Biology and Life Sciences

Abstract:

Recently, a strain of Streptococcus agalactiae serotype Ia sequence type 7 clonal complex 1 (SaIa ST7 CC1) has emerged in Latin American tilapia aquaculture as an international threat. This study evaluated outbreaks of acute streptococcosis occurring between 2021 and 2025 on commercial Nile tilapia (Oreochromis niloticus) farms located in six Latin American countries, with an aim to combine molecular, clinical, pathological and environmental data. In total, 360 moribund or recently dead fish at various production stages (larvae/fry, pre grow-out and grow out) were examined, and 25 S. agalactiae isolates were serotyped, subjected to real time PCR analysis multilocus sequence typing (MLST), virulence and antimicrobial resistance gene profiling and antimicrobial susceptibility testing. All isolates belonged to SaIa and had the same ST7 CC1 MLST profile, which created a highly homogeneous cluster that grouped with reference SaIa ST7 CC1 strains previously isolated from tilapia farms in Asia. These results are consistent with the regional spread of a single clonal line. At larval and fry stage, SaIa ST7 CC1 was associated with hyperacute septicemia, gastrointestinal hemorrhage and frequent intestinal intussusception; while in pre grow out and grow out fish neurological signs were more prominent followed by ocular signs, systemic hemorrhages and coelomic lesions. Histopathological examination showed profuse colonization of brain, spleen, liver, and intestine by Gram positive cocci accompanied by significant acute circulatory and inflammatory lesions and few chronic granulomatous responses consistent with a fast-progressing high aggressive infectious process. All outbreaks occurred during extended episodes of hot water (>32°C) with large day–night thermal gradients and reduced dissolved oxygen, suggesting that thermal stress may exacerbate disease expression in systems affected. All SaIa ST7 CC1 strains exhibited phenotypic susceptibility to florfenicol and amoxicillin, but 84% (21/25) and 100% (25/25) of them exhibited intermediate susceptibility to oxytetracycline and enrofloxacin, respectively. Five of the 21 isolates (23,8%) with intermediate susceptibility to oxytetracycline carried tetracycline resistance genes (tetM, tetO). These findings identify SaIa ST7 CC1 as a clinically relevant threat of emerging thermally facilitated and geographically expanded streptococcosis for tilapia production in Latin America. Immediate priorities include screening of imported broodstock using MLST or whole genome sequencing, harmonized regional molecular surveillance, climate adaptive farm management practices, prudent antimicrobial use and serotype matched vaccination and breeding strategies that improve both disease- as well as heat-resilience.

Abstract: Systematic surveillance of World Organization for Animal Health (WOAH)-listed protozoan parasites is essential for maintaining sanitary status for seafood export and detecting the introduction of exotic pathogens into coastal ecosystems. In 2023, we examined wild Mediterranean mussels Mytilus galloprovincialis and Pacific oysters Crassostrea gigas collected from small harbors adjacent to ten major trading ports along the west and south coasts of Korea to assess the occurrence of WOAH-listed protozoan parasites and emerging Perkinsus species. A total of 1,080 mussels and 1,080 oysters from 18 sites were sampled in spring and autumn, and gill and digestive gland tissues were pooled from six individuals for DNA extraction. Species-specific PCR assays targeting Perkinsus marinus, P. olseni, P. beihaiensis, Bonamia ostreae, B. exitiosa, and Marteilia refringens were performed using previously validated primer sets and positive controls. All PCR assays were negative for the six protozoan parasite species in both host species across all sampling sites, indicating no detectable infections in port-adjacent wild mussel and oyster populations during the survey period. These negative results contrast with recent reports of P. marinus in wild C. gigas and B. ostreae in Ostrea denselamellosa on the west coast of Korea, suggesting that infections may currently be focal, transient, and host-specific rather than widespread in port-associated M. galloprovincialis and C. gigas populations. The present study provides baseline data on the distribution of protozoan parasites in bivalves inhabiting high-risk harbor environments and underscores the need for continued surveillance of transboundary shellfish disease that is closely coupled with environmental monitoring.

