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Biological invasions create complex eco- logical and societal issues worldwide. Most of the knowledge about invasions comes only from success- ful invaders, but less is known about which processes determine the differential success of invasions. In this review, we develop a framework to identify the main dimensions driving the success and failure of invaders, including human influences, characteristics of the invader, and biotic interactions. We apply this frame- work by contrasting hypotheses and available evi- dence to explain variability in invasion success for 12 salmonids introduced to Chile. The success of On- corhynchus mykiss and Salmo trutta seems to be influenced by a context-specific combination of their phenotypic plasticity, low ecosystem resistance, and propagule pressure. These well-established invaders may limit the success of subsequently introduced salmonids, with the possible exception of O. tshawyts- cha, which has a short freshwater residency and limited spatial overlap with trout. Although propagule pressure is high for O. kisutch and S. salar due to their intensive use in aquaculture, their lack of success in Chile may be explained by environmental resistance, including earlier spawning times than in their native ranges, and interactions with previously established and resident Rainbow Trout. Other salmonids have also failed to establish, and they exhibit a suite of ecological traits, environmental resistance, and lim- ited propagule pressure that are variably associated with their lack of success. Collectively, understanding

The relationship between invaders and the pathogens encountered in their new environment can have a large effect on invasion success. Invaders can become free from their natural pathogens and reallocate costly immune resources to growth and reproduction, thereby increasing invasion success. Release from enemies and relaxation of selective pressures could render newly founded populations more variable at immune-related genes, such as the major histocompatibility complex (MHC), particularly when they have different origins. Using rainbow and brown trout, two of the world's most successful fish invaders, we tested the general hypothesis that invaders should display high intrapopulation immunogenetic diversity and interpopulation divergence, due to the interplay between genetic drift and successive waves of genetically divergent introductions. We analysed genetic diversity and signatures of selection at the MHC class II β immune-related locus. In both species, MHC diversity (allelic richness and heterozygosity) for southern hemisphere populations was similar to values reported for populations at their native range. However, MHC functional diversity was limited, and population immunogenetic structuring weaker than that observed using neutral markers. Depleted MHC functional diversity could reflect a decrease in immune response, immune-related assortative mating or selection for resistance to newly encountered parasites. Given that the role of MHC diversity in the survival of these populations remains unclear, depleted functional diversity of invasive salmonids could compromise their long-term persistence. A better understanding of the eco-immunology of invaders may help in managing and preventing the impact of biological invasions, a major cause of loss of biodiversity worldwide.

Neutrophils (PMN) are the largest leukocyte population in the blood of most mammals including horses, playing an important defensive role in many infectious diseases. However, the mechanisms that increase PMN as one of the main cellular subsets in the defense against pathogens, could also be involved in the pathophysiology of dysregulated inflammatory conditions. Mesenchymal stem/stromal cells (MSCs) are a heterogeneous population with a modulatory potential on the inflammatory response, and are known to interact with nearly all cells of the immune system including PMN. In this study, we investigate the in vitro modulation of equine bone marrow-derived MSCs on phagocytosis, ROS production, and NETs generation from equine PMN. We found that in co-culture with MSCs, unstimulated PMN produces less ROS (2.88% ± 1.43) than PMN in single culture (5.89% ± 2.63); interestingly, co-cultured PMN remains conditioned to produce fewer ROS after PMA stimulation in comparison to PMN not cultured with MSCs. We also found that inhibition of ROS production by co-cultured PMN occurred not only after prolonged PMN-MSC co-incubation (4 hours), but also when MSC were present in the culture at the moment of adding the stimuli (30% less than control), suggesting that MSCs don’t only modulate PMN functions prior to their arrival to the inflammatory site, but also at the inflammatory niche itself. Additionally, we found that incubation with MSC supernatant strongly inhibited ROS production (83% ± 6.35 less than control) without affecting phagocytosis or capacity for NETosis. These results support the potential use of MSCs in equine inflammatory conditions where neutrophils are the main effector inflammatory cells

Aquaculture is a major source of invasive aquatic species, despite the fact that cultured organisms often have low genetic diversity and tend to be maladapted to survive in the wild. Yet, to what extent aquaculture escapees become established by means of high propagule pressure and multiple origins is not clear. We analysed the genetic diversity of 15 established populations and four farmed stocks of non-native rainbow trout in Chile, a species first introduced for recreational fishing around 1900, but which has in recent decades escaped in large numbers from fish farms and become widespread. Aquaculture propagule pressure was a good predictor of the incidence of farm escapees, which represented 16% of all free-ranging rainbow trout and were present in 80% of the study rivers. Hybrids between farm escapes and established trout were present in all rivers at frequencies ranging between 7 and 69%, and population admixture was positively correlated with genetic diversity. We suggest that non-native salmonids introduced into the Southern Hemisphere could benefit from admixture because local adaptations may not have yet developed, and there may be initially little fitness loss resulting from outbreeding depression.

Rainbow trout Oncorhynchus mykiss and brown trout Salmo trutta are the world’s two most widespread exotic fishes, dominate the fish communities of most coldtemperate waters in the southern hemisphere and are implicated in the decline and extirpation of native fish species. Here, we provide the first direct comparison of the impacts of rainbow and brown trout on populations of a native fish by quantifying three components of exotic species impact: range, abundance and effect. We surveyed 54 small streams on the island of Chilo ´ e in Chilean Patagonia and found that the rainbow trout has colonized significantly more streams and has a wider geographic range than brown trout. The two species had similar postyearling abundances in allopatry and sympatry, and their abundances depended similarly on reach-level variation in the physical habitat. The species appeared to have dramatically different effects on native drift-feeding Aplochiton spp., which were virtually absent from streams invaded by brown trout but shared a broad sympatric range with rainbow trout. Within this range, the species’ post-yearling abundances varied independently before and after controlling for variation in the physical habitat. In the north of the island, Aplochiton spp. inhabited streams uninvaded by exotic trouts. Our results provide a context for investigating the mechanisms responsible for apparent differences in rainbow and brown trout invasion biology and can help inform conservation strategies for native fishes in Chilo ´ e and elsewhere.

