Marine transmissible cancer navigates urbanized waters, threatening spillover.

Inter-individual transmission of cancer cells represents a unique form of microparasites increasingly reported in marine bivalves. In this study, we sought to understand the ecology of the propagation of Mytilus trossulus Bivalve Transmissible Neoplasia 2 (MtrBTN2), a transmissible cancer affecting four Mytilus mussel species worldwide. We investigated the prevalence of MtrBTN2 in the mosaic hybrid zone of M. edulis and M. galloprovincialis along the French Atlantic coast, sampling contrasting natural and anthropogenic habitats. We observed a similar prevalence in both species, probably due to the spatial proximity of the two species in this region. Our results showed that ports had higher prevalence of MtrBTN2, with a possible hotspot observed at a shuttle landing dock. No cancer was found in natural beds except for two sites close to the hotspot, suggesting spillover. Ports may provide favourable conditions for the transmission of MtrBTN2, such as high mussel density, stressful conditions, sheltered and confined shores or buffered temperatures. Ships may also spread the disease through biofouling. Our results suggest ports may serve as epidemiological hubs, with maritime routes providing artificial gateways for MtrBTN2 propagation. This highlights the importance of preventing biofouling on docks and ship hulls to limit the spread of marine pathogens hosted by fouling species.

Integrative phylogenetic, phylogeographic and morphological characterisation of the Unio crassus species complex reveals cryptic diversity with important conservation implications.

The global decline of freshwater mussels and their crucial ecological services highlight the need to understand their phylogeny, phylogeography and patterns of genetic diversity to guide conservation efforts. Such knowledge is urgently needed for Unio crassus, a highly imperilled species originally widespread throughout Europe and southwest Asia. Recent studies have resurrected several species from synonymy based on mitochondrial data, revealing U. crassus to be a complex of cryptic species. To address long-standing taxonomic uncertainties hindering effective conservation, we integrate morphometric, phylogenetic, and phylogeographic analyses to examine species diversity within the U. crassus complex across its entire range. Phylogenetic analyses were performed using cytochrome c oxidase subunit I (815 specimens from 182 populations) and, for selected specimens, whole mitogenome sequences and Anchored Hybrid Enrichment (AHE) data on âˆ¼ 600 nuclear loci. Mito-nuclear discordance was detected, consistent with mitochondrial DNA gene flow between some species during the Pliocene and Pleistocene. Fossil-calibrated phylogenies based on AHE data support a Mediterranean origin for the U. crassus complex in the Early Miocene. The results of our integrative approach support 12 species in the group: the previously recognised Unio bruguierianus, Unio carneus, Unio crassus, Unio damascensis, Unio ionicus, Unio sesirmensis, and Unio tumidiformis, and the reinstatement of five nominal taxa: Unio desectusstat. rev., Unio gontieriistat. rev., Unio mardinensisstat. rev., Unio nanusstat. rev., and Unio vicariusstat. rev. Morphometric analyses of shell contours reveal important morphospace overlaps among these species, highlighting cryptic, but geographically structured, diversity. The distribution, taxonomy, phylogeography, and conservation of each species are succinctly described.

Gut microbiome resilience of green-lipped mussels, Perna canaliculus, to starvation.

Host gut microbiomes play an important role in animal health and resilience to conditions, such as malnutrition and starvation. These host-microbiome relationships are poorly understood in the marine mussel Perna canaliculus, which experiences significant variations in food quantity and quality in coastal areas. Prolonged starvation may be a contributory factor towards incidences of mass mortalities in farmed mussel populations, resulting in highly variable production costs and unreliable market supplies. Here, we examine the gut microbiota of P. canaliculus in response to starvation and subsequent re-feeding using high-throughput amplicon sequencing of the 16S rRNA gene. Mussels showed no change in bacterial species richness when subjected to a 14-day starvation, followed by re-feeding/recovery. However, beta bacteria diversity revealed significant shifts (PERMANOVA p-value < 0.001) in community structure in the starvation group and no differences in the subsequent recovery group (compared to the control group) once they were re-fed, highlighting their recovery capability and resilience. Phylum-level community profiles revealed an elevation in dominance of Proteobacteria (ANCOM-BC p-value <0.001) and Bacteroidota (ANCOM-BC p-value = 0.04) and lower relative abundance of Cyanobacteria (ANCOM-BC p-value = 0.01) in the starvation group compared to control and recovery groups. The most abundant genus-level shifts revealed relative increases of the heterotroph Halioglobus (p-value < 0.05) and lowered abundances of the autotroph Synechococcus CC9902 in the starvation group. Furthermore, a SparCC correlation network identified co-occurrence of a cluster of genera with elevated relative abundance in the starved mussels that were positively correlated with Synechococcus CC9902. The findings from this work provide the first insights into the effect of starvation on the resilience capacity of Perna canaliculus gut microbiota, which is of central importance to understanding the effect of food variation and limitation in farmed mussels.