Abstract: Aquatic macroinvertebrates inhabit virtually all freshwater ecosystems, yet communities in extreme saline environments remain largely undescribed, particularly in the Tropical Andes. This study characterizes the taxonomic diversity of aquatic macroinvertebrates in a travertine-fed saline stream (salinity: 12.5 ± 0.2 g/L; 2520 m a.s.l., southern Ecuador) and compares it with an adjacent freshwater stream. Macroinvertebrates were sampled on four occasions (n = 4 events per stream) using a multi-habitat D-net technique; physicochemical variables were compared with Mann–Whitney U exact tests, and diversity metrics with exact permutation tests (C(8,4) = 70 permutations) supplemented with Cliff’s delta as effect-size estimator. Community composition was assessed with ANOSIM and non-metric multidimensional scaling (NMDS). A total of 919 individuals were collected. The freshwater stream harbored significantly greater richness (49 genera, 28 families), abundance, and Shannon diversity than the saline stream (14 genera, 8 families; all p = 0.029, Cliff’s δ = 1.00), while Pielou’s evenness did not differ between stream types. Community composition was fully separated (ANOSIM R = 1.00, p = 0.028), with salinity (R² = 0.95, p < 0.01) and water temperature (R² = 0.79, p = 0.03) as the primary environmental drivers. The saline stream was dominated by halotolerant Diptera (Ceratopogonidae, Stratiomyidae) and water mites (Hydrachnidae), with virtually no EPT (Ephemeroptera–Plecoptera–Trichoptera) representation. These findings establish the first macroinvertebrate diversity baseline for a travertine-associated saline stream in the Tropical Andes, highlighting salinity and temperature as key environmental filters of aquatic biodiversity in extreme Andean lotic ecosystems.

Abstract: To explore the genetic diversity and adaptive evolutionary mechanism of Mastacembelus armatus in the Dongjiang and Ganjiang River Sources, whole-genome resequencing was performed on three populations of M. armatus from Xunwushui (XW) and Jiuqu River (DN) in the Dongjiang River Source, and Taojiang (XF) in the Ganjiang River Source. Population genetics methods were integrated to analyze their genetic structure, differentiation characteristics and selection signals. The results showed that a total of 209.05 Gbp of Clean Data was obtained from the three populations, with the Q30 base percentage reaching 94.42% and the average mapping rate to the reference genome being 97.85%, indicating high reliability of the sequencing data. A mean of 7,459,686 single nucleotide polymorphisms (SNPs) were detected, with a transition/transversion ratio of 1.52 and a heterozygous SNP ratio of 2.22%. The total number of genome-wide insertions and deletions (InDels) was 1,902,722±23,247. Gene Ontology (GO) functional annotation revealed a consistent variation pattern of core genes among the three populations. Phylogenetic tree, Admixture and principal component analysis (PCA) confirmed that the three populations belonged to a single evolutionary clade and shared a genetic origin from two ancestral populations (the lowest cross-validation error at K=2), while significant genetic differentiation was observed among populations: XW and DN populations had similar genetic backgrounds and closer genetic relationships, both biased towards the blue ancestral component, whereas XF population was inclined to the red ancestral component, with the DN population showing the highest degree of genetic admixture. Individuals within the XF population had more distant genetic relationships and the longest linkage disequilibrium (LD) decay distance, which was speculated to be associated with its small population size and low recombination rate; in contrast, the XW population had the shortest LD decay distance, corresponding to the characteristics of large population size and high recombination rate. Analysis of population genetic diversity indicated that XW and DN populations were classified as the high-diversity group (with more than 440,000 polymorphic markers, expected heterozygosity >0.31 and polymorphism information content (PIC) ≈0.25), while the XF population was the low-diversity group (with 342,646 polymorphic markers, expected heterozygosity of 0.2608 and PIC of 0.2073). Only the minor allele frequency (MAF) of the XF population (0.2829) was slightly higher than that of the other two populations. This study systematically elucidated the characteristics of genetic differentiation and diversity differences of M. armatus in the Dongjiang and Ganjiang River Sources, providing a genome-level scientific basis for the conservation of genetic resources, development of molecular markers and analysis of environmental adaptive mechanisms of this species.

Abstract: Benthic macroinvertebrates are widely used as bioindicators for assessing freshwater ecosystem health. This study investigated the diversity patterns and community structure of benthic macroinvertebrates across 21 sampling sites along the middle and lower reaches of the Yangtze River. A total of 74 species belonging to 3 phyla, 7 classes, 17 orders, 37 families, and 58 genera were identified, with aquatic insects dominating the assemblages. Alpha diversity indices showed no significant differences among river sections, whereas multivariate analyses (NMDS and PERMANOVA) revealed significant spatial variation in community composition, indicating that beta diversity plays a key role in structuring assemblages at the basin scale. Canonical correspondence analysis (CCA) identified nutrient variables (TN and NH₄⁺-N), as well as pH and conductivity, as the main environmental drivers influencing community distribution. The results suggest that benthic macroinvertebrate diversity patterns in large river systems are jointly shaped by regional environmental gradients and local habitat conditions. These findings provide insights into biodiversity conservation and ecological management of large river ecosystems.

