Francisco Hontoria

The American brine shrimp as an exotic invasive species in the western Mediterranean

The hypersaline environments and salterns present in the western Mediterranean region (including Italy, southern France, the Iberian Peninsula and Morocco) contain autochthonous forms of the brine shrimp Artemia, with parthenogenetic diploid and tetraploid strains coexisting with the bisexual species A. salina. Introduced populations of the American brine shrimp A. franciscana have also been recorded in these Mediterranean environments since the 1980s. Based on brine shrimp cyst samples collected in these countries from 1980 until 2002, we were able to establish the present distribution of autochthonous brine shrimps and of A. franciscana, which is shown to be an expanding invasive species. The results obtained show that A. franciscana is now the dominant Artemia species in Portuguese salterns, along the French Mediterranean coast and in Cadiz bay (Spain). Co-occurrence of autochthonous (parthenogenetic) and American brine shrimp populations was observed in Morocco (Mar Chica) and France (Aigues Mortes), whereas A. franciscana was not found in Italian cyst samples. The results suggest these exotic A. franciscana populations originate as intentional or non-intentional inoculations through aquacultural (hatchery effluents) or pet market activities, and suggest that the native species can be rapidly replaced by the exotic species.

Two novel Anemia enrichment diets containing polar lipid

Abstract Two novel Anemia enrichment diets were tested against control diets of Super Selco (SS) (Artemia Systems, INVE, Ghent) and bakers yeast. The first experimental diet consisted of tuna orbital oil emulsified with 12% herring roe polar lipid (P-T). The second test diet comprised liposomes incorporating the phosphatidylcholine (PC) fraction of herring roe. Enrichment efficiency was measured in terms of lipid class and fatty acid composition of enriched nauplii, with particular attention being paid to PC content, docosahexaenoic acid (DHA) levels and DHA:eicosapentaenoic acid (EPA) ratios. The P-T emulsion yielded Artemia nauplii with 14% DHA (% total fatty acids) and a DHA:EPA ratio of 1.8, significantly higher than in nauplii fed the other three diets. Polar lipid levels in both P-T and SS enriched nauplii were similar (32.4 mg g−1 and 34.7 mg g−1 dry body weight (DBW) of nauplii, respectively). Lower %DHA and DHA:EPA ratios were obtained in liposome-fed nauplii (2% and 0.3, respectively) However, they yielded significantly higher levels of naupliar polar lipid (40.1 mg g−1 DBW) than those fed the two oil emulsion treatments. The significance of these findings is discussed.

Some aspects of Artemia biology affected by cestode parasitism

Artemia individuals from a wild population, bearing cestode cysticercoids (Hymenolepididae) were kept in the laboratory during four months to observe influences of the parasite on the host biology. No differences were found between parasitized and unparasitized shrimps regarding final adult size. The higher survival of parasitized animals suggests that parasitism is not pathogenic. The most dramatic effect was host castration. Parasitized individuals showed higher total lipid levels, probably linked to carotenoid pigments conveying a red color to parasitized shrimps.

Diversification of substrate specificities in teleostei Fads2: characterization of Δ4 and Δ6Δ5 desaturases of Chirostoma estor.

Currently existing data show that the capability for long-chain PUFA (LC-PUFA) biosynthesis in teleost fish is more diverse than in other vertebrates. Such diversity has been primarily linked to the subfunctionalization that teleostei fatty acyl desaturase (Fads)2 desaturases have undergone during evolution. We previously showed that Chirostoma estor, one of the few representatives of freshwater atherinopsids, had the ability for LC-PUFA biosynthesis from C18 PUFA precursors, in agreement with this species having unusually high contents of DHA. The particular ancestry and pattern of LC-PUFA biosynthesis activity of C. estor make this species an excellent model for study to gain further insight into LC-PUFA biosynthetic abilities among teleosts. The present study aimed to characterize cDNA sequences encoding fatty acyl elongases and desaturases, key genes involved in the LC-PUFA biosynthesis. Results show that C. estor expresses an elongase of very long-chain FA (Elovl)5 elongase and two Fads2 desaturases displaying Δ4 and Δ6/Δ5 specificities, thus allowing us to conclude that these three genes cover all the enzymatic abilities required for LC-PUFA biosynthesis from C18 PUFA. In addition, the specificities of the C. estor Fads2 enabled us to propose potential evolutionary patterns and mechanisms for subfunctionalization of Fads2 among fish lineages.

