Search Results (519)

Introduction: As apex and mesopredators, elasmobranchs help maintain marine ecosystem balance by shaping food-web structure and habitat connectivity, yet more than one-third of species are threatened with extinction. Identifying where and when they aggregate within atoll systems is therefore a prerequisite for spatially explicit conservation planning. Lhaviyani Atoll, in the central Maldives, lies within a recognised Indian Ocean elasmobranch hotspot and hosts two Important Shark and Ray Areas (ISRAs), yet fine-scale information on aggregation sites, habitat partitioning and seasonal use remains limited. Objective: To map persistent activity hotspots, characterise habitat partitioning between sharks and batoids, quantify seasonal and inter-annual dynamics, and provide an ecological basis for habitat-focused conservation in Lhaviyani Atoll. Methodology: Using a seven-year (2017–2024) opportunistic dive-log dataset of 12,732 SCUBA surveys and 142,994 elasmobranch records across 94 dive sites, spatial kernel-density estimation was applied separately to sharks and batoids to identify activity hotspots and visualise spatial overlap. Habitat associations were examined across substrate types and reef geomorphic zones. Seasonal and inter-annual dynamics in relative abundance and diversity (Shannon, Pielou’s evenness) were quantified across monsoon phases and the 2017–2024 period. Results: Twenty-eight species (14 sharks, 14 batoids) were recorded, including 23 listed as threatened on the IUCN Red List (4 Critically Endangered, 12 Endangered, 7 Vulnerable). Four persistent activity hotspots were identified along the northern atoll rim, two overlapping with the Fushifaru Kandu and Kuredhu–Huravalhi–Komandoo ISRAs. Sharks were concentrated along more complex exposed and semi-sheltered slopes and high-flow channels, with significantly higher occurrence on reef and sheltered reef slopes and lower occurrence on rubble and sand substrates; batoids were distributed broadly within lagoonal habitats with no strong substrate or geomorphic preferences. Relative abundance and diversity peaked during the late southwest monsoon (August–September) and declined into the northeast monsoon (December–March); after 2021, diversity and evenness increased while overall abundance declined. Conclusions: Persistent hotspots, contrasting habitat use by sharks and batoids, and consistent monsoonal seasonality support the ecological relevance of existing ISRAs in Lhaviyani Atoll, while providing finer-scale information on habitat partitioning and additional priority areas for threatened elasmobranchs, including four Critically Endangered species. Full article

The aims of this study were to determine the geographical range and habitats of the Verbascum species in the Arabian Peninsula and to assess their conservation status at national, regional, and global levels by using the International Union for Conservation of Nature (IUCN) Red List categories and criteria. Verbascum is represented by 16 species with four varieties in the area of the study, and most of these species are endemic to Saudi Arabia, Yemen, Oman, and the United Arab Emirates (UAE). This study is based on an ecogeographic survey, which was conducted using herbaria collections, literature sources, and fieldwork. The findings showed that the genus is distributed in three main regions in the Arabian Peninsula, which include northern Saudi Arabia, the Asir and Yemen highlands, and the Hajar mountains in Oman and the UAE. In addition, most species of Verbascum in the region are at high risk of extinction. Nine taxa are threatened, four of which are assessed as Critically Endangered, four as Endangered, and one as Vulnerable. Furthermore, four species are assessed as Near Threatened, while another five species are assessed as of Least Concern. Threats to the Verbascum species in the region are overgrazing, suburban and agricultural expansion, climate change, invasive species, recreational activities, tourism, war, and civil unrest, leading to human intrusion and disturbances. Some important strategies for conserving and managing Verbascum species on the Arabian Peninsula are recommended here. Full article

