Bivalve Species Research Articles

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Al-Dalmaj marsh is one of the most important marshes in Iraq; it extends from Al-Qadisiyah Province in the west to Wasit Province in the east, south of the Tigris and Euphrates Rivers. In order to study the malacological diversity of this site, a survey of the marsh molluscs species was made during this study. About 177 specimens were collected, seven species of gastropods belonging to six families and two species of Bivalves belonging to one family were identified, remarks on the nomenclature, taxonomy and distribution of these species. According to this study Al-Dalmaj Marsh includes diverse molluscs species and the presented results will provide important information for future studies concerned with the molluscs or Invertebrates biodiversity state of this important ecosystem in Iraq.

KEANEKARAGAMAN DAN POLA DISTRIBUSI BIVALVIA DI TELUK PANGPANG BLOK JATI PAPAK TAMAN NASIONAL ALAS PURWO BANYUWANGI

Alas Purwo National Park in Banyuwangi is one of the conservation areas of mangrove forest potential big enough one of them is the Teluk Pangpang Blok Jati Papak which is the intertidal area, a lot of marine life that live in the region one of which is the bivalves. This study aims to determine diversity and the distribution pattern of bivalves in the Teluk Pangpang Blok Jati Papak. This study was conducted in 25 Mei - June 1, 2016. Determination of the sampling method used in this research is purposive sampling. Sampling sites are divided into three stations, with the distance between stations is 500 m, in each station there are four transects on each transect contained 10 plot. set the distance between transects 15 m and the distance between the plots 5 m with a plot measuring 2 × 2m. Measurement parameters abiotic do is measure temperature, salinity and pH. The research found 8 species of bivalves that Anomalodiscus squamosus, Placamen chlorotica, Pitar citrus, Chamelea gillina, Mactra grandis, Hiatula chinensis, Tellina timorensis, Anadara granosa. An index value of diversity bivalves in the Teluk Pangpang Blok Jati Papak categorized as low, with the highest index value at station 1 at 0.766 and the lowest at station 2 by 0.66. Biavalvia distribution patterns in the region are random in species Anomalodiscus squamosus, Pitar citrus, Chamelea gillina, Mactra grandis, Hiatula chinensis, Tellina timorensis, Anadara granosa and are clustered in Placamen chlorotica species.

Drivers for the Diversity of Mollusc Communities in Unique Calcareous Fen Habitats

The research was carried out in calcareous fen habitats which share coverage with Natura 2000 sites designated under the EU Habitats and the Birds Directive. A total of 27 taxa of molluscs were recorded: 23 gastropod and 4 bivalve species. Anisus vorticulus, one of the species of Community interest whose conservation requires designation of special conservation areas within the Habitats Directive Natura 2000, was subrecedent and accedent in mollusc communities. Calcareous fen habitats offer the aquatic organisms harsh environmental conditions including a relatively high temperature of the water up to 33.29 °C (undrained fens), oxygen deficits in the water, high pH of up to 11.08 (fen pools) and conductivity above 3000 μS cm−1 (fen ditches). Therefore molluscs have to face extreme environmental conditions. Temperature of the water, pH, dissolved oxygen and conductivity were the parameters most associated with the distribution of mollusc species in the calcareous fen habitats. The abundance of submerged and floating macrophytes, the degree of habitat persistence and the fish predation pressure on molluscs also exerted a significant effect on their distribution. The calcareous fen habitats that are listed in Annex I of the European Union Habitats Directive create a unique valuable ecosystem that contributes to the natural diversity of aquatic organisms.

Chromosomal-scale genome assembly of the Mediterranean mussel Mytilus galloprovincialis

The Mediterranean mussel, Mytilus galloprovincialis, is a significant marine bivalve species that has ecological and economic importance. This species is robustly resilient and highly invasive. Despite the scientific and commercial interest in studying its biology and aquaculture, there remains a need for a high-quality, chromosome-scale reference genome. In this study, we have assembled a high-quality chromosome-scale reference genome for M. galloprovincialis. The total length of our reference genome is 1.41 Gb, with a scaffold N50 sequence length of 96.9 Mb. BUSCO analysis revealed a 97.5% completeness based on complete BUSCOs. Compared to the four other available M. galloprovincialis assemblies, the assembly described here is dramatically improved in both contiguity and completeness. This new reference genome will greatly contribute to a deeper understanding of the resilience and invasiveness of M. galloprovincialis.

