Brine Shrimp Artemia Research Articles

Phenotypic but no genetic adaptation in zooplankton 24 years after an abrupt +10°C climate change.

The climate is currently warming fast, threatening biodiversity all over the globe. Populations often adapt rapidly to environmental change, but for climate warming very little evidence is available. Here, we investigate the pattern of adaptation to an extreme +10°C climate change in the wild, following the introduction of brine shrimp Artemia franciscana from San Francisco Bay, USA, to Vinh Chau saltern in Vietnam. We use a resurrection ecology approach, hatching diapause eggs from the ancestral population and the introduced population after 13 and 24 years (∼54 and ∼100 generations, respectively). In a series of coordinated experiments, we determined whether the introduced Artemia show increased tolerance to higher temperatures, and the extent to which genetic adaptation, developmental plasticity, transgenerational effects, and local microbiome differences contributed to this tolerance. We find that introduced brine shrimp do show increased phenotypic tolerance to warming. Yet strikingly, these changes do not have a detectable additive genetic component, are not caused by mitochondrial genetic variation, and do not seem to be caused by epigenetic marks set by adult parents exposed to warming. Further, we do not find any developmental plasticity that would help cope with warming, nor any protective effect of heat‐tolerant local microbiota. The evolved thermal tolerance might therefore be entirely due to transgenerational (great)grandparental effects, possibly epigenetic marks set by parents who were exposed to high temperatures as juveniles. This study is a striking example of “missing heritability,” where a large adaptive phenotypic change is not accompanied by additive genetic effects.

Chitosan-harvested polyhydroxybutyrate-rich Zobellella denitrificans ZD1 as a multifunction feed for aquaculture

The security of the aquaculture industry is jeopardized by antibiotics overuse and increasing demand for aquaculture feeds, which remain heavily derived from capture fisheries. Biopolymer poly(3-hydroxybutyrate) (PHB) and some microorganisms are promising replacements for antibiotics and aquaculture feed, respectively. Therefore, we investigated the potential of using chitosan-harvested PHB-rich Zobellella denitrificans ZD1 (designated as CP-ZD1 hereafter) as a multifunction feed for brine shrimp Artemia (model species). Both PHB and chitosan and their intermediates (3-hydroxybutyrate and chitosan oligosaccharides) showed antimicrobial properties toward three known aquaculture pathogens (Vibrio campbellii, Aeromonas hydrophila, and Streptococcus agalactiae) and non-pathogens (non-pathogenic Escherichia coli, Bacillus megaterium, and Rhodococcus jostii RHA1). Low doses of 3-hydroxybutyrate and chitosan oligosaccharides mixtures effectively suppressed the growth of the pathogens. When supplied with CP-ZD1, the starved Artemia showed prolonged survival and a healthy gut microbiome, suggesting that CP-ZD1 can serve as a feed/energy source. Up to 80% enhanced survival and immune response was observed in pathogenic V. campbellii-challenged Artemia when fed with CP-ZD1. Overall, the results showed that CP-ZD1 could serve as an efficient biocontrol agent, a feed/energy source, and an immunostimulant in support of sustainable aquaculture.

The Origin of Asexual Brine Shrimps.

AbstractDetermining how and how often asexual lineages emerge within sexual species is central to our understanding of sex-asex transitions and the long-term maintenance of sex. Asexuality can arise "by transmission" from an existing asexual lineage to a new one through different types of crosses. The occurrence of these crosses, cryptic sex, variations in ploidy, and recombination within asexuals greatly complicates the study of sex-asex transitions, as they preclude the use of standard phylogenetic methods and genetic distance metrics. In this study we show how to overcome these challenges by developing new approaches to investigate the origin of the various asexual lineages of the brine shrimp Artemia parthenogenetica. We use a large sample of asexuals, including all known polyploids, and their sexual relatives. We combine flow cytometry with mitochondrial and nuclear DNA data. We develop new genetic distance measures and methods to compare various scenarios describing the origin of the different lineages. We find that all diploid and polyploid A. parthenogenetica likely arose within the past 80,000 years through successive and nested hybridization events that involved backcrosses with different sexual species. All A. parthenogenetica have the same common ancestor and therefore likely carry the same asexuality gene(s) and reproduce by automixis. These findings radically change our view of sex-asex transitions in this group and show the importance of considering scenarios of asexuality by transmission. The methods developed are applicable to many other asexual taxa.