Introduction: Brown trout (Salmo trutta L.) is a salmonid fish considered a genetically and geographically highly structured species. The species is catalogued as vulnerable in the Spanish Red List since 1992. Based on morphological differentiation, some authors have proposed splitting Salmo trutta into many taxa and in recent years, several binomials involving morphologically differentiated Western Mediterranean brown trout morphs have regained relevance as distinct species and are now assessed in the IUCN Red List. However, Spanish legislation still considers a single species, S. trutta, inhabiting Atlantic and Mediterranean rivers. Analyses of mitochondrial DNA variation across the species’ native range have revealed numerous matrilineal lineages and helped disentangle the phylogenetic relationships and biogeographic history of brown trout. Four largely distant evolutionary lineages defined by sequencing the mitochondrial control region (Adriatic, AD, Mediterranean, ME, Atlantic, AT and Duero, DU) are native among the Iberian brown trout populations. Stocking activities have resulted in introgressive hybridization of these native populations with non-native northern Atlantic stocks throughout the Iberian rivers and compromise the evolutionary singularities of brown trout in the Iberian Peninsula. Methodology: In this study, we compare complete mitogenomes from Iberian brown trout specimens with those from other regions, using both newly sequenced samples and whole mitogenomes from the GenBank database and estimate their divergence times relative to those observed among species of other Salmoninae genera, such as Oncorhynchus and Salvelinus, to assess patterns of species-specific divergence among Iberian brown trout populations. Results: The evolutionary relationships of the specimens using their mitogenomes fitted with previous analyses using partial mitochondrial sequences and confirmed the strong differentiation among the Iberian lineages. All the branches involving distant Iberian mitogenomes are sister branches with taxa historically described under different binomials (such as Salmo macrostigma, S. multipunctatus, S. pallaryi). Conclusions: The results provide evidence supporting the existence of potentially distinct and undescribed native Salmo species in the Iberian rivers. Full article

Introduction: Elasmobranchs play a vital role in marine food webs through top-down control and the structuring of ecosystem stability, yet more than one-third of species face extinction. The Maldives, a recognised Indian Ocean hotspot for shark and batoid diversity, designated its EEZ as a shark sanctuary in 2010, but multispecies elasmobranch occurrence patterns and environmental drivers remain poorly characterised in Lhaviyani Atoll in the central Maldives, which hosts two Important Shark and Ray Areas (ISRAs). Recreational SCUBA networks can turn routine dive activity into long-term conservation evidence, already informing nearly 10% of the western Indian Ocean ISRAs. Objective: To characterise spatiotemporal patterns of elasmobranch assemblages in Lhaviyani Atoll (2017–2024), quantify how environmental and geomorphic drivers shape relative abundance, diversity, and hotspots, and provide evidence for targeted elasmobranch conservation. Methodology: A seven-year opportunistic dive-log dataset of 12,732 SCUBA surveys and 142,994 elasmobranch records across 94 dive sites was analysed. Effort-standardised relative abundance and community metrics (Shannon diversity, Pielou’s evenness) were modelled against sea surface temperature (SST), salinity, dissolved oxygen, chlorophyll-a, zonal current velocity, substrate type, and reef geomorphology using generalised additive models (GAMs). Spatial analyses identified persistent northern-rim aggregation areas aligned with ISRAs. Results: Twenty-eight species (14 sharks, 14 batoids) were recorded, including 23 threatened on the IUCN Red List (4 Critically Endangered, 12 Endangered, 7 Vulnerable). Relative abundance and diversity peaked during the late southwest monsoon (August–September) and declined during the northeast monsoon (December–March). After 2021, diversity and evenness increased while overall abundance declined. Relative abundance was primarily driven by SST, salinity, and current velocity; for sharks, dissolved oxygen and chlorophyll-a were additionally significant, whereas batoid abundance was driven mainly by temperature, oxygen, and current velocity. Four persistent hotspots along the northern atoll rim were identified, with sharks concentrated along exposed slopes and channels, and batoids distributed broadly within lagoonal habitats. Conclusions: Long-term citizen science dive-log monitoring is cost-effective for elasmobranch conservation in remote tropical seascapes. These results show how dive-industry partnerships can inform conservation governance over a decade after sanctuary designation, supporting targeted, habitat-focused management as shark and batoid conservation frameworks continue to evolve. Full article

