Abstract: Aquaculture plays a strategic role in food security and rural development in coastal regions. However, structural, economic, and institutional constraints affect small-scale producers in heterogeneous ways. This study analyzes how small-scale aquaculture producers in Manabí (Ecuador) perceive the main challenges affecting their activity, based on a typology comprising three production systems: Backyard, Transitional, and Commercial. A structured questionnaire was administered to 98 producers, including 20 variables assessed using a five-point Likert scale. The analysis combined non-parametric univariate tests (Kruskal–Wallis with Dunn post-hoc comparisons) and multivariate techniques to identify statistically significant differences and structured perception patterns across production systems. Significant differences were detected in variables related to biological input supply, market conditions, and structural production constraints. In particular, larvae and fingerling supply, selling prices, buyer availability, and pond surface area showed differentiated perception patterns across systems. Most differences occurred between Backyard farms and the other two production systems, while Transitional and Commercial farms displayed more similar perception profiles. Transversal constraints shared across systems included high feed costs, energy expenditure, and regulatory requirements. Principal Component Analysis identified two main perception gradients related to market and input constraints and to structural and managerial limitations. Discriminant analysis further confirmed the ability of these dimensions to differentiate production systems. These findings highlight the multidimensional nature of constraints affecting small-scale aquaculture and suggest that production systems are better interpreted as gradients of pressures rather than strictly discrete categories. The results underline the need for adaptive governance approaches combining transversal measures with system-specific interventions. Overall, the study provides empirical evidence to support the design of differentiated and context-sensitive policies aimed at strengthening the sustainable development of small-scale aquaculture in Manabí and similar territories.

Abstract:

Urban coastal wetlands along the Peruvian Pacific coast are increasingly affected by urban expansion, pollution, and hydrological alterations, compromising their ecological integrity. In this context, the spatiotemporal variation of the aquatic macrophyte community and its relationship with limnological conditions and drivers of change were evaluated in the Santa Rosa wetland (Chancay, Lima). The objective is to evaluate the spatiotemporal variation of the aquatic macrophyte community in the Santa Rosa wetland and analyze its relationship with physicochemical limnological variables and drivers of change. Sampling was conducted during two contrasting hydrological seasons in 2022: T1 (summer) and T2 (winter), at six sampling points (P1–P6). Physicochemical variables (water depth, temperature, pH, conductivity, TDS, TSS, dissolved oxygen, turbidity, nitrate, ammonium, phosphorus, and dissolved organic matter) were measured, and the relative abundance of aquatic macrophytes was evaluated. Drivers of change were identified through direct observation and a structured matrix, with a PCoA performed to summarize spatiotemporal trends. Data were analyzed using Principal Component Analysis (PCA), Co-inertia analysis, and Multi-Response Permutation Procedures (MRPP). Significant spatiotemporal variation was observed in physicochemical parameters (p < 0.05), with moderate covariation between the two matrices (RV = 0.47). A total of ten aquatic macrophyte species were recorded, with higher abundance of Pontederia crassipes and Pistia stratiotes in T1, and Hydrocotyle ranunculoides and Bacopa monnieri in T2. The most relevant drivers of change were solid waste, livestock grazing, organic contamination, and urban expansion. Spatial heterogeneity was observed in the drivers of change affecting the Santa Rosa wetland, forming a mosaic of areas with different impact profiles. Despite multiple anthropogenic pressures, the Santa Rosa wetland maintains a limnological structure and a functionally coupled macrophyte community, evidencing ecological resilience to environmental degradation. The observed covariation between physicochemical conditions and vegetation confirms the persistence of essential ecological processes, even within an altered urban context. This study demonstrates that integrating biotic components, limnological variables, and drivers of change is fundamental to understanding and monitoring the ecological dynamics of urban wetlands along the Peruvian coast.

