Search Results (154)

The Senegalese sole (Solea senegalensis Kaup, 1858) is a highly valuable species in European aquaculture and capture fisheries. Efficient monitoring of its populations is essential for sustainable management, yet traditional survey methods are invasive and labor-intensive. Environmental DNA (eDNA) analysis offers a powerful non-invasive alternative by detecting DNA fragments shed by organisms into the environment. In this study, we developed a species-specific TaqMan quantitative PCR (qPCR) assay targeting the mitochondrial cytochrome c oxidase subunit I (COI) gene to detect S. senegalensis eDNA. We evaluated assay performance, eDNA release, and persistence under controlled aquarium conditions. The assay demonstrated robust analytical sensitivity and specificity and showed an efficiency of 77.4%, an R² of 0.986, and an analytical limit of detection at the 10⁻⁵ dilution. Density had a statistically significant effect on the values observed (one-way ANOVA: F_3,16 = 3.903, p = 0.0287). To ensure accuracy, context-dependent operational quantification cycle (Cq) thresholds were defined: a stringent cutoff (Cq < 30) prevents false positives in complex marine environments, while a permissive cutoff (Cq < 36) maximizes detection in controlled settings. Aquarium trials confirmed that eDNA concentration correlates directly with fish density and accumulation time. Following fish removal, rapid eDNA degradation was observed, falling below strict quantifiable limits within 72 h, although trace signals persisted at late amplification cycles. This optimized qPCR protocol provides a foundational molecular tool that, pending further in situ validation, could support non-invasive S. senegalensis monitoring in ecological assessments and aquaculture management. Full article

Mangrove prop root epifaunal communities support coastal biodiversity by providing habitat and refuge for associated sessile species and contributing to larval supply. Yet, regional surveys across latitudinal gradients in southeast Florida remain scarce. Understanding how these communities vary spatially and temporally is essential for forecasting biodiversity responses to environmental change. This study tested how macrobenthic assemblage composition and beta diversity on red mangrove prop roots vary from Key West to Melbourne, Florida. Presence-absence data from 32 sites in four zones were analyzed using beta diversity partitioning, indicator species analysis, and temporal turnover metrics. A strong biogeographic boundary near Palm Beach County delineated a species-rich southern pool, formed by the Florida Keys and Miami-Dade and characterized by tropical sponges. Of the 41 indicator species, 34 were associated with these two southern zones, while neither northern zone had exclusive indicators. Northern beta diversity was dominated by nested subsets of a larger species pool rather than species replacement. Over the three years, only Broward-Palm Beach gained species, while the other three zones lost species, though this was not statistically significant. These findings highlight the ecological significance of the potential biogeographic ecotones and provide a baseline study from which to gain insight into how climate-driven mangrove range expansion may impact coastal biodiversity and ecosystem resilience. Full article

Hypersaline semi-enclosed seas impose physiological constraints on marine bivalves by increasing osmotic regulation costs and limiting somatic growth. This study examined life-history variation in natural populations of the pearl oyster Pinctada radiata across contrasting salinity regimes along the eastern and western coasts of Bahrain in the Arabian Gulf. Environmental conditions, shell morphometrics, growth modeling, oocyte abundance, physiological condition indicators, and the production-to-biomass ratio (P:B) were assessed to determine whether high salinity constrains somatic growth while reproductive persistence is maintained. Monthly surveys were conducted from June 2021 to May 2022 at one pearl oyster bed on each coast, comprising 12 surveys per coast. The two coasts formed a salinity gradient, averaging approximately 42‰ in the east and 55‰ in the west. Oysters from the western coast were smaller, with a mean shell height decreasing from 63.12 ± 6.47 mm in the east to 45.88 ± 3.41 mm in the west. The Gompertz model indicated a lower asymptotic shell height in the more saline population. The population-level P:B ratio was 0.23 yr⁻¹ on the eastern coast and 7.46 yr⁻¹ on the western coast. Despite reduced shell size, western oysters maintained strong seasonal oocyte abundance. The higher biomass turnover in the west partly reflected greater oyster density. This pattern is consistent with osmoregulatory costs and constrained shell biomineralization under chronic hypersalinity. Reproductive activity followed a bimodal pattern on both coasts. These findings are consistent with a life-history trade-off in which pearl oysters exposed to chronic salinity stress maintain reproductive activity despite constrained growth. Overall, this study links environmental forcing, growth limitation, population-level biomass turnover, and reproductive activity, providing field-based evidence that chronic hypersalinity constrains somatic growth while reproductive persistence is maintained in a benthic bivalve inhabiting hypersaline coastal systems under climate-related stress. Full article

