Euryhaline Species Research Articles

Sharks and Rays of Northern Australia's Roper River, with a Range Extension for the Threatened Speartooth Shark Glyphis glyphis.

Northern Australia is considered a 'lifeboat' region for globally threatened shark and ray species (elasmobranchs), although much of the region is understudied. The Roper River in the Northern Territory's Gulf of Carpentaria has been inadequately surveyed, with most elasmobranch data gained opportunistically through freshwater fish surveys. This study aimed to report the occurrence of elasmobranch species in the Roper River through targeted field surveys conducted between 2016 and 2024 and to review data from other sources. Four euryhaline species were recorded, comprising two sharks, a sawfish, and a stingray. Records of the globally Vulnerable speartooth shark (Glyphis glyphis) represented a significant range extension and the documentation of a new reproductive population. Records of the Critically Endangered largetooth sawfish (Pristis pristis) extended almost 400 km upstream, highlighting extensive use of the river system. A predominantly marine species, the Critically Endangered giant guitarfish (Glaucostegus typus) was observed in brackish estuarine waters, approximately 15 km upstream from the river mouth. Further research is required to develop a more thorough understanding of abundance, life history, and population connectivity for these species in this river system. Given the documentation of threatened species, the potential impacts of fisheries, water allocations, and climate change require assessment.

Comparative transcriptomic analysis reveals osmoregulatory mechanisms of juvenile Lateolabrax maculatus responses to long term hypotonic and hypertonic acclimation

Salinity limits the abundance and distribution of some fishes in a particular ecological niche. The spotted sea bass (Lateolabrax maculatus), an euryhaline species, exhibits remarkable adaptability to various salinity levels. To elucidate the osmoregulation mechanisms of this species, the growth performance, serum biochemical parameters and gill transcriptomic profiles of the juvenile spotted sea bass subjected to long term hypotonic (0 ppt) and hypertonic environment (30 and 45 ppt), with the isotonic environment (12 ppt) as the control, were investigated. During the 30 days' salinity acclimation, the growth performance of the juvenile sea bass was inhibited significantly (P < 0.05) at hypertonic condition of 45 ppt, while no significant differences were observed among those at 0, 12, and 30 ppt. The serum biochemical indicators of plasma osmolality, concentration of Na+, Cl−, glucose, urea, total protein, and ALT and AST activities significantly increased during the hypertonic acclimation. Transcriptome analysis identified 1179, 103, and 443 differentially expressed genes in the 0, 30, and 45 ppt salinity groups, respectively, compared to the isotonic (12 ppt) group. Bioinformatics analysis revealed that signal transduction pathways were promoted during hypotonic acclimation, while energy metabolism pathways were activated during hypertonic acclimation. Protein-protein interaction and WGCNA analysis identified hub genes that may play important functions during acclimation. Among them, protein synthesis related-genes including Rps15, Rps16, Rps9, Rpl4, Rpl15, Rpl30, Rpl31, Rpl13a and Eef2 were down-regulated under hypotonic acclimation, metabolic related-genes including Cs, Idh2, Idh3, Mdh2, Pck1, Pck2, Pdha1 and Ldhb were up-regulated under the hypertonic condition. Rac1 were up-regulated in both conditions. This study provides new insights into the osmoregulatory mechanisms of spotted sea bass in response to long-term hypotonic and hypertonic acclimation.

The genome and comparative transcriptome of the euryhaline model ciliate Paramecium duboscqui reveal adaptations to environmental salinity