Microplastics in fish and a bivalve species sampled from freshwater environment and retail outlets, and the assessment of human exposure

The issue of microplastic pollution has emerged as a significant environmental concern in recent times, exerting adverse effects on both aquatic ecosystems and human health. Multiple studies have indicated that the prevalence of microplastics was greater in fish and bivalves obtained from retail outlets (non-farmed) compared to those collected live from freshwater environments. In this study, black clams (Villorita cyprinoides) and fishes (Etroplus suratensis, Etroplus maculatus) were collected from the freshwaters of Periyar River and also from the local retail outlets to analyse the microplastic abundance. Microplastics were significantly higher in numbers from the fish and clams obtained from the retail outlets than the ones collected from the river. Fibres were the dominant morphotype. Polyethylene, polypropylene and polystyrene were majorly obtained. Humans are at risk of consuming approximately 936 microplastics annually from the consumption of two species of fish and 26 microplastics per 100g of clam meat consumed. The presence of microplastics in the species purchased from the retail outlets indicates that there is a possibility for human exposure and this finding raises serious concerns regarding food safety.

Microscale analysis reveals nature of hydrophobic biopolymers in aragonite bivalve shells with crossed-lamellar architecture

Bivalve shells with crossed-lamellar architecture consist of random orientation of anisotropic crystallographic directions that adds to the optimization of the mechanical properties of shell biominerals. The source of these anisotropic distortions has been attributed to the organic macromolecules in the inorganic unit. However, very little is known about the organic macromolecules in shells with crossed-lamellar architecture because it is believed that the organics in this shell ultrastructure can hardly be characterized owing to its low content, about 1 wt%. Here, the shells of two bivalve species (Callista kingii and Anadara trapezia) with crossed-lamellar architecture, have been studied by microRaman spectroscopy, FTIR, and histochemical analysis. For the first time, organic macromolecules and inorganic components were simultaneously identified. Using spectroscopic techniques (microRaman and FTIR) and a confocal scanning fluorescence microscopy, the results herein demonstrated minor chitin in the studied samples and document structural protein, collagen-like matrix as the major organic component. The SEM observations revealed a morphological biopolymer meshwork composed of a polygonal network. Based on those combined evidence, this study suggests that the interactions between polysaccharide-based biomolecules and collagen-like matrix are crucial for the mechanical properties of crossed-lamellar layers in bivalve shells. This study highlights the importance of using in-situ approaches for these types of biomaterials and provides another source of biomaterials.

Assessing the accuracy of MUR high resolution satellite sea surface temperature data

Marine bivalve mollusks are valuable proxies for El Niño-Southern Oscillation (ENSO) events in paleoclimate research, reflecting changes in sea surface temperature (SST) and other ambient marine conditions in their shell chemistry. However, the use of several Peruvian species of bivalves as paleoENSO proxies needs to be established by comparing their shells’ δ18O-derived SST records with instrumental SST measurements. Along the Peruvian coast, the limited spatial coverage of in-situ coastal monitoring stations hinders such comparisons. This study aims to assess the accuracy of the Multi-scale Ultra-high Resolution (MUR) satellite-derived SST dataset as an alternative source of SST information for paleoENSO studies in Peru, which could advance research on Peruvian bivalve species. This study compares MUR satellite data with in-situ measured SST from ten coastal monitoring stations operated by the Instituto del Mar del Perú (IMARPE). The correlation between the datasets is evaluated, and systematic and non-systematic variations are examined. Environmental factors that may impact the accuracy of satellite SST measurements, such as clouds and aerosols, are also investigated. Results show that MUR data generally correlate with overall trends in SST variability captured by in-situ measurements. However, there are regional variations in the accuracy of MUR data, with some areas showing consistent temperature offsets. Differences in measurement methodologies and environmental variables are explored as potential causes of variations between the datasets. Overall, the study demonstrates the potential of using high-resolution satellite SST data for assessing δ18O SST records from bivalves in locations without local SST records. It provides insights into the accuracy and limitations of using MUR data as an alternative source of SST information for paleoENSO studies in coastal Peru.