Stable primary embryonic cells of Artemia are suitable for tracing the process of V. anguillarum and V. parahaemolyticus infection

The cell line is an important experimental tool to investigate the mechanism of host-pathogen interactions and to diagnose and cure diseases. However, their application in aquatic invertebrates is limited because they lack immortalized cell lines. The brine shrimp Artemia produces encysted diapause gastrula embryos under stress conditions. The biological advantages of Artemia embryos, such as quick switching on of the cell cycle upon short-term hydration and easy control of microbial contamination via decapsulation, makes them a candidate material for cell culture in vitro. This study identified five subpopulations of embryonic cells at the gastrula stage based on morphological characteristics. After 3–4 h of hydration, embryonic cells were derived from the cysts and successfully cultured for 10 days in 1.2 × L-15 medium containing 15% fetal bovine serum, with a cell viability of more than 90%. Using this primary cell culture system, Vibrio anguillarum and V. parahaemolyticus strains were screened as possible infectious Vibrio strains using laser confocal microscopy observations. The pathological features of viable Vibrio-challenged embryonic cells were further studied by comparing formaldehyde-inactivated and autoclaved Vibrio and polystyrene beads using SEM observation. The results confirmed that both Vibrio strains could challenge embryonic cells and cause some cytopathological features, such as cell aggregation and concaves. Our study provides the first evidence that in vitro cell culture of Artemia embryos can be used to demonstrate the characteristics of Vibrio infection. The primary cell culture system established in this study will facilitate research on the mechanism of host-pathogen interactions in aquatic animals.

Nutritional and biological analysis of the peel and pulp of Pouteria campechiana fruit cultivated in Bangladesh

Pouteria campechiana fruit is newly cultivated in Bangladesh. Nutritional and biological analysis of the peel and pulp of P. campechiana species was done according to standard protocols. The physicochemical parameters revealed that specific gravity, viscosity, total soluble solids (TSS), and pH contents were more evident in the pulp than the peel. According to the nutritional analysis, 7.46% fat, 4.15% dietary fiber, 41.54% carbohydrate and 247.28% energy were found in the peel. These values were higher and significant (p < 0.01) when compared to pulp; in contrast, larger amounts of moisture (54.44%), ash (2.92%) and protein (8.75%) were observed in the pulp of P. campechiana compared to peel, and these values were highly significant (p < 0.001). Large amounts of Cu, Zn, Fe and K were present in the peel of P. campechiana (p < 0.001; p < 0.01), while Ca, Mg and Na were significantly higher in the pulp of P. campechiana . Vitamin A was enrich in pulp (51.15 mg/100g) but vitamin C was enrich in peel (106.42 mg/100g) (p < 0.01). The total phenolics and flavonoids content per 100g ranged from 84 to 205 mg GAE and 256.34–930.33 mg QE, respectively. P. campechiana peel contains a significantly (p < 0.01; p < 0.001) high amount of phenolics, flavonoids, and showed potential antioxidant, anti-inflammation activities as compared to the pulp. Furthermore, a brine shrimp ( Artemia salina L.) lethality assay revealed the peel was significantly less toxic than the pulp (LC 50 = 701.66 μg/mL). The findings suggest that P. campechiana can be a rich source of nutrition as well as potential biological activity. • Peel part are rich in essential mineral contents viz. copper, Zinc, iron, potassium and vitamin C. • P. campechiana are superior for dietary fiber, protein, energy, phenolics, flavonoids and these could be responsible for anti-oxidant, anti-inflammatory, cytotoxic effects. • P. campechiana fruit could be a good source of nutritive value as well as potential biological activity.

Essential oils loaded on polymeric nanoparticles: bioefficacy against economic and medical insect pests and risk evaluation on terrestrial and aquatic non-target organisms.