BackgroundAs a potential model organism for studies of environmental and cell biology, Paramecium duboscqui is a special euryhaline species of Paramecium that can be found in fresh, brackish, or marine water in natural salinity ranges between 0‰ and 33‰. However, the genome information as well as molecular mechanisms that account for its remarkable halotolerant traits remain extremely unknown. To characterize its genome feature, we combined PacBio and Illumina sequencing to assemble the first high-quality and near-complete macronuclear genome of P. duboscqui. Meanwhile, comparative transcriptomic profiles under different salinities gave underlying insight into the molecular mechanism of its adaptations to environmental salinity.ResultsThe results showed that the MAC genome of P. duboscqui comprises 160 contigs, with 113 of them possessing telomere (~ 28.82 Mb haploid genome size). Through comparative genomic analyses with the other ciliate, we found that gene families encoding transmembrane transporter proteins have been expanded in P. duboscqui, showing enormous potential in salinity adaptation. Like other Paramecium, P. duboscqui utilizes TGA as its only termination codon and has reassigned TAA and TAG to encode glutamine. P. duboscqui showed different growth rates under different salinities, with an optimum growth rate in 5‰ salinity. A comparison of the transcriptomic profiles among P. duboscqui grown under different concentrations showed that genes involved in protein folding, oxygen respiration, and glutathione-dependent detoxification were upregulated in the high-salt group, whereas genes encoding DNA-binding proteins and transcription factors were upregulated in the low-salt group, suggesting distinct mechanisms for responding to low and high salinity. Weighted gene coexpression network analysis (WGCNA) linked the hub genes expressed at 30‰ salinity to cysteine-type peptidase activity, lipid transfer, sodium hydrogen exchange, and cell division, with the hub genes expressed at 0‰ salinity involved in transmembrane transport and protein localization.ConclusionsThis study characterizes a new euryhaline model Paramecium, provides novel insights into Paramecium evolution, and describes the molecular mechanisms that have allow P. duboscqui to adapt to different osmotic environments.

Hypersalinity tolerance of mummichogs (Fundulus heteroclitus): A branchial transcriptomic analysis

Along the east coast of North America, mummichogs (Fundulus heteroclitus) are subjected to a broad range of salinities in their nearshore habitats. However, there is a paucity of information regarding the molecular and cellular processes that mummichogs (and other highly osmotolerant fishes) engage to survive environmental salinities greater than seawater (SW). To reveal branchial processes underlying their extraordinarily broad salinity tolerance, we performed an RNA-Seq analysis to identify differentially expressed genes (DEGs) in mummichogs residing in 3, 35, and 105 ppt conditions. We identified a series of DEGs previously associated with both freshwater (FW)- and SW-type ionocytes; however, the heightened expression of anoctamin 1a, a Ca2+-activated Cl− channel, in 35 and 105 ppt indicates that an undescribed Cl−-secretion pathway may operate within the SW-type ionocytes of mummichogs. Concerning FW-adaptive branchial processes, we identified claudin 5a as a gene whose product may limit the diffusive loss of ions between cellular tight junctions. Further, in response to hypersaline conditions, we identified DEGs linked with myo-inositol synthesis and kinase signaling. This study provides new molecular targets for future physiological investigations that promise to reveal the mechanistic bases for how mummichogs and other euryhaline species tolerate hypersaline conditions.

Freshwater exploitation at Ajvide - Pitted ware culture fishing practises investigated through laser ablation facilitated strontium isotope analyses

The importance of marine resources for the Neolithic hunter-fisher-gathers of the Pitted Ware Culture of Gotland, Sweden, is well documented through zooarchaeological analyses and diet studies of human remains. Terrestrial areas were important for living and supplementing the diet but the extent of the terrestrial territories and regions of land use for different groups is largely unknown. The presence of euryhaline species in recovered zooarchaeological assemblages indicates that freshwater fishing or fishing in the brackish estuaries of the Baltic Sea was part of the subsistence practises. To explore if the inland freshwaters of Gotland were used and, if exploited, where they were located, 18 teeth from euryhaline fish from the Pitted Ware Culture site Ajvide on Gotland were selected. The 87Sr/86Sr isotope ratios in the fish teeth were analysed using laser ablation-multi collector-inductively coupled plasma-mass spectrometry and correlated with an updated bioavailable baseline of Gotlandic water sources. Through this approach, the habitational origin of the fish was shown to primarily stem from at least six freshwater sources located in the west-central area of Gotland, in close relation to the site, with a few individuals originating from within the Baltic Sea. The study highlights the significance of ichthyoarchaeological analysis in understanding the territorial practice of past foraging societies and recommends further studies on euryhaline species to expand our knowledge of fish habitat, human resource utilization and land use.

