This study develops and validates a scale designed to measure safe diving culture among aquaculture divers. It also examines occupational health and safety behaviors by considering the individual, environmental, and organizational factors that influence safe diving practices. The study followed a methodological design combining descriptive analysis and scale development. Participants were professional aquaculture divers working in fish farming facilities in Türkiye (n = 613). Data was collected through an online survey. Exploratory factor analysis (EFA), confirmatory factor analysis (CFA), and structural equation modeling (SEM) were conducted in AMOS, and all items were rated on a 5-point Likert scale. According to the EFA results, four factors accounted for 57.7% of the total variance: pre-dive planning and safety awareness, safe behavior during the dive, equipment and environmental safety, and post-dive risk management with behavioral attention. CFA supported this four-factor structure with excellent fit indices (χ2/df = 1.165; CFI = .988; TLI = .986; RMSEA = .026). Internal consistency values were high (α = .851-.877). SEM further confirmed the expected relationships among the subscales, indicating that diving safety reflects not only technical knowledge but also behavioral attitudes and organizational safety climate. The "Safety Behavior Scale for Aquaculture Divers" offers a sound psychometric tool for evaluating behavioral safety culture in aquaculture diving. The scale provides a structured tool for assessing self-reported safe diving behaviors among aquaculture divers. By addressing diving behavior through multiple dimensions, the study provides a meaningful contribution to occupational health literature.
Symbioses between remoras (Family Echeneidae) and marine megafauna are well-documented across diverse lineages. However, despite recent advancements in understanding the intricacies of these interactions, the dynamics of these relationships remain poorly understood, largely due to the highly mobile nature of both host and symbiont. Here we report seven observations of Echeneidae cloacal diving behavior in manta rays. These observations span all three currently described species of manta rays (Mobula yarae, Mobula birostris, and Mobula alfredi), demonstrate that large Echeneidae can perform cloacal diving behavior in both juvenile and adult manta rays, and show that this behavior occurs across multiple ocean basins. We also document one observation of Echeneidae attachment beneath a host's gill slit and several occurrences of gill injuries consistent with Echeneidae intrusion. These observations contribute to the growing database of Echeneidae-host behavioral interactions and provide an important foundation for understanding the extent, diversity, and dynamics underlying these highly debated, cryptic megafauna-symbiont interactions in marine environments. By providing new evidence of the complexity of symbiotic relationships in marine environments, this study also offers a multi-species natural history context that may inform future research and conservation considerations.
Cave diving involves prolonged bottom times and limited ascent routes, markedly increasing inert gas load and the risk of decompression illness (DCI). The presence of a patent foramen ovale (PFO) further elevates this risk. A dive trainer developed DCI with severe portal venous air embolism after a 2.5-h cave dive. Symptoms included >20 min of mental confusion, skin rashes, and mild abdominal discomfort. Hyperbaric therapy improved his condition. Transesophageal echocardiography revealed a grade III, high-risk PFO. Following shared decision-making, percutaneous PFO closure was successfully performed. After 4 months of abstinence, the patient completed 150 subsequent dives without the recurrence of DCI. We continue to encourage adherence to all available measures to minimize nitrogen load. Venous bubbles, including portal venous air embolism, cannot be reliably mitigated solely by PFO closure. Extreme nitrogen loading during cave diving with a high-risk PFO substantially increases the likelihood of DCI, underscoring the importance of nitrogen-minimizing strategies and the need for targeted PFO screening in divers with repeated high-exposure profiles.
Simulated diving and decompression can impair endothelial function, but the upstream oxidant sources and their relationship with endothelial nitric oxide synthase (eNOS) coupling in the pulmonary circulation remain unclear. We investigated whether NADPH oxidase 2 (NOX2) is associated with oxidative stress, tetrahydrobiopterin (BH4) depletion, altered eNOS coupling, and pulmonary endothelial dysfunction after simulated air diving. Eighteen male Sprague-Dawley rats were assigned to three groups: control, decompression stress, and decompression stress with the NOX2 inhibitor GSK2795039 (100 mg/kg, intraperitoneal) administered before pressurization. Decompression stress was induced by hyperbaric exposure to 600 kPa for 1 h followed by decompression to ambient pressure; pulmonary arteries were collected 1 h after decompression. We evaluated NOX2 expression, oxidative stress indices, BH4 content, eNOS phosphorylation and dimer/monomer ratio, nitric oxide metabolites (nitrate plus nitrite), markers associated with endothelial activation, and vasoreactivity. Compared with controls, decompression stress increased NOX2 expression, reactive oxygen species and lipid peroxidation, decreased superoxide dismutase activity, reduced BH4 and nitric oxide metabolites. It also caused a shift in eNOS towards a lower dimer/monomer ratio, increased endothelin-1 and adhesion molecules, and impaired endothelium-dependent relaxation, though endothelium-independent relaxation remained intact. GSK2795039 pretreatment attenuated oxidative stress, improved BH4 availability, restored nitric oxide metabolites, and decreased markers of endothelial activation, partially improving endothelium-dependent relaxation. These findings suggest that NOX2-associated oxidative stress contributes to reduced BH4 availability and eNOS coupling imbalance, leading to pulmonary endothelial dysfunction after decompression.
