Search Results (75)

The mantle of bivalves plays a fundamental role in shell formation and maintenance through biomineralization. Experiments performed on mantle–shell preparations using different experimental techniques revealed the presence of phosphorus (P)-containing compounds in the shell as the first mineral phase formed at the growing edge of the periostracum in the freshwater bivalve Limnoperna fortunei. The low P concentration in the shells suggests that phosphate is restricted to the growth regions and occurs at concentrations too low to be detected by techniques such as X-ray diffraction (XRD). Nevertheless, a crystal morphology closely resembling that of hydroxyapatite (HAp) was identified at the shell growth front, and a Ca/P ratio of 1.67, consistent with HAp, was determined in two of these regions. Fourier transform infrared (FTIR) spectroscopy also revealed the principal and most intense absorption band of the phosphate group (PO₄³⁻) at 1024 cm⁻¹. Enzymes such as carbonic anhydrase (CA), or proteins with equivalent functions, are likely involved in phosphate dissolution and the subsequent precipitation of calcium carbonate. In addition, the occurrence of calcium phosphate was confirmed in the shells of the marine bivalve Perna perna. Phosphate dissolution and carbonate precipitation during biomineralization suggest two important evolutionary advantages: first, the release and availability of phosphate, an essential nutrient for energy production and other metabolic functions; and second, the formation of a calcium carbonate shell, a structure indispensable for the protection, mechanical support, and survival of mollusks. Full article

Unrinsed surimi production has emerged as a sustainable alternative to conventional rinsed surimi due to its substantial water savings, reduced nutrient loss, and lower environmental footprint. However, poor gel strength and water-holding capacity remain major bottlenecks limiting its industrial application. This study investigated the effects of κ-carrageenan (κ-CG) on the rheological properties, textural characteristics, water distribution, intermolecular interactions, and microstructure of unrinsed surimi gels. The results showed that κ-CG enhanced gel properties in a concentration-dependent manner. At 0.75% κ-CG, gel strength increased to 47.0 g·cm (a 2.2-fold increase vs. control), water holding capacity (WHC) reached 97.9%, and cooking loss decreased to 4.0%. In contrast, at 1.0% κ-CG, gel strength and hardness further increased, but WHC declined slightly. Low-field nuclear magnetic resonance analysis revealed that κ-CG promoted the conversion of free water to immobilized water, with the relative peak area of T₂₂ (immobilized water) increasing from 85.9% to 88.9% at 0.75% κ-CG. Protein solubility measurements indicated that hydrophobic interactions and disulfide bonds appeared to be the major contributors stabilizing the gel network. FTIR revealed enhanced hydrogen bonding via an O–H red shift and intensification with κ-CG, and amide I deconvolution showed that 0.75% κ-CG maximized β-sheet content while reducing α-helix, indicating ordered protein reorganization during heating. Quantitative SEM analysis further verified that 0.75% κ-CG produced the densest protein network with the maximum fractal dimension and minimum lacunarity, alongside reduced average pore area and porosity. These findings demonstrate that κ-CG at an appropriate level effectively improves the gel properties of unrinsed tilapia surimi by strengthening intermolecular interactions and optimizing water distribution, offering a practical approach for developing high-quality surimi products. 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

Commensalism, a frequent type of interaction among freshwater invertebrates, remains poorly studied. Some turbellarians (Platyhelminthes: Temnocephalidae) are specialized obligate commensals of crustaceans, mollusks, insects, and turtles. In the Neotropics, Temnocephala iheringi inhabits the mantle cavity of snails (Mollusca: Gastropoda) from Pantanal (Brazil) to the Pampean region of Argentina, where several species serve as hosts. This study aimed to molecularly characterize several populations of T. iheringi and to analyze their genetic and morphological variability across different host species and geographic areas. Using the mitochondrial COI marker, we assessed populations associated with five of its seven known host species through phylogenetic reconstructions, species delimitation approaches, and haplotype network analyses. Combined with morphological data, results support COI as an effective identification tool for Temnocephalidae. Several genetic lineages were identified and were largely congruent with collection localities. However, specimens associated with hosts displaying high dispersal capabilities (i.e., Pomacea canaliculata and P. maculata) showed low mitochondrial genetic differentiation and minimal phylogenetic structure across large distances, which may be consistent with recent dispersal and/or ongoing connectivity among populations. These findings provide new insights into the evolutionary dynamics of this specific temnocephalid–snail association. Given that some hosts are highly invasive and even considered pests in several countries, the data and genetic sequences generated in this study may prove valuable for future research on symbiont diversity and dispersal. Full article