Introduction: Freshwater habitats underpin global biodiversity and provide an array of essential ecosystem services to humans. However, threat hotspots like the Iberian Peninsula combine severe anthropogenic impacts (habitat degradation, climate change, and biological invasions, among others) with a high number of endemic range-restricted freshwater species. Despite the urgency, current conservation actions fall short of providing adequate protection. The irreplaceability index has been proposed as a useful assessment tool to focus limited efforts on areas that provide the highest benefit for threatened species. However, the transboundary nature of many rivers in the Iberian Peninsula can be a source of inefficiencies in protection if prioritisation efforts are conducted at a national rather than a peninsular scale. Objective: The aim of this study is to identify priority conservation basins for threatened native freshwater fish in the Iberian Peninsula and to evaluate the impact of national versus transboundary management strategies on the spatial protection afforded to these species. Methodology: The irreplaceability index was calculated for each basin by integrating basin richness, species rarity and their IUCN Red List conservation status. First, we modelled the species’ probability of presence using field observations recorded since 2000. Rarity was then calculated as the ratio between the modelled probability and the total number of basins within the species’ theoretical natural distribution. We then weighted each species’ rarity by its IUCN Red List conservation status, with higher weights to threatened species. We then calculated the basin irreplaceability index as the sum across all the species present in the basin of their conservation status-weighted rarity and ranked them according to this index. We replicated this approach considering Spain and Portugal independently, and both countries as one conservation planning unit. Results and Conclusions: The most irreplaceable basins were those harbouring a high density of threatened, narrow-range endemics. The priorities in each country differ depending on whether management strategies adopt a national or a broader geographical approach. Therefore, effective conservation requires transboundary planification to safeguard the shared biodiversity across countries. Full article

Introduction: Skates (Rajidae) are cornerstone elasmobranchs, yet their intrinsic biological constraints, like slow growth, late maturation, and low fecundity, render them exceptionally susceptible to anthropogenic pressure. Despite their ecological and economic importance, tracking their population trajectories is historically hindered by “taxonomic blurring” and aggregated reporting in commercial fisheries. Objective: This study evaluates long-term conservation trends and exploitation dynamics of Rajidae species in the Northeast Atlantic and the Mediterranean Sea. Methodology: We analyzed 31 Rajidae species across the Northeast Atlantic and the Mediterranean Sea (FAO Areas 27 and 37) by integrating IUCN Red List assessments, species-specific life-history traits (maximum body size and depth distribution), and FAO fisheries landing data from 1992 to 2023. Descriptive analyses and Spearman correlations were used to assess temporal trends in conservation status and exploitation patterns. Results: Our synthesis reveals that some species show improvements in IUCN Red List category assessments, likely driven by recent management interventions such as species-specific reporting, catch quotas, and targeted retention bans. However, we also identify a critical mismatch between policy and biology: current Total Allowable Catches (TACs) and minimum landing sizes often do not explicitly incorporate species-specific life-history traits, inadvertently favoring smaller, less-marketable taxa while leaving larger, vulnerable species at risk. While FAO landings offer a valuable broad-scale overview of exploitation, the results highlight the limitations of aggregated fisheries statistics for species-level conservation assessments. Conclusions: These findings underline the need to adopt more precise and species-specific fisheries management approaches for Rajidae, including expanded regional monitoring programs, the use of data collected by on-board observers or electronic monitoring tools, and improved control of data reporting procedures, to prevent continued aggregation of species-level data. Full article