Abstract: The aim of the study is to determine physico-chemical parameters and eutrophication criteria in the Aegean Sea. The pH, temperature, salinity, dissolved oxygen, turbidity, conductivity, phosphate, ammonium nitrogen, nitrite nitrogen, nitrate nitrogen and chlorophyll-a parameters were determined. The sampling was conducted at 25 stations (Enez, Saros Bay, Gökçeada, Yeniköy, Bozcaada, Babakale, Altınoluk, Ayvalık, Dikili, Çandarlı, Foça, Bostanlı, Urla, Ildır, Çeşme, Sığacık, Kuşadası, Didim, Güllük, Bodrum, Akyaka, Gökova, Datça, Bozburun 1, Bozburun 2) during the spring-summer-autumn seasons of 2022 and 2023. In the Aegean Sea, the mean values were determined as follows: pH 8.05, temperature 21.80 °C, dissolved oxygen 7.86 mg/L, salinity 34.13‰, turbidity 25.15 mg/L, electrical conductivity 50.27 µS/cm, phosphate 9.39 µg/L, ammonium nitrogen 29.59 µg/L, nitrite nitrogen 0.5 µg/L, nitrate nitrogen 1.9 µg/L, and chlorophyll-a 1.76 µg/L.

Abstract: Abstract Low-salinity stress poses a critical constraint on the commercial aquaculture and survival of the sea cucumber (Apostichopus japonicus). This study investigated the regulatory network involving lncRNA011760, miR-novel-91, and their target gene NIPA2 in response to salinity fluctuations. Using integrated in vivo and in vitro functional assays, we demonstrate that lncRNA011760 acts as a competitive endogenous RNA (ceRNA) to sponge miR-novel-91, thereby alleviating the post-transcriptional repression of NIPA2. Based on these molecular dynamics, we propose a novel inhibition-adaptation-survival three-stage model. Initially (0–3h), acute NIPA2 upregulation enhances Mg²⁺ transport efficiency to mitigate osmotic shock. During the mid-stage (3–24 h), miR-novel-91-mediated NIPA2 suppression creates a transient biosynthetic window, facilitating a shift from passive tolerance to active metabolic adaptation. Ultimately (24–48 h), lncRNA-driven NIPA2 restoration sustains Mg²⁺ homeostasis, allowing the organism to enter a low-metabolism survival mode. These stage-specific shifts reflect the inherent physiological strategies of sea cucumbers as osmoconformers. Our findings elucidate the complex epigenetic orchestration of osmotic stress tolerance and highlight the lncRNA011760/miR-novel-91/NIPA2 axis as a promising molecular target for the marker-assisted breeding of salt-tolerant strains.

Abstract: Fluorescence is known to occur in varying surfaces across crustacea but only cited in sporadic reports despite being a potentially important visual signal and changing with development and within moult cycles. Here, we present the occurrence of fluorescence in some common Northeast Atlantic crustaceans and highlight differences by age and sex to bring attention to this potentially important facet of their biology.

Abstract: The present study describes the reproductive cycle of the razor clam (Solen marginatus) from the Ria Formosa lagoon in the Algarve region (southern Portugal), using histological preparations of gonads from samples collected monthly over 18-month period, more precisely from January 2023 to June 2024. Simultaneously, the mean gonadal index (GI) was estimated and its relationship with fluctuations in seawater temperature and chlorophyll concentration was examined. The reproductive cycle of S. marginatus showed a seasonal pattern, with a resting period between August and October, followed by the onset of gametogenesis in November, which lasted until March. Ripe individuals were observed between February – March and May, with the spawning period occurring primarily between May and July. The mean GI reflected the temporal variation of the gonadal cycle, and it was observed that reproduction in this species is strongly influenced by fluctuations in seawater temperature, but is not significantly correlated with chlorophyll concentration. The information gathered in this study is of utmost importance, as it enables the proposal of evidence-based management measures, aimed at promoting the sustainable exploitation of this resource. According to these new findings, a closed season prohibiting the razor clam harvesting in Ria Formosa lagoon between May and July is proposed.