Caffeine (CAF) is a widely consumed psychostimulant known to modulate adenosine receptors and neurotransmitter systems, although its effects in invertebrates remain poorly understood. Environmentally relevant concentrations (5, 30, and 50 µg/L) are associated with altered behavior, including locomotion, exploration, and feeding, in the freshwater gastropod Physella acuta. This study examined molecular responses underlying these effects. Adult snails were exposed to CAF for 24 h and 7 days. Gene expression related to the nervous system and stress pathways was analyzed by RT-PCR, including A1AR, ADORA2B, AChE, GLRA2, DRD2, RYR, HSD11β, HSP70, SLC6A2, and SLC6A1. After 24 h, exposure to 50 µg/L CAF altered A1AR expression and caused downregulation of AChE, GLRA2, and DRD2, associated with observed behavioral changes. A1AR upregulation may indicate compensatory adjustment in adenosine signaling. After 7 days, A1AR remained upregulated, while genes linked to inhibitory neurotransmission showed partial recovery. Increased expression of genes involved in dopamine regulation and steroid metabolism suggested physiological adaptation. Overall, CAF induced dose- and time-dependent molecular responses in P. acuta, linking neurochemical disruption with behavioral changes and highlighting its ecological risk as an emerging freshwater contaminant. Full article

Boule is the ancestral member of the Deleted in Azoospermia (DAZ) family and is pivotal for gametogenesis and male fertility in most animals. However, there is a dearth of information on molluscan boule. Here, we identified a counterpart (Pcbol) from the genome of Pomacea canaliculata, which has emerged as a cosmopolitan alien species and notorious pest that causes devastating damage to aquatic biodiversity, freshwater ecosystems and crop production in invaded ranges. This study aimed to investigate the biological roles of Pcbol in male reproduction and to decipher the molecular mechanisms underpinning its modulation via dsRNA-delivered RNA interference (RNAi). The bioinformatic analysis showed that the Pcbol genomic sequence is 12,934 nt in length, harboring an open reading frame of 294 nt that encodes 97 aa residues, with an RRM domain evolutionarily conserved among molluscan orthologues. Spatiotemporal expression profiling indicated the predominant abundance of Pcbol in adult males and testis tissues. dsPcbol, injected at a dose of 4 μg/per snail for 5 days, yielded optimal silencing at both transcript and translation levels of Pcbol, as revealed by qRT-PCR and Western blotting. Immunofluorescence echoed a pronounced reduction in Pcbol signal intensity following RNAi. In addition to the arrested reproductive gland phenotype, the number of sperm cells substantially dwindled upon dsPcbol treatment relative to the dsGFP control. In biochemical and fecundity assays, Pcbol depletion triggered a significant decrease in Te/SP/Arg content and suppressed the number of deposited eggs and hatchability. Furthermore, spermatogenic genes like CDC25/TSSK1/SPATA17/DDX4/Dmrt2/Sox2/Kelch10/SPO11 displayed considerable downregulation post Pcbol silencing, with molecular docking predicting a strong affinity between CDC25 and Pcbol. These molecular modules may interact with Pcbol to mediate knockdown effects on spermatogenesis dysfunction. Collectively, our findings not only confirmed that boule was indispensable for spermatogenesis and male fertility in a mollusk, but also highlighted the Pcbol-based male sterile technique (MST), which can be incorporated into precision pest management (PPM) strategies for sustainable control of P. canaliculata. Full article

The family Flaviviridae has been expanded to include the highly divergent flavi-like viruses into three new families, Flaviviridae, Pestiviridae, and Hepaciviridae, in the order Amarillovirales. Classical flavivirids are small, enveloped viruses with positive-sense ssRNA genomes lacking a 3′ poly(A) tail and ~9.0–13.0 kb in length, with a single open reading frame (ORF) encoding structural proteins at the N-terminus and nonstructural proteins at the C-terminus. Members infect a wide range of mammals, birds, and insects, and many are host-specific and pathogenic. Although the RNA-directed RNA polymerase (RdRP) gene sequences of the flavi-like viruses group phylogenetically with those of classical flavivirids, flavi-like viruses often encode larger polyproteins and possess substantially longer genomes of up to ~40 kb, and some have a 3′ poly(A) tail. Their host range extends across the whole animal kingdom and angiosperm plants. This review describes the reported flavi-like viruses of aquatic animals, providing a meaningful update on all three new families in Amarillovirales that have been discovered using metagenomics in fish, crustaceans, mollusks, and echinoderms. These amarilloviruses include pathogenic viruses of aquatic animals, such as Cyclopterus lumpus virus (CLuV) detected in moribund lumpfish, and infectious precocity virus (IPV) found in iron prawn syndrome (IPS)-affected farmed giant freshwater prawns. Full article