The fundamental operational range of cyborg insects, which are hybrid robots that combine a living insect with an electronic controller, is inherently restricted to the host's natural environment. To extend their operational range, we developed a wearable diving suit for terrestrial insects. The suit integrates a miniaturised oxygen generation module with a flexible waterproof shell, enabling continuous oxygen supply and isolation from surrounding water. By fitting a cockroach, which is a terrestrial species, into this diving suit, we allowed it to survive and operate in oxygen-deprived environments such as underwater, transforming it into an amphibious cyborg robot capable of operation across land and water. The suit sustained respiration and locomotion for up to 3 h underwater, establishing amphibious cyborg insects that combine biological adaptability with engineered protection for prolonged exploration in extreme, confined environments.
Cetaceans face the risk of thromboembolism due to diving and decompression responses. However, cetaceans maintain normal blood circulation. This study explores the molecular mechanisms cetaceans use to mitigate diving-associated hemostatic challenges during diving. Forty-six species were analyzed, including 18 cetaceans, 9 artiodactyls, and 19 other terrestrial mammals. Thirty-nine anticoagulant genes and proteins were examined, identifying 6 genes (ANXA2, ANXA5, FGA, FGB, PLAUR, and PLG) with conserved evolution, 4 genes (ANXA2, PDGFB, SH2B3, THBS1) with positive selection, and 12 proteins (APOH, FGA, FGB, FGG, GP1BA, PLAU, PRKCD, PRKG1, SERPINF2, SERPING1, TMPRSS6, and TMX1) with specific amino acid sites in cetaceans. Ancestral state reconstruction revealed independent evolution of deep diving behavior in different cetacean lineages, particularly within Odontoceti. Correlation analysis linked the evolution of the APOE gene with diving depth, suggesting its role in diving adaptation. These analyses suggest that cetaceans may help reduce the risk of thrombosis during diving by lowering platelet activity, enhancing fibrinolysis, and modulating the coagulation cascade. These analyses suggest that cetaceans may mitigate diving-associated thrombotic risk by modulating platelet activity, fibrinolysis, and the coagulation cascade. Overall, this study identifies candidate anticoagulant-related genes and amino acid substitutions for future functional validation of hemostatic adaptation in cetaceans.
Wing-propelled diving birds flap their wings to move through air and water, yet the wing morphology and kinematics that enable this behavior remain poorly understood because of the difficulty of collecting in situ data. The impact of flapping frequency, wing size, and stiffness on locomotion in-and transition between-the two media are still unknown. We compared data from diving birds against experiments using a flapping-wing robot capable of flying, swimming, plunge diving, and exiting the water. We show that frequency adaptation, flexible wings, and powerful actuation enable seamless transitions without folding wings or legs, that large wings enhance flight without substantially reducing underwater efficiency, and that tail-body distance and egress angle affect water exit. These results clarify how birds (and robots) balance multifluid locomotion constraints.
Inspired by the hovering, diving, and cooperative hunting behaviors of the pied kingfisher, the Pied Kingfisher Optimizer (PKO) has demonstrated competitive performance in optimization tasks. However, it exhibits several phase-specific limitations, including uneven population distribution caused by random initialization, insufficient use of historical information during exploration, over-reliance on the global best during exploitation, and weakly guided perturbation in the symbiosis phase. To address these issues, this study proposes an Improved Pied Kingfisher Optimizer (IPKO), which incorporates biologically inspired adaptive strategies. Drawing inspiration from the kingfisher's diverse perching, gaze adjustment during hovering, evasive diving after failed strikes, and territory shifting based on flock position, four mechanisms are developed. Specifically, sine chaotic opposition-based initialization enhances population diversity; adaptive directional search regulates the exploration-exploitation balance; stochastic perturbation-based information fusion improves the ability to escape local optima; and centroid-based adaptive boundary handling strengthens constraint adaptability. The performance of IPKO is evaluated on the CEC2017 benchmark suite (10, 30, 50, and 100 dimensions) and two real-world engineering problems. Experimental results show that IPKO achieves superior overall performance compared with eleven state-of-the-art algorithms, with statistical significance confirmed by the Friedman test and Holm's post-hoc procedure. Ablation studies further verify the contribution of each strategy. In engineering applications such as cold chain logistics and dynamic multi-UAV cooperative path planning, the IPKO algorithm demonstrates superior solution quality, robustness, and constraint-handling capability compared with competing algorithms. These results demonstrate that IPKO is a robust and effective bio-inspired optimization approach for solving complex, high-dimensional constrained engineering problems.