Abstract: While productivity increases in the production of aquaculture have contributed to reductions in greenhouse gas emissions per unit of production, additional reductions in green-house gas emissions can be attained by modifying the ingredients in the selected studied species, i.e., Nile tilapia, salmon and shrimp diets. In this paper, a baseline diet, for a given studied species, was aggregated from at least four commercial diets to have a better representation of the real world. Then using the same list of feed ingredients, an alternative scenario was defined not only balancing the ration from energy, protein and fat nutrient requirements, and constraining the cap at 150% for individual feed ingredient from the baseline diet but also minimizing the greenhouse gas emission. For all three studied species, 8.4% less plant-based protein meals, 23.9% less grains, and 36.8% more animal protein meals were used in the scenario diet. In consequence, total greenhouse gas emissions was reduced by 15.3% from the baseline diet and total acres of land use was decreased by 20%.

Abstract: Monosex all-male culture of the giant freshwater prawn (Macrobrachium rosenbergii) maximizes aquaculture yield due to a male growth advantage, but direct hormonal treatment of grow-out populations poses significant food safety risks. This study evaluated the efficacy of dietary 17β-estradiol (E2) in inducing functional neo-females from a fully all-male postlarval population to support an indirect monosex seed production strategy. All-male postlarvae were fed diets supplemented with E2 at concentrations of 0, 50, 100, 150, and 200 mg/kg for 36 days, followed by a 150-day hormone-free post-treatment period to assess growth performance, feminization rates, and gonadal histology. E2 administration successfully induced feminization across all treatments, reaching a peak rate of 35.5% at 150 mg/kg, whereas the control group remained entirely male. During the 36-day treatment period, E2 supplementation transiently enhanced specific growth and survival rates but concurrently reduced feed conversion ratios. Notably, these physiological differences disappeared completely over the 150-day post-treatment phase. Histological assessments confirmed that E2-induced neo-females exhibited normal oogenesis, with gonadosomatic index (GSI) values and oocyte diameters similar to those of wild-caught females. This establishes a definitive, physiologically safe, and non-surgical protocol for producing the neo-female broodstock necessary to sustain high-yield commercial monosex populations.

Abstract: The olfactory system plays a crucial role in mediating fish behavior, including reproduction. Senegalese sole (Solea senegalensis) is an important aquaculture flatfish species in Europe in which reproductive dysfunction in captive males has been linked to potential alterations in chemical communication. Despite the expanded repertoire of olfactory receptor genes described for this species, detailed information on the cellular organization of its olfactory organs remains limited. This study provides a comprehensive histological, immunohistochemical, lectin-histochemical, and ultrastructural characterization of the olfactory rosettes of S. senegalensis across multiple life stages, including premetamorphic larvae, fry, juveniles and adults. Although the olfactory organs undergo substantial structural changes following metamorphosis, differentiated and functionally active olfactory sensory neurons (OSNs) are already present in premetamorphic larvae. Subsequently, two epithelial regions were distinguished along the olfactory lamellae: a sensory epithelium containing abundant OSNs and supporting cells, and a nonsensory epithelium dominated by goblet and other secretory cells. Ciliated and microvillous OSNs were distinguished from 60 dph onward based on morphological and ultrastructural features and confirmed through immunoreactivity with CR, CB, Gγ8 and PGP. Crypt cells showed immunolabelling with S100, NSE and CYK8. Furthermore, lectin histochemistry revealed ontogenetic changes in epithelial glycoconjugates, with early diffuse binding patterns evolving into stratified and region-specific distributions. Overall, these results demonstrate the structural and functional complexity of the olfactory epithelium in S. senegalensis, significantly enriching the limited available morphological and neurochemical information on the species.

Abstract: Results indicated that pre-treatment with carvacrol significantly increased the survival rate of infected Sebastes schlegelii. Conversely, post-infection administration alleviated intestinal pathological damage. Carvacrol regulated host immunity by modulating the transcription of immune-related genes NF-κB/RelA and IL-15. It had no significant effects on SOD, MDA and CAT, suggesting that the oxidative defense pathway was not involved. Analysis of intestinal Vibrio pathogen load confirmed that carvacrol could inhibit the growth and colonization of intestinal Vibrio, thereby maintaining microbial homeostasis. Immunohistochemistry and peripheral blood flow cytometry showed that carvacrol enhanced the adaptive immunity of fish by increasing the proportions of CD4‑1⁺ T cells and CD79a/CD79b⁺ B cells in tissues. In conclusion, carvacrol enhances the resistance of S. schlegelii against V. harveyi by inhibiting pathogenic bacteria, improving intestinal morphological structure, reducing pathogenic bacterial load to maintain microbial homeostasis, and enhancing the adaptive immunity of the organism. This study provides a theoretical basis and data support for the substitution of antibiotics and the development of green feed additives in aquaculture.

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 Lactiplantibacillus 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.