Macroalgae plays a significant role in the formulation of innovative and environmentally sustainable approaches to address food challenges. Specifically, green macroalgae serve as dietary supplements aimed at improving the health, growth, and feeding efficiency of various species of marine and freshwater fishes, as well as mollusks. The effects of Chaetomorpha linum extract (CLE) on growth performance, physiological responses, and disease resistance are studied in Bellamya bengalensis against Aeromonas hydrophila. In this experiment, adult B. bengalensis (4412 ± 165.25 mg) were randomly divided into 15 rectangular glass aquariums (35 snail/aquaria; 45 L capacity) and their basal diet was supplemented with different levels of CLE, including 0 (CLE0), 1 (CLE1), 2 (CLE2), 3 (CLE3), and 4 (CLE4) g/kg for 60 days. The growth performance in the CLE3 dietary group was significantly higher that of the CLE0 group, exhibiting both linear and quadratic trends in relation to dietary CLE levels (p < 0.05). The activities of pepsin, amylase, and lipase were found to be highest in CLE3 and lowest in CLE0. Both linear and quadratic responses to dietary CLE levels in digestive enzymes were observed (p < 0.05). The activities of superoxide dismutase and catalase in the hepatopancreas were found to be elevated in snails due to the synergistic effect of the supplemented CLE diet. Among different levels of diet given, CLE2-supplemented snails showed an increase in their enzyme activity (p < 0.05). Interestingly, all the CLE-treated snails expressed elevated levels of mucus lysozyme and mucus protein when compared to control (p < 0.05). Additionally, hepatopancreatic acid phosphatase and alkaline phosphatase activity were elevated in snails consuming CLE3 (p < 0.05). The transcription levels of immune-related genes, including mucin-5ac and cytochrome, were significantly elevated in snails that were fed a diet supplemented with 2–4 g of CLE/kg. Furthermore, the transcription level of the acid phosphatase-like 7 protein gene also increased in snails receiving CLE-supplemented diets. After a 14-day period of infection, snails that consumed a diet supplemented with 3–4 g/kg of CLE exhibited a notable increase in survival rates against virulent A. hydrophila. Based on the above findings, it is suggested that a diet supplemented with 3 g/kg of CLE may enhance growth, antioxidant and immune defense, and disease resistance in the freshwater snail B. bengalensis. Full article

Niclosamide has been the primary molluscicide for schistosomiasis control for over 50 years, but its chronic effects on inter-organ interactions in non-target mollusks remain poorly understood. Cipangopaludina cathayensis, a dominant species in East Asian schistosomiasis-endemic regions, was chronically exposed to environmentally relevant concentrations of niclosamide to assess its toxic effects. Digestive glands accumulated more niclosamide than the foot tissues. Prolonged exposure was associated with metabolic impairment of the digestive glands, characterized by tubular atrophy, inflammatory reactions, and depletion of nutrient components. Foot tissues exhibited epithelial lesions and muscle fiber atrophy. Alterations in foot structure were associated with changes in digestive gland nutrient status. Niclosamide exposure may weaken the metabolic coupling between these organs, thereby impairing locomotor function. At the population level, persistent niclosamide exposure may destabilize mollusk trophic-level populations, ultimately leading to ecological consequences. Our findings demonstrate the toxicological risks of niclosamide to freshwater mollusks. Full article