Multidrug resistant Vibrio spp. identified from mussels farmed for human consumption in Central Italy.

AIMS: This study investigated phenotypic and genotypic antimicrobial resistance profiles of Vibrio strains identified from Mytilus galloprovincialis farmed for human consumption in the Adriatic Sea Central Italy. METHODS AND RESULTS: A total of 475 mussels (M. galloprovincialis) were involved in the present study, and culture-dependent microbiological methods permitted to identify a total of 50 Vibrio strains that were tested for antibiotic susceptibility followed by the genetic determinant detections. Antibiograms showed resistance against ampicillin (36.0%), amoxicillin-clavulanic acid (30.0%), gentamycin (14.0%), and imipenem (18.0%). Biomolecular assays amplified a total of 264 antibiotic resistance genes harbored by both susceptible and resistant Vibrio species. Among resistance genes, aacC2 (62.0%) and aadA (58.0%) for aminoglycosides, blaTEM (54.0%) for beta-lactams, qnrS (24.0%) for quinolones, tetD (66.0%) for tetracyclines, and vanB (60.0%) for glycopeptides were mainly amplified by PCR assays. CONCLUSIONS: Vibrio genus is involved in the antibiotic resistance phenomenon diffusion in the aquatic environments, as demonstrated by the harboring of many genetic determinants representing a kind of genetic "dark world".

Identification and expression analysis of two steamer-like retrotransposons in the Chilean blue mussel (Mytilus chilensis).

BACKGROUND: Disseminated neoplasia (DN) is a proliferative cell disorder of the circulatory system of bivalve mollusks. The disease is transmitted between individuals and can also be induced by external chemical agents such as bromodeoxyuridine. In Mya arenaria, we have cloned and characterized an LTR-retrotransposon named Steamer. Steamer mRNA levels and gene copy number correlates with DN and can be used as a marker of the disease. So far, the only mollusk where a retrotransposon expression relates to DN is Mya arenaria. On the other hand, it has been reported that the Chilean blue mussel Mytilus chilensis can also suffers DN. Our aim was to identify retrotransposons in Mytilus chilensis and to study their expression levels in the context of disseminated neoplasia. RESULTS: Here we show that 7.1% of individuals collected in August 2018, from two farming areas, presents morphological characteristics described in DN. Using Steamer sequence to interrogate the transcriptome of M. chilensis we found two putative retrotransposons, named Steamer-like elements (MchSLEs). MchSLEs are present in the genome of M. chilensis and MchSLE1 is indeed an LTR-retrotransposon. Neither expression, nor copy number of the reported MchSLEs correlate with DN status but both are expressed at different levels among individual animals. We also report that in cultured M. chilensis haemocytes MchSLEs1 expression can be induced by bromodeoxyuridine. CONCLUSIONS: We conclude that SLEs present in Mytilus chilensis are differentially expressed among individuals and do not correlate with disseminated neoplasia. Treatment of haemocytes with a stressor like bromodeoxyuridine induces expression of MchSLE1 suggesting that in Mytilus chilensis environmental stressors can induce activation of LTR-retrotransposon.

Quantification of Photobacterium swingsii and characterisation of disease progression in the New Zealand Greenshell™ mussel, Perna canaliculus.