Introduction: The Catalan chub (Squalius laietanus) is a freshwater cyprinid endemic to Catalonia, from the lower course of the Ebro River to the Tech, Tet, Agly, and Massane rivers in France. Classified as Vulnerable in the IUCN Red List (2024), its populations face significant threats due to anthropogenic pressures and the potential hybridization with the European chub (Squalius cephalus). Objective: This study aimed to characterize the genetic variation of the mitochondrial control region (CR) of S. laietanus across the main Catalan river basins to determine the population genetic structure of this species in the core of its distribution range. Methodology: A 789 bp fragment of the CR was sequenced in 334 chubs from 24 sampling sites collected by electrofishing between 2021 and 2025. The S. laietanus specific matrilineage of all these specimens had been previously detected by sequencing the Cytochrome c oxidase subunit I (COI) but this marker did not detect clear genetic structuring among basins. Results: In contrast to the low diversity within and among locations reported by COI, the CR showed a population structure distinguishing between northern (Muga, Fluvià, Daró, Ter, and Tordera rivers) and southern basins (Besòs, Llobregat, Gaià, Francolí, and Ebro rivers). In the southern rivers, a single haplotype, (H1), was present. This haplotype declined in abundance towards the north, being replaced with H2. In the Muga River, native Catalan chub populations showed the fixed H3 haplotype, suggesting strong isolation, while populations from the Daró River contained a private haplotype (H4). In contrast, the presence of a common and single haplotype in southern basins possibly resulted from genetic drift under strong summer droughts. Conclusions: Overall, these results reveal population structuring in S. laietanus and highlight the importance of considering regional differentiation in conservation and management strategies. Full article

The Iberian Peninsula hosts one of the world’s most endemic fish faunas. Its extensive evolutionary, palaeogeographic, and geological history has produced a distinctive freshwater fish fauna. Many of these species have very limited distributions, making them especially vulnerable to habitat disturbance. Past monitoring of this biodiversity has revealed alarming results, indicating that most native Spanish species are at risk. The causes of this serious situation are varied and reflect the ongoing deterioration of freshwater ecosystems. The main pressures faced by populations include pollution, loss of river connectivity caused by hydraulic infrastructure, regulation of watercourses, water extraction, fishing, and the presence of invasive species. Additionally, the effects of climate change worsen the risk of extinction for these populations, particularly through the increased frequency and intensity of droughts and heatwaves. It is evident that current planning models and investments are inadequate to conserve freshwater fish. To prevent the extinction of many populations in Spain, especially Iberian endemics, it is crucial to change the management of aquatic ecosystems and adopt integrated solutions that halt population declines and promote the sustainable use of aquatic resources. The IUCN Red Lists of Threatened Species are vital indicators of biodiversity health and are widely used to guide and structure conservation efforts. These lists, published in the Red Books, result from a thorough evaluation process that employs specific categories and criteria to assess the extinction risk of species, both globally and regionally. This report presents preliminary findings from a monitoring study on the current state of freshwater fish in Spain. The monitoring results reveal that, based on IUCN assessment criteria, two species are classified as extinct (EX), four as critically endangered (CR), eighteen as endangered (EN), and twenty-one as vulnerable (VU). Of fifty-seven species documented, 79% are considered threatened. The project’s final outcome is the development of the Atlas and Red Book of Freshwater Fish of Spain. This resource includes the main native and invasive freshwater and diadromous fish species, offers detailed information on their biological and ecological traits, and provides an up-to-date inventory of records along with an assessment of their conservation status. Full article

Introduction: Fish species represent 25% of all vertebrates across the globe and are one of the most threatened animal groups. At least 40% of the fish fauna occurs in rivers for part of their life cycle. European rivers are home to more than 600 fish species, while also being some of the most impaired and altered ecosystems. Objective: The objective was to assess the vulnerability of freshwater fish communities in European river basins. Methodology: Using RivTool and the CCM2 database, we developed the River Restoration Units (R2Us), a set of spatial units that takes into account river network functioning and allows a higher spatial discretisation than river basins. We developed RivFish, a database about the presence of native freshwater-dependent fish in 1556 Europeans river basins. For this, we collected data from 77 references and validated synonyms and scientific names for 667 species. We used the latest International Union for Conservation of Nature (IUCN) Red List assessment to define species distributions in European rivers. After intersecting with the R2U layer, we curated and validated species names and spatial occurrence using RivFish. To map the vulnerability of freshwater fish communities, we used the Habitats Directive (HD) and the IUCN datasets. These consider a distinct number of species and assess conservation status differently: the HD evaluated 165 species, while the IUCN evaluated 516 species. The HD data allowed calculating the composite indicator of Conservation Status, whereas the IUCN data enabled calculating the vulnerability index. Results: Both ana-lyses show higher richness in central Europe, particularly in the Danube basin. Spatially, both highlight southern Europe as the area where fish communities have the highest vulnerability. However, the HD analysis also indicates the Danube and the western Atlantic basins as having high vulnerability. The IUCN analysis shows the Anatolian and Mediterranean biogeographical regions as those with the highest vulnerability values. Conclusions: Southern Europe’s higher vulnerability is likely associated with restricted distribution ranges and high levels of endemicity in Mediterranean fish communities. Overall, these findings improve current knowledge and show that input data may be key to effort allocation towards the management and conservation of European freshwater fish communities. Full article