Zooplankton diversity in shallow salt lakes of the Andean countries in South America is low and distribution is highly dependent on salinity, which varies from moderate to high. At salinities lower than 90 g/l, the halophilic copepod Boeckella poopoensis (Marsh, 1906) predominates, whereas above that level the anostracan Artemia franciscana (Kellogg, 1912) is the exclusive component of the habitat. This constitutes, however, fragmentary information only. A review of the available literature for Andean saline lakes in Bolivia, Chile, and Peru, confirms that presence and distribution of both species is significantly driven by salinity levels. The results of a species co-occurrence null model analysis, indicates that species associations are not random, and these results are supported by the correlation analysis, which indicates a significant, inverse correlation between species number and salinity, and a significant direct relation of species number with surface of the habitat. The low species diversity characteristically seen in these habitats and their dependence on salinity changes effectuated by weather conditions, provide a good model-system for monitoring weather change. La diversidad del zooplankton en lagos salinos poco profundos de Sudamerica es baja y su distribucion depende altamente de la salinidad, la cual varia de moderada a alta. A salinidades menores a 90 g/l predomina el copepodo halofilico Boeckella poopoensis (Marsh, 1906), mientras que a salinidades superiores a ese nivel, el anostraco Artemia franciscana (Kellogg, 1912) es el componente exclusivo de los habitats. Esto constituye sin embargo una informacion parcial. En una revision de la literatura disponible para lagos salinos Andinos en Bolivia, Chile y Peru se confirma que la presencia y distribucion de ambas especies esta significativamente regulada por el nivel de la salinidad. Los resultados del modelo nulo de co-ocurrencia de especies indican que las asociaciones de especies no son aleatorias, y estos resultados estan respaldados por el analisis de correlacion, el cual indica una relacion inversa significativa entre numero de especies con salinidad, y hubo relaciones directas significativas entre numero de especies con la superficie del habitat. El bajo numero de especies que es caracteristico de estos habitats y su dependencia con los cambios de salinidad efectuado por las condiciones climaticas provee un buen modelo de sistema de monitoreo de cambios climaticos.

Previous researches have established that the swim speed of some microcrustaceans is influenced by chemical compounds emitted by conspecifics. We examined the hypothesis that cuticular compounds present on the body surface of A. franciscana, the most widespread member of Artemia genus, play a role in the swim speed of conspecific males. The movements (swim) of one male confronted to a sponge soaked with female or male cuticular extract, were recorded during 30 minutes and the swim speed was determined using a behavioral tracking software (Ethovision 3.1, Noldus Technologies). As a control, the movements of one male confronted to a sponge soaked with salty water or with a mixture of the solvents used in the extraction (chloroform-methanol), was recorded. The results showed that cuticular compounds from either female or male increase 1.5 (ca.) times the swim speed of males in comparison with the controls treatments salty water and the solvents. There was no a significant difference between the controls (salty water and chloroform-methanol). Chemical characterization was developed by sterification of the cuticular extracts and analyses by GC-FID and GC-MS. Four saturated fatty acid (myristic acid, palmitic acid, estearic acid, arachidic acid) and five insaturated fatty acids (oleic acid, linoleic acid, linoleic acid 3n3, cis-11-eicosanoic acid, euric acid) were identified. Myristic acid was found in female cuticular extract, but not in male cuticular extract. Results suggest that chemical compounds present in the cuticular surface of A. franciscana females could have an important role in the intra-specific recognition in this specie.

espanolLa universidad debe disponer de la capacidad administrativa y academica para monitorear y evaluar la calidad de la gestion desarrollada (gobernanza). Una encuesta realizada a expertos universitarios de 19 paises de Iberoamerica (858 casos) demuestra preliminarmente que el comportamiento etico del rector es altamente valorado, pues esta dotado de autoridad y se le ha conferido la responsabilidad para llevar a cabo las politicas y objetivos establecidos en el plan institucional. Su liderazgo y conducta etica son esenciales —en un ambiente complejo, dinamico y selectivo— para coordinar e integrar con responsabilidad y con vision estrategica los recursos y talentos disponibles para alcanzar optimos resultados. Bajo esta premisa se discute el doble rol, y la opinion general de los expertos reafirma que superar este problema esta relacionado con la conducta etica de la maxima autoridad universitaria. La sentencia anterior, se estructura independiente del tipo de universidad, sexo, anos de servicio de los expertos y de algunas caracteristicas estructurales de las universidades a las cuales pertenecen. EnglishThe university must have administrative and academic capabilities to monitoring and evaluating management quality (governance). A survey responded by university experts from 19 Iberoamerican countries (858 cases) shows preliminarily the ethical behaviour of the president or principal (rector in Spanish) is highly valued since he or she has the authority, and has been given the responsibility to carry out the policies and aims established in the institutional development al plan. Rector leadership and behaviour is essential —under a complex and dynamic and selective environment— to coordinate with responsibility and strategic vision the resources and talents of the university to achieve the best possible results. Under these assumptions the double role often played by the rector in some universities is discussed. In general, experts highly value the ethical behaviour of the rector to overcome this problem. This statement is independent of the university type, sex of the experts, years in the university, and of some structural characteristics of the university to which they belong.

Se realizaron dos experimentos conductuales para evaluar que A. franciscana muestra patrones de cortejo especificos, que en parte, serian gobernados por semioquimicos liberados por hembras. El etograma del cortejo, construido a partir de la grabacion individual de 30 parejas adultas virgenes (1 hembra v/s 1 macho) durante 1 hora, revelo que los machos mostraron cuatro patrones de actividad independientes: 1) acercamiento y toque, 2) nado en retroceso, 3) intento de monta, y 4) exito de monta. El analisis de las transiciones entre los patrones observados sugirio dos maneras de conseguir una monta exitosa, en ambas el patron acercamiento y toque fue fundamental. La primera transicion consistio en que una vez que los machos se acercan y tocan a las hembras, intentan montar a las hembras (27% de probabilidad de ocurrencia), pero si esto no ocurre los machos comienzan nuevamente a acercarse y tocar a las hembra (23% de probabilidad de ocurrencia) para finalmente lograr una monta exitosa (19% de probabilidad de ocurrencia). La ruta alternativa es mediante la aproximacion y toque para luego desarrollar el nado en retroceso (7% de probabilidad de ocurrencia) y montaje exitoso (5% de probabilidad de ocurrencia). El rol de los semioquimicos liberados por hembras fue evaluado mediante el uso de la solucion polar (SP) obtenida desde agua acondicionada con 40 hembras virgenes. Machos virgenes fueron empapados con SP para obtener pseudo hembras. Luego, se enfrentaron 1 pseudo hembra, 1 hembra, 1 macho control a ya sea 1 o 5 machos. En todos los casos, la conducta fue registrada durante 1 hora (n=10), y se analizaron las frecuencia de ocurrencia de cada uno de los patrones de cortejo. Los resultados mas importantes mostraron que: 1) la hembra virgen y pseudo hembra elicito la misma frecuencia de respuesta en 1 macho en los cuatro patrones de cortejo (P˃0,05); b) hembras virgenes y pseudo hembras obtuvieron la misma respuesta cuando se evaluaron contra 5 machos en acercamiento y toque, nado en retroceso e intento de monta (P˃0,05). El hecho que en todo los casos el macho control siempre elicito el menor valor de frecuencia en cada patron de cortejo sugiere el posible rol de semioquimicos sexuales en la conducta de cortejo de A. franciscana. La combinacion de senales quimicas y conductuales sugieren un elaborado reconocimiento de pre-cortejo.