Estuarine ichthyofauna of Kamchatka: formation conditions, species diversity and ecological characterisation

Species composition of the estuarine ichthyofauna is described for the first time on a regional scale for Kamchatka Territory based on the materials of author’s field studies carried out in 2010–2022, as well as on the analysis of all available information (literature, archival, survey, fishery, etc.). Specific features of the conditions of formation of estuarine ichthyofauna of the region are revealed. Fish species dominating in abundance in Kamchatka estuaries are indicated. The main ecological groups (guilds) of estuarine fishes are outlined. It was found that 1 species of cyclostomes and 60 species of fishes belonging to 44 genera and 23 families can be attributed to the estuarine ichthyofauna of Kamchatka. All these species are, to varying degrees, euryhaline and therefore may utilize individual Kamchatka estuaries as habitats at various stages of the life cycle. The basis of species diversity of the ichthyofauna of Kamchatka estuaries is formed by marine fishes (at least 34 species), the second in importance are anadromous species (1 species of cyclostomes and 14 species of fishes), the minimum contribution belongs to freshwater resident fishes (13 species), which are found only in estuaries of some rivers of the region. Fish that can be referred to the ecological group of “solely estuarine” (i. e., those whose full life cycle takes place in estuaries) are probably absent in Kamchatka. The maximum species diversity of fish communutues is observed either in big Kamchatka estuaries that are largely open to the sea or in river basins with a diverse freshwater ichthyofauna. Environmental conditions in such estuaries are more favorable for the migrations and habitat of marine fish species (mainly coastal ichthyocene). At the same time, all anadromous or some freshwater euryhaline species may also use these same estuaries as temporary habitats at certain stages of the life cycle. Fish species diversity is significantly higher in the estuaries of the eastern coast of Kamchatka, which is explained by the milder climatic conditions of this area (compared to the coast of the Sea of Okhotsk), as well as by the greater typological diversity of estuaries. A separate section summarizes the currently available information on the biology and ecology of all species of fishes and fish of Kamchatka estuaries, which is presented in the form of brief species sketches (including, external view at individual stages of the life cycle; key morphological characters; maximum size and age; distribution over the territory of the region; habitat specifics, lifestyle and migrations; peculiarities of reproduction and development; feeding preferences; abundance in the region, commercial or economic importance).

Unveiling osmoregulation and immunological adaptations in Eleutheronema tetradactylum gills through high-throughput single-cell transcriptome sequencing

The fourfinger threadfin fish (Eleutheronema tetradactylum) is an economically significant species renowned for its ability to adapt to varying salinity environments, with gills serving as their primary organs for osmoregulation and immune defense. Previous studies focused on tissue and morphological levels, whereas ignored the cellular heterogeneity and the crucial gene information related to core cell subsets within E. tetradactylum gills. In this study, we utilized high-throughput single-cell RNA sequencing (scRNA-seq) to analyze the gills of E. tetradactylum, characterizing 16 distinct cell types and identifying unique gene markers and enriched functions associated within each cell type. Additionally, we subdivided ionocyte cells into four distinct subpopulations for the first time in E. tetradactylum gills. By employing weighted gene co-expression network analysis (WGCNA), we further investigated the cellular heterogeneity and specific response mechanisms to salinity fluctuant. Our findings revealed the intricate osmoregulation and immune functions of gill cells, highlighting their crucial roles in maintaining homeostasis and adapting to fluctuating salinity levels. This comprehensive cell-type atlas provides valuable insights into the species adaptive strategies, contributing to the conservation and management of this commercially significant fish as well as other euryhaline species.

Resilience to changes in salinity and predator diversity in representative Gulf of Mexico estuarine fish predator-prey interactions

Predators strongly influence ecological communities and subsequent ecosystem function by directly consuming prey individuals and indirectly by inciting alterations in prey behavior, termed non-consumptive effects (NCEs). Gulf of Mexico estuaries support complex food webs structured by numerous species interactions maintained in constant environmental flux from variation in salinity. Environmental variation presents a source of physiological stress for estuarine fish and plays a role in their distributions and subsequent interactions. Here, we present the results of a mesocosm experiment examining if acute changes in salinity disrupt NCEs of different predators on estuarine prey. We exposed Gulf killifish (Fundulus grandis) to visual and/or olfactory cues from a common estuarine predator, red drum (Sciaenops ocellatus), and from a freshwater predator that is a transient species in lower portions of estuaries, largemouth bass (Micropterus salmoides), under either decreasing, constant, or increasing salinity. Killifish decreased shoal size and movement in response to olfactory cues or both visual and olfactory cues compared to when they were exposed to no cues or visual cues, demonstrating variable perceived risk dependent on cue type. Behavioral response did not vary by predator species, implying a generalized response to different fish predators. Prey did not change behavior when exposed to decreasing salinity compared to constant salinity. However, prey movement increased with increasing salinity, indicating that salinity changes may provide cues to search for different habitats instead of a stressor. Our experiment indicates that estuarine predator-prey interactions may be resilient to acute salinity changes given the broad tolerances of euryhaline species.