This paper introduces the lethal, sublethal, and ecotoxic effects of peppermint and palmarosa essential oils (EOs) and their polymeric nanoparticles (PNs). The physicochemical analyses indicated that peppermint PNs were polydisperse (PDI > 0.4) with sizes of 381nm and loading efficiency (LE) of 70.3%, whereas palmarosa PNs were monodisperse (PDI < 0.25) with sizes of 191nm and LE of 89.7%. EOs and their PNs were evaluated on the adults of rice weevil (Sitophilus oryzae L.) and cigarette beetle (Lasioderma serricorne F.) and the larvae of Culex pipiens pipiens Say. On S. oryzae and L. serricorne, PNs increased EOs' lethal activity, extended repellent effects for 84h, and also modified behavioral variables during 24h. Moreover, EOs and PNs generated toxic effects against C. pipiens pipiens. On the other hand, peppermint and palmarosa EOs and their PNs were not toxic to terrestrial non-target organisms, larvae of mealworm (Tenebrio molitor L.), and nymphs of orange-spotted cockroach (Blaptica dubia S.). In addition, PNs were slightly toxic to aquatic non-target organisms, such as brine shrimp (Artemia salina L.). Therefore, these results show that PNs are a novel and eco-friendly formulation to control insect pests.

Induction of transgenerational innate immune memory against Vibrio infections in a brine shrimp (Artemia franciscana) model

The occurrence of transgenerational innate immune memory in invertebrates possibly offers an opportunity for the creation of offspring with increased resistance against infectious diseases. Shrimps, being invertebrates rely on their innate immune system as the main defence mechanism to combat invading pathogens. Thus, creating transgenerational innate immune memory could be used for disease prevention in shrimp farming. However, the mechanisms behind the induction of transgenerational innate immune memory and the creation of a broad spectrum protective immune memory are still not fully understood. Here, the creation of transgenerational innate immune memory and the mechanisms involved were studied using the brine shrimp (Artemia franciscana) as a model for shrimps. Hereto, a parental generation was primed by exposure to a live or dead Vibrio parahaemolyticus PV1 while another parental generation was primed with live or dead Vibrio campbellii LMG21363. Both Vibrio strains are known to cause diseases in farmed shrimps, resulting in significant economic losses. Axenic larvae of three subsequent generations were exposed either to the homologous or heterologous (viable) Vibrio species and their survival was recorded. In general, progenies from primed F0 parents developed innate immune memory as compared to offspring of non-primed control F0 parents as they were significantly protected against a subsequent Vibrio infection. Protection in the infected offspring was more pronounced when they were infected with the homologous Vibrio strain. Disease resistance was associated with significantly increased transcription of especially peroxinectin (pxn), prophenoloxidase (proPO), lipopolysaccharide and β-1,3-glucan-binding protein (LGBP), high mobility group box 1 (HMGB1) and heat shock protein 90 (hsp90) genes and significant changes in histone H3 and H4 acetylation and m6A RNA methylation. Overall, results might lead to procedures at shrimp brood stock level for parental conditioning and creation of transgenerational innate immune memory in offspring.

Brine shrimps adrift: historical species turnover in Western Mediterranean Artemia (Anostraca)

Brine shrimps (Artemia) have undergone geographic range and demographic expansions as a result of their interaction with humans since the beginning of salt harvesting. This interaction has favoured the expansion of some species but compromising the survival of others. Mediterranean native populations of Artemia salina from coastal salterns and lagoons are facing the presence and expansion of the introduced and invasive American species Artemia monica (= A. franciscana). However, this species could not be the only threat. Parthenogenetic populations of the Asian species A. urmiana and A. sinica are widespread along the Mediterranean and other areas of the world. In this work, with the use of large cox1 and mitogenomic datasets, phylogenetic and phylogeographic inferences, and a time calibrated tree, we confirmed the Asian origin and recent arrival of the current Western Mediterranean parthenogenetic populations of Artemia. In addition, the replacement of Iberian populations of A. salina by Asiatic parthenogenetic populations lead us to recognize parthenogens as invasive. Current salterns development and commercial importance of Artemia make human-mediated introduction probable. These results demonstrate again the impact that changing human interests have on population expansion or decline of species adapted to anthropogenic habitats. Artemia salina decline makes urgent the implementation of conservation measures such as its use in fish farming and salt production or its inoculation in inland salterns.