Knowledge about the genetic underpinnings of invasions—a theme addressed by invasion genetics as a discipline—is still scarce amid well documented ecological impacts of non-native species on ecosystems of Patagonia in South America. One of the most invasive species in Patagonia’s freshwater systems and elsewhere is rainbow trout (Oncorhynchus mykiss). This species was introduced to Chile during the early twentieth century for stocking and promoting recreational fishing; during the late twentieth century was reintroduced for farming purposes and is now naturalized. We used population- and individual-based inference from single nucleotide polymorphisms (SNPs) to illuminate three objectives related to the establishment and naturalization of Rainbow Trout in Lake Llanquihue. This lake has been intensively used for trout farming during the last three decades. Our results emanate from samples collected from five inlet streams over two seasons, winter and spring. First, we found that significant intra- population (temporal) genetic variance was greater than inter-population (spatial) genetic variance, downplaying the importance of spatial divergence during the process of naturalization. Allele frequency differences between cohorts, consistent with variation in fish length between spring and winter collections, might explain temporal genetic differences. Second, individual-based Bayesian clustering suggested that genetic structure within Lake Llanquihue was largely driven by putative farm propagules found at one single stream during spring, but not in winter. This suggests that farm broodstock might migrate upstream to breed during spring at that particular stream. It is unclear whether interbreeding has occurred between “pure” naturalized and farm trout in this and other streams. Third, estimates of the annual number of breeders (N b) were below 73 in half of the collections, suggestive of genetically small and recently founded populations that might experience substantial genetic drift. Our results reinforce the notion that naturalized trout originated recently from a small yet genetically diverse source and that farm propagules might have played a significant role in the invasion of Rainbow Trout within a single lake with intensive trout farming. Our results also argue for proficient mitigation measures that include management of escapes and strategies to minimize unintentional releases from farm facilities.

Aim Two species of the brine shrimp, namely Artemia franciscana Kellogg and A. persimilis Piccinelli and Prosdocimi, inhabit Chile. Most studies so far have shown that A. franciscana is the most widely distributed species in Chile, with A. persimilis present only in Chilean Patagonia. In general, there is good agreement between morphological and genetic comparisons of Chilean populations with respect to species discrimination. However, a number of results indicate an overlap with some populations tending to diverge from A. franciscana and/or resembling A. persimilis. Prior to the mid 90's the use of DNA markers in Artemia was rather limited, despite their successful application in numerous other species. In this study, we investigate whether the conclusions drawn from traditional comparative tools are congruent with the pattern of genetic divergence depicted by DNA analysis at the mitochondrial level. Location Eight sites in Chile and two reference samples of A. franciscana and A. persimilis from San Francisco Bay (USA) and Buenos Aires (Argentina), respectively. Methods Restriction fragment length polymorphism (RFLP) analysis of a 535 bp segment of the mitochondrial 16S rRNA gene with nine restriction enzymes in 240 individuals. Results No haplotype was shared between the two species. Five restriction enzymes produced species-specific patterns, enabling the unambiguous assignment of populations to species. Very high (100%) bootstrap values supported the clustering of haplotypes in two groups corresponding to the two species. The two species were clearly differentiated with average sequence divergence of 12.3%. High genetic differentiation was also found among con-specific populations of A. franciscana with an FST estimate of 91%. Main conclusions The mitochondrial DNA (mtDNA) results of this study show a broadly similar pattern to those of previous allozyme and nuclear DNA analyses, with the two New World species appearing as highly divergent. The presence of A. persimilis in southern Chile (Chilean Patagonia) was confirmed. Hence, a species previously regarded as geographically restricted mainly to Argentina, appears to have expanded its range. Populations of A. franciscana appear highly structured with a level of inter-population genetic differentiation much higher for mtDNA than previously reported with allozymes. Clustering of these populations does not follow a clear geographic pattern. The identification of population-specific genetic markers for A. persimilis and A. franciscana will help to tackle further aspects of the speciation patterns of these species.

Hatchery-reared Argopecten purpuratus larvae were fed a Dunaliella tertiolecta-diet (DUN-diet) supplemented with 0%, 20% or 40% of a highly unsaturated fatty acid (HUFA) lipid emulsion (ICES Reference Emulsions), rich in docosahexaenoic acid (22:6n−3, DHA) and eicosapentaenoic acid (20:5n−3, EPA). A standard diet (ST-diet), consisting of a mixture of Isochrysis galbana (T-iso) and Chaetoceros neogracile was used as a positive control. The supplementation of 20% and 40% HUFA-emulsion to the DUN-diet led to a significantly better daily growth rate (136–177% as compared to DUN-diet) and a higher percentage of eyed-pediveliger larvae in comparison with the non-supplemented DUN-diet. Practically no eyed-larvae were present when fed with D. tertiolecta only, whereas 17% of the larvae developed an eyespot when fed a 20% HUFA-supplement. An increase of the lipid supplement from 20% to 40% further improved the larval performance, although the difference was not significant and less than compared with the changes between the non-supplemented DUN-diet and the DUN+20%-diet. The poor performance of larvae that received D. tertiolecta only was attributed to the depletion of the lipid reserves in the triglyceride fraction and possibly to the very low levels of saturated fatty acids 14:0 and 16:0, rather than to the low levels of EPA and DHA (in absolute terms). Limited biosynthesis of DHA from EPA as a precursor molecule is proposed. Despite similar relative and absolute fatty acid levels of DHA and EPA in larvae that received the ST-diet and the DUN+40%HUFA-diet, the former performed significantly better. Other factors such as the arachidonic acid (20:4n−6) content and the n−3/n−6 ratio are suggested to play a determining role.

The impact of dietary fatty acids on the fatty acid composition and content in different organs (digestive gland, adductor muscle and male and female gonad) of Argopecten purpuratus was evaluated during the process of gonad maturation under controlled laboratory conditions. A mixed algal diet of Isochrysis galbana (clone T-Iso), Pavlova lutheri , Chaetoceros gracilis and Tetraselmis suecica was either fed alone (Al) or supplemented with 50% lipids (expressed as % of the algal dry weight (DW)) using an emulsion rich in 22:6 n −3 (Al+EmDHA) or an emulsion rich in 20:5 n −3 (Al+EmEPA). Results showed the algal diet having the greatest impact on the fatty acid composition (mainly an increase of 18:1 n −9, 18:2 n −6; 18:3 n −3 and a decrease of 20:5 n −3) of the digestive gland and female gonad, moderate in the male gonad while the fatty acid composition of the adductor muscle was hardly affected. Our data indicated that 16:1 n −7 and 18:1 n −9 were partially elongated to 18:1 n −7 and 20:1 n −9, respectively. The supplementation of the algal diet with EmDHA or EmEPA (which contained 45% and 19% 22:6 n −3, respectively) increased significantly the concentration of 22:6 n −3 (mg g −1 DW) in the digestive gland, female gonad and male gonad with 78%, 57% and 51%, respectively, for (Al+EmDHA)-fed scallops and 18%, 33% and 19%, respectively, for (Al+EmEPA)-fed scallops, while the 22:6 n −3 concentration in the adductor muscle was not affected. Broodstock conditioning was associated with a significant increase of the lipid content in the female and to a lesser extent in the male gonad. The significant increase (as compared to the initial sample) of the 22:6 n −3 concentration in the digestive gland, female gonad and eggs of A. purpuratus fed 22:6 n −3-rich lipid illustrated that recently ingested fatty acids did significantly contribute to the lipid accumulation process in the maturing female gonad. The similarities between the fatty acid composition of the female gonad and digestive gland suggest that lipids were transferred from the lipid-rich digestive gland to the female gonad.

