine shrimp (Artemia parthenogenetica)

We examined genetic variation in sympatric diploid and polyploid brine shrimp Artemia parthenogenetica from each of three populations (China, Italy and Spain). Italian and Spanish tetraploids are closely related (I=0.964). Diploids and tetraploids within each of the two European populations are also closely related (mean I=0.905). Most alleles found in diploids also exist in sympatric polyploids. In contrast, the asexual Artemia (2N, 4N and 5N) in our study share few alleles with their close sexual relative, A. tunisiana (mean I=0.002). These results, as well as the work of other authors, strongly suggest that at least the tetraploid Artemia in our study have an autopolyploid origin.Clonal diversity of polyploid Artemia can be very high at least in some population. Both diploids and polyploids had low clonal diversities in the populations dominated by polyploids and high clonal diversities in the population dominated by diploids.The most common genotypes of sympatric diploid and polyploid Artemia frequently differed. Some alleles occurred only in diploids, while others were restricted to polyploids. These results suggest that polyploidy in Artemia has led to genetic divergence from diploid progenitors, and that ploidy-level variation must also be considered in developing an understanding of spatial and temporal allozyme polymorphism in asexual populations.     

A model for growth of Artemia franciscana cultures based on food ration-dependent gross growth efficiencies

Laboratory cultures of Artemia franciscana grown under batch regimes at constant temperatures (28 °C) and salinity (35 g l^–1), three initial food concentrations (0.1, 0.4 and 1 M cells ml^–1), various daily food rations (0.1–9M Dunaliella tertiolecta cells Artemia ^–1), and different population densities (1–16 ind ml^–1) were used to develop a model of population growth. Growth rates and gross growth efficiencies (K ₁) were largely independent of population densities and initial food concentrations but determined by age and daily amount of food ingested. While maximum growth rates were found with the highest rations, K _{1 max} peaked at rations of 0.5 million cells d^–1 and decreased at feeding levels above this. A contour plot showing the trend relating K ₁ to Artemia size and ingestion rate in combination and was used to model growth in analogous controlled feeding conditions. Computer simulations using this model paralleled published results of final 15-day average individual sizes of Artemia. Optimal results for near constant food utilization are predicted for high initial population densities (100 Artemia nauplii ml ^–1) and daily culls of enough animals to equilibrate food demand with food availability. This strategy could permit a range of Artemia sizes harvested, maximize final individual sizes and retain high total yields (> 1.2 kg dry wt 1^–1). Effects of different culture strategies are discussed.     

Attraction of Aurelia and Aequorea to prey

Previously it has been assumed that medusae make random contact with their prey. Medusae were tested in a flow-through aquarium with inflow at each end and a central outflow. Aurelia aurita and Aequorea victoria were attracted to either end of the chamber if Artemia prey were present in a screened compartment. A. aurita was also shown to be attracted to water conditioned by Artemia, and to ammonium chloride added to one or other of the inflow currents.     

不同营养模式下内蒙古沙漠小型盐湖卤虫种群特征与环境负载力

通过对桑根达莱淖尔卤虫的养殖实验与卵囊解剖,研究了内蒙古沙漠小型盐湖投饵、施肥与自然状态3种营养模式下卤虫的生境、种群动态、生殖特征,分析了环境对卤虫资源的负载力。结果表明:1在起始种群相同的情况下,不同营养模式对种群结构与密度有显著影响;2不同营养模式对个体生长速度影响存在差异,投饵对加快个体生长速度效果最明显,但在性成熟速度方面不同营养模式没有出现统计学显著差异;3不同营养模式对卤虫的怀卵量、卵生/卵胎生比例有显著影响;与空白组相比,投饵组平均怀卵量提高了35.52%—72.71%,施肥组提高了11.34%—26.15%;4卤虫资源的环境负载力为0.3—0.4 kg/m3,加以补充肥料,可提高到0.45 kg/m3,在投喂饲料的情况下可以达到0.5 kg/m3;5卤虫蛋白可开发量按环境负载力的1/3估计,对照组、施肥组和投饵组的相应年开发量分别为2.61—2.98 kg/m3、4.5—5.4 kg/m3和7.51—8.67 kg/m3,滞育卵产量分别为0.73、1.10 g/m3和1.17 g/m3。     

Diet-induced variations in fatty acid content and composition of two on-grown stages of Artemia Salina

Three species of microalgae, the freshwater Euglena gracilis and themarine Dunaliella salina and Tetraselmis suecica, were fed tothe brine shrimp Artemia salina in order to compare their suitabilityin terms of fatty acid enrichment, and their effect on the biometric parametersof the zooplankter. The fatty acid content and composition were analyzed for the post-larval and pre-adult stages of Artemia fed the algae and theresults compared to the initial content of unfed 24-hour post-hatch nauplii.Differences in the total fatty acid content occurred between the three stages,the fatty acid profile being determined by the composition of the diet. A decreasing trend for almost all the individual fatty acids occurred throughdevelopment from post-larva to pre-adult with each of the three algal diets.Biometrical differences between Artemia fed the marine algae and that fed Euglena were not consistent in the post-larval stage, but became considerable in the pre-adult stage. Artemia fed with Euglena achieved twice the weight of animals fed the marine algae and showed thehighest length. The implications for the use of on-grown Artemia as afeed in larviculture of marine and freshwater fish and crustaceans are considered.     