Growth of black molly Poecilia sphenops (Poecilidae: Pisces) Reared in closed recirculating water system

The experiment was conducted study the effect of temperature and food composition on growth, food conversion efficiency, food conversion rate and quantity of food intake by larvae of black molly Poecilia sphenops in closed recirculating water system Three types of food were employed. The first (I) was live food, brine shrimp Artemia, the second (II) was experimental artificial diet and the third (III) was commercial diet. The three diets were served under two temperature: (28±1°C and 22±1°C). Results showed that under temperature 28±1°C, the total weight increment and relative growth rate were 2.98-5.87 g and 1865.62- 3671.87 respectively. In the temperature 22±1°C these values were significantly lower (p&lt;0.05). The I and II higher values than treatments III with significant difference (p&lt;0.05) in both thermal degrees. In the temperature (22±1°C) the food conversion rate and efficiency rate attained 2.052 and 48.746 respectively in treatment II which were higher than that of treatment III (2.686 and 37.220 respectively), the two items were greater in temperature 28±1°C, and at treatment II (1.662 and 60.177 respectively) in comparison with the treatment III (2.220 and 45.064 respectively), the treatment II higher values than III with significant difference(p&lt;0.05) in both degrees. The food intake larger in the 28±1°C than degree 22±1°C with significant difference for both treatments II and III, food intake in treatment II was larger significantly (p&lt;0.05) than III at degree 22±1°C and non significantly (p&gt;0.05) at degree 28±1°C.

Antioxidant and Toxic Activity of Helichrysum arenarium (L.) Moench and Helichrysum italicum (Roth) G. Don Essential Oils and Extracts.

Helichrysum arenarium (L.) Moench (sandy everlasting) is the only species from genus Helichrysum Mill that grows spontaneously in Lithuania. The chemical composition of the essential oils (EOs) from inflorescences and leaves of H. arenarium wild plants was analysed by GC-MS. Palmitic (≤23.8%), myristic (≤14.9%) and lauric (6.1%) acids, n-nonanal (10.4%), and trans-β-caryophyllene (≤6.5%) were the major constituents in the EOs. For comparison, the main components in EO from flowers (commercial herb material) of H. italicum were γ-curcumene (21.5%), β-selinene (13.6%), α-selinene (8.1%), β-eudesmol (8.3%), and α-pinene (6.5%). Composition of H. arenarium methanolic extracts was investigated by HPLC-DAD-TOF. The main compounds were the following: luteolin-7-O-glucoside, naringenin and its glucoside, apigenin, chlorogenic acid, arenol, and arzanol. Antioxidant activity of EOs and extracts was tested by DPPH● and ABTS●+ assays. Sandy everlasting extracts exhibited significantly higher radical scavenging activities (for leaves 11.18 to 19.13 and for inflorescences 1.96 to 6.13 mmol/L TROLOX equivalent) compared to those of all tested EOs (0.25 to 0.46 mmol/L TROLOX equivalent). Antioxidant activity, assayed electrochemically by cyclic and square wave voltammetry correlated with total polyphenolic content in extracts and radical scavenging properties of EOs and extracts. The toxic activity of EOs of both Helichrysum species was evaluated using a brine shrimp (Artemia salina) bioassay. H. italicum inflorescence EO was found to be toxic (LC50 = 15.99 µg/mL) as well as that of H. arenarium (LC50 ≤ 23.42 µg/mL) oils.

Transcriptomic analysis of brine shrimp Artemia franciscana across a wide range of salinities.

Brine shrimp Artemia franciscana, a commercially important species, can thrive in a wide range of salinities and is commonly found in hypersaline lakes and solar salterns. Transcriptome analysis can enhance the understanding of the adaptative mechanisms of brine shrimp in aquaculture. RNA sequencing (RNAseq) data was generated from A. franciscana adults that were salt-adapted for 2-4weeks at five salinities: 35, 50, 100, 150, and 230psu. Long-read isoform sequencing (IsoSeq) data was used to construct a high-quality transcriptome assembly. Also, the gene expression patterns in A. franciscana adults were examined. Notably, the transcriptional response of A. franciscana's acclimation to intermediate salinities (50-150psu) displayed frequently and differentially U-shaped or inverted U-shaped expression patterns. In addition, the types of genes showing two nonmonotonic expression patterns were distinct from each other. The coordinated shifts in gene expression suggest different homeostatic strategies of A. franciscana at specific salinities; such strategies may enhance population fitness at extreme salinities. Our study should promote a scientific concept for the gene expression patterns of A. franciscana along a broad salinity gradient, and a variety of salinity and prey should be monitored for testing the gene expression pattern of this important aquaculture species.