Stable isotopic composition of tissues and shells in the Mediterranean mussel, Mytilus galloprovincialis, in estuarine and aquaculture settings

The Mediterranean mussel, Mytilus galloprovincialis Lamarck, 1819 is a widely distributed commercially important bivalve species, and is one of two cultivated bivalve species in the Adriatic Sea, with the Krka River estuary being a key aquaculture location. Understating the feeding ecology of M. galloprovincialis could help aquaculture be more efficient. The aim of this study is to use stable isotopes to advance our understanding of M. galloprovincialis feeding ecology, as well as explore the potential of their shell as proxies for environmental change. We analyzed stable isotope composition (hereafter, δ13C and δ15N), of M. galloprovincialis soft tissue, as well as the δ15N signature of its shell, over one year at multiple sites in the Krka River estuary. Mussels showed differences in the isotopic niche depending on the site, indicating that feeding varies according to geographic location, likely due to specific conditions in the Krka River estuary and differences in food availability. During our entire survey period, marine organic carbon was the dominant source in the mussels cultivated in the Krka estuary. However, in the period from late summer to late autumn, the contribution of freshwater carbon sources increased for both sites situated in the middle estuary. The distinct feeding patterns observed at each sampling site could be attributed to a combination of factors such as local hydrographic conditions, food availability, and the presence of other competing species. Overall, the stable isotope results present valuable information on the feeding ecology of Mytilus galloprovincialis, highlighting the complex interactions between environmental factors and feeding habits. The results of our study contribute to the isotope data archive for M. galloprovincialis. Furthermore, this work shows the potential of M. galloprovincialis shell δ15N values as an indicator for nitrogen loading in aquaculture settings and coastal marine environments.

Combined effects of toxic Microcystis aeruginosa and high pH on antioxidant responses, immune responses, and apoptosis of the edible freshwater bivalve Corbicula fluminea

Due to increasing anthropogenic perturbation and water eutrophication, cyanobacterial blooms (CYBs) have become a global ecological and environmental problem. Toxic CYBs and elevated pH are considered to be the two key stressors associated with eutrophication in natural waters, particularly in the event of CO2 depletion induced by dense blooms. However, previous research has been focused on investigating the impacts of toxic CYBs or pH changes in isolation, whereas the interactive effects of such stressors on edible bivalves that inhabit CYB waters still lack information. In this study, the combined effects of toxic Microcystis aeruginosa and pH shifts on the antioxidant responses, immune responses, and apoptosis of the edible freshwater bivalve Corbicula fluminea were explored. The results showed that the activity of antioxidant enzymes was significantly impacted by the interactive effects between toxic M. aeruginosa exposure and time course, yet pH shifts showed no significant effects on the activities of these antioxidant enzymes, implying that the antioxidant response in C. fluminea was mainly triggered by toxic M. aeruginosa exposure. Toxic M. aeruginosa also induced an increased production of reactive oxygen species and malondialdehyde in treated clams, particularly under high pH settings. The elevated lysosomal enzyme activity helped C. fluminea defend against toxic M. aeruginosa exposure under high pH conditions. The principal component analysis (PCA) and the integrated biomarker response (IBR) results suggested that the treated clams were subjected to the elevated toxicity of toxic M. aeruginosa in conditions of high pH. The heat shock proteins-related genes might be triggered to resist the oxidative damage in treated clams. Moreover, the upregulation of TNF and casp8 genes indicated the potential activation of the caspase8-mediated apoptotic pathway through TNF receptor interaction, potentially resulting in apoptosis. The TUNEL assay results further confirmed that apoptosis appeared in treated clams. These findings improve our understanding of the combined toxicological effects of harmful algae and pH shifts on bivalves, which will provide insights into a comprehensive ecological risk assessment of toxic CYBs to edible bivalve species.