The endemic marine gastropod Chorus giganteus represents a significant part of the benthic biomass subject to heavy exploitation by artisanal fisheries in Chile. Overexploitation has restricted its formerly wide distribution to few sites, and this study deals with the electrophoretic characterisation of three populations from the two main fishing grounds in the south coast of Chile (37–39°S). While frequency of polymorphic loci is high (41–50%), the observed heterozygosity is low (between 0.028 and 0.040) though within the range for molluscs. Heterogeneity in allelic frequencies at six polymorphic loci suggests potential for population substructuring. All these loci showed significant heterozygote deficits. The calculated number of migrants per generation ( N e m =4.75), based on a Wright’s F ST mean value of 0.05, accounts for low gene flow among populations in line with breeding behaviour (locally restricted). These preliminary results set a baseline for further evaluation of the intraspecific genetic diversity of an overexploited mollusc with low larval dispersal ability, and hence limited ability for colonisation. Since basic culture techniques are not yet available, genetic monitoring of this species throughout its entire distribution should be promoted for proper management and/or conservation of the species gene pool, in addition to current regulations aimed at restricting further exploitation.

The brine shrimp Artemia, a typical inhabitant of hypersaline environments and characterized by a highly subdivided population structure, was used as a model to evaluate, under standardized laboratory conditions (at 65 ppt), primary reproductive traits (offspring quality and quantity) along with levels of reproductive isolation and degrees of divergence among populations. Intrapopulation experimental crosses and cross-fertility tests were evaluated in five populations (mostly A. franciscana) from coastal and inland environments in Chile, and in reference samples of A. franciscana (San Francisco Bay, U.S.A.) and A. persimilis (Buenos Aires, Argentina), which are the species likely to be found in Chile. The populations compared displayed significant variability in fecundity (total offspring, brood size) as well as in the ratio encystment/oviviparity. Hybrid offspring, produced abundantly in cross-fertility tests with reference populations, showed a pronounced switch to the encystment mode, particularly in crosses with A. persimilis. Exposure to a broad range of ecological conditions seems to have optimized a generalist reproductive strategy in the Artemia populations studied that combines variation in both the quantity and quality of zygotes. Laboratory cross-fertility tests evaluated prime reproductive characteristics in individual crosses with fair repeatability, as well as testing barriers to laboratory reproductive isolation. The lack of efficient mechanisms for reproductive isolation in the allopatric Artemia populations studied follows a trend often seen in other anostracods. Formerly allopatric populations have not achieved sympatry later as required by the allopatric speciation paradigm, and this is a probable explanation for production of the laboratory hybrids.

The brine shrimp Artemia (Crustacea, Branchiopoda), a paradigmatic inhabitant of hypersaline lakes, has molecular features to survive under stressful conditions, such as the p26 heat shock protein. We report the RFLP fingerprinting pattern (four restriction enzymes) of a 217 bp fragment of exon2 of the Hsp26 gene in six Artemia franciscana and four Artemia persimilis populations, the most genetically divergent Artemia species co-occurring in latitudinal extremes of Chile. The species-specific RFLP pattern observed is a simple and cost-effective single-locus tool for species delimitation and experimental testing the habitat-induced isolation barrier between them.

Dietary supplementation with lipid emulsions during broodstock conditioning of Argopecten purpuratus was used to manipulate the fatty acid composition of the eggs. The scallops were fed a mixed algal diet either alone (Al) or supplemented with an emulsion rich in ethyl esters of docosahexaenoic acid (DHA; Al+EmDHA) or eicosapentaenoic acid (EPA; Al+EmEPA) at a concentration of 50% lipids per algal dry weight (DW). The longer induction period and the lower fecundity in scallops fed solely on algae indicated a higher food value for the lipid-supplemented diet compared to the non-supplemented diet. Lipid supplementation resulted in a significant increase of the total lipid content (mg/g DW) of the eggs. The fatty acid quality of the diet had no significant effect on the fatty acid profile of the polar lipids. However, the supplementation of the DHA-rich emulsion resulted in a significant increase of the DHA level (% of total fatty acids) in the total and neutral lipids of the eggs compared to eggs from scallops fed solely algae. The absolute DHA content (mg/g DW) increased by 47%. The EPA level in the total and neutral lipids of eggs from broodstock supplemented with EmEPA was significantly higher than in eggs from scallops fed Al+EmDHA but no significant differences were detected with eggs from the non-supplemented diet (Al). The absolute EPA concentration in eggs from scallops fed Al+EmEPA was, respectively, 19 and 17% higher than in eggs from broodstock fed, respectively, solely algae (Al) or Al+EmDHA. The results illustrated that fatty acids, supplied as emulsified ethyl esters, could be ingested and assimilated by adult A. purpuratus and were at least partially allocated to the eggs.

This paper describes the distribution of lipids and fatty acids in different organs of Argopecten purpuratus broodstock. The female gonad and the digestive gland showed the highest lipid content, moderate lipid levels were present in the gills and male gonad while the mantle and especially the adductor muscle exhibited the lowest lipid content. A principal component analysis of the fatty acids of the total lipids separated the organs in four major groups: gills and mantle (I), adductor and male gonad (II), female gonad (III) and digestive gland (IV). A special feature of the gills and mantle was the presence of high levels of plasmalogens recognized by the peaks for vinyl methyl ethers from dimethylacetal degradation accompanying peaks for methyl esters of fatty acids in the GC profiles, and an unidentified fatty acid (22?). The highest level of n-3 polyunsaturated fatty acids (mainly EPA and DHA) was found in the adductor. Similarities between the fatty acid composition of the triglyceride fraction of the female gonad and the digestive gland (e.g. the high level of 14:0 and 18:4n-3) indicated the transfer of lipids from the lipid-rich digestive gland to the female gonad. Trimethyltridecanoic acid (TMTD) was found nearly exclusively in the polar lipid fraction of the digestive gland.

An Artemia population from a site recently described in Chile and located in a semi-arid and humid hydrographical zone (Torres del Paine National Park), was electrophoretically characterized and cross-bred (followed through F 3) to reference samples of A. franciscana (San Francisco Bay, California, U.S.A.) and A. persimilis (Buenos Aires, Argentina), which are the species most likely to be found in Chile. The population exhibited high levels of genetic variability as judged by the percentage of polymorphic loci (P=53.3), mean number of alleles per locus (n=2.2) and mean heterozygosity ( $$\bar H$$ =0.176). Based on the analysis of 15 loci it seems to be closer to A. persimilis (D Nei=0.211) than to A. franciscana (D=0.591). Laboratory cross-fertility tests do not suggest barriers to gene flow or infertility in accordance with eletrophoretic results (genetic distance values or population-specific alleles), though offspring quality tended to be biased toward the production of cysts rather than nauplii, most obviously in F33, which may be an indication of post-zygotic reproductive isolation.