Effective complete replacement of fish oil by linseed oil in diets for thick-lipped grey mullet (Chelon labrosus) juveniles reared at three environmental salinities

One of the major challenges for fish oil replacement by alternative oils is the limited capacity of marine fish species to convert 18C fatty acids into long-chain poly unsaturated fatty acids (LC-PUFA). Since salinity markedly affects this conversion capacity, euryhaline species, such as thick-lipped grey mullet (Chelon labrosus), may have a good potential to use diets without inclusion of fish oil. To test this hypothesis, thick-lipped grey mullet juveniles were fed two different diets based on fish oil (FO diet) or linseed oil (LO diet) at three different salinities: 46 ppt, 35 ppt, and 16 ppt. At the end of the trial, the biochemical and fatty acid composition of whole-body, liver, and muscle, as well as the relative expression of the genes codifying for the elongase Elovl5 and the desaturase Fads2 in liver, were determined. The results showed the good capacity of mullet juveniles to convert 18C fatty acids into LC-PUFA, which was enhanced by the replacement of FO by LO and the reduction of salinity to an isosmotic level (16 ppt). Besides, these juveniles efficiently used diets with complete replacement of FO by LO with growth performance, body composition, and LC-PUFA fatty acid profiles similar to those of fish fed FO, particularly when reared at 16 ppt.

Transcriptional upregulation of the myo-inositol biosynthesis pathway is enhanced by NFAT5 in hyperosmotically stressed tilapia cells.

Euryhaline fish experience variable osmotic environments requiring physiological adjustments to tolerate elevated salinity. Mozambique tilapia (Oreochromis mossambicus) possess one of the highest salinity tolerance limits of any fish. In tilapia and other euryhaline fish species, the myo-inositol biosynthesis (MIB) pathway enzymes, myo-inositol phosphate synthase (MIPS) and inositol monophosphatase 1 (IMPA1.1), are among the most upregulated mRNAs and proteins indicating the high importance of this pathway for hyperosmotic (HO) stress tolerance. These abundance changes must be precluded by HO perception and signaling mechanism activation to regulate the expression of MIPS and IMPA1.1 genes. In previous work using a O. mossambicus cell line (OmB), a reoccurring osmosensitive enhancer element (OSRE1) in both MIPS and IMPA1.1 was shown to transcriptionally upregulate these enzymes in response to HO stress. The OSRE1 core consensus (5'-GGAAA-3') matches the core binding sequence of the predominant mammalian HO response transcription factor, nuclear factor of activated T-cells (NFAT5). HO-challenged OmB cells showed an increase in NFAT5 mRNA suggesting NFAT5 may contribute to MIB pathway regulation in euryhaline fish. Ectopic expression of wild-type NFAT5 induced an IMPA1.1 promoter-driven reporter by 5.1-fold (P < 0.01). Moreover, expression of dominant negative NFAT5 in HO media resulted in a 47% suppression of the reporter signal (P < 0.005). Furthermore, reductions of IMPA1.1 (37-49%) and MIPS (6-37%) mRNA abundance were observed in HO-challenged NFAT5 knockout cells relative to control cells. Collectively, these multiple lines of experimental evidence establish NFAT5 as a tilapia transcription factor contributing to HO-induced activation of the MIB pathway.NEW & NOTEWORTHY In our study, we use a multi-pronged synthetic biology approach to demonstrate that the fish homolog of the predominant mammalian osmotic stress transcription factor nuclear factor of activated T-cells (NFAT5) also contributes to the activation of hyperosmolality inducible genes in cells of extremely euryhaline fish. However, in addition to NFAT5 the presence of other strong osmotically inducible signaling mechanisms is required for full activation of osmoregulated tilapia genes.

Limited Parallelism in Genetic Adaptation to Brackish Water Bodies in European Sprat and Atlantic Herring.