Jeju Haenyeo are traditional female breath-hold divers from Jeju Island, the southernmost and largest island of the Republic of Korea, who harvest marine products without modern diving equipment (1). During diving, they are repeatedly exposed to cold seawater, breath-holding, and pressure changes (2). The upper airway may be particularly vulnerable, as it is the first anatomical region directly exposed to seawater and pressure-related stimuli.
Professional divers work in safety-critical environments that require sustained attention, rapid judgment, and stable emotional control. Neuroticism is a vulnerability trait related to negative affectivity, perceived stress reflects appraisal of recent demands, and psychological resilience may be associated with weaker stress-related associations. This study examined how these factors were associated with pre-dive state anxiety in professional divers. This cross-sectional study used a de-identified, code-linked, two-component survey design in China from January to February 2026. A total of 300 professional divers completed the baseline web-based questionnaire, and 277 were included in the final analysis after eligibility and data-quality screening. The baseline questionnaire assessed demographic characteristics, neuroticism, perceived stress, and psychological resilience. The State scale of the State-Trait Anxiety Inventory (STAI-S) was completed separately on the day of a scheduled diving task, shortly before the dive. Pearson correlations, adjusted linear regression models, and exploratory interaction analyses were conducted controlling for age, education, and years of diving experience. Neuroticism was positively correlated with state anxiety (r = 0.77, p < 0.001) and perceived stress (r = 0.29, p < 0.001), whereas resilience was negatively correlated with neuroticism (r = -0.49, p < 0.001) and state anxiety (r = -0.58, p < 0.001). After adjustment, neuroticism was strongly associated with state anxiety (B = 0.81, SE = 0.04, β = 0.78, p < 0.001), and perceived stress was also associated with state anxiety after accounting for neuroticism (B = 0.16, SE = 0.05, β = 0.13, p = 0.001). Resilience did not significantly moderate the direct neuroticism-state anxiety association (B ≈ 0.000, p = 0.837), but it moderated the neuroticism-perceived stress and perceived stress-state anxiety associations (both B = -0.011, p < 0.001). These associations were weaker at higher resilience. In this convenience sample of Chinese professional divers, higher neuroticism and perceived stress were associated with higher pre-dive state anxiety, whereas greater resilience was associated with lower state anxiety and with weaker selected stress-related associations. The mean STAI-S score was in a low-to-moderate range; therefore, the findings should not be interpreted as showing clinically elevated anxiety or as implying that all pre-dive arousal is maladaptive. Longitudinal and repeated-measures studies are needed to clarify temporal ordering, practical significance, and intervention implications.
The cenotes of the Yucatán Peninsula are unique subterranean ecosystems that host stigobiontic fauna, yet contamination of groundwater organisms remains poorly understood. Microplastics (MPs) are emerging pollutants widely documented in aquatic environments, but data on their occurrence in groundwater fauna are scarce. This study provides baseline information on the presence and characteristics of MPs in the stigobiontic isopod Creaseriella anops (Isopoda: Cirolanidae), collected via scuba diving at a depth of 30 m in the Xelactún cenote (Kinchil, Yucatán, México). Organisms were chemically digested, and the residues were vacuum-filtered and analyzed under a stereomicroscope. Suspected MPs were quantified and categorized by shape and color, and polymer composition was determined using μFTIR spectroscopy. Only fibers were detected, with a mean abundance of 12.29 ± 3.65 MPs g-1 w.w., predominantly transparent (75.64%). Identified polymers included polyester (20%), polyethylene (7%), rayon (7%), and polypropylene (2%). Given the ecological fragility, high endemism, and importance of cenotes as a regional water source, the relatively high MP concentrations observed highlight the need for further research using C. anops as a model species to assess groundwater contamination.