Greenshell™ mussels (Perna canaliculus) are endemic to New Zealand and support the largest aquaculture industry in the country. Photobacterium swingsii was isolated and identified from moribund P. canaliculus mussels following a mass mortality event. In this study, a challenge experiment was used to characterise, detect, and quantify P. swingsii in adult P. canaliculus following pathogen exposure via injection into the adductor muscle. A positive control (heat-killed P. swingsii injection) was included to account for the effects of injection and inactive bacterial exposure. Survival of control and infected mussels remained 100% during 72-hour monitoring period. Haemolymph was sampled for bacterial colony counts and haemocyte flow cytometry analyses; histology sections were obtained and processed for histopathological assessments; and adductor muscle, gill, digestive gland were sampled for quantitative polymerase chain reaction (PCR) analyses, all conducted at 12, 24, 48 h post-challenge (hpc). The most profound effects of bacterial injection on mussels were seen at 48 hpc, where mussel mortality, haemocyte counts and haemolymph bacterial colony forming were the highest. The quantification of P. swingsii via qPCR showed highest levels of bacterial DNA at 12 hpc in the adductor muscle, gill, and digestive gland. Histopathological observations suggested a non-specific inflammatory response in all mussels associated with a general stress response. This study highlights the physiological effects of P. swingsii infection in P. canaliculus mussels and provides histopathological insight into the tissue injury caused by the action of injection into the adductor muscle. The multi-technique methods used in this study can be applied for use in early surveillance programs of bacterial infection on mussel farms.

Benthic invaders control the phosphorus cycle in the world's largest freshwater ecosystem.

The productivity of aquatic ecosystems depends on the supply of limiting nutrients. The invasion of the Laurentian Great Lakes, the world's largest freshwater ecosystem, by dreissenid (zebra and quagga) mussels has dramatically altered the ecology of these lakes. A key open question is how dreissenids affect the cycling of phosphorus (P), the nutrient that limits productivity in the Great Lakes. We show that a single species, the quagga mussel, is now the primary regulator of P cycling in the lower four Great Lakes. By virtue of their enormous biomass, quagga mussels sequester large quantities of P in their tissues and dramatically intensify benthic P exchanges. Mass balance analysis reveals a previously unrecognized sensitivity of the Great Lakes ecosystem, where P availability is now regulated by the dynamics of mussel populations while the role of the external inputs of phosphorus is suppressed. Our results show that a single invasive species can have dramatic consequences for geochemical cycles even in the world's largest aquatic ecosystems. The ongoing spread of dreissenids across a multitude of lakes in North America and Europe is likely to affect carbon and nutrient cycling in these systems for many decades, with important implications for water quality management.

Photoaging Elevated the Genotoxicity of Polystyrene Microplastics to Marine Mussel Mytilus trossulus (Gould, 1850).

Micro-sized particles of synthetic polymers (microplastics) are found in all parts of marine ecosystems. This fact requires intensive study of the degree of danger of such particles to the life activity of hydrobionts and needs additional research. It is evident that hydrobionts in the marine environment are exposed to microplastics modified by biotic and abiotic degradation. To assess the toxic potential of aging microplastic, comparative studies were conducted on the response of cytochemical and genotoxic markers in hemocytes of the mussel Mytilus trossulus (Gould, 1850) after exposure to pristine and photodegraded (UV irradiation) polystyrene microparticles (µPS). The results of cytochemical tests showed that UV-irradiated µPS strongly reduced metabolism and destabilized lysosome membranes compared to pristine µPS. Using a Comet assay, it was shown that the nuclear DNA of mussel hemocytes showed high sensitivity to exposure to both types of plastics. However, the level of DNA damage was significantly higher in mussels exposed to aging µPS. It is suggested that the mechanism of increased toxicity of photo-oxidized µPS is based on free-radical reactions induced by the UV irradiation of polymers. The risks of toxic effects will be determined by the level of physicochemical degradation of the polymer, which can significantly affect the mechanisms of toxicity.

Characterization of NR1J1 Paralog Responses of Marine Mussels: Insights from Toxins and Natural Activators.