An allozyme survey was conducted in three naturalized populations of rainbow trout, Oncorhynchus mykiss (Walbaum), from rivers in two Andean lakes of southern Chile. The analysis was based on 32 presumed loci, 10 of which were variable, and revealed that the mean percentage of polymorphic loci (P= 21.8%; range = 15.6-28.1%), the mean number of alleles per locus (n=1.26; range = 1.2-1.3) and the mean observed heterozygosity (HO=7.0%; range = 6.0-8.2%) are high, although within the range reported for rainbow trout. Although the mean genetic distance between the samples was low (D = 0.003), and only 5.2% of the total observed genetic variation can be accounted by interpopulation differences (FST= 0.052), eight out of 10 polymorphic loci exhibited significant allelic heterogeneity. Some loci, notably EST-1*, IDHP-3,4*, MEP-1* and PGM-1*, showed considerable discriminatory capacity among the samples. Rainbow trout has a longer history in Chilean waters since salmonid introduction started earlier this century. Under current intensive farming practices, the preliminary information provided in the present paper is likely to be helpful in setting up a baseline for further characterization and/or monitoring of naturalized populations.

Six Artemia populations from coastal and inland sites in Chile, ranging from 20 to 50 degrees latitude south, were compared morphologically. The study included reference samples of A. franciscana (San Francisco Bay, California-USA) and A. persimilis (Buenos Aires, Argentina). These species are likely to be found in Chile. Samples from Peru (Piura) and Brazil (Macau, Rio Grande do Norte) are two known examples of deliberate introduction of A. franciscana. The hypothesis of A. franciscana being the dominant species in South America was tested by multivariate morphological analysis based on ten body measurements. In addition, laboratory cross-fertility tests were performed in order to evaluate levels of reproductive isolation among these widely distributed populations. The analysis showed that A. franciscana and A. persimilis are morphologically divergent. A number of populations overlap with the San Francisco Bay sample, two are morphologically close to Buenos Aires, whilst others lie morphologically in between. Interpopulation morphological differences along with geographical and, probably, ecological divergence do not reflect reproductive isolation, at least of the pre-mating type. The morphological similarity of two Chilean samples with A. persimilis suggests that the distribution of A. persimilis should be further investigated. A multi-trait approach for Artemia characterization is stressed as a way to obtain better descriptions and interpretations of the biological diversity in the genus.

In order to enhance genomic resources for the brine shrimp Artemia franciscana, RNA-Seq analysis was conducted for adult females and males. Through de novo assembly, 36,896 high quality contigs were obtained, of which 13,749 sequences were annotated with arthropod sequences. Just 4.5% matched against previously reported sequences for Artemia spp. Additionally, different transcriptional patterns between males and females were found, evidencing sex-related transcriptional responses. Furthermore, 221 and 534 putative SNPs were identified exclusively in males and females, respectively. These results will build the foundation for further genomic studies in A. franciscana.

The ability of invasive species to adapt to novel conditions depends on population size and environmental mismatch, but also on genetic variation. Away from their native range, invasive species confronted with novel selective pressures may display different levels of neutral versus functional genetic variation. However, the majority of invasion studies have only examined genetic variation at neutral markers, which may reveal little about how invaders adapt to novel environments. Salmonids are good model systems to examine adaptation to novel pressures because they have been translocated all over the world and represent major threats to freshwater biodiversity in the Southern Hemisphere, where they have become invasive. We examined patterns of genetic differentiation at seven putatively neutral (microsatellites) loci and one immune-related major histocompatibility complex (MHC class II-β) locus among introduced rainbow trout living in captivity (farmed) or under natural conditions (naturalized) in Chilean Patagonia. A significant positive association was found between differentiation at neutral and functional markers, highlighting the role of neutral evolutionary forces in shaping genetic variation at immune-related genes in salmonids. However, functional (MHC) genetic diversity (but not microsatellite diversity) decreased with time spent in the wild since introduction, suggesting that there was selection against alleles associated with captive rearing of donor populations that do not provide an advantage in the wild. Thus, although high genetic diversity may initially enhance fitness in translocated populations, it does not necessarily reflect invasion success, as adaptation to novel conditions may result in rapid loss of functional MHC diversity.

The brine shrimp Artemia is a micro-crustacean, well adapted to the harsh conditions that severely hypersaline environments impose on survival and reproduction. Adaptation to these conditions has taken place at different functional levels or domains, from the individual (molecular-cellular-physiological) to the population level. Such conditions are experienced by very few equivalent macro-planktonic organisms; thus, Artemia can be considered a model animal extremophile offering a unique suite of adaptations that are the focus of this review. The most obvious is a highly efficient osmoregulation system to withstand up to 10 times the salt concentration of ordinary seawater. Under extremely critical environmental conditions, for example when seasonal lakes dry-out, Artemia takes refuge by producing a highly resistant encysted gastrula embryo (cyst) capable of severe dehydration enabling an escape from population extinction. Cysts can be viewed as gene banks that store a genetic memory of historical population conditions. Their occurrence is due to the evolved ability of females to "perceive" forthcoming unstable environmental conditions expressed by their ability to switch reproductive mode, producing either cysts (oviparity) when environmental conditions become deleterious or free-swimming nauplii (ovoviviparity) that are able to maintain the population under suitable conditions. At the population level the trend is for conspecific populations to be fragmented into locally adapted populations, whereas species are restricted to salty lakes in particular regions (regional endemism). The Artemia model depicts adaptation as a complex response to critical life conditions, integrating and refining past and present experiences at all levels of organization. Although we consider an invertebrate restricted to a unique environment, the processes to be discussed are of general biological interest. Finally, we highlight the benefits of understanding the stress response of Artemia for the well-being of human populations.

The conservation of data deficient species is often hampered by inaccurate species delimitation. The galaxiid fishes Aplochiton zebra and Aplochiton taeniatus are endemic to Patagonia (and for A. zebra the Falkland Islands), where they are threatened by invasive salmonids. Conservation of Aplochiton is complicated because species identification is hampered by the presence of resident as well as migratory ecotypes that may confound morphological discrimination. We used DNA barcoding (COI, cytochrome b) and a new developed set of microsatellite markers to investigate the relationships between A. zebra and A. taeniatus and to assess their distributions and relative abundances in Chilean Patagonia and the Falkland Islands. Results from both DNA markers were 100% congruent and revealed that phenotypic misidentification was widespread, size-dependent, and highly asymmetric. While all the genetically classified A. zebra were correctly identified as such, 74% of A. taeniatus were incorrectly identified as A. zebra, the former species being more widespread than previously thought. Our results reveal, for the first time, the presence in sympatry of both species, not only in Chilean Patagonia, but also in the Falkland Islands, where A. taeniatus had not been previously described. We also found evidence of asymmetric hybridisation between female A. taeniatus and male A. zebra in areas where invasive salmonids have become widespread. Given the potential consequences that species misidentification and hybridisation can have for the conservation of these endangered species, we advocate the use of molecular markers in order to reduce epistemic uncertainty.