The European sprat is a small plankton-feeding clupeid present in the northeastern Atlantic Ocean, in the Mediterranean Sea, and in the brackish Baltic Sea and Black Sea. This species is the target of a major fishery and, therefore, an accurate characterization of its genetic population structure is crucial to delineate proper stock assessments that aid ensuring the fishery's sustainability. Here, we present (i) a draft genome assembly, (ii) pooled whole genome sequencing of 19 population samples covering most of the species' distribution range, and (iii) the design and test of a single nucleotide polymorphism (SNP)-chip resource and use this to validate the population structure inferred from pooled sequencing. These approaches revealed, using the populations sampled here, three major groups of European sprat: Oceanic, Coastal, and Brackish with limited differentiation within groups even over wide geographical stretches. Genetic structure is largely driven by six large putative inversions that differentiate Oceanic and Brackish sprats, while Coastal populations display intermediate frequencies of haplotypes at each locus. Interestingly, populations from the Baltic and the Black Seas share similar frequencies of haplotypes at these putative inversions despite their distant geographic location. The closely related clupeids European sprat and Atlantic herring both show genetic adaptation to the brackish Baltic Sea, providing an opportunity to explore the extent of genetic parallelism. This analysis revealed limited parallelism because out of 125 independent loci detected in the Atlantic herring, three showed sharp signals of selection that overlapped between the two species and contained single genes such as PRLRA, which encodes the receptor for prolactin, a freshwater-adapting hormone in euryhaline species, and THRB, a receptor for thyroid hormones, important both for metabolic regulation and the development of red cone photoreceptors.

Megahabitats shape fish distribution patterns on the Amazon coast

The Brazilian North Coast (BNC) encompasses the intersection of multiple oceanographic features such as strong currents, a large continental shelf under the influence of the Amazon River freshwater and sediment outflow, extensive muddy and sand bottom, as well as a mesophotic reef system. As a result, the BNC hosts a diverse fish fauna, consisting of estuarine and freshwater species, including species endemic to the region. These fish species are distributed across a mosaic of megahabitats within the region. Here, we present the first comprehensive effort to understand the distribution patterns of ray-finned fishes and cartilaginous fishes among these different megahabitats. On 1891 samples, we recorded 616 species from 147 families distributed across five distinct megahabitats. The Continental Slope megahabitat had the highest number of families and consisted primarily of pelagic species, indicating its close association with the open sea. The Sand and Mud megahabitats exhibited high species richness and shared similar generalist fish families in terms of habitat use. The Amazon Plume megahabitat was characterized by freshwater and marine euryhaline species, emphasizing the influence of the Amazon River on the BNC's ecological dynamics. The Reef megahabitat had species closely associated with consolidated substrates and shared many species with the Sand megahabitat. This study offers valuable insights into fish species distribution and composition in the BNC, contributing to biodiversity assessments and conservation efforts in the region.

Responses of zooplankton assemblages to environmental variability among brackish coastal ponds, New Zealand

Coastal brackish waters, including estuaries, lagoons and coastal ponds, experience fluctuations in physicochemical properties, particularly in salinity, due to the differential forcing of marine and freshwater inflows. Most research concerning brackish waters is skewed towards lagoons and estuaries, while relatively little exists on small coastal ponds. This study examined variability in zooplankton community composition relative to environmental conditions among brackish coastal ponds in Auckland, New Zealand. Eight coastal stormwater ponds, four freshwater ponds, and four marine sites were selected to represent a wide salinity gradient and sampled for zooplankton and environmental variables. Marked spatial and temporal variability in environmental conditions was observed among the coastal ponds. Salinity of the ponds was, on average, lower in winter, influenced by higher rainfall, while in summer reduced rainfall led to significantly lower freshwater inputs. Zooplankton communities within the coastal ponds were a mix of those in freshwater and marine sites, along with unique species not observed in each of the adjoining ecosystems. Salinity was the most important factor driving zooplankton community composition among sites, as widely reported for estuaries and lagoons. The degree of temporal change in salinity within ponds also affected community composition, with euryhaline copepods such as Sulcanus conflictus and Mesochra parva most abundant at sites with larger seasonal salinity changes. Salinity increases due to sea-level rises may lead to the disappearance of species that are less tolerant to salinity, with a move to dominance by euryhaline species.