Unravelling biochemical responses in the species Mytilus galloprovincialis exposed to the antineoplastics ifosfamide and cisplatin under different temperature scenarios

This study investigates the chronic impact of two of the most widely consumed antineoplastic drugs, Ifosfamide (IF) and Cisplatin (CDDP), on the bivalve species Mytilus galloprovincialis under current (17 °C) and predicted warming conditions (21 °C). Accompanying the expected increase in worldwide cancer incidence, antineoplastics detection in the aquatic environment is also expected to rise. Mussels were exposed to varying concentrations of IF (10, 100, 500 ng/L) and CDDP (10, 100, 1000 ng/L) for 28 days. Biochemical analyses focused on metabolic, antioxidant and biotransformation capacities, cellular damage, and neurotoxicity. Results showed temperature-dependent variations in biochemical responses. Metabolic capacity remained stable in mussels exposed to IF, while CDDP exposure increased it at 1000 ng/L for both temperatures. Antioxidant enzyme activities were unaffected by IF, but CDDP activated them, particularly at 21 °C. Biotransformation capacity was unchanged by IF but enhanced by CDDP. Nevertheless, cellular damage occurred at CDDP concentrations above 100 ng/L, regardless of temperature. Integrated biomarker responses highlighted CDDP's greater impact, emphasizing the critical role of temperature in shaping organismal responses and underscoring the complexity of environmental stressor interactions.

Adaptations to nitrogen availability drive ecological divergence of chemosynthetic symbionts.

Bacterial symbionts, with their shorter generation times and capacity for horizontal gene transfer (HGT), play a critical role in allowing marine organisms to cope with environmental change. The closure of the Isthmus of Panama created distinct environmental conditions in the Tropical Eastern Pacific (TEP) and Caribbean, offering a "natural experiment" for studying how closely related animals evolve and adapt under environmental change. However, the role of bacterial symbionts in this process is often overlooked. We sequenced the genomes of endosymbiotic bacteria in two sets of sister species of chemosymbiotic bivalves from the genera Codakia and Ctena (family Lucinidae) collected on either side of the Isthmus, to investigate how differing environmental conditions have influenced the selection of symbionts and their metabolic capabilities. The lucinid sister species hosted different Candidatus Thiodiazotropha symbionts and only those from the Caribbean had the genetic potential for nitrogen fixation, while those from the TEP did not. Interestingly, this nitrogen-fixing ability did not correspond to symbiont phylogeny, suggesting convergent evolution of nitrogen fixation potential under nutrient-poor conditions. Reconstructing the evolutionary history of the nifHDKT operon by including other lucinid symbiont genomes from around the world further revealed that the last common ancestor (LCA) of Ca. Thiodiazotropha lacked nif genes, and populations in oligotrophic habitats later re-acquired the nif operon through HGT from the Sedimenticola symbiont lineage. Our study suggests that HGT of the nif operon has facilitated niche diversification of the globally distributed Ca. Thiodiazotropha endolucinida species clade. It highlights the importance of nitrogen availability in driving the ecological diversification of chemosynthetic symbiont species and the role that bacterial symbionts may play in the adaptation of marine organisms to changing environmental conditions.

Differences in growth patterns among three bivalve species and in relation to exposure and implications for aquaculture and ecological functions

In this paper, similarities and differences in growth patterns, measured as changes in soft tissue weight and shell length, among three bivalve species in Sweden (blue mussels, Pacific oysters and European flat oysters) were studied with the aim to achieve information on spatial and temporal variability among these commercially important species. The study showed that there are significant differences in spatial growth pattern between blue mussels and both of the oyster species, where oysters grew faster in more protected locations compared to mussels, which had a generally faster growth in the exposed localities. The weight: length ratio also differed among species, where mussels had a lower ratio compared to oysters. Potential causes of the observed patterns and consequences for bivalve farming as well as implications for ecological functions are discussed. The results are valuable in site-selection processes at both local (individual farmers) and regional/national scales (planning processes etc), and indicates that spatial planning of bivalve aquaculture need inclusion of species specific growth parameters.

