Search Results (78)

This article documents the widespread absence of sessile species in bedrock intertidal habitats at the head of the St. Lawrence Estuary, a large macrotidal estuary located in eastern Canada. Extensive observations revealed that no seaweeds or sessile invertebrates occurred anywhere (including cracks and crevices) on substrate areas that become exposed to the air during low tides. Only one sessile species, a green filamentous alga, was found submerged in tidepools. The lack of truly marine sessile species is likely explained by the very low water salinity of this coast, while the absence of sessile freshwater species on intertidal substrates outside of tidepools likely responds to a combination of oligohaline conditions during high tides and daily exposures to the air during low tides, which freshwater species are typically not adapted to. Influences of winter ice scour and coastal suspended sediments are likely secondary. Experimental research could unravel the interactive effects of these abiotic stressors. Overall, this “intertidal desert” could be a useful model system to further explore the boundaries of life on our planet. Full article

Background: The genus Dugesia (Platyhelminthes: Tricladida) includes a large diversity of free-living freshwater flatworms and is important for studies on regeneration and evolution. This study aims to describe a newly discovered asexual planarian species from southern China and explore its genetic characteristics and regenerative abilities. Methods: An integrative taxonomic analysis was conducted using morphology, karyology, histology, molecular phylogeny (18S, 28S, COI, mitogenome), and genome size estimation via flow cytometry. Regeneration was assessed by standardized amputations, and long-term asexual propagation was observed under laboratory conditions for three years. Results: Phylogenetic analyses using nuclear (18S, 28S rDNA) and mitochondrial (COI, mitogenome) markers confirmed that Dugesia cantonensis Guang Yang & Zhinan Yin, sp. nov. forms a distinct clade within Dugesia. Its 18,125 bp mitogenome contains 36 genes but lacks atp8. D. cantonensis displays a distinctive morphology, notably a pharynx located near the head. All body fragments regenerated into complete individuals within nine days. Remarkably, one individual produced ~10⁵ clonal descendants over three years via repeated amputation, maintaining stable regenerative ability and growth across generations. Karyological analysis revealed a diploid karyotype (2n = 16) consisting of eight chromosome pairs. The nuclear genome size was estimated at approximately 2.5 Gb using Danio rerio as an internal standard. Histological examination showed no detectable reproductive organs, confirming the species as an exclusively asexual lineage. Conclusions: D. cantonensis represents a new planarian strain with stable propagation and regeneration. These features make it a valuable resource for regenerative biology and comparative genomic studies. Full article

To compare the quality and nutritional differences of crayfish under freshwater and saline-alkali water aquaculture conditions, this study systematically analyzed the biochemical composition, physical properties, and nutritional evaluation of crayfish (Procambarus clarkii) cultivated in saline-alkali water (PC-SW) and freshwater aquaculture (PC-FW), respectively. The results showed that crayfish from PC-SW had higher crude protein, crude fat, water content, and ash content. At the same time, PC-SW had a higher meat yield (16.18 ± 0.74%) than PC-FW (p < 0.05), with no significant changes in the head weight ratio or hepatopancreas weight ratio, indicating superior crayfish quality. The trace element content of PC-SW differed significantly from that of PC-FW (p < 0.05), with the exception of Cu. To some extent, the amino acid and fatty acid compositions were similar. The no essential amino acids content of crayfish cultivated under freshwater and saline-alkali conditions was higher than the essential amino acids content. The total branched-chain amino acids (BCAAs) content was higher than the total aromatic amino acids (AACs) content in both groups; however, the BCAA to AAC ratio was similar, at approximately 2.14. The essential amino acid index results were 69.01 and 68.02, respectively. Finally, betaine and nucleotide concentrations increased and geosmin content was significantly reduced in PC-SW (3.13 ± 0.09 μg/kg) compared to PC-FW (4.32 ± 0.09 μg/kg) (p < 0.05), implying that PC-SW crayfish had a better flavor. Our findings revealed that cultivating crayfish under saline-alkali conditions can significantly improve the nutritional quality and flavor of muscle. Full article

To investigate the effects of water-soluble taste substances (WSTSs) on the physical properties and thermal coagulation properties of reconstituted surimi gels, this study used large yellow croaker muscle (FM) and the WSTS from by-product minced meat (MM) (skin, tail, and head meat (HM)). It was observed that these exogenous additions could effectively improve the surimi gel’s whiteness, gel strength and umami amino acid content. When these were added, the relaxation times of bound water in FM, MM and HM groups were shorter in the 10% exogenous addition treatment, and the surimi particle size (D10, D50, D90, d4, 3, d2, 3) was smaller. This implies a correlation between the WSTS and the moisture preservation capacity of recombinant surimi gels, whereby WSTS facilitates the cross-linking of protein molecules, leading to the formation of a densely interconnected network architecture. This research can provide theoretical guidance for the processing of surimi gel combined fish flavor substances and freshwater surimi, thereby improving the flavor characteristics of freshwater surimi gel. Full article

