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.

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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.

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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.

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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.

Abstract: The kelp genus Eisenia Areschoug is represented by two species in the Southeast Pacific: Eisenia cokeri, distributed in Peru and Chile, and E. gracilis, endemic to Peru. However, the taxonomic distinction between these two species has been questioned. Additionally, it is uncertain whether E. cokeri is conspecific with the Northeast Pacific species E. arborea. To address these issues, we examine, for the first time, the morphology and the molecular phylogenetics of E. cokeri and E. gracilis across their geographic range. Sampling for morphological and molecular analyses was conducted at subtidal zones in five locations in Peru. Furthermore, a locality in Chile was sampled for molecular studies, where E. cokeri was documented. Peruvian Eisenia species exhibited notable differences in morphological characters, including size, holdfast diameter, stipe modifications (e.g., longitudinal division and pseudostipe formation), frond division, frond margins, and roughness, as evidenced by differences in thallus morphometric variables. Phylogenetic analyses using mitochondrial and chloroplast markers revealed three distinct genetic lineages and two endemic species: E. cokeri and E. gracilis from Peru, and a new Eisenia sp. from Chile. Moreover, we confirmed the distinctiveness of E. cokeri from E. arborea and provided updated information on the distribution of E. cokeri and E. gracilis in the Southeast Pacific. These findings are crucial for the management and conservation of these endemic, foundational species.

Abstract: Tardigrades, commonly known as water bears or moss piglets, are microscopic extremophiles famed for their resilience to harsh environments, including extreme temperatures, radiation, and desiccation. Beyond their unique survival traits, recent discoveries of their symbiotic microbial partners open exciting avenues for biotechnological innovation. This review explores the untapped potential of tardigrades and their symbionts as novel sources for next-generation superfoods, cosmetics and pharmaceuticals. Leveraging CRISPR gene-editing technology, we discuss strategies to enhance their nutritional profiles, stress tolerance, and metabolic pathways for sustainable food production. Integrating extremophile biology with cutting-edge genome engineering could revolutionize food systems by introducing robust, nutrient-dense, and environmentally resilient bioresources.

Abstract: Biomarkers are increasingly recognized as essential tools for assessing fish nutrition, stress, health, and environmental interactions in aquaculture, yet little is known about their awareness, use, and perceived value among European stakeholders. This study aimed to characterize current knowledge, applications, barriers, and future needs through a questionnaire-based survey distributed to researchers, industry professionals, and other aquaculture stakeholders across Europe. The survey, conducted via Google Forms, gathered responses from 38 participants representing 17 countries and diverse production systems. Results showed high familiarity with biomarker concepts, particularly those related to stress and health assessment, and identified blood biochemistry, histology, cortisol, oxidative stress markers, and gene expression as the most commonly used indicators, mainly in trout, seabass, and seabream. Although biomarker data occasionally informed decisions—especially regarding health treatments and feed adjustments—their wider adoption was constrained by high analytical costs, limited technical capacity, and lack of standardized protocols. Respondents emphasized the need for training, user-friendly diagnostic tools, funding support, and harmonized methodologies to enhance implementation. Overall, findings reveal strong interest and clear potential for expanded biomarker integration in European aquaculture, while highlighting critical gaps that must be addressed to support evidence-based and sustainable farm management.

Abstract: Seaweeds are photosynthetic organisms with ecological, social, and economic significance, and they serve as effective bioindicators in marine ecosystems. This study assessed trace element concentrations in beach-cast seaweeds collected from four beaches along the Espírito Santo coast in Brazil - an area impacted by mining-related contamination. Samples of Zonaria tournefortii and Sargassum natans, gathered during low tide (July–August 2022), were analyzed for 15 elements. Aluminum (Al), iron (Fe), and magnesium (Mg) were the most abundant (>100 mg/kg), while minor elements included barium (Ba), arsenic (As), zinc (Zn), vanadium (V), nickel (Ni), chromium (Cr), copper (Cu), lead (Pb), cobalt (Co), cadmium (Cd), silver (Ag), and mercury (Hg). Elemental profiles exceeded those reported in other global regions and closely resembled iron ore tailings. These findings - first for beach-cast seaweeds in this region - suggest that the contamination is related to the collapse of the Fundão dam in Mariana, Minas Gerais, which occurred in 2015, resulting in one of the most serious environmental disasters in Brazilian history. The incident released approximately 60 million cubic meters of mining tailings, that traveled approximately 600 km through the Rio Doce Basin, reaching the north of Espírito Santo and arriving at the ocean.

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In order to investigate the effects of choline on the synthesis of endogenous phospholipids in Eriocheir sinensis, this experiment was conducted by adding 0%, 0.2% and 0.4% choline to low phospholipid (0% PL) and normal phospholipid (2% PL) diets, respectively, and feeding the crabs with an initial body weight of 0.4 g for 8 weeks. The results showed that diets supplementation with 0.4% choline significantly upregulated the relative mRNA expression of neuropathy target enzyme 1 (nte1), phospholipase A2 (pla2) and phospholipase B (plb) in the low phospholipids condition. In addition, dietary 0.4% choline significantly increased the relative mRNA expression of hepatopancreatic fatty acid binding protein 3 (fabp3), fatty acid transporter protein 4 (fatp4), carnitine palmitoyltransferase-2 (cpt-2), carnitine acetyltransferase (caat), carnitine palmitoyltransferase-1a (cpt-1a) and carnitine palmitoyltransferase-1b (cpt-1b) in juvenile Chinese mitten crab. Dietary 0.2% choline significantly up-regulating the relative expression of fatty acid synthase (fas), and fatty acid elongase 6 (elovl6) mRNA relative expressions in the 2% PL diets. This study shows that dietary supplementation with 0.4% choline could improve phospholipids synthesis of Chinese mitten crab under low phospholipids condition, and 0.2% Choline could improve the decomposition and remodeling of phospholipids in the normal phospholipids condition.