Abstract: Otolith microchemistry was used to investigate habitat use and connectivity of the estuarine catfish Genidens genidens across three estuaries in southeastern Brazil. A total of 58 individuals were analyzed using laser ablation inductively coupled plasma mass spectrometry, focusing on strontium-to-calcium (Sr:Ca) and barium-to-calcium (Ba:Ca) ratios. Variations in elemental ratios along otolith transects allowed the reconstruction of individual ontogenetic trajectories along the estuarine–marine gradient. Most individuals exhibited combined use of estuarine and marine environments, while trajectories restricted to freshwater were rare. The complexity of chemical profiles increased with age, indicating more frequent habitat shifts throughout ontogeny. These patterns reveal high ecological plasticity and partial migration within populations of G. genidens. Strontium-to-calcium ratios were effective indicators of salinity-related habitat transitions, whereas Ba:Ca ratios provided complementary information associated with continental influence. Overall, this study demonstrates the applicability of otolith microchemistry to infer individual life-history pathways and highlights the role of estuaries as key habitats for feeding, growth, and recruitment in G. genidens.

Abstract: Water quality plays a central role in determining the environmental performance and sustainability of pond-based tropical aquaculture systems. This study aimed to evaluate the relative environmental sustainability of different tropical pond-based aquaculture systems by identifying multivariate water quality patterns that allow their discrimination and comparison under commercial production conditions. Four pond-based production systems were evaluated: an aquaponic system (APS), a recirculating aquaculture system (RAS), a conventional earthen pond system (CEP), and an integrated rice–chame system (RCS). Eleven physicochemical water quality variables were monitored throughout the production cycle under real commercial conditions to characterize system functioning and environmental dynamics. Multivariate discriminant analysis was applied to identify the variables with the highest discriminatory power and to evaluate the ability of water quality patterns to correctly classify observations among production systems. The results revealed a clear multivariate separation between the technologically intensive systems (APS and RAS) and the less intensive and integrated systems (CEP and RCS), reflecting distinct water quality structures and environmental functioning. Variables associated with mineralization and nutrient dynamics, including electrical conductivity, salinity, total hardness, and ammonium, contributed most strongly to system discrimination. The discriminant functions achieved a high overall correct classification rate, demonstrating the robustness of the multivariate approach. These findings demonstrate that water quality variables provide consistent environmental signatures for distinguishing tropical pond-based aquaculture systems and offer an operational framework for assessing their relative environmental sustainability. Discriminant analysis emerges as a valuable tool for system characterization and comparative evaluation, supporting environmentally informed management and optimization of chame aquaculture under tropical conditions.

Abstract: Sea urchin gonads (“roe”) are a valuable seafood product and a chemically complex matrix whose composition varies with physiology and environment. We present a biphasic extraction and ¹H NMR workflow to build a reusable reference inventory of polar metabolites and apolar lipid features in Paracentrotus lividus. Gonads from 37 adults (23 males, 14 females) collected at two sites (Alicante and Jávea–Dénia, Spain; October 2024) were lyophilized, extracted with methanol/chloroform/water, and analysed by 400 MHz ¹H NMR in buffered aqueous solution (polar) and CDCl₃ (apolar). Polar metabolite identification combined 1D patterns with database matching and ¹H–¹³C HSQC confirmation on representative samples, yielding 71 annotated resonances corresponding to 37 metabolites spanning amino acids, osmolytes/quaternary amines, carbohydrates/aminosugars, and nucleoside/purine-related compounds. Polar fingerprints enabled supervised modelling: PLS-LDA separated sexes with low cross-validated error, and SPA/COSS ranking highlighted glycine, alanine, creatine and osmolyte-associated signals as key discriminants; pathway mapping supported enrichment of amino-acid and one-carbon/purine networks. Apolar spectra were annotated at motif level and used for lipid-index estimation, indicating substantial unsaturation but low DHA and modest sex effects. The curated peak lists and reporting framework facilitate reproducible NMR annotation and future comparative studies of P. lividus gonads.

