Freshwater Molluscs Research Articles

Absolute Abundance of Dominant Freshwater Mollusks of an Irrigation Canal

Mollusks are a diverse group of invertebrates that perform fundamental ecological functions within freshwater ecosystems. This study evaluated the absolute abundance of dominant freshwater benthic mollusks in an irrigation canal, utilizing a partial count method across seven established sampling stations. Results revealed that the endemic freshwater snail (Jagora spp.) was the most abundant species, followed by golden apple snail (Pomacea spp.) and freshwater clam (Corbicula spp.), which are both invasive species. Effective monitoring and management strategies are essential to mitigate the adverse effects of the invasive species in their particular environment.

The Contamination of Microplastics Ingested by Freshwater Molluscs in the Mun River, Thailand

The Contamination of Microplastics Ingested by Freshwater Molluscs in the Mun River, Thailand

Update of the non-marine (terrestrial & freshwater) molluscs systematic inventory occurring in Santa Catarina State/ SC, Central Southern Brazil region

Introduction: The survey of the mollusc fauna (malacofauna) of a geopolitical region (State) is important from several aspects, reaching several important sectors of knowledge. So if all regions could do the same we would have within, a few years, expanded and completed the catalog of molluscs in Brazil, with much still to be added with regard to terrestrial and freshwater fauna. Objective: Updated general rеᴠiеw of the inventory of non-marine molluscs occurring in the Santa Catarina State/ SC, subtropical Central Southern portion of the Brazilian territory. Methodology: Organization of a occurring State species taxonomic checklist and their corresponding reference database, comprising the regional knowledge formally produced around the theme at least since the year 2003. Results and Conclusions: Confirmed and recorded regional total of 241 species (202 Gastropoda & 39 Bivalvia), among which at least 86 (79 Gastropoda & 7 Bivalvia) exhibit radicals synonymical (among others) changes recently reported through the global platform "MolluscaBase" and available literature of recent production, taxonomically included all in 95 genera (83 Gastropoda & 12 Bivalvia) and 40 families (35 Gastropoda & 5 Bivalvia), with aggregated additional information about their known biogeographical distribution in the territorial space of the State.

Potential of integrated multitrophic aquaculture to make prawn farming sustainable in Bangladesh

Farmed freshwater prawn (Macrobrachium rosenbergii) and black tiger shrimp (Penaeus monodon) comprise a significant portion of Bangladesh’s seafood exports, raising concerns about their environmental impacts. Freshwater prawn farms, which require a relatively high amount of feed supply, release 1.0 MT CO2-equivalents/year, equating to 18.8 kg CO2e/MT prawn, contributing significantly to global warming and climate change risks. Integrated Multi-Trophic Aquaculture (IMTA) offers an alternative farming method to conventional prawn farming systems, as it minimizes greenhouse gas (GHG) emissions and climate change impacts. Systematically reviewing 112 scientific articles on IMTA, this article offers recommendations for adopting IMTA to promote sustainable freshwater prawn farming in Bangladesh. IMTA is undergoing extensive experimentation and practice in many parts of the world, offering economic benefits, social acceptability, and environmental sustainability. In addition to native prawn species, various indigenous organic extractive freshwater mollusks, and inorganic extractive plants are available which can seamlessly be used to tailor the IMTA system. Extractive organisms, including aquatic mollusks and plants within prawn farms, can capture blue carbon effectively lowering GHG emissions and helping mitigate climate change impacts. Aquatic mollusks offer feed for fish and livestock, while aquatic plants serve as a dual food source and contribute to compost manure production for crop fields. Research on IMTA in Bangladesh was primarily experimented on finfish in freshwater ponds, with the absence of studies on IMTA in prawn farms. This necessitates conducting research at the prawn farmer level to understand the production of extractive aquatic mollusk and plants alongside prawn in the prawn-producing regions of southwestern Bangladesh.

Acute ammonia stress affects the immune response, oxidative stress, ammonia transport and detoxication in the hepatopancreas of freshwater mollusk Solenaia oleivora

Ammonia is a common and major pollutant in aquatic systems. Excessive ammonia has toxic effects on hepatopancreas in aquatic animals. In this study, we investigated the toxic effects of acute ammonia (concentration: 10 mg/L; test duration: 48 h) stress on the hepatopancreas of a freshwater mollusk, Solenaia oleivora. Transcriptome analysis identified 3355 differentially expressed genes (DEGs), including 1432 up-regulated and 1923 down-regulated genes. Many DEGs were associated with immune and stress responses, including heat shock proteins, pattern recognition receptors, and lysozyme. In addition, some DEGs were related to ammonia transport and detoxification, such as aquaporins, K+channel, V-ATPase, cytochrome p450, glutathione transferase, and glutamine synthetase. Physiological analysis showed that ammonia stress increased the activities of antioxidant enzymes (superoxide dismutase and catalase) and non-specific immune enzymes (acid phosphatase) and the levels of liver injury markers (malonaldehyde, aspartate aminotransferase, and alanine transaminase). TdT-mediated dUTP nick-end labeling assay revealed that ammonia stress induced apoptosis in the hepatopancreas. These results indicated the toxic effects of ammonia on hepatopancreas in the immune response, oxidative stress, ammonia transport and detoxification of S. oleivora. Our findings will accumulate data on the toxic effects of ammonia on the hepatopancreas of aquatic animals.