Microplastic (MP) contamination has become a defining feature of twenty-first century environmental change, yet the toxicological and ecological consequences for amphibians and reptiles—two vertebrate classes already facing severe extinction pressures—remain fragmented across taxa, regions, and methodological traditions. Here, we synthesize field and experimental evidence from five continents to provide a taxonomically balanced, mechanistically grounded, and geographically explicit assessment of MP exposure, bioaccumulation, and toxicity in herpetofauna, drawing on a structured literature search in Web of Science, Scopus, and PubMed (January 2015—March 2026). Field detection rates of MPs in amphibian larvae range from 26% in conservatively screened Central European populations to 73–80% in anuran tadpoles from high-anthropogenic-pressure Anatolian catchments, with fibrous polyethylene terephthalate (PET), polyethylene (PE), and polypropylene (PP) particles dominating the detected burden. Mechanistic evidence converges on oxidative stress cascades, hypothalamic–pituitary–thyroid axis disruption, gut and cutaneous microbiome dysbiosis, and compromised antiviral and antifungal immunity, with the latter potentially amplifying vulnerability to Batrachochytrium dendrobatidis and to ranavirus. Among reptiles, sea turtles display near-universal MP ingestion with documented maternal transfer to eggs; freshwater turtles, terrestrial squamates, and crocodilians remain critically understudied. Three structural asymmetries constrain current ecotoxicological risk characterization: taxonomic bias toward anurans and sea turtles, geographic bias toward the Global North, and experimental bias toward acute, supra-environmental laboratory exposures using pristine, single-polymer particles that fail to capture the chemical complexity of weathered field mixtures. We argue that MP burden may warrant consideration as a candidate stressor criterion within IUCN Red List assessments and within environmental risk assessment frameworks for freshwater and terrestrial biodiversity once a robust quantitative relationship between MP burden and demographic decline or population-level fitness has been established, and propose six hypothesis-driven research priorities: methodological standardization, reptile toxicokinetics, transgenerational epigenetics, MP–pathogen microbiome interactions and their translation into population viability models, temperature × MP interaction under climate warming, and population-genetic consequences of contemporary MP-driven selection, as the most tractable avenues for ecotoxicological progress and for the development of herpetofauna-specific risk characterization frameworks. Full article

We document and illustrate Primula xideensis, a new species collected from Xide County, Sichuan Province, China. Morphologically, it resembles P. stenocalyx, P. farinosa s.l., and P. pulchella, but differs by its roots densely covered with multicellular hairs; elliptic to obovate leaves with non-revolute, irregularly and deeply dentate margins, both surfaces efarinose, shortly hairy, and scabrous; tubular calyx parted to the middle; corolla mouth densely white-farinose; stamens positioned at mid-corolla tube in pin flowers and near the throat in thrum flowers; styles reciprocally placed; and an oblong capsule shorter than the persistent calyx. To clarify its phylogenetic placement, we constructed phylogenetic trees using two datasets: 63 complete chloroplast genome sequences and 75 nuclear ribosomal DNA internal transcribed spacer (nrITS) sequences. Both trees showed similar topologies, consistently placing the new species within a monophyletic group of Sect. Aleuritia, supporting its assignment to this section. For a deeper comparison between the new species and other members of Sect. Aleuritia, we incorporated chloroplast genomes of seven additional species from this section. The results revealed highly conserved chloroplast genomes among all eight species, with only minor differences between the new species and the others. Primula xideensis is currently known only from its type locality. Based on IUCN Red List criteria, its conservation status is assessed as Data Deficient (DD). Full article