Coral islands are home to unique underground freshwater bodies generally known as freshwater lenses. There are differences in the development, formation, and properties of steady-state freshwater lenses among different coral islands because of the influence of tides, precipitation, island sizes, and hydrogeological conditions. This study investigated the response pattern of the groundwater system of coral islands to tides and precipitation based on field observation. Moreover, numerical simulation was performed to explore the effect mechanism of precipitation and tides on the formation of the freshwater lens. Field observation data and simulation boundary data were processed at three time scales to analyze the effect of the time scale on the simulation results. The groundwater chloride concentration (converted from monitored conductivity) of coral islands fluctuates periodically. In particular, tides mainly affect the periodicity of the fluctuation, whereas precipitation mainly affects the peak concentration. Monthly data are suitable for revealing the overall trend of groundwater properties, while hourly data are suitable for revealing the periodicity. During the formation and development of the freshwater lens, precipitation mainly affects the groundwater chloride concentration, whereas tides mainly affect the groundwater hydraulic head. The stabilization time point and chloride concentration of the freshwater lens are mainly affected by precipitation factors. The larger the minimum time scale of the boundary condition, the greater the simulation error. Time scales have a greater effect on the error of the steady-state chloride concentration of the freshwater lens than on the errors of the stabilization time point and steady-state hydraulic head. Full article

Salt stress significantly reduces rice yield and deteriorates rice quality. The present study was conducted to explore the regulatory effects of sole and combined application of S-abscisic acid (S-ABA) and soil conditioner on rice under high salt stress. The experimental treatments comprised 0.1% S-ABA alone (T1), the application of soil conditioner (T2), the combined application of both S-ABA and halotolerant microorganism soil conditioner (T3), and a control without any regulatory substance (CK). The treatments were arranged in a randomized complete block design in triplicate. To simulate high salinity stress, a 0.6% saltwater solution (by mixing natural seawater with freshwater) was used for irrigation. The results showed that T3 alleviated the phytotoxic effects of high salt stress and substantially improved rice yield. Furthermore, the numbers of effective panicles, grains per panicle, and 1000-grain weight under T3 treatment were 13.3–14.5%, 8.9–14.1%, and 4.9–5.5% higher than CK owing to improvement in dry matter accumulation, SPAD values, leaf area index, antioxidant enzyme activity, and reduced malondialdehyde and sodium ion content in rice. Moreover, the T3 treatment increased the output, output rate, and conversion rate of stem sheath matter after the heading stage; improved the milling yield, starch paste viscosity, starch stickiness, and gelatinization enthalpy; and reduced rice chalkiness. In addition, the T3 treatment also increased the amylose contents and decreased the total protein contents, thereby improving the taste of the rice. Overall, the results indicated that the application of exogenous S-ABA and soil conditioner is an effective strategy to alleviate the severity of salt stress in rice. Full article

Cadmium (Cd) pollution poses an important problem, but limited information is available about the toxicology effects of Cd on freshwater invertebrates. We investigated the accumulation, oxidative stress, microbial community changes, and transcriptomic alterations in apple snails (Pomacea canaliculata) under Cd stress. The snails were exposed to the 10 μg/L Cd solution for 16 days, followed by a 16-day elimination period. Our results showed that the liver accumulated the highest Cd concentration (17.41 μg/g), followed by the kidneys (8.00 μg/g) and intestine-stomach (6.68 μg/g), highlighting these tissues as primary targets for Cd accumulation. During the elimination period, Cd concentrations decreased in all tissues, with the head-foot and shell exhibiting over 30% elimination rates. Cd stress also resulted in reduced activities of superoxide dismutase (SOD), catalase (CAT), and glutathione transferase (GST) compared to the control group. Notably, even after 16 days of depuration, the enzyme activities did not return to normal levels, indicating persistent toxicological effects. Cd exposure significantly reduced the diversity of gut microbiota in P. canaliculata. Moreover, transcriptome analysis identified differentially expressed genes (DEGs) primarily associated with lysosome function, motor proteins, protein processing in the endoplasmic reticulum, drug metabolism via cytochrome P450 (CYP450), arachidonic acid metabolism, and ECM–receptor interactions. These findings suggest that Cd stress predominantly disrupts cellular transport and metabolic processes. Overall, our study provides comprehensive insights into the toxicological impact of Cd on P. canaliculata and emphasizes the importance of understanding the mechanisms underlying Cd toxicity in aquatic organisms. Full article