Exposure of gnotobiotic Artemia franciscana larvae to abiotic stress promotes heat shock protein 70 synthesis and enhances resistance to pathogenic Vibrio campbellii

Larvae of the brine shrimp Artemia franciscana serve as important feed in fish and shellfish larviculture; however, they are subject to bacterial diseases that devastate entire populations and consequently hinder their use in aquaculture. Exposure to abiotic stress was shown previously to shield Artemia larvae against infection by pathogenic Vibrio, with the results suggesting a mechanistic role for heat shock protein 70. In the current report, combined hypothermic/hyperthermic shock followed by recovery at ambient temperature induced Hsp70 synthesis in Artemia larvae. Thermotolerance was also increased as was protection against infection by Vibrio campbellii, the latter indicated by reduced mortality and lower bacterial load in challenge tests. Resistance to Vibrio improved in the face of declining body mass as demonstrated by measurement of ash-free dry weight. Hypothermic stress only and acute osmotic insult did not promote Hsp70 expression and thermotolerance in Artemia larvae nor was resistance to Vibrio challenge augmented. The data support a causal link between Hsp70 accumulation induced by abiotic stress and enhanced resistance to infection by V. campbellii, perhaps via stimulation of the Artemia immune system. This possibility is now under investigation, and the work may reveal fundamental properties of crustacean immunity. Additionally, the findings are important in aquaculture where development of procedures to prevent bacterial infection of feed stock such as Artemia larvae is a priority.     

Stress resistance induced by paramylon treatment in Artemia sp.

A study was undertaken to investigate the effectiveness of paramylon extracted from the non-photosynthetic WZSL mutant of Euglena gracilis in potentiating the resistance of the brine shrimp Artemia sp. to stress conditions resulting from poor growth medium quality and daily handling. The experimental design incorporated four different treatments: I) paramylon addition/no growth medium replacement; II) no paramylon addition/no growth medium replacement; III) paramylon addition/growth medium replacement; IV) noparamylon addition/growth medium replacement. As shown by the survival curves of Artemia sp., the addition of paramylon significantly reduced susceptibility of animals to the stressors. Paramylon effectively increased also the ability of offspring to withstand poor water quality and handling damages. Without paramylon almost all offspring died before adulthood, whereas addition of paramylon allowed the animals to moult to the adult stage. Moreover, reproductive success (higher number of living offspring) was enhanced considerably in animals treated with paramylon treated under both stress conditions. These results show that paramylon extracted from Euglena represents a promising biologically active compound for aquaculture purposes. It could be used as a purified product or as component of whole cells, since the Euglena mutant, because of the high intracellular amount of paramylon it can accumulate, could be added to the feed or to water in tanks and ponds without prior processing. This revised version was published online in August 2006 with corrections to the Cover Date.     

International study on Artemia XLIX. Salinity effects on survival,maturity, growth,biometrics, reproductive and lifespan characteristics of a bisexual and a parthenogenetic population of Artemia

Two Artemia populations, a bisexual from San Francisco Bay (California, USA) and a parthenogenetic from Tanggu area (Tianjin province, People's Republic of China) are assayed for their tolerance and fitness in various salinity levels. This study was carried out under laboratory conditions where salinity effects upon special characteristics of the two Artemia populations, such as survival, growth rate, maturation, morphology, fecundity and life duration, were recorded. This evaluation revealed that the two populations examined exhibits significant differences in their response against elevated salinity levels. Furthermore, specific biometric parameters can be a useful tool for the discrimination and/or determination of their distribution in a mixed population, which, in fact, is the case in Tanggu salt works. Artemia franciscana seems to be a more effective colonizer at higher salinities. The data presented in this study may generate useful suggestions for proper management of the solar saltworks at Tanggu although further experimentation is needed.International interdisciplinary study on Artemia populations coordinated by the Laboratory of Aquaculture & Artemia Reference Center, University of Ghent, Belgium.     