Recent taxonomic revisions within the family Molidae have clarified the validity and diagnostic characters of the bump-head sunfish Mola alexandrini (Ranzani, 1839), a species historically confused with Mola mola. Despite its circumglobal distribution, confirmed records of M. alexandrini in the Mediterranean Sea remain limited, particularly in the Adriatic Sea. Here, we report the occurrence of an adult female M. alexandrini stranded along the north-western Adriatic coast (Ravenna, Italy) in March 2026. Species identification was assessed through an integrative approach combining external morphology, morphometric measurements, and mitochondrial COI sequencing. The specimen exhibited diagnostic morphological traits consistent with M. alexandrini, including a rounded clavus lacking lobes and back-fold, a deep laterally compressed body, and characteristic coloration patterns. Phylogenetic analysis based on COI sequences clustered the specimen within the M. alexandrini clade, clearly separating it from M. mola. This finding provides further evidence of the occurrence of M. alexandrini in the Adriatic Sea and highlights the importance of combining molecular and morphological approaches to resolve taxonomic uncertainty within the genus Mola. The study also highlights that historical misidentification may have contributed to an underestimation of the occurrence of M. alexandrini in the Mediterranean basin. Full article

Larvae of Pycnopscyche guttifer, a large, leaf-shredding caddisfly, have become common in rivers of northern Nova Scotia, Canada, where they may greatly accelerate decomposition rates of leaf litter. How the larvae find litter patches in the complex environment of a stream bottom, and how they decide which litter types to feed on, have not been fully examined. In field and laboratory experiments, I determined the preference of P. guttifer to conditioned leaf litter from four species of deciduous trees ranging from recalcitrant and nutrient poor (red oak) to soft and nutrient rich (speckled alder). In field experiments, larvae exhibited a strong preference toward speckled alder and red maple litter, while trembling aspen and especially red oak litter were rarely used. The abundance of larvae on red maple litter varied according to whether aspen or oak litter was nearby. In laboratory choice experiments, larvae searched actively, moving in straight lines in random directions. They deserted less-favoured litter types sooner than favoured litter types, but sometimes abandoned favoured litter types as well. In a complex environment containing many kinds of litter in scattered patches, a restless larva that periodically searches for new food patches may maximize its intake of energy or essential nutrients and obtain a selective advantage over those that remain on acceptable patches. Full article

Freshwater ecosystems are increasingly exposed to metal contamination arising from natural and anthropogenic activities, potentially affecting fish physiology and ecosystem health. However, limited information is available regarding metal accumulation and associated biological responses in fish populations from Dukan Lake, northern Iraq. Therefore, this study investigated metal concentrations in water and tissues of common carp (Cyprinus carpio) and evaluated their relationships with selected fish health indicators. Water and fish samples were collected monthly from Dukan Lake, and a total of 60 fish were classified into three length groups (20–29 cm, 30–39 cm, and 40–49 cm). Metal concentrations in water, liver, and gonad tissues were analyzed using ICP-OES, while condition factor (CF), gonadosomatic index (GSI), and hepatosomatic index (HSI) were used to assess fish physiological condition. Sodium (Na), magnesium (Mg), potassium (K), iron (Fe), zinc (Zn), and barium (Ba) were detected in both water and fish tissues, with concentrations in water ranging from 50 to 7069 μg/L. In contrast, chromium (Cr), manganese (Mn), nickel (Ni), selenium (Se), silver (Ag), cadmium (Cd), antimony (Sb), lead (Pb), copper (Cu), and arsenic (As) were below detection limits. Biometric analysis revealed significant differences (p < 0.05) in the gonadosomatic index (GSI) among fish length groups, indicating size-dependent reproductive development. However, no significant relationship was observed between fish length and either the CF or HSI, suggesting relatively stable somatic condition or liver status across size classes. Correlation analysis showed no significant associations between water metal concentrations and CF or GSI. A significant positive correlation was identified between Zn concentration and HSI in the 30–39 cm length group, indicating a possible link between Zn exposure and hepatic physiological response. The findings indicate that essential elements dominate the metal profile in Dukan Lake, with limited evidence of toxic metal contamination. No major adverse effects on the general condition of the fish were observed. These results contribute to understanding metal bioaccumulation patterns and their implications for fish health in freshwater ecosystems. Full article