Indian Freshwater Elasmobranchs: Ongoing Threats along with IUCN Current Status and Conservation of Protecting Hidden Treasures: A Review

We always thought that elasmobranchs inhabit marine environments, but this is only partially true. About 5% of known elasmobranch species are the freshwater compared to 40% of teleost species. A systematic checklist is available for Indian freshwater elasmobranches with names and IUCN status. A total of 13 species belonging to 3 orders, 3 families and 10 genera were enlisted from secondary data. Euryhaline and obligate species include sharks as Carcharhinus, Glyphis (Carcharhinidae), Chiloscyllium (Hemiscylliidae), sawfishes or Pristis (Pristidae), stingrays or Himantura (whiprays) and Pastinachus (cowtailed rays) (Dasyatidae). We focus on distribution, feeding habits, threats and conservation. Freshwater excursions are relatively rare in extant elasmobranchs than other groups of fish. The low growth rate is probably due to late age at maturity and low fecundity, long gestation periods, slow growth and productivity (small, infrequent litters), high natural survivorship for all age classes and long life. Despite this, some species of freshwater elasmobranchs can tolerate and even thrive in freshwater.

First Insights into Body Localization of an Osmoregulation-Related Cotransporter in Estuarine Annelids.

The expression of the Na+-K+-2Cl- cotransporter (NKCC), widely associated with cell volume regulation, has never been directly demonstrated in annelids. Its putative presence was firstly recovered in silico, and then using immunofluorescence, its signal was retrieved for the first time in different tissues of four species of estuarine annelids from southern Brazil that are regularly subjected to salinity fluctuations. We tested two euryhaline species (wide salinity tolerance), the nereidids Alitta yarae and Laeonereis acuta (habitat salinity: ~10-28 psu), and two stenohaline species (restricted salinity tolerance), the nephtyid Nephtys fluviatilis (habitat salinity: ~6-10 psu), and the melinnid Isolda pulchella (habitat salinity: ~28-35 psu). All four species showed specific immunofluorescent labelling for NKCC-like expression. However, the expression of an NKCC-like protein was not homogeneous among them. The free-living/burrowers (both euryhaline nereidids and the stenohaline nephtyid) displayed a widespread signal for an NKCC-like protein along their bodies, in contrast to the stenohaline sedentary melinnid, in which the signal was restricted to the branchiae and the internal tissues of the body. The results are compatible with NKCC involvement in cell volume, especially in annelids that face wide variations in salinity in their habitats.

Expansion of the Distribution Range and Size of the Invasive Blue Crab on the Turkish Coast of the Black Sea

The blue crab (Callinectes sapidus Rathbun, 1896) is an euryhaline species originally native to the western Atlantic Ocean. However, it has expanded its range into the Black Sea, including the Turkish coastal waters. Blue crab specimens were sampled along the Black Sea coast of Türkiye, covering the stretch from Cape Taşkana to the Georgian border. The monitoring studies spanned the period from 2017 to 2024. Analysis of the 16 specimens revealed a carapace width range of 14.8 to 20.3 cm, with males exhibiting larger sizes compared to females. Notably, two of the sampled females were observed to be carrying eggs, highlighting reproductive activity in the region. This study also reports the discovery of the largest blue crab ever recorded on the Turkish coasts of the Black Sea, with a male specimen measuring 20.33 cm in carapace width and weighing 565.1 g. Additionally, a male specimen sampled in the Rize region suggests the species has expanded its range to the easternmost part of the Black Sea. The findings contribute significantly to our understanding of the distribution and growth potential of the blue crab in the Black Sea. The larger sizes observed in males and the presence of ovigerous females indicate successful adaptation and potential establishment of a self-sustaining population. As invasive species, blue crabs can significantly influence benthic communities and food chains, highlighting the importance of a prudent management approach to fisheries biology and ecosystem management

Evidence for Selection on Mitochondrial OXPHOS Genes in the Mediterranean Killifish Aphanius fasciatus Valenciennes, 1821.

Mitochondrial oxidative phosphorylation (OXPHOS) genes are a system subject to selection under determined environmental constraints despite a neutral evolution model that has long been hypothesized for the mitochondrial genome. In this study, the sequences of ND1, Cytb, and COI OXPHOS genes were analyzed in six populations of the eurythermal and euryhaline killifish A. fasciatus, to detect non-synonymous mutations leading to amino acid changes and to check whether selection acted on them using tests of recombination and selection. The results indicate a high COI and Cytb gene diversity and a high percentage of private haplotypes in all populations. In the Greek population, non-synonymous nucleotide substitutions were observed in the N-terminal region of COI and Cytb. Positively selected sites were also found. The information we obtained from the mitochondrial DNA sequences of A. fasciatus adds to the growing data on selective pressure acting on mitochondrial DNA in non-model species. These results should be explored from the perspective of the local adaptation of eurythermal and euryhaline species and supported using experimental evidence to better understand the interplay between historical climatic events and local adaptation and how each of them contributes to shaping the genetic structure of this species.