Highly repetitive DNA sequence in parthenogeneticArtemia

Summary The study of the structural organization of the eukaryotic genome is one of the most important tools for disclosing the evolutionary relationships between species.Artemia (Crustacea, Phyllopoda) offers a very interesting model for speciation studies. The genus, distributed all over the world, comprises both bisexual sibling species and parthenogenetic populations, exhibiting different chromosome numbers (diploidy, polyploidy, and heteroploidy).Digestion of genomic DNA of the parthenogeneticArtemia sp. from Tsing-Tao (China) with the restriction enzymes Eco RI and Alu I reveals that a highly repetitive sequence of 133 bp is present. The Eco RI fragment has been cloned and characterized by genomic organization. The distribution of the Eco RI family of repeats was also studied in several bisexual and parthenogeneticArtemia populations and compared with an Alu I repetitive fragment previously identified inArtemia franciscana.     

Natural vitamin E enrichment of Artemia salina fed freshwater and marine microalgae

Three species of microalga, the freshwater Euglena gracilis and the marine Dunaliella salina and Tetraselmis suecica, were compared in terms of vitamin E enrichment and survival and growth of the brine shrimp Artemia salina. The tocopherol content was investigated using HPLC for the post-larval and pre-adult stages of Artemia fed the microalgae and the results compared to the initial content of unfed newly hatched nauplii. There was a markedly higher content of tocopherols (about two-fold) in Artemia fed Euglena. Since this microalga contains other antioxidants such as -carotene, vitamin C and glutathione, bioactive molecules such as PUFA, and the immunostimulant polysaccharide -glucan, it represents a valuable alternative for enriching the diets of Artemia and increase its nutritional value as a food item.     

Xenopus Xotx2 and Drosophila otd share similar activities in anterior patterning of the frog embryo

Despite the obvious anatomical differences between the fly and the vertebrate body plans, several genes involved in their development are largely conserved. In this work we provide evidence that overexpression of the Drosophila orthodenticle (otd) gene in Xenopus laevis has a similar effect to that of its homolog Xotx2. Injections of otd mRNA in whole embryos lead to posterior truncations and to induction of ectopic cement glands, similar to Xotx2 injections. In animal cap assays, otd, like Xotx2, is able to activate the cement gland marker XAG and to suppress the expression of the epidermal marker XK81. Finally, as assayed by Einsteck transplantation assays, otd, like Xotx2, is able to respecify a tail/trunk organizer to a head organizer. In this work we also show that Xotx2 and otd share molecular functions that regulate early regional specification of the Xenopus anterior neural plate. Gain-of-function experiment targeting low doses of either otd or Xotx2 mRNAs in the neural plate promote reduction of Xrx1 and Xbf1 expression domain; no changes are observed for the anterior mesodermal marker Xgsc, the dorsal diencephalic marker Xbh1, and the midbrain/hindbrain marker Xen2. otd/Xotx2 inhibition activity of Xrx1 and Xbf1 expression is consistent with the strong inhibition of Xfgf8 expression in the anterior neural ridge observed upon otd/Xotx2 mRNA injection.     

Zooplankton distribution in four ponds of different salinity: a seasonal study in the solar salterns of Sfax (Tunisia)

The seasonal distribution of metazooplankton and large-sized ciliates was studied in four ponds of different salinity in the solar salterns of Sfax (Tunisia). Total zooplankton abundance varied from 1 × 10³ to 4.7 × 10⁶ ind m^–3. Salinity had a negative effect on the abundance of copepods and rotifers which were absent in the pond with the highest salt concentration (180) in which the number of taxa was low and Artemia or the ciliate Fabrea largely dominated the zooplankton community. Temperature and the presence of Dunaliella salina as prey appeared as key factors in controlling the abundance of Artemia, while organic detritus appeared as important in the diet of Fabrea. Change in zooplankton species composition along the hypersaline gradient (40–90) was primarily related to salinity. However, our data suggest the importance of both the abundance and composition of food in the spatial and temporal variations of some zooplankton species.     

Life histories of two clonal populations of Stratiotes aloides L.

Cysts of parthenogenetic Artemia strains collected from the Citros and M. Embolon saltworks in Northern Greece are evaluated for their potential use in aquaculture. The following characterizations were performed: cyst and naupliar biometrics, cyst hatching characteristics, fatty acid profile of the nauplii, caloric content of nauplii stored at 25 °C and in a refrigerator (4–8 °C). The above evaluation reveals that the two Artemia strains studied exhibit good qualities for use in aquaculture, especially in culturing fresh-water species. The biometrical analysis of cysts, nauplii and adults shows a high degree of similarity with other parthenogenetic strains from various geographical sources, but especially with tetraploid Artemia from Spain. The Greek Artemia strains cannot be considered as sources for aquacultural uses unless proper management of the saltworks is assured.     