Biogeography of the genusArtemia (Crustacea, Branchiopoda, Anostraca) in Spain

This is an updated study on the biogeographic distribution of the populations of the genusArtemia (Branchiopoda, Anostraca) in Spain, with special focus on populations inhabiting salt lagoons and inland salterns. The populations recorded (40) belong to the bisexual speciesA. tunisiana and to the asexual groupA. parthenogenetica (diploid and tetraploid strains). They usually appear in three different hypersaline ecosystems: solar salterns and lagoons filled with sea water, solar salterns and lagoons containing brines of diluted mineral salts, and lagoons filled with athalassic (endorheic) brines. The brines in salinas are chemically characterized by high Cl− concentrations, especially in inland salinas, whose brine sources are geologically associated with evaporitic formations developed in the Triassic and Lower Liassic of eastern Spain. Brines in athalassic lagoons, geologically associated with Mesozoic and Cenozoic periods, show higher levels of sulfate (up to 40–50%) as well as Mg2+. From a geographical point of view, bisexual and diploid asexual populations are mainly found in coastal and inland salinas or lagoons below 40° N, while asexual tetraploid populations are found in inland salinas and athalassic lagoons above that latitude. These populations have been biologically characterized by the morphology of their adults through multivariate analysis.

Competition between sexual and parthenogenetic Artemia: temperature and strain effects

Previously reported competition experiments among Artemia (brine shrimp) species have not incorporated abiotic variability into their experimental design. Recent field and laboratory investigations point to temperature as a critical factor in determining the biogeographic distribution and competitive ability of sexual and parthenogenetic Artemia. One sexual diploid strain A. tunisiana Bowen (S) and two A. parthenogenetica Barigozzi strains [one diploid (PD) and one tetraploid (PT)] were raised as single populations and as competitive cultures at 15 °, 24 ° and 30 °C. Cultures were scored for competitive outcome (coexistence, exclusion) and were periodically monitored for population age-structure density and female parturition mode (encysted vs. non-encysted offspring). Temperature affected competitive outcome as follows: at 15 °C, S > PD > PT; at 24 °C, PD > S > PT; at 30 °C, PD > PT > S. When physiological responses and demographic traits were examined, factors that contribute to competitive abilities could be identified. At 30 °C, S die before reproductive maturity, an obvious factor contributing to their elimination at warm temperatures. For PT more than 73% of the offspring were encysted. While this would be advantageous for reestablishing the population following adverse field conditions and/or colonization of new sites, it is disadvantageous in continuous sympatric cultures where competitor strains produce primarily non-encysted embryos.

Potential use of liposomes in larviculture as a delivery system through Artemia nauplii

Abstract Nauplii of the brine shrimp, Artemia, are extensively used as food for fish and shrimp larvae. In this study we examined the possibility of utilizing them as carriers of liposome-trapped nutrients, drugs, or other treatment substances. Extruded unilamellar liposomes were easily formed in seawater. They held a suitable stability for 3 days at room temperature. We also demonstrated that when the liposomes were freeze-dried, they could be stabilized for long-term storage. Artemia nauplii showed maximum ingestion and accumulation inside the digestive tract of the radioactive and fluorescent markers after 30 h incubation in liposome suspensions. The advantages of this technique are discussed.

Distribution and characterization of Chilean populations of the brine shrimp Artemia (Crustacea, Branchiopoda, Anostraca)

Hypersaline habitats in Chile, from marine solar salt pans to saline lagoons and pools in Andean salars, were prospected in search of Artemia populations. These saline ecosystems were characterized through physico-chemical parameters and ionic composition of their brines. Biometrics of cysts and nauplii, as well as morphometrics by using multivariate discriminant analysis for adult specimens evidenced that the Chilean populations of brine shrimp belong to A. franciscana. Cross-breeding results supported the former hypothesis of conspecific Chilean populations, and their differences with A. persimilis, also endemic to the New World, but restricted to Argentinean sites.

Preliminary characterization of some Argentinean Artemia populations from La Pampa and Buenos Aires provinces

Artemia populations were sampledin four hypersaline ecosystems in continentalevaporitic basins from the Argentinean provinces of LaPampa and Buenos Aires. Biometrics of cysts andnauplii were performed. The morphometrics of adultfemales under standard culture conditions, studied bymultivariate discriminant analysis, provided evidencethat these populations belonged to the species A.persimilis; this was further supported bycross-breeding tests established between one of thesepopulations (Salinas Grandes de Hidalgo, province ofLa Pampa) and a population of A. franciscanafrom San Francisco Bay (California, USA), which showedreproductive isolation and barriers to gene flowbetween both populations.

Effect of different dietary levels of docosahexaenoic acid (DHA, 22:6w-3) on the DHA composition of lipid classes in sea bass larvae eyes

The effect of different dietary levels of docosahexaenoic acid (DHA, 22:6w-3) on the corresponding composition of lipid classes of the eyes of sea bass, Dicentraxrchus labrax, larvae was studied using Artemia nauplii enriched with different products: oil emulsions, liposomes, a dry microalga and bakers yeast. DHA was found to be a major constituent of phosphatidylserine and phosphatidylethanolamine of visual tissues. The different DHA dietary levels were markedly reflected in the fatty acid composition of the lipid classes of eyes, suggesting a dose-dependent relationship between DHA in the food and in visual tissue lipids of sea bass larvae. The possible implications of this dietary effect are discussed.