Abstract: The valorization of agricultural by-products as functional feed additives represents a promising strategy for sustainable aquaculture. This study evaluated the effects of dietary fermented longan peel (FLP), produced through enzymatic hydrolysis and Lactiplanti-bacillus plantarum fermentation, on growth performance, digestive physiology, gut morphology, innate immunity, and gene expression in Nile tilapia (Oreochromis niloticus) cultured under a biofloc system. Five experimental diets were formulated with graded FLP levels (0, 5, 10, 20, and 40 g kg-1) and fed to fish for eight weeks. Growth indices, including final weight, weight gain, and specific growth rate, improved significantly in fish receiving 20 g kg-1 FLP, following a strong quadratic response pattern. In vitro di-gestibility assays showed enhanced carbohydrate and protein digestibility, coinciding with increased intestinal amylase and protease activities. Histological analysis indicated that moderate FLP inclusion (10–20 g kg-1) promoted villus height, crypt depth, and epithelial organization. Innate immune parameters, including lysozyme, peroxidase, and alternative complement activity, were markedly elevated in serum and mucus, partic-ularly at 20–40 g kg-1 after eight weeks. Gene expression profiling revealed significant up-regulation of growth-related (IGF-1, GH, NPY-α, Galanin), immune-related (TLR-7, TNF-α, NFκB), and antioxidant-related (hsp70, Keap-1, nrf-2, GST-α) genes in fish fed higher FLP levels, with responses plateauing beyond 20 g kg-1. Overall, FLP supple-mentation at 20 g kg-1 optimally enhanced growth, digestive efficiency, intestinal health, and innate immune status. These findings demonstrate the potential of fermented longan peel as a cost-effective, bioactive, and sustainable functional feed ingredient for tilapia and other warm-water aquaculture species.

Abstract:

Freshwater macrophytes shape not only the morphological “architecture” of shallow-water ecosystems but also their chemical milieu via low-molecular-weight organic compounds (LMWOCs) that may regulate phytoplankton, periphyton, and the microbiome within the leaf/shoot diffusive boundary layer and the surrounding water column. In this study, GC–MS (gas chromatography–mass spectrometry) was used to identify major LMWOCs of the low-molecular-weight metabolome (LMWM) in 11 widely distributed macrophyte species (Myriophyllum spicatum L., Sparganium emersum Rehm., Sparganium gramineum Georgi, the hybrid Sparganium × foliosum A. A. Bobrov, Volkova, Mochalova et Chemeris, Persicaria amphibia (L.) Delarbre, Potamogeton perfoliatus L., Nuphar lutea (L.) Sibth. & Sm., Potamogeton pectinatus L., Potamogeton natans L., Lobelia dortmanna L., and Ceratophyllum demersum L.). Compounds contributing more than 1% to the total LMWOCs pool were considered major, increasing the ecological realism of interpretations by focusing on metabolites more likely to reach effective concentrations in the plant microenvironment. For interspecific comparisons, the maximum recorded values of relative abundance and concentrations were used to estimate species “potential”. In total, 137 major LMWOCs were detected (four remained unidentified), and their numbers varied markedly among taxa (from 11 in Nuphar lutea to 71 in P. perfoliatus). Similarity analyses (Jaccard, Sørensen–Czekanowski, Morisita–Horn) indicated that similarity based on compound lists and similarity based on dominance structure may diverge, reflecting differences between the “LMWOCs set” and the quantitative architecture of LMWOCs within the LMWM. Fatty acids formed the core of the major fraction in all species: they were among the top three compounds in all 11 macrophytes and ranked first or second in 10 of 11, highlighting the lipid module as a universal “structure–signaling–defense/allelopathy” hub in aquatic plants. Also, an analysis of the ecological-biochemical role of the main major LMWOCs in the studied aquatic macrophytes is presented. Overall, the data offer a comparable, ecologically oriented framework for interpreting chemical regulation of communities in macrophyte-dominated habitats and for selecting target compounds/species for subsequent bioassay and field studies.

Abstract:

The global prevalence of obesity continues to rise, posing serious risks to human health largely because obesity itself leads to metabolic disorders of carbohydrate and lipids. Currently, effective and healthy interventions for lowering blood glucose, reducing blood lipids, and promoting weight loss remain limited due to the complexity of obesity development. Lactobacillus plantarum (GDMCC 1.140) was shown to promote catabolic process and reduce hepatic lipid accumulation in largemouth bass fed with high-starch feed (HSF) in our previous study; however, molecular mechanisms underlying the function of this probiotic remain unclear. Here, we evaluated the effects of L-carnosine, one of metabolites from Lactobacillus plantarum, on carbohydrate and lipid metabolisms in an obesity model of zebrafish, which was induced by HSF. Histopathological analyses of livers from different groups indicated that dietary supplement with L-carnosine can alleviate hepatic impairment and reduce lipid accumulation in the hepatocytes of obese zebrafish. Transcriptomic analyses revealed that L-carnosine supplementation can reverse the expression of about 70 HSF-induced genes, mainly gene-specific transcription regulators and metabolite interconversion enzymes. Furthermore, about 250 HSF-inhibited genes were found to be up-regulated by L-carnosine toward the levels in normal-starch feed (NSF) zebrafish. These L-carnosine-targeted and HSF-inhibited genes are highly enriched in GO terms such as lipid metabolic process, small molecule metabolic process, and cellular response to chemical stimulus, followed by monocarboxylic acid metabolic process, modified amino acid metabolic process and aldehyde metabolic process, and in KEGG pathways of carbohydrate, lipid, and amino acid metabolisms, such as pentose and glucuronate interconversions, glycolysis/gluconeogenesis, glycerolipid metabolism, pentose phosphate pathways, fatty acid degradation, beta-alanine metabolism and arginine and proline metabolism. These findings provide functional and molecular evidence that L-carnosine can ameliorate HSF-induced disorders of carbohydrate and lipid metabolisms.

Abstract: This study reports on the presence of two uncommon tetraodontiform fishes and reviews the presence of species of this order in Spanish marine waters. Two tetraodontid specimens (Family Tetraodontidae) were caught in Atlantic waters of the coast of Galicia, northwestern Spain. A specimen of Sphoeroides pachygaster was collected in 2021 off the Costa da Vela, and a specimen of Ephippion guttifer was captured in 2025 within the Ría de Pontevedra, both locations situated in southern Galicia. Morphological analyses, supported by photographic evidence and DNA barcoding, confirmed the preliminary taxonomic identification of both species. The histological reproductive analysis of the Ephippion guttifer specimen showed a female in spawning capable phase. These findings constitute the first verified record of S. pachygaster and the second of E. guttifer in Galician waters. A comprehensive list of tetraodontiform species found in Spanish waters across five geographical demarcations has been compiled and updated. Historically, a total of 26 species across five families have been reported in Spanish waters, counting 22 in the Canary Islands and 15 in the Spanish Iberian Peninsula and Balearic Islands. Additionally, a review of the presence of the neurotoxic tetrodotoxins (TTXs) or paralytic shellfish toxins (PSTs) in each species is also included, bringing an up-to-date overview of a largely unexplored field in European waters. The increasing occurrence of tetraodontiform fishes in Spanish waters provides further evidence of the progressive tropicalization of the Spanish marine environment.

Abstract: Swimming crab (Portunus trituberculatus) is a commercially valuable species in the Yellow Sea, where recent fluctuations in resource levels have raised concerns about sustainable management. This study aimed to enhance the estimation of the carapace length at 50% maturity (L₅₀) through machine learning techniques, offering a more objective alternative to traditional visual inspection. Using geometric image augmentation (e.g., rotation, flipping, brightness adjustment), Hue-Saturation-Value (HSV) color segmentation, and algorithms such as Extreme Gradient Boosting (XGB), Support Vector Machine (SVM), Random Forest (RF), and ensemble models, we classified the maturity of female crabs based on gonad color features. Model performance was evaluated using Accuracy, AUC, and TSS, with the ensemble model showing the highest predictive capability. The machine learning-based L₅₀ was estimated at 64.63 mm (±1.73 mm), which was more precise than the visually derived L₅₀ of 65.47 mm (±2.89 mm). These results suggest that machine learning techniques can serve as reliable tools for developing science-based management strategies, ultimately supporting sustainable fisheries resource management.