Constitutive and activated toxigenic activity ofHalomicronema metazoicum(Cyanoprokaryota, Cyanophyta)

AbstractPhormidium‐like cyanobacteria produce a variety of biologically active molecules. We isolated a free‐living strain ofHalomicronema metazoicum, previously known uniquely as a symbiont of marine sponges, and demonstrated that its spent medium was toxic for various protozoans and fish parasites. However, we still ignore if its mats contain constitutive or activated defences influencing the physiology of other organisms, with potential influences on organisms that share the same environment. The goal of this study is to clarify ifPhormidium‐like cyanobacteria accumulate toxic bioactive molecules in the colony tissues, for example for anti‐grazing purposes, or if they constitutively secrete them in the medium, with a potential allelopathic function. To address this hypothesis, the toxigenic power of cyanobacterial spent medium and of disintegrated cells (to simulate lysis) was assayed using standard toxicity‐tests on nauplii of the brine shrimpArtemia salina. Toxigenic effects were triggered by the spent culture medium, but the homogenates (disintegrated cyanobacteria cells) did not show any acute toxicity. In addition, chronic toxicity tests of the spent medium demonstrated a reduced but still present toxigenic effect, with an inverse correlation between toxicity and medium dilution. The present research contributes to the understanding of cyanobacteria chemical‐ecology and shows that they may play fundamental ecological roles, influencing the survival and the blooms of various co‐habiting species by constitutively releasing toxic exudates. Since the bioactive compounds produced byH. metazoicumare stable in water, and considering the bioactivity of exudates on invertebrates' physiology, our results might be exploited for the development of novel biotechnologies in the fields of aquaculture, ecological conservation and medicine, due to the potential antitumoral and anti‐parasitic activity demonstrated in strictly related species.

Sub-acute exposure to nanoplastics via two-chain trophic transfer: From brine shrimp Artemia franciscana to small yellow croaker Larimichthys polyactis

This study investigated the trophic transfer of nanoplastics in marine food chains. We fed nanoplastic-exposed Artemia franciscana (brine shrimp) to Larimichthys polyactis (small yellow croaker) daily for eight days. Subsequently, the overall health condition, histopathological damage to the liver and digestive tract, and swimming ability of the fish were measured. After the sub-acute exposure to nanoplastics via trophic transfer, the fish showed inhibited growth, severe liver damage, as well as a poorer swimming ability compared to the control. The swimming ability was especially affected, in terms of the overall movement as well as thigmotaxis. The results thus clarified that even an indirect exposure to nanoplastics could induce neurotoxic effects and affect the swimming ability of the fish. As fish are well-known human food resources, the possibility of such trophic transfers affecting higher trophic level organisms, such as humans, cannot be ruled out.

Utilization of Live‐Food Enrichment with Polyunsaturated Fatty Acids (PUFA) for the Intensive Culture of Yellow Perch Larvae

AbstractChallenges associated with first feeding have impeded the intensive culture of larval Yellow Perch Perca flavescens. Live‐food enrichment with polyunsaturated fatty acids (PUFAs) can increase the growth and survival of larval fish, but this method has not been tested with Yellow Perch. This study includes two experiments that were meant to evaluate (1) the relative proportion of docosahexaenoic acid (DHA; 22:6[n‐3]) and arachidonic acid (ARA; 20:4[n‐6]) in enrichment emulsions and (2) the provision of PUFA emulsions in ethyl ester (EE) or triacylglycerol (TG) form on Yellow Perch growth and survival. Fish were provided with live rotifers Brachionus plicatilis and brine shrimp Artemia nauplii for the first 10 d of exogenous feeding within a specialized recirculating system (phase I). Fish were then transferred to flow‐through tanks and were fed Artemia nauplii for 3 d before gradually transitioning to a formulated starter diet (5–7 d; phase II). Fish size, growth, survival, swim bladder inflation rates, and lipid/fatty acid concentrations were evaluated after each phase. Overall, rotifers assimilated ARA in higher concentrations (23.3% of total fatty acids) than Artemia (0.6–0.7% of total fatty acids). Rotifers also tended to assimilate PUFAs better in EE form than in TG form (71.3% versus 66.5% Σn‐3 + n‐6 fatty acids). In the first experiment, fish from the ARA‐ and DHA‐enriched diet groups had greater swim bladder inflation rates (phase I) and growth rates (phase II) than the unenriched control group. In phase I of the second experiment, the EE enrichment group had a significantly faster growth rate than the TG enrichment group (specific growth rate: mean ± SD = 40.5 ± 0.9% and 36.6 ± 1.8%, respectively). Fatty acid composition of zooplankton was heavily influenced by enrichments, and fatty acid composition of larvae/juveniles reflected that of their live prey. The results of this study suggest that PUFA enrichment of live feeds can accelerate Yellow Perch growth and reduce the time spent in the critical period of early development.