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.

Rhizobacteria are capable of stimulating plant growth through a variety of mechanisms that include improvement of plant nutrition, production and regulation of phytohormones, and suppression of disease causing organisms. While considerable research has demonstrated their potential utility, the successful application of plant growth promoting rhizobacteria (PGPR) in the field has been limited by a lack of knowledge of ecological factors that determine their survival and activity in the plant rhizosphere. To be effective, PGPR must maintain a critical population density of active cells. Inoculation with PGPR strains can temporarily enhance the population size, but inoculants often have poor survival and compete with indigenous bacteria for available growth substrates. PGPR often have more than one mechanism for enhancing plant growth and experimental evidence suggests that the plant growth stimulation is the net result of multiple mechanisms of action that may be activated simultaneously. The aim of this review is to describe PGPR modes of action and discuss practical considerations for PGPR use in agriculture.

Exotic salmonids were deliberately introduced to the southern hemisphere during the last part of the 20th century, initially to boost sport fishing and later to develop an aquaculture industry. Early introductions were justified by governments on purely utilitarian arguments as it was felt that translocated salmonids would capitalize on otherwise ‘underutilized’ aquatic niches. A century later, exotic salmonids are established in nearly all places where they were originally introduced and beyond, and constitute one of the main threats to endemic fish fauna, amongst which galaxiid fishes have perhaps been impacted the most. We screened the literature to document the changing perspectives on exotic salmonids in the southern hemisphere, and employed SWOT analysis to assess the conservation prognosis of native galaxiids in the face of salmonid invasions. Our analysis indicates that opinions differ and contradictions abound as to how to prevent further salmonid encroachment. This is largely due to lack of info...

Chromosomal rearrangements have played a key role in the speciation of the New World sexual Artemia species (Crustacea, Anostraca) A. franciscana and A. persimilis. The species differ by a chromosome duplication (2n+2=44 in A. persimilis vs 2n=42 in A. franciscana), and a greater amount of heterochromatin (HCH) in A. franciscana. To investigate this difference in HCH, four parameters were compared for the first time in Artemia: 1) the absolute sizes of one A. persimilis and four A. franciscana karyotypes; 2) the relative lengths of all chromosome; 3) the number of heterochromatic bands and 4) the relative amounts of HCH per chromosome and its position. The two A.franciscana karyotypes with the largest HCH amount (26%), have twice (139.26 microm and 134.05 microm) the absolute size of the A.persimilis karyotype (64.91 microm; HCH: 1.97%). Interspecific and intraspecific (A. franciscana) differences in chromosome size and HCH were observed, although the two sets of information are not positively correlated. While A. persimilis shares plesiomorphic karyological traits with Old World species, A. franciscana has apomorphic features such as longer chromosomes and greater HCH content, mainly dispersed towards telomeres. The impacts of such chromosome rearrangements are discussed in relation to the wider geographic distribution, greater colonizing ability, and life history plasticity of A. franciscana. An additional, though preliminary, point of this paper is the observation that the female would be the heterogametic sex.

The brine shrimp Artemia is a well known animal extremophile adapted to survive in very harsh hypersaline environments. We compared the small stress proteins artemin and p26, and the chaperone hsc70 in encysted embryos (cysts) of the New World species, A. franciscana and A. persimilis. Cysts of the former, from San Francisco Bay, USA (SFB), were used essentially as a reference for these proteins, while both species were from locations in Chile where they occur in habitats at latitudinal extremes, the Atacama desert and Patagonia. These two species are phylogenetically distant, A. persimilis being closer to the Old World species, whilst A. franciscana is considered younger and undergoing evolutionary expansion. Using western blotting we found all three stress proteins in cysts from these five populations in substantial although variable amounts. The protein profiles revealed by Coomassie staining after electrophoresis (SDS-PAGE) were similar qualitatively, in spite of marked differences in the habitats from which these populations originated, and the long time since they diverged. We interpret these findings as further evidence for the adaptive importance of these three conserved proteins in coping with the variable, but severe stresses these encysted embryos endure.

We used an invaded stream fish community in southern Chile to experimentally test whether the diversity of exotic species affects their competitive impact on a native species. In artificial enclosures an established invasive, rainbow trout, Oncorhynchus mykiss, and a potential invader, Atlantic salmon, Salmo salar, reduced the growth rate of native peladilla, Aplochiton zebra, by the same amount. In enclosures with both exotic salmonids, the growth rates of all three species were the same as in single exotic treatments. While neither species identity nor diversity appeared to affect competitive interactions in this experiment, the impact of salmonid diversity may vary with the type of interspecific interaction and/or the species identity of the exotics. Our experiment links two prominent concepts in invasion biology by testing whether the result of invasional meltdown, an increase in the diversity of exotic species, affects their impact through interspecific competition, the mechanism invoked by the biotic resistance hypothesis.

Background A preliminary biometric and ecologic database for the brine shrimp Artemia from Mexico and Chile is presented. The area abounds in small and seasonal ponds and large inland lakes, the latter mainly located in Mexico, although relatively large and isolated lakes are found in complex hydrological settings in pre-high plateau areas of Chile. This paper summarizes research efforts aimed at the localization, characterization, and evaluation of the aquaculture potential of Artemia populations in Mexico and Chile, which exhibit great habitat diversity (ponds, salterns, coastal lagoons, sea arms, coastal and inland lakes), contrasting weather conditions and different levels of isolation and human intervention. Results This study covered locations between 29° north latitude (Baja California, Mexico) to 50° south latitude (Puerto Natales, Chile). Biological characteristics considered are species name, reproductive mode, cyst diameter, chorion thickness, and nauplius length, whereas ecological data include pond size, pH, salinity, temperature, and water ionic composition. Artemia franciscana is the only species found in Mexico, it exists together with A. persimilis in Chile, though separated geographically. Ecological differences in habitat exist between both regions but also within countries, a pattern particularly clear with regard to water composition. Surprisingly, a Mexican (Cuatro Ciénegas, A. franciscana) and a Chilean location (Torres del Paine, A. persimilis) share habitat characteristics, at least for the period when data were collected. The discriminat analysis for cyst diameter and nauplius length shows that Artemia from only one location match in cyst diameter with those from San Francisco Bay (SFB) (Point Lobos), and one (Marquez) is far apart from SFB and all the others. The Chilean locations (Pampilla, Cejar, Cahuil, Llamara, Yape) share cyst diameter, but tend to differ from SFB. The remaining Mexican locations (Juchitan, Ohuira, Yavaros) are well separated from all the others. With regard to nauplii length, populations tend to distribute in a relatively random manner, being Marquez the location differing the most in cyst diameter from SFB. Conclusion This database will contribute to the knowledge of radiation centers and serves as a baseline for further biogeographic studies, population characterization, management, and monitoring of Artemia biodiversity. Likewise, the impact of colonization and translocations for aquaculture purposes can be better assessed with a baseline for reference. Mexico and Chile exemplify the need to increase and further integrate regional information to tackle fundamental problems underlying practical utilization of Artemia.