The pregnane X receptor (PXR) is a nuclear hormone receptor that plays a pivotal role in regulating gene expression in response to various ligands, particularly xenobiotics. In this context, the aim of this study was to shed light on the ligand affinity and functions of four NR1J1 paralogs identified in the marine mussel Mytilus galloprovincialis, employing a dual-luciferase reporter assay. To achieve this, the activation patterns of these paralogs in response to various toxins, including freshwater cyanotoxins (Anatoxin-a, Cylindrospermopsin, and Microcystin-LR, -RR, and -YR) and marine algal toxins (Nodularin, Saxitoxin, and Tetrodotoxin), alongside natural compounds (Saint John's Wort, Ursolic Acid, and 8-Methoxypsoralene) and microalgal extracts (Tetraselmis, Isochrysis, LEGE 95046, and LEGE 91351 extracts), were studied. The investigation revealed nuanced differences in paralog response patterns, highlighting the remarkable sensitivity of MgaNR1J1γ and MgaNR1J1δ paralogs to several toxins. In conclusion, this study sheds light on the intricate mechanisms of xenobiotic metabolism and detoxification, particularly focusing on the role of marine mussel NR1J1 in responding to a diverse array of compounds. Furthermore, comparative analysis with human PXR revealed potential species-specific adaptations in detoxification mechanisms, suggesting evolutionary implications. These findings deepen our understanding of PXR-mediated metabolism mechanisms, offering insights into environmental monitoring and evolutionary biology research.

The role of warming in modulating neodymium effects on adults and sperm of Mytilus galloprovincialis.

The use of rare earth elements (REEs) has been increasing and one of the most used is neodymium (Nd). Being an emergent contaminant, its negative impacts are poorly understood. Aquatic organisms are also threatened by climate change-related factors, as is the case of warming, which can change the effects of REEs. Thus, the impacts of Nd, warming, and the combination of both stressors were studied in adult mussels and sperm of the species Mytilus galloprovincialis, after an exposure period of 28 days (adults) and 30 min (sperm). The effects were evaluated through the analysis of biochemical and histopathological alterations in adults and biochemical and physiological responses given by sperm. The results showed that mussels only activated their biotransformation capacity when exposed to the stressors acting alone, which was insufficient to avoid lipid peroxidation. Furthermore, warming (alone and combined with Nd) also produces damage to proteins. The digestive gland was the most sensitive organ to Nd, presenting several histopathological alterations. In the case of sperm, all stressors induced lipid peroxidation, a higher oxygen demand, and a decrease in velocity, even if the sperm viability was maintained. It seems that warming influenced the effects of Nd to some extent. The present findings contribute significantly to the field of REEs environmental toxicology by offering valuable insights into the impacts of Nd on various biological levels of mussels. Additionally, within the context of climate change, this study sheds light on how temperature influences the effects of Nd. The obtained results indicate that both stressors can potentially compromise the overall health of mussel populations, thereby affecting other species reliant on them for food and habitat. Moreover, this study highlights impaired sperm health, which could adversely affect their reproductive capacity and ultimately lead to population decline.

Bisphenol a (BPA) aggravate the adverse effect on physiological and biochemical response in freshwater mussel potomida littoralis.

Bisphenol A (BPA) is a chemical compound extensively employed in plastic manufacturing, and this pollutant has been detected in diverse aquatic organisms, notably bivalves. In order to comprehend the ecological and toxicological consequences of BPA Bisphenol A in these organisms, it is essential to examine the physiological and biochemical effects and identify areas where our understanding is lacking. This knowledge is crucial for determining the environn ental threat posed by bisphenol A and assisting decision-makers in establishing the appropriate priorities. This investigation aimed to assess the impact of BPA on the biochemical and physiological parameters of the freshwater mussel Potomida littoralis. In a laboratory setting, mussels were subjected to two different levels of BPA (20 and 100 µg/L) for a duration of 21 days. Filtration rate was calculated from the clearance of neutral red, fed to mussels at different BPA concentrations. The mussel's filtration rate capacity declined as BPA exposure intensified, potentially due to the mussel's attempt to close its valves and minimize BPA absorption, thus preventing cellular damage. In the digestive gland tissue, key antioxidant and detoxification defenses, including catalase (CAT) activity, glutathione-S-transferase (GST) activity, and levels of H2O2 and glutathione (GSH), were activated, particularly at the 100 µg/L BPA concentration. This activation helped protect against lipid damage at higher BPA concentrations. This study underscores the significance of preventing and regulating BPA release into the environment to avert detrimental consequences for aquatic ecosystems.

An assessment and characterization of pharmaceuticals and personal care products (PPCPs) within the Great Lakes Basin: Mussel Watch Program (2013-2018).