Podophyllum hexandrum Royle (1834) (Himalayan Mayapple), a key Himalayan medicinal plant and source of podophyllotoxin for anticancer drugs, is declining due to overharvesting, habitat loss, and climate change. This study, conducted from May to September 2024 across nine populations in Swat, Pakistan, assessed its ethnobotanical importance and conservation status. A total of 331 participants (270 individual surveys + 61 group discussions) were included. Using ethnobotanical surveys, IUCN-CMP threat frameworks, and spatial analysis, results showed high cultural value (Use Value = 0.63–0.92) and strong consensus for rheumatism (ICF = 0.91) and fever (ICF = 0.89). Fidelity levels were 94% for rheumatism and 88% for fever. Only 35% of respondents demonstrated conservation awareness. Overharvesting was the main threat, followed by habitat degradation and climate change. The species showed restricted distribution (EOO = 4250 km²; AOO = 295 km²), high fragmentation (0.68), and a 35% population decline over 10 years. It is assessed as Endangered (EN B1ab (iii, v)). This study provides the first integrated ethnobotanical–GIS assessment of P. hexandrum in the Hindu Kush–Himalaya region of Pakistan, offering measurable conservation baselines and community perception data previously unavailable. Findings align with global medicinal plant decline trends and support integration with CBD, SDGs (3 and 15), and potential CITES listing. Urgent conservation actions are required, including community-based management, habitat restoration, sustainable harvesting, ex situ conservation, and policy enforcement. Full article

The genus Tulipa L. is a common group of ornamental plants, characterized by high morphological variability and a complex taxonomy. Despite considerable interest in this group, assessments of its species composition remain inconclusive, as evidenced by discrepancies between contemporary taxonomic sources. The number of recognized taxa varies across major taxonomic databases, including Plants of the World Online, World Flora Online, and Euro+Med PlantBase, reflecting ongoing taxonomic revisions and differences in species concepts. In terms of distribution patterns, 7.6% are widely distributed taxa across transcontinental regions, 28.0% occur across multiple countries within a continent, and 66.9% are range-restricted taxa. The latter group includes 4.2% transnational endemics, 44.1% single-country endemics, 8.5% single-region endemics, and 10.2% single-site endemics. Recent taxonomic and evolutionary studies of Tulipa increasingly rely on molecular approaches, particularly DNA barcoding and chloroplast genome analyses, which have improved phylogenetic resolution and species delimitation in several cases. However, truly comprehensive studies combining morphological, cytogenetic, and molecular datasets remain limited and are typically restricted to individual taxa or species complexes rather than the genus as a whole. Modern molecular genetic studies demonstrate the high informativeness of both nuclear and plastid markers for studying the phylogeny, systematics, and genetic diversity of Tulipa species. Natural populations of Tulipa are under pressure from anthropogenic factors and climate change, resulting in reduced range and habitat degradation. According to the International Union for Conservation of Nature Red List of Threatened Species, among 118 taxa of the genus Tulipa, T. sprengeri Baker is classified as Extinct in the Wild, 5.9% as Critically Endangered, 5.9% as Endangered, 8.5% as Vulnerable, 11.9% as Near Threatened, and 11.0% as Least Concern. The use of exclusively national assessments to determine species extinction risk may be insufficiently objective, whereas global assessments provide a more informative and reliable approach for evaluating conservation status. In this review, we combine investigations of the morphology, taxonomy, and geographic diversity; population genetic structure and molecular diversity; and molecular phylogenetics and plastome-based genomics of the genus Tulipa. Furthermore, the review examines current challenges and future research prospects, emphasizing that studies of the genus Tulipa should integrate morphological, genomic, and ecological approaches to refine taxonomy and conserve genetic resources. Full article