Brine shrimp (Artemia salina Leach) as an alternative model for assessing thein vivoantioxidant activity of rutin

Brine shrimp (Artemia salina Leach) as an alternative model for assessing thein vivoantioxidant activity of rutin

Toxicity of bioceramic and resinous endodontic sealers using an alternative animal model: Artemia salina.

Aims:The present study assessed the toxicity of a novel calcium silicate-based root canal sealer (Bio-C Sealer) in comparison to Endosequence BC Sealer and AH Plus through a lethality assay involving brine shrimp (Artemia salina).Methods:Brine shrimp cysts were incubated for 24 h for the hatching of the larvae, which were then exposed to different concentrations (2.5, 5, 10, 20, 40, 80, and 100 μg/mL) of the test endodontic sealers for 24 h, followed by the determination of the survival rate.Statistical Analysis Used:One-way repeated-measures ANOVA and the Newman–Keuls post hoc test were used to compare the different materials as well as different concentrations of the same material. Dunnett's test was used to compare the different concentrations and different sealers to the control. The lethal concentration of each endodontic sealer necessary to kill 50% of the brine shrimp larvae (LC50) was also determined.Results:The toxicity of Bio-C (10, 20, 40, 80, and 100 μg/mL) and Endosequence BC Sealer (20, 80, and 100 μg/mL) was lower than that of AH Plus. No significant difference was found between Bio-C and Endosequence BC Sealer or among the different intragroup concentrations of these sealers. In the AH Plus group, concentrations ≥5.0 μg/mL exhibited greater toxicity compared to the concentration of 2.5 μg/mL and the control. AH Plus had the lowest LC50 (59.95 μg/mL), whereas Bio-C and Endosequence BC Sealer had LC50 values >200 μg/mL.Conclusions:Bio-C Sealer proved to be less toxic than AH Plus and exhibited similar toxicity to that of Endosequence BC Sealer.

Phytochemical and Biological Investigation of Bridelia tomentosa Blume Growing in Bangladesh

Bridelia tomentosa Blume is a small evergreen tree which has enormous folklore applications in the treatment of colic, traumatic injury, epidemic influenza and neurasthenia. The main purpose of this study was to isolate bioactive compounds from the stem bark of B. tomentosa growing in Bangladesh. Extensive chromatographic separation and purification of the methanolic extract of stem bark of B. tomentosa led to the isolation of four compounds. The purified constituents were identified as friedoolean-5(6),14(15)-dien-3-one (1), β-taraxerol (2), D4- stigmasterone (3) and lupeol (4) by extensive analysis of NMR spectroscopic data. While compound 1 is appeared to be new, the other compounds (2-4) have been isolated for the first time from this plant. β-taraxerol (2) demonstrated significant cytotoxic activity against the brine shrimp Artemia salina and moderate to strong antimicrobial efficacy with the highest inhibitory potential against Salmonella Typhi (zone of inhibition = 21.3 mm) and Sarcina lutea (zone of inhibition =20.8 mm). In conclusion, B. tomentosa has been found to be a rich source of secondary metabolites and thus it may be studied further in order to isolate of more bioactive constituents. Dhaka Univ. J. Pharm. Sci. 20(2): 213-218, 2021 (December)

Effects of heat shock protein 70 knockdown on the tolerance of the brine shrimp Artemia franciscana to aquaculture-related stressors: Implications for aquatic animal health and production