Defining the environmental occurrence and distribution of chemicals of emerging concern (CECs), including pharmaceuticals and personal care products (PPCPs) in coastal aquatic systems, is often difficult and complex. In this study, 70 compounds representing several classes of pharmaceuticals, including antibiotics, anti-inflammatories, insect repellant, antibacterial, antidepressants, chemotherapy drugs, and X-ray contrast media compounds, were found in dreissenid mussel (zebra/quagga; Dreissena spp.) tissue samples. Overall concentration and detection frequencies varied significantly among sampling locations, site land-use categories, and sites sampled proximate and downstream of point source discharge. Verapamil, triclocarban, etoposide, citalopram, diphenhydramine, sertraline, amitriptyline, and DEET (N,N-diethyl-meta-toluamide) comprised the most ubiquitous PPCPs (> 50%) detected in dreissenid mussels. Among those compounds quantified in mussel tissue, sertraline, metformin, methylprednisolone, hydrocortisone, 1,7-dimethylxanthine, theophylline, zidovudine, prednisone, clonidine, 2-hydroxy-ibuprofen, iopamidol, and melphalan were detected at concentrations up to 475 ng/g (wet weight). Antihypertensives, antibiotics, and antidepressants accounted for the majority of the compounds quantified in mussel tissue. The results showed that PPCPs quantified in dreissenid mussels are occurring as complex mixtures, with 4 to 28 compounds detected at one or more sampling locations. The magnitude and composition of PPCPs detected were highest for sites not influenced by either WWTP or CSO discharge (i.e., non-WWTPs), strongly supporting non-point sources as important drivers and pathways for PPCPs detected in this study. As these compounds are detected at inshore and offshore locations, the findings of this study indicate that their persistence and potential risks are largely unknown, thus warranting further assessment and prioritization of these emerging contaminants in the Great Lakes Basin.

Trace Metals in the Mussel Mytilus californianus from the West Coast of Baja California, Mexico.

This study assessed the concentrations of trace metals in tissues of Mytilus californianus from the west coast of Baja California, Mexico, during the cold and warm seasons. The concentrations of silver, cadmium, copper and zinc in mussel tissues were measured using Atomic Absorption Spectrophotometry. Silver concentrations ranged from 0.03 to 0.48 µg/g dry weight (d.w.) with significantly higher values registered at sites close to densely populated areas. Cadmium, copper, and zinc concentrations ranged from 0.57 to 7.83 µg/g d.w., 3.71 to 621 µg/g d.w., and 57.54 to 124.55 µg/g d.w., respectively. According to the WHO, values of copper and zinc were within acceptable limits. The maximum values of cadmium, however, exceeded the recommended limits set by the European Commission (2014). The human health risk of the metals analyzed was low (THQ and HI < 1). The regular monitoring of trace metals in M. californianus is recommended for a more definitive evaluation of contaminants.

An All-in-One "4A Hydrogel": through First-Aid Hemostatic, Antibacterial, Antioxidant, and Angiogenic to Promoting Infected Wound Healing.

Currently used wound dressings are ineffective. Hence, there is a need to develop introduce a high-performance medicament with multiple functions including rapid hemostasis and excellent antibacterial activity to meet the growing worldwide demand for wound healing products. Here, inspired by the strong adhesion of mussels and the enzyme-mimicking activity of nanometallic biomaterials, the authors developed an injectable hydrogel to overcome multiple limitations of current wound dressings. The hydrogel is synthesized via esterification reaction between poly(vinyl alcohol) (PVA) and 3,4-dihydroxyphenylalanine (DOPA), followed by catechol-metal coordination between Cu2+ and the catechol groups of DOPA to form a PVA-DOPA-Cu (PDPC) hydrogel. The PDPC hydrogel possesses excellent tissue adhesive, antioxidative, photothermal, antibacterial, and hemostatic properties. The hydrogel rapidly and efficiently stopped bleeding under different traumatic conditions, including otherwise-lethal liver injury, high-pressure carotid artery rupture, and even fatal cardiac penetration injuries in animal models. Furthermore, it is demonstrated that the PDPC hydrogel affected high-performance wound repair and tissue regeneration by accelerating re-epithelialization, promoting collagen deposition, regulating inflammation, and contributing to vascularization. The results show that PDPC hydrogel is a promising candidate for rapid hemorrhage control and efficient wound healing in multiple clinical applications.