Abstract:

A reliable and reproducible method for the isolation, culture, and identification of an osteoblast cell line from crucian carp (Carassius auratus) was established in this study using vertebral bone tissue from Chongming crucian carp, a locally important aquaculture strain from the lower Yangtze River region. Osteoblast cells were isolated using a tissue explant culture method, and optimal in vitro culture conditions were systematically evaluated. The established osteoblast cell line, designated Chongming Carassius auratus osteoblast cells (COBC), was characterized through chromosomal karyotype analysis, osteocalcin enzyme-linked immunosorbent assay (ELISA), and osteogenesis-related gene expression analysis. Additionally, cellular responses to environmental stress were assessed. The results showed that COBC exhibited optimal proliferation in L-15 medium supplemented with 20% fetal bovine serum at 28 ℃ under 5% CO₂. Alkaline phosphatase staining, Alizarin Red staining, and von Kossa staining all yielded positive results, thereby confirming that the isolated cells possessed typical and stable osteoblastic properties, with the osteocalcin content of 36,884 ng/L. Quantitative PCR analysis revealed that osteogenic marker genes, including runx2a and runx2b, were expressed at significantly higher levels in COBCs than in muscle tissue. Under hypoxia-reoxygenation stress, COBC exhibited enhanced apoptotic responses, marked alterations in related gene expression, and modulation of antioxidant enzyme activities, suggesting a certain degree of adaptive capacity to oxygen fluctuations. This study provides the first systematic description of the establishment and biological characterization of COBC, as well as its responses to hypoxic stress. These findings offer a valuable in vitro cell model and technical support for studies on fish bone tissue biology and the assessment of environmental stress effects.

Abstract: The Hedgehog (Hh) signaling pathway is a key regulator of adipogenesis and lipid metabolism. However, the specific role of its receptor, Patched2 (Ptch2), in these processes remains unknown. Here, using a CRISPR/Cas9-mediated ptch2 homozygous mutation model in Nile tilapia (Oreochromis niloticus), we found that Ptch2 deficiency induced visceral and perirenal lipomatosis characterized by small, multinucleated adipocytes. Comparative adipose transcriptomics revealed pronounced adipogenic reprogramming, with marked upregulation of genes governing de novo lipogenesis (e.g., acaca, fasn), fatty acid desaturation (e.g., scd, fadsd6), and triglyceride synthesis (e.g., dgat2, lpl). Biochemically, mutants exhibited elevated blood glucose and liver transaminases (alanine aminotransferase, aspartate aminotransferase) with reduced alkaline phosphatase, indicating systemic metabolic dysregulation and hepatic stress. Our findings demonstrate that loss of Ptch2 triggers lipoma formation and adipogenic transcriptome reprogramming, highlighting its essential role in maintaining adipose tissue homeostasis.

Abstract: Freshwater ecosystems in arid and semi-arid zones of the East European Plain are characterized by severe habitat degradation, which negatively impacts their biodiversity. This study attempts to comprehensively examine the species richness of molluscs and determine the influence of abiotic factors on their spatial distribution using the example of one of the river basins in southern Eastern Europe – the Yeruslan River basin (a tributary of the Volga River). Fifteen watercourses in the Yeruslan basin were surveyed, with 72 samples collected from the littoral and deepwater zones of the upper, middle, and lower reaches. A total of 28 mollusc species were identified in the samples, predominantly those with broad ranges (Holarctic, Palearctic, and Euro-Siberian). Estimating true species richness using nonparametric methods revealed that the collected samples contained at least 90% of the expected number of species. In the small tributaries of the Yeruslan River, the dominant species were the lymnaeids Lymnaea stagnalis (Linnaeus, 1758) and Radix auricularia (Linnaeus, 1758). The Yeruslan River is dominated by the non-native species Dreissena polymorpha (Pallas, 1771). The low values of Shannon diversity index recorded in the rivers of the Yeruslan basin are typical of desert and semi-desert riverine ecosystems with low stability and productivity, caused by the constant reduction of habitats due to periodic and/or permanent drying. It was established that the most significant abiotic factors determining the distribution of molluscs are the bottom substrate and the concentrations of nitrites and phosphates. Moreover, non-critical concentrations of the latter in the water likely had a beneficial effect on the productivity of streams in an arid climate.