The impact of supplementing lipid emulsions rich in eicosapentaenoic acid (EmEPA), docosahexaenoic acid (EmDHA) or saturated fatty acids (EmCOCO) to a standard algal diet [3:1 mixture of Isochrysis galbana (T-iso) and Chaetoceros neogracile, St-diet] on Argopecten purpuratus broodstock was evaluated. Broodstock fecundity was compared as well as the egg quality in terms of lipid content, fatty acid composition and lipid class distribution. Fecundity was defined as the number of eggs released in the spawning process, since spawning was virtually complete. Results indicated that the total lipid content of the eggs of A. purpuratus was diet independent. A greater energy reserve was spent on a larger number of oocytes and not on bigger sized oocytes with a higher lipid content. The lipids supplied through the emulsions were at least partially allocated to the eggs, demonstrating that the fatty acid composition of the eggs could be manipulated, especially the neutral lipid fraction. Levels of EPA changed more rapidly than DHA levels, supporting the observation that they fulfilled an energetic and structural role, respectively. The St-diet supplemented with 50%EmCOCO resulted in a significantly higher fecundity compared to the algal diet supplemented with 25%EmEPA + 25%EmDHA and the non-supplemented algal diet. It would seem that saturated fatty acids (SAFA) were more easily or preferentially incorporated in the female gonads of A. purpuratus. The relative content of SAFA and 18:2( n-6) in these eggs rose significantly. The relative content of the highly unsaturated fatty acids, EPA and DHA, on the other hand was substantially lower in the neutral lipid fraction, but hardly affected in the polar lipid fraction. It appeared that the maintenance of an adequate DHA/EPA ratio (approximately 1.2) was more important than the absolute levels of the two fatty acids, as long as a threshold value was reached.

Larvae of the Chilean-Peruvian scallop Argopecten purpuratus were fed a Dunaliella tertiolecta diet (Dun-diet) supplemented with lipid emulsions, rich in 20:5n-3 (EmEPA), 22:6n-3 (EmDHA) or in saturated fatty acids (EmCOCO). A mixed algal diet of Isochrysis galbana (T-iso) and Chaetoceros neogracile served as a positive control (St-diet). Lipid supplementation to the Dun-diet improved the larval growth and increased the percentage of eyed larvae significantly, compared to the non-supplemented Dun-diet because of the extra energy supplied and not because of its fatty acid composition. No significant differences were observed between supplementation with EmEPA, EmDHA or EmCOCO. A mixture of 20% EmEPA+20% EmDHA (40% EmHUFA) was more efficient in raising the total lipid content in larvae than 40% EmCOCO. Both emulsions increased the triacylglycerol content in larvae compared to the non-supplemented Dun-diet. The best result, however, was obtained with the St-diet, probably because of a more suitable 18:2n-6/18:3n-3 ratio and a higher level of arachidonic acid. A positive relationship between the 18:2n-6/18:3n-3 ratio and the larval performance was found. No significant difference was observed in post-settlement larval size or percentage of metamorphosed larvae between the St-diet and the St-diet supplemented with 20% EmHUFA or 20% EmCOCO. The metamorphosed larvae had a constant DHA/EPA ratio of 3.7, independent from the diet, which suggested a metabolic control of the two fatty acids and a species-dependency of the ratio.

The brine shrimp Artemia comprises a group of bisexual and parthenogenetic, morphologically similar, species very likely to have diverged from an ancestral form living in the Mediterranean area some 5.5 million years ago (Abreu-Grobois and Beardmore, 1982; Abreu-Grobois, 1987; Badaracco et al. 1987), though this estimate, based on allozymes, could be somewhat conservative as compared to that based on mitochondrial DNA (Perez et al. 1994). At that time the area was, according to geological indications, the only place in the world exhibiting for significant periods of time the very high salinity required for Artemia to thrive (Abreu-Grobois, 1987; Badaracco et al. 1987). The hypothesis of the Mediterranean as the centre of radiation for Artemia is also supported by the diversity of Artemia types currently found in the area, i.e. bisexuality and parthenogenesis on the one hand, together with diploidy and polyploidy on the other (see below).

Chromocentres, i.e. heavily stainable heterochromatic areas with highly repetitive DNA (a 130-bp repeat in the order of 6 x 105 copies per haploid genome) observed in the resting nucleus, are a reliable taxonomic trait and a good marker for speciation in Artemia. This chromosome marker was evaluated in populations of two New World sibling species: A. franciscana, from North, Central and South America, and A. persimilis from Argentina. Artemia persimilis showed the characteristically low average chromocentre numbers (3) of the ancestral Mediterranean species, whilst higher numbers (5) were seen in A. franciscana. The increase in chromocentre numbers from A. persimilis to A. franciscana occurred in a rather steady, continuous geographical pattern with an overlapping zone between both species. A north-south steady latitudinal decline of chomocentres was observed towards the equator in A. franciscana populations from the northern hemisphere, whilst the trait increased from this point towards southern latitudes with a population in Chilean Patagonia (below 52 degrees S) exhibiting the highest chromocentre frequency. Since chromocentres are positively correlated with repetitive DNA content, differentiation between the species through the amplification of heterochromatin or an increased DNA content in A. franciscana (although this species has a lower diploid chromosome number), might nevertheless reflect chromosomal reorganizations between the species. Chromocentres, together with other traits, reveal a probable hybrid zone between the two species in Chilean Patagonia.