Analysis of Genetic Diversity and Structure of Eight Populations of Nerita yoldii along the Coast of China Based on Mitochondrial COI Gene.

Nerita yoldii is a euryhaline species commonly found in the intertidal zone. To investigate the genetic diversity of 233 N. yoldii individuals from eight locations along the coast of China, we utilized the mitochondrial COI gene as a molecular marker. A total of 34 haplotypes were detected, exhibiting a mean haplotype diversity (Hd) of 0.5915 and a mean nucleotide diversity (Pi) of 0.0025, indicating high levels of genetic diversity among all populations. An analysis of molecular variance (AMOVA) indicated that the primary source of genetic variation occurs within populations. In addition, neutral tests and mismatch analyses suggested that N. yoldii populations may have experienced bottleneck events. Moderate genetic differentiation was observed between Xiapu and other populations, excluding the Taizhou population, and may be attributed to the ocean currents. Intensively studying the genetic variation and population structure of N. yoldii populations contributes to understanding the current population genetics of N. yoldii in the coastal regions of China. This not only provides a reference for the study of other organisms in the same region but also lays the foundation for the systematic evolution of the Neritidae family.

Obtaining microalgae biomass in a small scale reactor

In order to industrialize massive production of microalgae with biotechnologically important traits, it is essential to reduce production costs through the design and evaluation of different culture media, which are reflected in the value of the final product. It is important to know and understand the dynamics of growth and behavior of the strain of interest, as well as the response to different environmental factors, in order to obtain an adequate and permanent production of biomass. Tetraselmis sp. is an ellipsoidal mobile, compressed alga with four flagella and the acute rear end with the anterior end of four lobes. It is green bright, 7 µm in diameter and 10-16 µm in length. It is a euryhaline species with ability to form spores, whose limits of tolerance to physical variables are very broad. It contains 49.22% protein, 10.60% lipid and 16.38% from carbohydrates. The microalgae Tetraselmis sp. was massively cultivated with Guillard media, and their biomass was harvested every 72 h, we obtained an biomass average of 1.35 g/L/d.

Effect of water salinity on immature performance and lifespan of adult Asian tiger mosquito

BackgroundAedes albopictus (Skuse, 1894) is a vector for pathogens like dengue, chikungunya, and Zika viruses. Its adaptive capacity enables reproduction in temperate climates and development mainly in artificial containers with fresh water in urbanized areas. Nevertheless, breeding in coastal areas may also occur along with its aggressive invasiveness. Global warming and the consequent rise in sea levels will increase saline (> 30 ppt) or brackish (0.5–30 ppt salt) water in coastal regions. To address whether Ae. albopictus can breed in brackish water, we initiated the current study that analyses the survival of immature stages at different salinity concentrations and explores whether carryover effects occur in the resulting adults. This possible adaptation is important when considering the potential for development in new habitats and expansion of one of the world’s most invasive species.MethodsWe investigated the influence of salinity on the survival of Ae. albopictus larvae and adults under laboratory-controlled conditions. First instar larvae were exposed to different salinity concentrations (0 to 30 ppt) and their development time, pupation, adult emergence, and overall survival were monitored daily. We used Kaplan-Meier and Cox regression models to analyze the survival rates at different salinity levels. Furthermore, life tables were constructed under each salinity concentration.ResultsIncreasing salt concentrations significantly increased the mortality risk during immature development, while no significant effect was observed on adult mortality risk. A comparison between distilled and bottled water revealed a notable increase in overall mortality risk for individuals developing in distilled water. However, no significant effects were found when analyzing survival from the first larval stage to adult emergence and adult lifespan. The life expectancy of immature stages decreased with increasing salt concentrations, although salinity concentration did not significantly impact adult life expectancy.ConclusionsOur findings suggest that Ae. albopictus, previously considered freshwater species, can successfully develop and survive in brackish waters, even in the absence of characteristic structures found in euryhaline species. These adaptations may enable Ae. albopictus to establish new breeding sites and colonize unexplored territories. Knowledge of these physiological adaptations of Ae. albopictus to salinity should be pursued to increase the range of control of the species, and to make more accurate predictions of its dispersal and vectoring ability.Graphical