This study examined the morphometric variability and sex-related patterns in three freshwater mollusk species, Pila globosa, Lamellidens marginalis, and Parreysia corrugata from the Hakaluki Haor ecosystem, Bangladesh. All species showed strong linear relationships between shell length and body weight (p < 0.001). The R² values indicated moderate association in P. globosa (0.57) and L. marginalis (0.59) and a high association in P. corrugata (0.80). Most traits were similar across sexes; however, females of P. corrugata had significantly higher body weight and slightly wider shells, suggesting mild sexual dimorphism. Condition indices were species-specific, with males generally higher, notably in P. corrugata (p < 0.05). Violin box plots showed minor sex differences in P. globosa aperture and spire, with overlap. PCA revealed that size traits were major contributors, explaining 60–75% of the variation. Females of P. globosa scored higher on the size axis, indicating sexual size dimorphism, while L. marginalis and P. corrugata showed significant overlap. Overall, results highlight strong allometric scaling, limited species-specific sexual dimorphism, and body size as the main determinants of morphology. Full article

Short-term captivity is widely used in experimental studies but may unintentionally alter host-associated microbiomes, potentially confounding biological interpretation of experimental outcomes. Here, we evaluated the effects of 35 days of captivity on the gut microbiome of Fundulus heteroclitus collected from Long Island Sound (Milford, CT, USA) using 16S rRNA gene sequencing. Comparisons between Field Control (FC) and short-term Captive Treatment (CT) groups revealed a marked reduction in microbial diversity under captive conditions. Observed richness decreased approximately five-fold (Field Control: 1026 features; Captive Treatment: 221 features), and Shannon diversity declined from 8.89 to 5.93. Beta diversity analyses based on UniFrac distances demonstrated clear separation between groups, indicating substantial shifts in community composition. Taxonomic profiling revealed reduced community complexity in captive fish, with increased dominance of Proteobacteria and loss of diverse environmental taxa. Predicted enrichment of pathways associated with stress response, altered respiration, and metabolic flexibility in captivity reflects inferred functional potential rather than direct functional activity. Given the use of pooled samples with limited biological replication, these findings should be interpreted as strong community-level patterns rather than population-level inference. Collectively, these results indicate that short-term captivity alters the F. heteroclitus gut microbiome. Full article

This research investigates the effects of incorporating cyanobacterium Oscillatoria limnetica (OL) powder into aquafeeds on the growth rates, activity of digestive enzymes, antioxidant status, and innate immune responses of white-leg shrimp, Litopenaeus vannamei. The shrimps’ resistance against possible infection with Vibrio harveyi was also examined. For 12 weeks, shrimps (1.26 ± 0.088 g) were nourished on experimental diets with 0.0, 0.75, 1.5, 2.25, and 3.0 g OL/kg feed, represented as OL0, OL0.75, OL1.5, OL2.25, and OL3.0, respectively. At the end of the feeding trial, shrimps were challenged by V. harveyi, and their mortality was further observed for further ten days. The shrimps fed on OL-enriched diets, particularly OL3.0, showed significantly greater growth, digestive enzyme activities, and innate immunity performance than those fed on the control diet (OL0). Compared to the control group, enzymatic antioxidant parameters (CAT and SOD) were significantly (p < 0.05) higher; meanwhile, MDA levels showed marked declines in shrimps fed on OL-containing diets (particularly OL3.0). The relative mRNA expression of antioxidant-related genes (cMn-SOD, CAT, and GPx) and immune-related genes (HMC, Alpha2M, ProPO, and Pen3a) was upregulated in the OL-fed animals compared to the control group. The intestinal morphometry was markedly enhanced in the animals fed on OL-enriched diets, especially with respect to the OL3.0 diet. After the bacterial challenge assay against V. harveyi for ten days, shrimps fed on the control diet had 83.3% mortality; meanwhile, the mortality rate was lower in shrimp groups fed on OL diets, particularly OL3.0 (46.7%). This study demonstrates that L. vannamei benefits from dietary inclusion of O. limnetica (3.0 g/kg feed) through accelerating its growth due to better digestion of diets. Additionally, the OL meal acts as a functional ingredient that fortifies the shrimp against possible V. harveyi infection by enhancing their biological defense system. Full article