The genus Adontorhina (Bivalvia: Thyasiridae) from the northern Pacific Ocean: Description of two new species, an expanded description of Adontorhina cyclia S. S. Berry, 1947, and remarks on other species

We describe two new deep-sea species of bivalves of the genus Adontorhina that were found at a depth of 788–2532 m off the Kuril Islands and the southeastern coast of the Kamchatka Peninsula (Adontorhina inflata sp. nov.), as well as at a depth of 3210–3432 m in the Sea of Okhotsk and on the oceanic slope of the Kuril Islands (Adontorhina diaphana sp. nov.). Herein, we provide an expanded description of the amphi-Pacific Adontorhina cyclia, which is supplemented with new data on shell morphology, body anatomy, and distribution, based on the analysis of samples collected by 12 expeditions between 1949 and 2015 in various regions of the northwestern Pacific from the coast of Japan to the Bering Sea. The main feature distinguishing the new species from all other Adontorhina species is a unique sculpture of the prodissoconch consisting of thin folds and wrinkles of varying length, shape, and number. In addition, A. inflata sp. nov. differs from other Adontorhina species by having an obliquely ovate, strongly inflated shell with a poorly defined escutcheon and indistinct auricle; and A. diaphana sp. nov. is distinguished by having a subcircular shell with a long and strongly prominent auricle. A thorough study of the prodissoconch morphology of A. cyclia from the western and eastern Pacific, as well as Adontorhina sphaericosa and Adontorhina zelayi, showed that the sculpture of the prodissoconch in all species studied is unique and can be used as an important additional character for the identification and differentiation of Adontorhina species.

A Testis-Specific DMRT1 (Double Sex and Mab-3-Related Transcription Factor 1) Plays a Role in Spermatogenesis and Gonadal Development in the Hermaphrodite Boring Giant Clam Tridacna crocea.

The testis-specific double sex and mab-3-related transcription factor 1 (DMRT1) has long been recognized as a crucial player in sex determination across vertebrates, and its essential role in gonadal development and the regulation of spermatogenesis is well established. Here, we report the cloning of the key spermatogenesis-related DMRT1 cDNA, named Tc-DMRT1, from the gonads of Tridacna crocea (T. crocea), with a molecular weight of 41.93 kDa and an isoelectric point of 7.83 (pI). Our hypothesis is that DMRT1 machinery governs spermatogenesis and regulates gonadogenesis. RNAi-mediated Tc-DMRT1 knockdown revealed its critical role in hindering spermatogenesis and reducing expression levels in boring giant clams. A histological analysis showed structural changes, with normal sperm cell counts in the control group (ds-EGFP) but significantly lower concentrations of sperm cells in the experimental group (ds-DMRT1). DMRT1 transcripts during embryogenesis exhibited a significantly high expression pattern (p < 0.05) during the early zygote stage, and whole-embryo in-situ hybridization confirmed its expression pattern throughout embryogenesis. A qRT-PCR analysis of various reproductive stages revealed an abundant expression of Tc-DMRT1 in the gonads during the male reproductive stage. In-situ hybridization showed tissue-specific expression of DMRT1, with a positive signal detected in male-stage gonadal tissues comprising sperm cells, while no signal was detected in other stages. Our study findings provide an initial understanding of the DMRT1 molecular machinery controlling spermatogenesis and its specificity in male-stage gonads of the key bivalve species, Tridacna crocea, and suggest that DMRT1 predominantly functions as a key regulator of spermatogenesis in giant clams.