Decompression sickness (DCS) is a low-incidence but potentially severe consequence of hyperbaric exposure. Probabilistic decompression models offer a framework to quantify this risk, yet their calibration is challenged by the scarcity of empirical outcome data. In this study, we propose a gradient-based optimization model to predict DCS probability, trained on 924 dive profiles from the US Navy Experimental Diving Unit XVal-He-9 tables, representing predefined DCS probabilities (2.3% and 4%), and optimized based on actual body tissues grouped in five compartments. The model achieved high predictive accuracy (MAE: 0.535%; RMSE: 0.694%) with consistent performance across training and test sets, indicating limited overfitting. Reduced accuracy was observed in intermediate depth ranges (100-130fsw or 30-39msw). Out-of-sample evaluation on 31 high-risk dives (three DCS cases) showed general agreement between predicted and observed incidence while suggesting a potential contribution of repetitive exposures not accounted for in the model. These results demonstrate that gradient-based optimization, trained based on existing probabilistic tables, seems to be capable of satisfactorily predicting decompression sickness risk for a given dive profile. Additionally, future studies can further adjust the loss function to account for individual or dive-related indicators, leading to a more individualized risk function.
Mercury (Hg) contamination poses a significant threat to marine top predators, yet the drivers of short-term variation in Hg exposure remain largely unquantified. We investigated interannual variation in Hg accumulation in adult common murres (Uria aalge) during chick-rearing in the Gulf of St. Lawrence, Canada, over two breeding seasons (2021-2022). Red blood cell (RBC) Hg concentrations, reflecting recent dietary intake, were measured alongside GPS/Time-Depth Recorder (TDR) tracking and stable isotope analysis to quantify trophic position (δ15N), foraging habitat (δ13C, δ34S, GPS), and diving behavior (TDR). RBC Hg concentrations were significantly higher in 2022 (0.774-1.12 μg/g ww) than in 2021 (0.388-0.720 μg/g ww), coinciding with a shift toward higher trophic-level and more coastal/benthic feeding (higher δ15N; more negative δ13C and δ34S), as well as shallower dives and foraging closer to shore and the seafloor. These results highlight strong interannual variability in Hg exposure, potentially reflecting both ecological shifts and variation in environmental Hg availability. We conclude that integrating contaminant measurements with fine-scale tracking and isotopic data provides valuable context for interpreting exposure patterns in marine predators.
Exercise represents a dynamic integration of rapidly activated respiratory, cardiovascular and musculoskeletal responses to meet rising metabolic demands. While the human body has a remarkable ability for exertion and endurance, in disease states, and particularly in respiratory disease, these mechanisms are often compromised, resulting in dyspnoea and reduced exercise tolerance. This review outlines normal exercise physiology, including cardiac, ventilatory and skeletal muscle adaptations to enhance oxygen uptake and delivery to working muscle, and examines how these are altered in conditions such as asthma, chronic obstructive pulmonary disease, interstitial lung disease and pulmonary hypertension. Key management considerations are highlighted to support and optimise functional capacity in patients suffering from these conditions. The unique challenges of exercise, with and without respiratory disease, in specific contexts - including underwater diving, high altitude exposure, and pregnancy - are also discussed. We briefly review policies and prohibitions on medications for competitive athletes with respiratory disease, where adherence to anti-doping regulations, especially regarding inhaled beta-agonists and corticosteroids, is crucial. Overall, understanding the physiological basis for exercise limitation enables clinicians to be more effective in their assessment, therapeutic intervention and counselling for patients seeking to maintain activity and quality of life despite respiratory compromise.
Neurological decompression sickness (NDCS) is a potentially severe complication of diving, but its effects on autonomic cardiovascular regulation remain poorly understood. Heart rate variability (HRV) has emerged as a noninvasive method for assessing autonomic nervous system dynamics in both physiological and pathological conditions. To describe multidomain HRV patterns in divers presenting with NDCS prior to hyperbaric oxygen therapy (HBOT). This exploratory case series included eight divers diagnosed with NDCS at a tertiary hyperbaric medicine center. Continuous electrocardiographic monitoring was performed before HBOT, and HRV analysis was conducted using a standardized offline processing pipeline. Time-domain (SDNN, RMSSD, pNN50), frequency-domain (HF power, LF/HF ratio), and nonlinear metrics (Shannon entropy and two-dimensional Poincaré analysis) were evaluated. HRV parameters were analyzed both as absolute values and as Z-score normalized values relative to published reference populations. Conventional HRV indices demonstrated marked interindividual variability across cases. Some patients exhibited elevated global variability and vagally associated indices, whereas others showed reduced or near-reference values. Entropy-based measures also varied across the cohort, with near-reference values in some cases and lower values in others, particularly Cases 7 and 8. These findings suggest heterogeneous alterations in cardiac rhythm dynamics rather than a uniform HRV phenotype. NDCS may be associated with measurable but heterogeneous disturbances in autonomic cardiovascular regulation detectable through HRV analysis. Entropy-based measures may provide exploratory information on NN interval distributional irregularity, but these findings should be interpreted cautiously because of the small sample size, retrospective design, spontaneous respiration, and methodological sensitivity of entropy estimates. Larger prospective studies are needed to determine whether HRV can contribute to physiological characterization or monitoring of decompression illness.