Poyang Lake is the largest freshwater lake in China and plays a significant ecological role. Deep-learning-based video surveillance can effectively monitor bird species on the lake, contributing to the local biodiversity preservation. To address the challenges of multi-scale object detection against complex backgrounds, such as a high density and severe occlusion, we propose a new model known as the YOLOv8-bird model. First, we use Receptive-Field Attention convolution, which improves the model’s ability to capture and utilize image information. Second, we redesign a feature fusion network, termed the DyASF-P2, which enhances the network’s ability to capture small object features and reduces the target information loss. Third, a lightweight detection head is designed to effectively reduce the model’s size without sacrificing the precision. Last, the Inner-ShapeIoU loss function is proposed to address the multi-scale bird localization challenge. Experimental results on the PYL-5-2023 dataset demonstrate that the YOLOv8-bird model achieves precision, recall, mAP@0.5, and mAP@0.5:0.95 scores of 94.6%, 89.4%, 94.8%, and 70.4%, respectively. Additionally, the model outperforms other mainstream object detection models in terms of accuracy. These results indicate that the proposed YOLOv8-bird model is well-suited for bird detection and counting tasks, which enable it to support biodiversity monitoring in the complex environment of Poyang Lake. Full article

We describe four new species of the fossil genus Dapalis (Ambassidae), Dapalis absconditus sp. nov., Dapalis octospinus sp. nov., Dapalis parvus sp. nov. and Dapalis quintus sp. nov., based on articulated skeletons with otoliths in situ from a freshwater habitat of the lower Oligocene of Raljin/Strelac (Serbia). Besides in body shape (e.g., body length, body depth, head length, preanal length), the species differ in morphological characters like, e.g., the serration of the preopercle, the length of the first two spines of the first dorsal and the anal fin and the morphology of the sagittal otoliths (e.g., ratio of otolith height to otolith length, ratio of otolith width to otolith length). Together with D. pauciserratus, also described from Raljin, these four species represent the most species-rich assemblage of freshwater Dapalis known so far. The compartmentalization of the internal structure of the spines reveals the close relationship of Dapalis and extant Ambassidae. Additionally, we discuss a new character from the ventral field of the otolith, a ventral depression, only found in species from Raljin. This new character is unique among the European Dapalis species and allows us to separate these five species into two species groups. Full article

The common carp (Cyprinus carpio), a major economic freshwater fish, is suffering from a variety of bacterial infectious diseases because of its high-density, factory and intensive farming patterns. Aeromonas veronii is the causative agent of high mortality in common carp, causing severe economic losses in aquaculture. However, the regulatory mechanisms involved in the response of common carp to this bacterial infection remain poorly understood. In this study, we compared mortality, blood serum LZM (Lysozyme) and IgM (Immunoglobulin M) levels and transcriptome patterns of head kidney tissues after infection with different concentrations of Aeromonas veronii. We observed that mortality increased progressively with an increasing pathogen concentration. The concentrations of blood serum LZM and IgM significantly increased after infection. A total of 13 and 925 differentially expressed genes (DEGs) were identified after infection with low (T4) and high (T9) concentrations of bacterial suspension, respectively. KEGG and GO analyses of the DEGs highlighted multiple immune-related signaling pathways. Weighted gene co-expression network analysis (WGCNA) revealed that 136 and 83 hub genes were related to blood serum LZM and IgM, respectively. Finally, the gene expression in the head kidney was validated via RT–qPCR to be consistent with the transcriptome. These results provide insights into the mechanisms of the immune response to infection with different concentrations of Aeromonas veronii and offer useful information for further studies on immune defense mechanisms in common carp. Full article

Trichodinidae, a prevalent group of protozoan ectoparasites in aquaculture, cause rapid mortality in fish hatcheries. Despite their significance, knowledge about these parasites in farmed fish in South America, especially in native species that are currently being domesticated for aquaculture, remains limited. This study morphologically characterized the Trichodinid species that are infecting Pacific fat sleeper (Dormitator latifrons) larvae and evaluated their impact on larval rearing. Four pairs of broodstock were induced with GnRHA implants and placed in tanks containing 200 L of freshwater, with a water temperature of 28 ± 1.0 °C and a dissolved oxygen level of 4.00 ± 1.23 mg L⁻¹, with partial water exchanges being performed daily. The larvae hatched 7 to 8 h after fertilization and were transferred to tanks containing water with the same quality parameters. Twelve hours post-hatching, the presence of Trichodina was observed. Every 24 h, 60 larvae per tank (n = 180 per treatment) were sedated, and larval wet mounts were prepared, air-dried at room temperature, and impregnated with silver nitrate. Infection parameters and daily mortality were calculated. Trichodina was observed to parasitize the pelvic fins, caudal fins, and heads of fish larvae, which showed lethargy and erratic swimming movements. The Trichodina species showed a daily increase in the infection parameters, and a 58% rate of larval mortality was observed at the fourth day post-hatching (dph) in the infected tanks. In captivity, D. latifrons larvae typically survive up to 7 days post-hatching (dph) before reaching their point of no return due to the lack of adequate diet and feeding regimes. However, our study indicates that Trichodina infestation accelerates mortality, causing infected larvae to die more quickly than uninfected ones. Full article