The freshwater drum (Aplodinotus grunniens) is a promising aquaculture species due to its strong environmental adaptability, tolerance to low temperatures, rapid growth rate, high nutritional value, high-quality texture (garlic-clove-shaped flesh), and absence of intermuscular bones. Nevertheless, processing technologies related to freshwater drum remain largely unexplored. Salting pretreatment serves as a viable strategy for enhancing the quality attributes of frozen fish products. This study investigated the effects of different sodium chloride (NaCl) pickling concentrations (0.25, 1, and 3 mol/L) on the physicochemical properties and quality attributes of frozen–thawed freshwater drum (Aplodinotus grunniens). Results indicated that elevated NaCl concentrations (1–3 mol/L) significantly (p < 0.05) shortened the transit time through the maximum ice crystal formation zone during freezing, effectively mitigating structural damage to myofibrillar networks. As the NaCl concentration increased from 0 to 3 mol/L, the water content decreased from 71.26 ± 0.22% to 68.64 ± 0.50%, while the salt content increased from 0.31 ± 0.01% to 8.46 ± 0.12%. Pickling pretreatment markedly enhanced water-holding capacity and improved texture profiles, including hardness, springiness, gumminess, and chewiness. Histological analysis revealed preserved myofibril integrity in high-salt-treated samples, supported by reduced fluorescence intensity of myofibrillar proteins, indicating mitigated freeze-induced denaturation. Low-field NMR confirmed salt-induced redistribution of water states, with decreased free water proportion. Our results identify that pretreatment with NaCl at concentrations ≥ 1 mol/L is an effective strategy to preserve the post-thaw quality. Due to 3 mol/L NaCl resulting in a relatively high salt content, 1 mol/L NaCl pretreatment is more suitable for maintaining the quality of freeze–thawed freshwater drums. Full article

Ecosystems and biodiversity around the globe face multiple threats, including climate change and invasive species. Non-native species are known for their resilience to disturbances and their ability to thrive more successfully than native species in urbanized or otherwise disturbed areas, and some of them can become invasive. It is a complex challenge to detect, manage, and control such species, which require coordinated efforts from society, government, and the academic community. In this study, the eMIAS (South American Invasive Mollusks Specialists) research group (27 experts from seven South American countries) aim to provide foundational knowledge for management of these species. We compiled and synthesized information on the mollusc species that are native to South America and that have been introduced to other regions of the world. A total of 29 species were detected, including 10 marine, 10 freshwater, and 9 terrestrial. For each species, the area of origin, date and place of introduction, and current distribution were determined. We could determine that (1) most of these introductions have occurred in connection with globalization processes, such as an increase in trade. (2) The potential source regions of those 29 species are also areas that received non-native species from elsewhere (e.g., Europe, Asia). (3) Regions where species introductions have taken place are subject to the impacts of climate change and/or urbanization. Full article

Bisphenol A (BPA) and its substitutes have been identified as endocrine-disrupting chemicals (EDCs). However, little information is available on their reproductive endocrine disruptive effects in mollusks. This study cloned the full-length sequence (2434 bp) of the estrogen-related receptor (ERR) gene in the freshwater bivalve Corbicula fluminea and performed a bioinformatics analysis and tissue-specific expression analysis. We further examined the expression of the CfERR gene after exposure to E2, BPA, and their substitutes (BPS, BPF, and BPAF) at 1, 10, and 100 μg/L for 0, 1, 7, 14, 21, and 28 days. The results showed that CfERR is a nuclear protein with a typical structure. Phylogenetic analysis indicated a high degree of similarity among bivalve species. The high expression of CfERR in the gonad suggested its important role in reproductive regulation. The exposure experiment confirmed that CfERR showed a time- and dose-dependent upregulation in response to all pollutants, with BPS and BPAF exhibiting stronger estrogenic interference effects. This study facilitates a better understanding of the reproductive regulation of bivalves and provides data to support the toxicity evaluation of BPA and its substitutes. Full article

Perfluorooctane sulfonate (PFOS), which is known for its environmental persistence and bioaccumulation, poses substantial impacts to aquatic ecosystems. This study assesses the toxic effects of PFOS in the freshwater snail Lanistes carinatus using biomarkers for antioxidant activity, neurotoxicity, and tissue damage. Snails exposed to PFOS (1, 3, 10 mg/L for 14 days) displayed lipid peroxidation (LPO) levels that increased by 16.3–67.5%, and malondialdehyde (MDA) levels that rose by 10.0–58.4%, indicating oxidative damage. Enzyme activities for glutathione S-transferase (GST), glutathione peroxidase (GPx), and catalase (CAT) increased, ranging from 10.0 to 58.3%, 10.0 to 58.4%, and 10.0 to 58.4%, respectively, whereas levels of reduced glutathione (GSH) dropped by 15.0–41.5% and Superoxide dismutase (SOD) decreased by 15.0–41.4%. The activity of acetylcholinesterase (AchE) was reduced by a range of 15.0–40.0%, suggesting neurotoxic effects. Histopathological changes in the digestive gland were also noted. Further research on the effects of PFOS on mollusks is required, and investigation into sex-specific toxicity is needed. This shed light on L. carinatus as a sentinel species, providing helpful information for the monitoring and regulation of PFOS in aquatic environments. Full article