Abstract: This field study was conducted as part of efforts to introduce Integrated Multi-Trophic Aquaculture (IMTA) into Nigeria’s aquaculture system. It examined extant aquatic food production and marketing in three coastal states of Lagos, Ogun, and Ondo before IMTA across 15 Local Government Areas (LGAs) /Local Council Development Areas (LCDAs). Marketing mix practices in coastal aquatic food systems were explored through a structured, qualitative assessment using a multi-value chain perspective. Monthly sales volumes most frequently fell within the 1–5 tonnes range. The local market was dominant, with some sales into the international markets. Respondents asserted that post-harvest was diverse, and some were satisfied with the technology available to preserve their products. Cold storage practices across coastal states were hindered by unreliable power supply. Zero-channel distribution dominated among traders, with over 90% relying on word-of-mouth (WOM) to promote their products. Consumers show a strong preference for the quality of local products and expressed openness to incorporating seaweeds into their purchases. Health benefits and taste were widely recognized as key motivators for purchasing aquatic food products. Findings provide a baseline for IMTA in Nigeria, highlighting existing strengths, market dynamics, and infrastructure gaps that must be addressed to support sustainable integration.

Abstract: Background/objectives: Elastin is a highly hydrophobic extracellular matrix protein responsible for the extensibility and elastic recoil of various organs. The Windkessel effect in blood vessels dampens pressure variations during the cardiac cycle to provide continuous perfusion of tissues. Duplication of the elastin gene in teleost fish led to the neofunctionalization of the ElnB paralog, which confers the uniquely low stiffness of the bulbus arteriosus to protect the fragile gill capillaries from large pressure variations. Methods: We have examined the diversity of elastins in all major fish clades by searching for eln genes in the sequenced genomes. Results: Tetraploid salmonids have two elna genes but a single elnb, except for the tandem duplicated elnb genes in sockeye salmon and lake whitefish, while the tetraploid common carp possesses four elna and elnb genes on separate chromosomes. Rainbow trout showed strong elastin staining in the larval bulbus and ventral aorta, and elnb was highly expressed in the bulbus of juvenile and adult fish. Teleost ElnB differs from the ElnA paralog by containing considerably longer hydrophobic domains. The single elastin in cartilaginous and lobe-finned fish showed high overall hydrophobicity, and no relationship was found between the hydrophobicity levels of fish elastin and the ventral aortic blood pressure. Conclusion: The differential gene expression of teleost elna and elnb during cardiac development probably evolved together with the divergence in the genetic structure that resulted in larger hydrophobic domains of the ElnB paralog and decreases stiffness of bulbus arteriosus.

Abstract:

While Panulirus ornatus is one of the world’s most valuable aquaculture species, its complex feeding behaviour remains a limitation to industry development. Feed texture is central to feeding behaviour and is heavily influenced by the choice of binder. This study investigates binder-induced feed textures that enhance feeding behaviour and apparent feed intake of P. ornatus. Fifty P. ornatus were subjected to five dietary treatments over a 14-day period. Diet 1 (control) was formulated with wheat gluten as binder, while diets 2 to 5 combined wheat gluten with xanthan gum, guar gum, alginate, and transglutaminase, respectively. Feed texture was quantified using a texture analyzer, while feeding behaviour was assessed by EthoVision XT software. Guar gum exhibited the most durable and firmest pellets. However, wheat gluten optimised feeding behaviour, as indicated by the longest cumulative time spent in the feeding zone (87.46 ± 3.63%) and lowest frequency of entries and exits (21.67 ± 2.91 times). Moreover, wheat gluten yielded the highest apparent feed intake (0.98 ± 0.05 %BW/day). Pellets produced with other additional binders resulted in decreased feeding behaviour metrics and apparent feed intake. In summary, wheat gluten binder alone produced a suitable texture, optimising feeding behaviour and apparent feed intake.

Abstract:

Crayfish often become invasive when introduced to new waters. The mid-20th-century commercial import of North American species (e.g., Faxonius limosus, Pacifastacus leniusculus, Procambarus clarkii) into Europe for food, pets, and restocking after crayfish plague, succeeded due to their adaptability, high reproductive rates, and resilience. Extensive baited-trap monitoring of Piedmont lakes allowed us to confirm the occurrence of the Old Non-Indigenous Crayfish Species (F. limosus, P. leniusculus, and P. clarkii), and to record P. clarkii first-ever in three additional lakes (Pistono, San Michele, and Sirio), thereby expanding our knowledge of their distribution in Piedmont freshwaters. Since all detected species are listed as Invasive Alien Species of Union Concern, protecting the ecological integrity of Piedmont’s freshwaters requires coordinated action by member states, regional authorities, policymakers, and water managers to prevent and control their spread, and to improve information sharing. Non-native crayfish occurrence is influenced not only by hydrological and habitat connectivity, and predator–prey interactions, but also by illegal activities that supply the food market.