Declines in freshwater mussel density, size and productivity in the River Thames over the past half century.

A pioneering, quantitative study published in Journal of Animal Ecology in 1966 on freshwater mussel populations in the River Thames, UK, continues to be cited extensively as evidence of the major contribution that mussels make to benthic biomass and ecosystem functioning in global river ecosystems. Ecological alteration, as well as declines in freshwater mussel populations elsewhere, suggest that changes to mussel populations in the River Thames are likely to have occurred over the half century since this study. We resurveyed the site reported in Negus (1966) and quantified the changes in mussel population density, species composition, growth patterns and productivity. We found large declines in population density for all unionid species. The duck mussel Anodonta anatina decreased to 1.1% of 1964 density. The painter's mussel Unio pictorum fell to 3.2% of 1964 density. The swollen river mussel Unio tumidus showed statistically nonsignificant declines. In contrast to 1964, in 2020 we found no living specimens of the depressed river mussel Pseudanodonta complanata (classified as Vulnerable by the IUCN Red List) but found new records of the invasive, nonnative zebra mussel Dreissena polymorpha and Asian clam Corbicula fluminea. Additionally, we found strong decreases in size-at-age for all species, which now grow to 65-90% of maximum lengths in 1964. As a result of reduced density and size, estimated annual biomass production fell to 7.5% of 1964 levels. Since mussels can be important to ecosystem functioning, providing key regulating and provisioning services, the declines we found imply substantial degradation of freshwater ecosystem services in the River Thames, one of the UK's largest rivers. Our study also highlights the importance to conservationists and ecologists of updating and validating assumptions and data about wild populations, which in the present era of anthropogenic ecosystem alteration are undergoing significant and rapid changes. Regular population surveys of key species are essential to maintain an accurate picture of ecosystem health and to guide management.

Host Species and Environment Shape the Gut Microbiota of Cohabiting Marine Bivalves.

Pacific oysters (Crassostrea gigas) and Mediterranean mussels (Mytilus galloprovincialis) are commercially important marine bivalves that frequently coexist and have overlapping feeding ecologies. Like other invertebrates, their gut microbiota is thought to play an important role in supporting their health and nutrition. Yet, little is known regarding the role of the host and environment in driving these communities. Here, bacterial assemblages were surveyed from seawater and gut aspirates of farmed C. gigas and co-occurring wild M. galloprovincialis in summer and winter using Illumina 16S rRNA gene sequencing. Unlike seawater, which was dominated by Pseudomonadata, bivalve samples largely consisted of Mycoplasmatota (Mollicutes) and accounted for >50% of the total OTU abundance. Despite large numbers of common (core) bacterial taxa, bivalve-specific species (OTUs) were also evident and predominantly associated with Mycoplasmataceae (notably Mycoplasma). An increase in diversity (though with varied taxonomic evenness) was observed in winter for both bivalves and was associated with changes in the abundance of core and bivalve-specific taxa, including several representing host-associated and environmental (free-living or particle-diet associated) organisms. Our findings highlight the contribution of the environment and the host in defining the composition of the gut microbiota in cohabiting, intergeneric bivalve populations.

Mytilus galloprovincialis releases immunologically functional haemocytes to the intervalvar space in response to tissue injury and infection.

Haemocytes of Mytilus galloprovincialis represent the main component of the internal self-defence system. Although haemocytes from haemolymph are usually studied to analyse these animals' immune response, the presence of haemocytes in the intervalvar liquid, which is essentially sea water, led us to characterize them. Several functional (ROS production, phagocytosis, gene expression, travel velocity and distance) and morphological (area, size and granularity) assays were performed by applying different stimuli to the mussels (waterborne infection, shell injury and their combination). Our results revealed that intervalvar liquid haemocytes share common characteristics with haemolymph haemocytes (for instance, the cell morphology and the cell population structure divided in three main groups) but also show significant differences in size (usually smaller in the intervalvar liquid), mobility (commonly faster in the intervalvar liquid), ROS production (higher in non-stimulated intervalvar liquid cells) and gene expression (IL17, Myd88 and CathL are over expressed in liquid intervalvar cells compared to haemolymph cells). Moreover, differences were observed when mussels were subjected to the mentioned treatments. These free intervalvar haemocytes could constitute the first line of defence as external sentinels extending the immunological alert system outside of the mussel body.