The southern Gabès aquifer in southeastern Tunisia faces significant stress due to unsustainable groundwater extraction. This study employs a SEAWAT model to evaluate groundwater losses, salinization mechanisms, and the interaction between the confined aquifer and the Mediterranean Sea. The model, incorporating well pumping rates, regional freshwater inflows from the Matmata Mountain Range, and the Mediterranean Sea boundary, demonstrated high accuracy in simulating hydraulic heads. Findings reveal that regional inflow is only half of the current pumping rate, indicating unsustainable groundwater use. The study also assessed salinity dynamics by modeling the Mediterranean Sea as a constant head and salinity boundary. Results suggest limited exchange between the aquifer and the sea, challenging previous assumptions. While the immediate risks of salinization are low, continued over-extraction could compromise the aquifer’s long-term sustainability. This research highlights the need for stricter local groundwater management, offers insights into regional coastal aquifer interactions, and contributes to global discussions on managing stressed aquifer systems. Full article

Plastic is a growing global environmental problem. While much of the focus of anthropogenic microparticles has focused on microplastics and their occurrence in marine systems, anthropogenic microparticles are found in freshwater systems. The Charles River is a highly impacted and historically important river within Massachusetts and runs for 80 miles within the state of MA through a variety of land uses. Microparticle concentrations were found to vary along the length of the river and ranged in concentrations from 1–19 pieces/L, with generally higher concentrations downstream. Microfibers were the dominant (72%) type of microparticles found, and the majority (avg 76%) of microparticles were synthetic. The highest estimated flux of microparticles occurred in May, with an estimated flux of 2 billion microparticles per day via the Charles River into the Boston Harbor. The average annual concentration of microparticles was correlated with land use, with higher concentrations occurring in regions with higher impervious coverage and in areas designated as industrial or high-density residential. Polyester, polypropylene, and polyamides were the dominant plastic polymers. However, seasonal changes in the relative importance of each polymer, along with changes in the abundance and flux rates, indicate that there would be seasonal variability in the type of microparticles exported. Changes in composition occurred between stations and between the head and mouth of the river, suggesting particle retention due to either deposition, degradation, or biological consumption. Full article

Chlorpyrifos, an organophosphate insecticide widely used to control agricultural pests, poses a significant environmental threat due to its toxicity and persistence in soil and water. Our work aimed to evaluate the acute (survival) and chronic (regeneration, locomotion, and reproduction) toxicity of chlorpyrifos to the non-target freshwater planarian Girardia tigrina. The 48 h lethal concentration (LC₅₀) of the commercial formulation, containing 480 g L⁻¹ of chlorpyrifos, the active ingredient, was determined to be 622.8 µg a.i. L⁻¹ for planarians. Sublethal effects were translated into a significant reduction in locomotion and delayed head regeneration (lowest observed effect concentration—LOEC = 3.88 µg a.i. L⁻¹). Additionally, chlorpyrifos exposure did not affect planarian fecundity or fertility. Overall, this study demonstrates the potential of chlorpyrifos-based insecticides to harm natural populations of freshwater planarians at environmentally relevant concentrations. The observed toxicity emphasizes the need for stricter regulations and careful management of chlorpyrifos usage to mitigate its deleterious effects on aquatic ecosystems. By understanding the specific impacts on non-target organisms like G. tigrina, we can make more informed suggestions regarding the usage and regulation of organophosphate insecticides, ultimately promoting sustainable agricultural practices and environmental conservation. Full article

There is a growing concern about limited water supply and water scarcity in many river basins across the world. The agricultural sector is the largest user of freshwater on the planet, with a growing amount of water extracted for livestock systems. Here, we use data from the GLEAM model to advance previous studies that estimated livestock water footprints by quantifying water use for feed production, animal drinking water, and animal service water. We additionally account for the role of trade in accounting for feed water allocations to different animals in different countries and make use of a hydrologic model to estimate feed irrigation water requirements for individual crops at a high spatial resolution. Lastly, we estimate the contribution of livestock water abstractions to water stress at a small river basin scale for the entire globe. We find that feed production water accounts for the majority (>90%) of global livestock water withdrawals, though there is regional variation. Similarly, we find large regional variation in the water consumption per head by livestock species. Despite consuming >200 km³ of water per year, we find that reducing water use in the livestock system alone will rarely reduce water stress in high-stress basins. This study highlights the need for quantifying locally relevant water use and water stress metrics for individual livestock systems. Full article