During the fifties Brncic and the Dobzhansky's school, using the fruit fly Drosophila as a test organism, introduced the term integration of the genotype, or genetic coadaptation, which has had great impact on thinking in today's evolutionary biology. In this work we use the brine shrimp Artemia - in many respects a sort of aquatic Drosophila- as a model organism to evaluate the relationship between population structure, potential for divergence and the degree of morphological and/or genetic change. These aspects, tightly linked with the organization of the genotype, are important to understanding how recombination and adaptive release of genetic and phenotypic variation affect the speciation process in Artemia. Analysis of genetic (allozyme, diploid and chromocentre numbers), morphological (Mahalanobis distances) and reproductive data (cross-fertility tests) available for populations of the bisexual, endemic species of the Americas, Artemia franciscana and A. persimilis, indicate that: (i) A. franciscana and A. persimilis are morphologically distinct in correspondence with observed genetic differences (D Nei > 1; 2n = 42 and 44; 12.5 and 1.5 mean chromocentre numbers, respectively); (ii) populations from Chile and other South American localities (mainly A. franciscana) display high levels of genetic variability and a trend to develop large genetic distances between populations; (iii) the plasticity of Artemia gene pool is associated, at least in part, with ecological heterogeneity. Hence an adaptive divergence mode is thought to best define the speciation process in Artemia; (iv) the succesful production of laboratory hybrids in the allopatric Artemia populations studied in the Americas, a feature seen in other anostracods, could be explained by the fact that formerly allopatric populations have not achieved later sympatry, as required by the allopatric speciation paradigm En los años cincuenta Brncic y la escuela de Dobzhansky introdujeron el término integración del genotipo, o coadaptación genética, usando la mosca de la fruta Drosophila como organismo de experimentación, el cual ha tenido gran impacto en el la biología evolutiva actual. En este trabajo utilizamos al camarón de salmuera Artemia, en muchos aspectos una suerte de Drosophila acuática, como organismo modelo para evaluar la relación entre estructura poblacional, potencial de divergencia y el grado de cambio morfológico y/o genético. Estos aspectos, estrechamente ligados a la organización del genotipo, son importantes para entender como la recombinación y la liberación adaptativa de variación genética y fenotípica afectan el proceso de especiación en Artemia. El análisis de datos genéticos (aloenzimas, número diploide y de cromocentros), morfológicos (distancia de Mahalanobis) y reproductivos (pruebas de fertilidad cruzada) disponibles para las poblaciones bisexuales, endémicas de las Americas, Artemia franciscana y A. persimilis, indican que: (i) A. franciscana y A. persimilis son morfológicamente distintas en correspondencia con las diferencias genéticas observadas (D Nei > 1; 2n = 42 y 44; 12,5 y 1,5 número promedio de cromocentros, respectivamente); (ii) poblaciones de Chile y otras localidades Sudamericanas (principalmente A. franciscana) exhiben altos niveles de variabilidad genética y una tendencia a desarrollar grandes distancias genéticas entre poblaciones; (iii) la plasticidad del acervo de genes en Artemia está asociado, al menos en parte, con la heterogeneidad ecológica. Por este motivo el modelo de divergencia adaptativa es el que mejor define el proceso de especiación en Artemia; (iv) la producción de híbridos de laboratorio entre las poblaciones alopátricas de América estudiadas, un rasgo observado también en otros anostrácodos, podría explicarse por el hecho de que poblaciones originalmente alopátricas no han logrado posterior simpatría, como requiere el paradigma de especiación alopátrico

Mate choice significantly impacts upon population divergence and therefore speciation, recognition of equals being critical in cases where species and divergent populations coexist. The New World species of the brine shrimp Artemia, A. franciscana and A. persimilis, were compared through Scanning Electron Microscopy (SEM) for the following traits: shape and ornamentation of spine-like projections on the basal part of the penes; relative size, shape and ornamentation of the frontal knobs; cuticolar cones on the male second antenna, and ovisac (brood pouch) morphology. In particular, frontal knobs, described as playing a role in maintaining riding pairs attached (amplexus), and ovisac morphology, grouped all individuals into the corresponding species, but these differences seem too subtle to prevent inter-specific mating. In other words, mating between both species would be unspecific (not a key-lock type), an expected finding for allopatric species that would not have the chance to reinforce reproductive mechanisms in sympatry, as predicted by the allopatric mode. Additionally, both species inhabit selectively differential habitats that would prevent viability of migrants. At the population level, A. franciscana locations at the southern edge of the species distribution in the Americas (Chile) showed variation to the typical A. franciscana pattern, a somewhat expected finding for peripheral populations. The saltworks at Pichilemu (34° S, central Chile) appear to be a special environment where individuals from both species could eventually coexist, as inferred by the hybrid-like appearance of some individuals. This type of environment facilitates the testing of novel morphological variants which may affect the shaping of morphological divergence.

A preliminary biometric and ecologic database for the brine shrimp Artemia from Mexico and Chile is presented. The area abounds in small and seasonal ponds and large inland lakes, the latter mainly located in Mexico, although relatively large and isolated lakes are found in complex hydrological settings in pre-high plateau areas of Chile. This paper summarizes research efforts aimed at the localization, characterization, and evaluation of the aquaculture potential of Artemia populations in Mexico and Chile, which exhibit great habitat diversity (ponds, salterns, coastal lagoons, sea arms, coastal and inland lakes), contrasting weather conditions and different levels of isolation and human intervention. This study covered locations between 29° north latitude (Baja California, Mexico) to 50° south latitude (Puerto Natales, Chile). Biological characteristics considered are species name, reproductive mode, cyst diameter, chorion thickness, and nauplius length, whereas ecological data include pond size, pH, salinity, temperature, and water ionic composition. Artemia franciscana is the only species found in Mexico, it exists together with A. persimilis in Chile, though separated geographically. Ecological differences in habitat exist between both regions but also within countries, a pattern particularly clear with regard to water composition. Surprisingly, a Mexican (Cuatro Cienegas, A. franciscana) and a Chilean location (Torres del Paine, A. persimilis) share habitat characteristics, at least for the period when data were collected. The discriminat analysis for cyst diameter and nauplius length shows that Artemia from only one location match in cyst diameter with those from San Francisco Bay (SFB) (Point Lobos), and one (Marquez) is far apart from SFB and all the others. The Chilean locations (Pampilla, Cejar, Cahuil, Llamara, Yape) share cyst diameter, but tend to differ from SFB. The remaining Mexican locations (Juchitan, Ohuira, Yavaros) are well separated from all the others. With regard to nauplii length, populations tend to distribute in a relatively random manner, being Marquez the location differing the most in cyst diameter from SFB. This database will contribute to the knowledge of radiation centers and serves as a baseline for further biogeographic studies, population characterization, management, and monitoring of Artemia biodiversity. Likewise, the impact of colonization and translocations for aquaculture purposes can be better assessed with a baseline for reference. Mexico and Chile exemplify the need to increase and further integrate regional information to tackle fundamental problems underlying practical utilization of Artemia.

Biodiversity can be measured at different hierarchical levels, from genetic diversity within species to diversity of ecosystems, though policy-makers tend to use species richness. The 2010 goal of reducing biodiversity loss, agreed by the subscribers to the Convention on Biological Diversity, requires simple and reliable protocols to evaluate biodiversity at any level in a given ecosystem. Stakeholders, particularly policy makers, need to understand how ecosystem components interact to produce social and economic benefits on the long run, whilst scientists are expected to fulfil this demand by testing and modelling ideally simple (low diversity) ecosystems, and by monitoring key species. This work emphasizes the unique opportunity offered by inland, isolated salt lakes and the brine shrimp Artemia, an example of biodiversity contained at the intra-specific level, as simple models to understand and monitor biodiversity, as well as to assess its predicted positive association with ecosystem stability. In addition to having well identified species and strains and even clones, that allow to test reproductive effects (sexual versus asexual), Artemia benefits from the possibility to set up experimental testing at both laboratory scale and outdoor pond systems, for which a comprehensive cyst bank with sufficient amount of samples from all over the world is available.