Temperature, pH, salinity and ammonia stress adversely affect the performance and well-being of aquatic organisms, especially those used in aquaculture, a major food production sector. Management strategy to mitigate stress caused by abiotic factors in farmed aquatic organisms is scarce but is highly warranted considering the negative impact of these factors on the welfare and economic production of the farmed animals. The induction of heat shock proteins, mainly 70 kDa Hsp (Hsp70), in farmed fish and shellfish, including the live feed brine shrimp Artemia franciscana, by exposure to a non-lethal heat shock (NLHS) of 37 °C for 30 min followed by 6 h recovery period caused a significant improvement in the tolerance of the animals towards subsequent challenge with an abiotic stress. Although the protective effect of NLHS was associated with enhanced Hsp70 accumulation in these species, the induction of other members of Hsp and their collective involvement in the stress tolerance could not be ignored. This triggered an argument as to whether only Hsp70 or its combination with other Hsps was responsible for inducing stress tolerance phenotype in these species. In this study, we employed RNAi technology in the biological model organism Artemia to gain insight into the functional role of Hsp70 in stress tolerance. The results showed that upon exposure to a NLHS, the wild-type Artemia nauplii capable of producing Hsp70 exhibited significantly higher survival than the unexposed control in all the abiotic stress tolerance tests performed in this study. However, the Hsp70-deficient mutant nauplii did not exhibit increased stress-tolerant phenotypes as the survival percentage of the nauplii decreased by 29, 19, and 15%, respectively, upon challenge with a median lethal concentration of salinity, pH, and ammonia. These results suggest that Hsp70 was involved in inducing tolerance against stress caused by the abiotic factors, and hence can be a potential target for developing strategies to protect economically important aquaculture species from environmental disturbances.

Abundance, Distribution and Migration Patterns of North American Eared Grebes (Podiceps nigricollis)

Most North American Eared Grebes (Podiceps nigricollis) undertake a post-breeding migration to two hypersaline lakes in the USA: Mono Lake in California and Great Salt Lake in Utah. Single air photo surveys were conducted in mid-October at Mono Lake from 1996-2012 and multiple fall surveys were conducted from 2013-2018, the latter to determine variation in abundance patterns within and across years. In four of the six years with multiple fall surveys, peak abundance occurred in mid-October as expected. However, in 2014 and 2015, Eared Grebe numbers declined dramatically soon after arrival, coinciding with low levels of their primary food, brine shrimp (Artemia monica). Abundance remained low from 2016-2018, and this could have been due to a shift to Great Salt Lake or to a massive mortality event. In 2017 and 2018, Eared Grebes breeding in south-central British Columbia, Canada were marked with Very High Frequency (VHF) radio transmitters and light-level geolocator (GLS) tags. Contrary to 1996, when the majority of VHF-tagged birds were molting/staging on Mono Lake, our 2017-2018 telemetry data indicated that most individuals were on Great Salt Lake. Our study provides insight into the variable abundance patterns at Mono Lake and novel information on Eared Grebe migration patterns.

Dispersal of aquatic invertebrates by lesser black-backed gulls and white storks within and between inland habitats

Waterbirds can transport aquatic invertebrates internally, contributing to metapopulation dynamics between aquatic habitats in a terrestrial matrix. However, research into this dispersal process to date has focused on individual field sites or laboratory studies. We investigated the invertebrates dispersed by endozoochory by the lesser black-backed gull Larus fuscus wintering in Andalusia, south-west Spain in 2016–2017, comparing seven sites interconnected by their movements, with different degrees of anthropogenization [three landfills, two saltpan complexes, a natural lake, and a large (370 km2) ricefield area]. In the ricefields, we also compared invertebrates dispersed by gulls with those dispersed by the larger white stork Ciconia ciconia. A total of 642 intact invertebrates and their propagules (mainly plumatellid bryozoans, cladocerans, and other branchiopods) were recorded in excreta (faeces and pellets) from gulls and storks. A greater diversity and abundance of invertebrates were recorded in ricefields, notably 43 individuals of the alien snail Physella acuta. One snail was still alive in a gull pellet 3 weeks after being stored in a fridge. This represents the first record of snail dispersal within waterbird pellets. Viability was also confirmed for the cladoceran Macrothrix rosea recorded in ricefields, and the alien brine shrimp Artemia franciscana recorded mainly in saltpans. In ricefields, gulls and pellets had significantly fewer propagules and fewer taxa per gram of excreta than storks and faeces, respectively. Through their high mobility, gulls and storks can disperse invertebrates between different natural and artificial habitats, and even to landfills. They can promote metapopulation dynamics for native bryozoans and branchiopods, but also the spread of invasive snails and brine shrimp.