MiRNA-seq provides novel insight into the response to hyper- and hypo- salinity acclimation in Crassostrea hongkongensis

The Hong Kong oyster, Crassostrea hongkongensis, is a significant bivalve species with economic importance. It primarily inhabits the estuarine intertidal zones in southern China, making it susceptible to salinity fluctuations. Consequently, investigating the molecular mechanisms governing salinity regulation in C. hongkongensis is essential. In this study, we conducted miRNA-seq on C. hongkongensis to compare miRNA expression differences under varying salinities (5‰, 25‰, and 35‰). The miRNA sequencing revealed 51 known miRNAs and 95 novel miRNAs across nine small RNA libraries (S5, S25, and S35). Among these miRNAs, we identified 6 down-regulated differentially expressed (DE) miRNAs in response to hypo-salinity stress (5‰), while 1 up-regulated DE miRNA and 5 down-regulated DE miRNAs were associated with hyper-salinity stress (35‰). Additionally, we predicted 931 and 768 potential target genes for hypo- and hyper-salinity stress, respectively. Functional gene annotation indicated that the target genes under hypo-salinity stress were linked to vesicle-mediated transport and metal ion binding. Conversely, those under hyper-salinity stress were primarily involved in signal transduction and metabolic processes. These findings have provided insights into the regulatory role of miRNAs, their potential target genes and associated pathways in oyster hypo- and hyper-salinity stress, which establish a foundation for future studies on the roles of miRNAs in salinity acclimation mechanisms in C. hongkongensis.

Microplastic Status Of Bivalves In The Coastal Zones Of Capiz

The contamination of bivalves with microplastics in Capiz’s coastal zones presents a pressing environmental concern with potential ecological and health repercussions. This secondary research initiative delves into the microplastic status of bivalves in Capiz, offering insights into types, concentrations, distribution patterns, and potential impacts through a comprehensive review of relevant scientific literature. Microplastic concentrations vary among bivalve species and sampling locations, with higher levels near densely populated and human-activity-impacted areas. Spatial and temporal distribution patterns reveal contaminated hotspots and seasonal variations, particularly near urban and industrial areas. Contrasting to other regions unveil both commonalities and unique characteristics, attributed to specific coastal zones and environmental factors in Capiz. Results underscore the imperative for additional research on sources and pathways of microplastic contamination, necessitating effective mitigation strategies.

Heavy Metals In Bivalves From Coastal Municipalities Of C apiz,P hilippines

This research study is based on the current status of heavy metal contamination in bivalves within the coastal areas of Capiz, Philippines, drawing insights from accessible data. The findings shed light on the contamination’s extent, potential threats to human health, and the pollution’s origins. The researchers acknowledge the study’s limitations. As per the findings, elevated levels of heavy metals, such as lead, mercury, cadmium, arsenic, and chromium, in bivalves collected from Capiz’s coastal regions. Variations in metal concentrations are observed among different bivalve species and sampling sites, with identified geographical distribution patterns and potential contamination hotspots. An assessment of conformity to regulatory limits and guidance for heavy metal levels in shellfish consumption is conducted, identifying any exceedances or areas of concern. The research aims to establish the extent to which bivalves from Capiz aligns with legal requirements. Potential health risks allied to the bivalve consumption are evaluated based on the detected heavy metal levels, considering various exposure routes, population characteristics, and toxicity reference values. The research scrutinizes the impact of human activities, including industrial discharges, agricultural practices, and urban runoff, on heavy metal contamination in coastal ecosystems. The ongoing discussion underscores the need for further investigation and underscores the importance of addressing the issue to ensure the environmental sustainability and safety of coastal resources in Capiz.

Hedgehog signaling is required for larval muscle development and larval metamorphosis of the mussel Mytilus coruscus