Abstract:

Understanding stock structure is a priority for evaluating population dynamics of commercially fished cephalopods under fishing pressure and environmental changes. This study employed a multidisciplinary approach to clarify the stock structure of Todarodes pacificus, a highly migratory squid species exploited by Asia-Pacific countries. Based on the analysis of statolith increments, summer and autumn cohorts were identified. Low haplotype diversity was revealed by two mitochondrial DNA markers (COI, 16S) and one nuclear DNA (nuDNA) marker (ODH). There was no significant genetic differentiation through phylogenetic trees and haplotype networks. The overall shapes between cohorts were significantly different, along with high classification success, could be used as a classification marker. This result offers new insights into the influence of genetic and environmental factors on statolith shape. The integrated results provide a comprehensive understanding of the stock structure of T. pacificus, laying the foundation for resource development and the conservation of the species.

Abstract: The evaluation of nitrogen pathways in river systems and the identification of suitable aquatic ecosystem response indicators are essential for maintaining river health. Ni-trogen, in its various forms, is a key physico-chemical quality element that underpins the biological communities determining the ecological status of surface waters. Ele-vated nitrogen loads in freshwater ecosystems can trigger adverse processes such as eutrophication and acidification, both of which are linked to biodiversity loss. We hy-pothesize that specific biotic indicators can reflect nitrogen-related stress in aquatic ecosystems, acting simultaneously as biodiversity components and as bioaccumulating indicators. To test this hypothesis, we examined four study sites within the Koiliaris River watershed (Crete, Greece). Our approach aims to enhance understanding of ni-trogen dynamics at the river-basin scale by providing complementary insights into how nitrogen is processed, stored, and transferred within the aquatic ecosystem. To this end, total nitrogen content was quantified in four matrices: water, sediments, aquatic mosses, and macroinvertebrates. This study represents a pilot, exploratory assessment indicating that water may act as the primary pathway of nitrogen availability for aquatic biota in the studied streams.

Abstract: The impact of climate change on marine bivalves, particularly on their reproductive processes, is a current issue of concern. The aim of this study was to investigate how seawater temperatures influenced the gonadal development and overall condition of the grooved carpet shell clam population in the Baldaio Lagoon (NW Spain) over the last 20 years. Adult clams were collected and biometric, histological and biochemical analyses were performed. Gonadal development phases were assessed, several condition indices were calculated, water temperatures were recorded and statistical analyses were carried out. Results indicated variations in reproductive timing, including changes in gonadal maturation, an earlier spawning period and prolonged maturation phases which contrasted with previous reproductive patterns described for this species. These findings coincided with thermal changes in the lagoon, where mean minimum temperatures increased and maximum temperatures decreased, and the annual thermal range was reduced in comparison with historical data (1998-1999). Biochemical composition and condition indices also reflected variations linked to temperature fluctuations, suggesting that warmer water temperatures may alter energy storage and reproduction. This highlights the importance of continuous environmental monitoring to better understand the effects of climate change on marine invertebrate populations and to improve management strategies that could help to restore natural populations.

Abstract:

This study investigated the effects of copepods and copepod conditioning strategies on the growth and survivorship of long-snouted seahorse (Hippocampus guttulatus) juveniles from 1 to 60 days post-parturition (DPP). Four dietary treatments were tested: 24h Isochrysis galbana enriched Artemia (control), freshly collected copepods, 48h unfed copepods, and 24h I. galbana enriched copepods. Juveniles fed any copepod-based diet exhibited significantly higher growth (P < 0.05) and survival than those fed enriched Artemia. Mean standard length increased from 1.3 ± 0.1 cm at release to 5.9 ± 0.2, 7.5 ± 1.4, 7.1 ± 1.2, and 7.3 ± 1.1 cm at 60 DPP for the respective treatments. Wet weight rose from 0.002 ± 1 g to 0.44 ± 0.07, 0.81 ± 0.4, 0.68 ± 0.3, and 0.76 ± 0.4 mg, while final survival reached 20%, 60%, 33.3%, and 56%, respectively. Compared with Artemia, copepods markedly enhanced juvenile performance, supporting faster growth and promoting beneficial behavioral traits which contributed to improved survival. These results demonstrate that copepods as a superior live feed for early juvenile H. guttulatus, but copepod conditioning strategies directly influence their nutritional quality and, consequently, seahorse growth and survivorship. The use of copepods for the first 60 DPP is therefore not only feasible but strongly recommended.