Elucidating the consequences of the co-exposure of microplastics jointly to other pollutants in bivalves: A review.

The marine environment has numerous impacts related to anthropogenic activities including pollution. Abundances of microplastics (MPs) and other pollutants are continuously increasing in the marine environment, resulting in a complex mixture of contaminants affecting biota. In order to understand the consequences, a review of studies analyzing combined effects of MPs and other types of pollutants in bivalves has been conducted as species in this group have been considered as sentinel and bioindicators. Regarding studies reviewed, histological analyses give evidence that MPs can be located in the haemolymph, gills and gonads, as well as in digestive glands in the intestinal lumen, epithelium and tubules, demonstrating that the entire body of bivalves is affected by MPs. Moreover, DNA strand breaks represent the most relevant form of damage caused by the enhanced production of reactive oxygen species in response to MPs exposure. The role of MPs as vectors of pollutants and the ability of polymers to adsorb different compounds have also been considered in this review highlighting a high variability of results. In this sense, toxic impacts associated to MPs exposure were found to significantly increase with the co-presence of antibiotics or petroleum hydrocarbons amongst other pollutants. In addition, bioaccumulation processes of pollutants (PAHs, metals and others) have been affected by the co-presence with MPs. Histological, genetic and physiological alterations are the most reported damages, and the degree of harm seems to be correlated with the concentration and size of MP and with the type of pollutant.

Alterations to unionid transformation during agricultural and urban contaminants of emerging concern exposures.

Highly imperiled unionids have a complex life cycle including the metamorphosis of an obligate parasite life stage, larval glochidia, to the juvenile stage. Despite the known vulnerabilities of both glochidia and juveniles to pollutants, little is known on how metamorphosis success may be affected by chemical stress. Disruption of the transformation process in which glochidia encyst on the gills of a host fish, could lead to lowered recruitment and population declines. Transformation rates of Lampsilis cardium on host fish Micropterus salmoides were empirically derived from experimental exposures to low, medium, or high concentrations of an agricultural or urban mixture of contaminants of emerging concern (CECs) over two exposure durations. Transformation was characterized by: (1) a zero-inflated Poisson general linear mixed effects model to compare difference in transformation between exposure durations and (2) time response curves to describe the transformation curve using long-term exposure data. Lampsilis cardium transformation was similar between exposure durations. When compared to controls, CEC stress significantly reduced juvenile production (p « 0.05) except for the agricultural medium treatment and tended to increased encapsulation duration which while statistically insignificant (p = 0.16) may have ecological relevancy. Combining the empirically derived reduction of transformation rates with parameters values from the literature, a Lefkovich stage-based population model predicted strong declines in population size of L. cardium for all treatments if these results hold in nature. Management focus on urban CECs may lead to best conservation efforts though agricultural CECs may also have a concentration dependent impact on transformation and therefore overall recruitment and conservation success.

Anomaly Detection in Biological Early Warning Systems Using Unsupervised Machine Learning.

The use of bivalve mollusks as bioindicators in automated monitoring systems can provide real-time detection of emergency situations associated with the pollution of aquatic environments. The behavioral reactions of Unio pictorum (Linnaeus, 1758) were employed in the development of a comprehensive automated monitoring system for aquatic environments by the authors. The study used experimental data obtained by an automated system from the Chernaya River in the Sevastopol region of the Crimean Peninsula. Four traditional unsupervised machine learning techniques were implemented to detect emergency signals in the activity of bivalves: elliptic envelope, isolation forest (iForest), one-class support vector machine (SVM), and local outlier factor (LOF). The results showed that the use of the elliptic envelope, iForest, and LOF methods with proper hyperparameter tuning can detect anomalies in mollusk activity data without false alarms, with an F1 score of 1. A comparison of anomaly detection times revealed that the iForest method is the most efficient. These findings demonstrate the potential of using bivalve mollusks as bioindicators in automated monitoring systems for the early detection of pollution in aquatic environments.