Understanding the developmental processes and signaling pathways involved in larval myogenesis and metamorphosis is crucial for comprehending the life history and adaptive strategies of marine organisms. In this study, we investigated the temporal and spatial patterns of myogenesis in the mussel Mytilus coruscus (Mc), focusing on the emergence and transformation of major muscle groups during different larval stages. We also explored the role of the Hedgehog (Hh) signaling pathway in regulating myogenesis and larval metamorphosis. The results revealed distinct developmental stages characterized by the emergence of specific muscular components, such as velum retractor muscles and anterior adductor muscles, in D-veliger and umbo larvae, which are responsible for the planktonic stage. In the pediveliger stage, posterior ventral, posterior adductor, and foot muscles appeared. After larval metamorphosis, the velum structure and its corresponding retractor muscles degenerate, indicating the transition from planktonic to benthic life. We observed a conserved pattern of larval musculature development and revealed a high degree of conservation across bivalve species, with comparable emergence times during myogenesis. Furthermore, exposure to the Hh signaling inhibitor cyclopamine impaired larval muscle development, reduced larval swimming activity, and inhibited larval metamorphosis in M. coruscus. Cyclopamine-mediated inhibition of Hh signaling led to reduced expression of four key genes within the Hh signaling pathway (McHh, McPtc, McSmo, and McGli) and the striated myosin heavy chain gene (McMHC). It is hypothesised that the abnormal larval muscle development in cyclopamine-treated groups may be an indirect effect due to disrupted McMHC expression. We provide evidence for the first time that cyclopamine treatment inhibited larval metamorphosis in bivalves, highlighting the potential involvement of Hh signaling in mediating larval muscle development and metamorphosis in M. coruscus. The present study provides insights into the dynamic nature of myogenesis and the regulatory role of the Hh signaling pathway during larval development and metamorphosis in M. coruscus. The results obtained in this study contribute to a better understanding of the evolutionary significance of Hh signaling in bivalves and shed light on the mechanisms underlying larval muscle development and metamorphosis in marine invertebrates.

Investigating the role of mitochondrial membrane potential in paternal inheritance of mitochondria

Abstract The process of oxidative phosphorylation (OXPHOS) in mitochondria depends on an electrochemical gradient known as the mitochondrial membrane potential (Δψm). Reflecting high functionality, elevated Δψm usually depicts healthy mitochondria and contributes to organelle selection. This study investigates whether mitochondrial properties linked with bioenergetics, such as Δψm, play a role in paternal inheritance of mitochondria. More specifically, the study looks at how sperm Δψm responds to egg chemoattractants in bivalves characterized by distinct mitochondrial inheritance patterns: strict maternal inheritance (SMI) and doubly uniparental inheritance (DUI), the latter displaying sex-specific transmission of paternal mitochondrial DNA. Sperm Δψm was examined in four bivalve species: the blue mussel (Mytilus edulis) and the Manila clam (Ruditapes philippinarum) (DUI), plus the hard clam (Mercenaria mercenaria) and the soft-shell clam (Mya arenaria) (SMI). In the absence of egg chemoattractants, sperm Δψm did not vary between the two groups. However, there was a trend of increase in Δψm following egg detection only in sperm bearing paternally derived mitochondria (DUI). This suggests, along with bioenergetic changes, that Δψm modulation might be a specific property of at least some DUI species, possibly implicated in their unique ability to transmit their mitochondria in a sex-specific fashion.

Physiological effects of interacting native and invasive bivalves under thermal stress

Across many ecosystems in North America and Europe, native freshwater bivalves (Order Unionida) are threatened by fouling and competition for food by the invasive zebra mussel Dreissena polymorpha. In light of climate change, knowledge on the influence of water temperature on these competitive effects is important, yet poorly understood. This study examines the physiological impact of the interaction between D. polymorpha and the native European unionid Anodonta cygnea over a 28 day—period in response to water temperatures of 12, 19, and 25 °C by comparing their glycogen, glucose, lipid and protein concentrations. The laboratory experiment comprised three treatments: (1) fouling of A. cygnea by D. polymorpha, (2) both species present but not fouling; and (3) a control in which A. cygnea and D. polymorpha were placed separately. Increased water temperatures caused physiological stress in D. polymorpha as evident from reduced glycogen, glucose, lipid and protein concentrations. Dreissena polymorpha benefited from fouling of unionids, as individuals that fouled A. cygnea tended to have increased glycogen, glucose, lipid and protein concentrations. Competitive effects of D. polymorpha over the unionid bivalve species, however, were not intensified by elevated temperatures. Glochidia release, lower infestation intensity, and physiological stress of Dreissena at higher temperatures were likely confounding factors. The results of this study suggest that understanding the physiological consequences of species interactions at changing temperatures can be an important tool to assess future climate change impacts on freshwater bivalves and aquatic community structures.