Abstract: To optimize juvenile barramundi (Lates calcarifer) feeding strategies, this study compared cannibalism (CB), formulated feed (FF), and mixed feed (MIX: formulated + biological feed) on growth, physiology, and immune-related gene expression. 36-day-old juveniles (initial body weight) were randomized into 3 groups (1 Lates calcarifer was placed in each tank, with 15 replicates in each group.) for a 20-day trial. Growth performance: MIX group showed significantly higher weight gain rate (862.31 ± 346.66) and specific growth rate (93.2 ± 42.48) than FF and CB groups (P < 0.05); CB group outperformed FF (P< 0.05). Physiology: MIX had the highest alkaline phosphatase (AKP) and pyruvate kinase (PK) activities (P < 0.05), and significantly elevated alanine aminotransferase (ALT) activity, lipid peroxide (LPO) content, but the lowest catalase (CAT) activity (P < 0.05). Gene expression: CB group had the highest lysosomal protease (cts1a) and glycolytic gene (eno3) levels (P < 0.05); FF group showed higher heat-shock protein 90(hsp90) and pro-inflammatory cytokine (IL1β) expression (P < 0.05). FF exhibited the highest SOD activity and IL1β levels (P < 0.05), indicating strong antioxidant. Conclusion: MIX promotes growth but risks liver damage/oxidative stress; CB serves as emergency nutrition but requires management to avoid; FF exhibits significant antioxidant advantages despite poor growth performance. "Mixed feeding + immune enhancers" is recommended for industrial seedling production to balance growth and health.

Abstract: Rotifers, cladocerans, and copepods constitute the bulk of zooplankton biomass in freshwater ecosystems. An increase in salinity levels due to evaporation from fresh-water bodies affects species richness and zooplankton abundance. We exposed zoo-plankton in mesocosms to sub-oligohaline salt concentrations (0, 50, 100, or 200 µg/L of NaCl) for 18 days. We also measured selective physicochemical water parameters. Our results showed that pH, phosphates and chlorophyll a levels of the medium in the test jars decreased with time. However, conductivity values did not show any clear trends with time. The initial zooplankton composition consisted of 13 rotifer, 1 cladoceran and 2 copepod species. After being exposed to 200 mg/L salinity level for three weeks, only 5 rotifer species and 1 cyclopoid species survived, and in terms of densities, naupliar stages dominated. The densities of Brachionus calyciflorus, Keratella cochlearis, and Polyarthra vulgaris decreased with increasing salinity level and expo-sure time, while Brachionus angularis and Brachionus budapestinensis were eliminated. The low levels of salt used in this work had also adverse effects on species richness and abundances of zooplankton, over just a few days. Therefore sub-oligohaline lev-els of salinity may pose a threat to species richness and abundances of zooplankton in natural waterbodies.

Abstract: Water pollution poses a severe threat to global aquatic ecosystems, yet the adaptive mechanisms of aquatic organisms under such stress remain poorly understood. This study investigates the physiological and transcriptomic responses of the freshwater hydrozoan Craspedacusta sowerbii to two prevalent water pollutants: the antibiotic sulfamethoxazole (SMZ, 20 μM) and the heavy metal cadmium sulfate (Cd, 10 μM). Physiological observations revealed that SMZ exposure reduced motility and induced body shrinkage, while Cd exposure caused complete loss of motility, physical disintegration, and mortality within 24 hours. Transcriptomic analysis via RNA-seq identified significant alterations in gene expression patterns. SMZ exposure primarily up-regulated genes associated with oxidative stress, apoptosis, and immune responses, whereas Cd exposure resulted in extensive down-regulation of genes involved in metabolic pathways, cell cycle regulation, and anti-aging processes. Comparative analysis highlighted shared and distinct pathways affected by the two pollutants, including disrupted cell motility, cytokinesis, and molecular transducer activity. Notably, Cd exposure induced more severe transcriptional suppression, correlating with higher mortality. These findings underscore the ecological significance of C. sowerbii as a sensitive indicator of water quality and provide molecular insights into its adaptive strategies under pollution stress. Furthermore, the study offers critical implications for understanding the broader impacts of water pollutants on aquatic biodiversity, emphasizing the need for improved pollution control measures. Future research should focus on long-term multi-pollutant effects, field validation, and cross-species comparative studies to enhance ecological conservation strategies.