Biochemical characterization of Artemia ras p21

The biochemical properties of Artemia ras proteins (p21) have been studied after immunoprecipitation with the monoclonal antibody Y13-259. The ras products bind GTP and GDP, and have GTPase activity. Artemia p21 was unable to hydrolyze GP₄G, although this dinucleotide exhibits high affinity for the protein. Our results demonstrate that the protein(s) recognized by the Y13-259 antibody in this crustacean behave as typical mammalian ras p21s.     

Anatomy of the trunk mesoderm in tunicates: homology considerations and phylogenetic interpretation

The tadpole stage of tunicates has played a pivotal role in understanding chordate evolution. While the organization of the mesoderm has been given high importance in comparative anatomical studies of Bilateria, this morphological character remains largely unexplored in tunicate tadpoles. For larvae of the phlebobranch ascidian Ciona intestinalis, the presence of two mesodermal pockets had been claimed, raising the possibility that paired coelomes are present in the larval ascidian. Using computer assisted 3D-reconstructions based on complete series of 1 μm-sections analyzed by light microscopy complemented by TEM-investigation of selected regions a comparative anatomical study of tadpole stages from four major tunicate clades, Aplousobranchiata, Phlebobranchiata, Stolidobranchiata, and Appendicularia is presented. In the aplousobranch Clavelina lepadiformis numerous mesodermal cells are found throughout the entire trunk plus the unpaired ventral rudiment of the pericardium. In the phlebobranch Ascidia interrupta, massive mesodermal components occur in the posterior trunk, whereas more anteriorly situated mesoderm consists of loose streaks of cells or isolated cells. This is also the case in the stolidobranch ascidians Herdmania momus and Styela plicata. In the stolidobranch Molgula occidentalis and the appendicularian Oikopleura dioica the anterior trunk is entirely devoid of mesodermal cells. TEM-investigation revealed that all mesodermal structures in the trunk of tunicate tadpoles were mesenchymal with the exception of a ventral portion of the mesoderm in C. lepadiformis, which probably corresponds to the developing pericardium, and the differentiated pericardium of the juvenile O. dioica. Thus no evidence for paired coelomic cavities in Tunicata was found. Outgroup comparison suggests that the reduction of paired coelomic cavities is an apomorphic trait of Tunicata. Within Tunicata a stepwise evolutionary reduction of the anterior larval mesenchyme is documented.     

An improved technique for sampling lotic invertebrates

The electrophoretic characterization of an Artemia population from a saline lake of the Chilean Andes with unusual ecological features (Salar de Atacama, 23° 30′ S; 68° 10′ W) was carried out with the aim of comparing its genetic variation with, and genetic similarity to, representative populations of A. persimilis (Buenos Aires, Argentina) and A. franciscana (San Francisco Bay, USA). Based on the analysis of 22 loci it is concluded that the Chilean population and that from San Francisco are conspecific (D = 0.144), while the Chilean strain and A. persimilis are congeneric species (D = 1.171), differing in more than 40% of the loci. Parameters measuring genetic variation (e.g., percentage of loci polymorphic, mean number of alleles per locus, mean heterozygosity per locus) demonstrate that values for the Chilean Artemia (50.0, 1.68, 0.126, respectively) are within the range for bisexual Artemia in general and A. franciscana in particular.     

Sediment cores from Lake Urmia (Iran) suggest the inhabitation by parthenogenetic Artemia around 5,000?years ago

In Lake Urmia area, northwestern Iran, parthenogenetic Artemia and the bisexual Artemia urmiana Günther 1890 are found to occupy different ecological niches determined by salinity. Given the fluctuations of the lake over geological times, we thus hypothesized that species identification of Artemia cysts, buried in the sediments, can provide information on lake conditions in the past. Therefore, encysted embryos of Artemia were recovered from lake sediments by augering at a site near the present shoreline. Cysts and associated plant remains from two studied levels yielded radiocarbon ages in the range 5,000–6,700 YBP. For determination of the type of Artemia, the constant synonym mutation in exon-7 of the Na/K ATPase gene was verified, and the diameter of the recovered cysts was compared with that of modern cysts from the Lake Urmia region. The results show that the cysts represent a parthenogenetic type of Artemia, whose cyst diameter is somewhat different from that of present-day local parthenogenetic Artemia. The present study firstly confirms the stability of DNA in ancient Artemia cysts for molecular analysis. Moreover, it suggests variation in Lake Urmia’s conditions over time, and based on comparison with salinity preferences of contemporary Artemia populations, it more specifically suggests that Lake Urmia was a brackish lake dominated by a parthenogenetic Artemia population in the geological period sampled. It finally illustrates how, like in the study of freshwater propagule banks, paleogenetic analysis of Artemia DNA recovered from sediment cores can be used as a tool in the paleoecological study of generally highly fluctuating saline habitats.