The genus Desmidorchis Ehrenb. (Apocynaceae) is a characteristic component of the succulent flora of the Arabian Peninsula, where high levels of endemism and increasing environmental pressures highlight the need for integrated genomic and conservation research. This study assessed the conservation status of three ethnomedicinally important endemics—D. adenensis, D. arabica, and D. awdeliana—and characterizes their complete plastomes to resolve their evolutionary and temporal history. Conservation assessments were conducted following IUCN Red List criteria, and complete plastomes were sequenced and compared within a dataset of 15 subtribe Stapeliinae taxa. Comparative analyses examined the genome structure, divergence hotspots, repetitive sequences, codon usage bias, and selection pressure, while divergence times were estimated using fossil-calibrated molecular clock analyses. All three species were classified as Near Threatened (NT), primarily due to anthropogenic and environmental pressures. Plastome analyses revealed a highly conserved genome structure; however, hypervariable regions, particularly ycf1 and clpP1, exhibited elevated sequence divergence and phylogenetic informativeness. Simple sequence repeats (SSRs) were also identified as potentially informative features at the genus level. Codon usage and Ka/Ks analyses further indicated that most plastid protein-coding genes are under strong purifying selection, whereas only a few loci, particularly clpP1, showed comparatively elevated evolutionary rates. Phylogenomic analyses supported the monophyly of Desmidorchis, with molecular dating indicating recent Pleistocene diversification (~0.34–1.51 Ma), potentially associated with Quaternary climatic oscillations. Overall, this study provides an important genomic foundation for future taxonomic, evolutionary, and conservation studies of rare Arabian taxa. Full article

Ochetobibus elongatus (Kner) is a migratory fish found in the Yangtze River basin and areas south of it, and listed as a critically endangered (CR) fish on the China Red List of Vertebrates. To achieve group recovery and artificial breeding, this study investigated the dietary characteristics of O. elongatus based on high-throughput sequencing of its intestinal contents, and its digestive system morphology, and its histology. Results showed that the digestive system of O. elongatus lacked a stomach and mainly consisted of the oropharynx, pharyngeal teeth, esophagus, intestine, and anus. The gut index was 0.88, with clear segmentation of the foregut, midgut, and hindgut, and the visceral mass index was 7.35%. Histological analysis of the digestive system revealed the presence of keratinized dental plates or pharyngeal teeth in the pharynx, as well as a high density of taste bud cells in the soft palate of the oral cavity. The surface layer of the intestinal villi contained numerous mucous cells, with the average number of mucous cells per villus gradually increasing from the esophagus to the hindgut, and the foregut having the longest and most abundant mucosal folds. The esophagus exhibited well-developed circular and longitudinal muscle layers, while in the hindgut, both the circular and longitudinal muscle layers were slightly thicker than those in the midgut. High-throughput sequencing of the intestinal contents of O. elongatus revealed the following phyla based on 18S V4 meta-barcoding: Chlorophyta, Diatoms, Arthropoda, Basidiomycetes, and Ascomycetes, with the genus Hypophthalmichthys and algae being the main classifications. In contrast, based on COI meta-barcoding, the study newly identified the phyla Cnidaria and Mollusca, with the genera Chlorophyta, Scenedesmus, Pectinodesmus, and zooplankton such as Pseudodiaptomus. Metagenomic sequencing revealed that the gut microbiota at the phylum level was predominantly composed of Pseudomonadota, Ascomycota, Basidiomycota, Chytridiomycota, and Bacillota, with key genera including Cetobacter, Pseudomonas, Acinetobacter, Aeromonas, and Clostridium. This study indicates that O. elongatus is an omnivore with carnivorous tendencies. Basic biological research on O. elongatus is of great significance for the restoration of the population, artificial breeding, and the development of its artificially formulated feed. It also provides important data for the formulation of biodiversity conservation measures. Full article