Freshwater ecosystems are increasingly affected by anthropogenic stressors, necessitating the assessment of sensitive biomarkers of sublethal impact. This study assessed the seasonal variability of oxidative stress parameters in the amphipod Gammarus lacustris from three tributaries of Lake Sevan (Armenia)—the Gavaraget, Karchagbyur, and Argichi Rivers—with contrasting hydrophysical and hydrochemical conditions. During 2022–2024, lipid peroxidation (MDA), antioxidant enzymes (CAT, SOD, GR, and GST), and glutathione (GSH) were measured in specimens collected in May, July, and October and related to temperature, dissolved oxygen, nutrients, major ions, and trace elements. Biomarker levels generally increased from spring to summer and declined in autumn, following temperature and photoperiod patterns. Statistically significant seasonal dynamics were most consistent in the Karchaghbyur River, while, in the Gavaraget and Argichi Rivers, they varied by biomarker and year. Amphipods from the Gavaraget River exhibited consistently elevated levels of oxidative stress biomarkers, consistent with elevated nutrient concentrations and stronger anthropogenic impacts. A short-term increase in all biomarkers in the Argichi River in 2023 indicated episodic acute stress. Overall, the response of oxidative stress biomarkers in G. lacustris reflected both the natural seasonal variability and spatial differences in environmental pressure, confirming their potential as a tool for monitoring Lake Sevan’s tributaries. Full article

Significant cyanobacterial proliferations dominated by Lyngbya have been increasingly reported since the 2000s, posing environmental, economic, and human-health risks. This review synthesizes their distribution, predictors, toxicity, and management strategies of all identified Lyngbya species, including species historically classified as Lyngbya despite later taxonomic changes. Research has focused mainly on Lyngbya majuscula and Lyngbya wollei. For L. majuscula, bloom initiation is driven by proximate abiotic factors such as nutrients, light, and temperature; while broader conditions, including bottom currents, sediment nutrients, rainfall, and land use, set the stage for proliferation. Toxin production appears related to nutrient levels and temperature, although mechanisms remain poorly understood. Management of L. wollei commonly relies on copper-based chelated algaecides, despite their risks to non-target organisms, highlighting the need for more sustainable tools used in managing other cyanobacteria. Existing predictive models for Lyngbya proliferation show limited accuracy, partly due to insufficient in situ data. This review argues that novel monitoring approaches could provide the data needed to strengthen predictive models, also offering insights into a new modeling approach, supporting more proactive and effective Lyngbya bloom management. It is particularly valuable for research in water resource management and environmental science, as it synthesizes current knowledge essential for advancing management strategies. Full article

Eastern Boundary Upwelling Systems (EBUSs) are among the most productive marine biomes globally, renowned for their substantial pelagic fisheries. While the role of wind-driven upwelling in stimulating primary production is well-documented, the integral contributions of the marine benthos in maintaining ecosystem productivity and fishery yields are often underrepresented. This article analyzes evidence from the Humboldt, California, Benguela, and Canary Current systems to delineate the critical functions of the seabed and its resident communities. Three primary pathways through which the benthos supports fisheries are described: (1) by facilitating the efficient regeneration of nutrients from sedimenting organic matter, thereby replenishing the inorganic nutrient pool for subsequent primary production; (2) by providing essential habitat structure that supports the life history of a myriad of species, including demersal and coastal fish species, serving as nursery and feeding grounds; and (3) by forming the foundational trophic base for benthic-feeding fishes and invertebrates of commercial importance. By comparing system-specific characteristics, such as the influence of oxygen minimum zones on benthic community structure, the integrity of the benthic subsystem as a fundamental determinant of the productivity and sustainability of EBUS fisheries is demonstrated. A holistic management approach that includes benthic habitat conservation is therefore paramount. Full article

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 an 18-month period, from January 2023 to June 2024. Simultaneously, the mean gonadal index (GI) was estimated and its relationship with fluctuations in seawater temperature and chlorophyll a 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 in the gonadal cycle. Reproduction in this species was strongly influenced by fluctuations in seawater temperature, but was not significantly correlated with chlorophyll a 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 (June or July) prohibiting razor clam harvesting in the Ria Formosa lagoon between May and July is proposed. Full article

The physiological performance of the Pacific oyster Magallana gigas in subtropical lagoon systems is shaped by the interaction between environmental variability, reproductive dynamics, and oxidative stress. This study quantified monthly changes in the growth and proximate composition of oysters cultivated in Estero La Cruz, Sonora, and evaluated their relationship with temperature and chlorophyll-a as proxies for thermal stress and trophic availability. Shell growth was continuous, while somatic biomass increased markedly during winter, indicating high thermal tolerance and metabolic flexibility. Proximate composition showed pronounced seasonal oscillations, with energy reserves accumulating during periods of high primary productivity and declining sharply in December, coinciding with peak gametogenic activity. Antioxidant enzyme activities (SOD, CAT, GPx) increased toward winter, reflecting elevated oxidative stress. Correlation and regression analyses revealed consistent relationships among environmental variables and biological responses, identifying temperature as the main factor associated with growth variability. Overall, these results demonstrate a strong coupling between environmental forcing, energy allocation, and oxidative stress, providing an integrative framework for understanding oyster performance and supporting aquaculture management in subtropical coastal systems. Full article