The Chinese giant salamander (Andrias davidianus), a species of high ecological and conservation value, shows abnormal respiratory behaviors as early signs of health decline. Accurate assessment of its pulmonary respiration is crucial for improving captive breeding and post-breeding parental care-key strategies for its survival and population recovery. However, its nocturnal and cave-dwelling nature makes traditional observation extremely difficult. Manual monitoring suffers from poor visibility at night, while conventional detection methods often miss subtle respiratory movements, limiting behavioral and health research. To address these challenges, this study presents the first automated method for monitoring respiratory behaviors in this species. We propose Mamba-YOLO-SRC, a novel hybrid detection framework that combines Mamba and YOLO architectures to accurately identify four key behaviors: diving (Dive), head-raising (HeadUP), inhalation (Inhale), and exhalation (Exhale). The proposed model achieves a mean average precision (mAP@0.5) of 0.944, with per-class average precision scores of 0.975 for Dive, 0.925 for HeadUP, 0.948 for Exhale, and 0.928 for Inhale. Mamba-YOLO-SRC provides a feasible and referable technical solution for advancing research on the Chinese giant salamander in both captive and natural settings.
Pinnipeds (true seals, eared seals and walruses) are the only mammals that can hear effectively in both air and water. How and when they achieved the ability to negotiate such contrasting auditory media remains unknown. Here, we apply 3D shape and phylogenetic comparative analyses to a large dataset of extant and extinct caniform carnivorans (119 species, 217 specimens) to study the emergence of amphibious hearing in pinnipeds despite significant evolutionary constraints. We find support for the cavernous tissue as a functional and evolutionary mechanism for amphibious hearing. This tissue fills with blood during diving to equalize air pressure in the ear, enabling a shift from in-air to underwater hearing by matching the ear's acoustic impedance to that of the surrounding water. We found that early diverging freshwater pinnipeds had impaired hearing underwater. The first ancestral marine pinnipeds could hear amphibiously but with limited hearing ranges, probably reducing attenuation and harm from loud underwater sounds. Subsequently, otariids (eared seals) and phocids (true seals) independently acquired middle ear adaptations that expanded their underwater hearing range. This iterative evolution probably facilitated the exploration of novel auditory adaptive zones by crown pinnipeds, resulting in rare acoustic abilities like ultrasonic singing, vocal learning and rhythm.
The development of digital photogrammetry techniques has revolutionized the study of marine ecosystems, enabling the generation of high-precision three-dimensional models from conventional imagery. Structure from Motion (SfM) algorithms have become effective tools for mapping and monitoring underwater habitats, offering a non-invasive and cost-effective alternative to traditional methods. This study presents a pilot methodological validation of SfM-based underwater photogrammetry for the non-invasive morphometric monitoring of vulnerable benthic species, using Pinna rudis. The research focused on refining photogrammetric methodologies for marine conservation, addressing technical challenges such as variations in light conditions, water turbidity, and image acquisition complexity. The study area, the Cabrera Archipelago Maritime-Terrestrial National Park, is a pristine marine environment in the western Mediterranean, hosting diverse benthic communities, including an abundant Pinna rudis population. Data acquisition comprises sampling by scuba diving techniques at depths ranging from 26 to 31 m, performed during the July 2022 field campaign within a permanent demographic plot established in 2013 and the methodology applied involved generating three-dimensional models using SfM, allowing for direct measurements of the seabed and extraction of morphometric parameters of sessile species. The characterization of the Pinna rudis aggregation was based on specimen density and size structure, determined using maximum shell width. The 3D model of the pilot plot covers 86.1 m2, hosting 31 individuals. Morphometric measurements derived from SfM-based 3D models were validated against in situ diver measurements of maximum shell width. The results showed that the average maximum width obtained from 3D models (15.19 ± 3.23 cm) was consistent with in situ measurements (15.35 ± 3.48 cm). The mean difference between methods was -0.16 ± 0.82 cm, indicating a negligible systematic bias. The mean absolute error was 0.65 cm, corresponding to an average relative error of 4.34%, and a strong linear relationship was observed between both methods (r = 0.97). These results confirm that underwater photogrammetry is a reliable and non-invasive tool for monitoring vulnerable benthic species, providing high-resolution spatial and morphometric data to support conservation strategies in marine protected areas and allowing the collection of additional data compared to in situ surveys.