Characterization of two carbonic anhydrase isoforms in the pulmonate snail (Lymnaea Stagnalis) and their involvement in Molluskan calcification

Calcifying organisms are suffering from negative impacts induced by climate change, such as CO2-induced acidification, which may impair external calcified structures. Freshwater mollusks have the potential to suffer more from CO2-induced acidification than marine calcifiers due to the lower buffering capacity of many freshwater systems. One of the most important enzymes contributing to the biomineralization reaction is carbonic anhydrase (CA), which catalyzes the reversible conversion of CO2 to bicarbonate, the major carbon source of the calcareous structure in calcifiers. In this study we characterized two α-CA isoforms (LsCA1 and LsCA4) from the freshwater snail Lymnaea stagnalis using a combination of gene sequencing, gene expression, phylogenetic analysis and biochemical assays. Both CA isoforms demonstrated high expression levels in the mantle tissue, the major site for biomineralization. Furthermore, expression of LsCA4 during development parallels shell formation. The primary protein structure analysis, active site configuration and the catalytic activity of LsCA4 together suggest that the LsCA4 is embedded in the apical and basolateral membranes of mantle cells; while LsCA1 is proposed to be cytosolic and might play an important role in acid-base regulation. These findings of LsCA isoforms form a strong basis for a more detailed physiological understanding of the effects of elevated CO2 on calcification in freshwater mollusks.

Bacterial Communities within the Freshwater Lymnaeid Snail Kamtschaticana kamtschatica (Middendorff, 1850) in Northeastern Siberia

This is the first report on microbial communities associated with the freshwater snail Kamtschaticana kamtschatica inhabiting diverse types of water basins in Eastern Siberia and the Russian Far East. Using metabarcoding data based on the 16S rRNA gene fragments, taxonomic profiling of bacterial communities associated with snails from three basins of the Magadan Oblast was carried out. Predominant phyla in the studied bacterial communities were Pseudomonadota, Bacillota, Cyanobacteriota, Actinomycetota, Verrucomicrobiota, Planctomycetota, and Bacteroidota. The highest alpha-diversity, according to the Chao1 index, was revealed in the mollusks from the Orotukan reservoir. The relative abundance of bacteria of the genera Snowella, Leptolyngbya, Nodosilinea, Arenimonas, and Polaromonas significantly distinguished the mollusks of this habitat from those of the other two. The greatest similarities in the composition of the microbiota in K. kamtschatica were found for the genus Pseudomonas, which was present in the majority of samples in the amount of more than 1% and was not found in the sediment samples. Obtained data on the diversity and composition of bacterial communities associated with lymnaeid snails are of fundamental importance for the ecology of freshwater mollusks.

The first record of Aspidogaster conchicola (Trematoda: Aspidogastridae) in the freshwater mussel Unio pictorum in Croatia

Although Aspidogaster conchicola is a common and widespread parasite of freshwater molluscs, knowledge about its distribution and hosts in Croatia is still insufficient. The aim of our research was to investigate the presence of A. conchicola in the freshwater mussel Unio pictorum, which is widely distributed in the rivers of Europe. The study was conducted in the Mrežnica River, where U. pictorum is a common species. Five specimens of U. pictorum were collected by scuba diving in October 2021. The dissection of mussels was carried out in the laboratory, and all tissues were inspected under a stereo microscope. Determination of the parasite was performed based on the number and arrangement of alveoli. The results showed that the prevalence of infection was 40% (two out of five mussels were infected), and the intensity of infection was 2 to 3 specimens per mussel. All parasites were detected in the mussels’ pericardial cavity. In conclusion, this is the first record of A. conchicola in U. pictorum in Croatia.

Habitat suitability of Aotearoa New Zealand for the recently invaded gold clam (Corbicula fluminea)

ABSTRACT The gold clam (Corbicula fluminea) is a highly invasive freshwater mollusc, which was detected in Aotearoa New Zealand in 2023. Currently, C. fluminea has only been observed in the Waikato catchment, but there is significant concern it will spread across the country. There is an urgent need to identify suitable habitat for the species beyond the Waikato, given the high probability of spread. Here, we used a Maximum Entropy (MaxEnt) model to predict habitat suitability across Aotearoa for C. fluminea. The model was parametrised with 9,544 observations from across the species’ native and invaded ranges and seven climate, environmental and habitat variables associated with the species’ distribution. The highest risk area are mostly located in Te Ika-a-Māui (North Island), in particular, northern Waikato, Auckland, Northland, Bay of Plenty, Hawke’s Bay and in Te Waipounamu (South Island) areas with the highest habitat suitability included Marlborough, North Canterbury and Christchurch. Our findings suggest there are many invadable areas beyond the Waikato and a strategy of containment and suppression of existing C. fluminea populations should now be a priority, given the difficulty of eradication once further spread has occurred and new populations are well established.

Environmentally relevant concentrations of the tricyclic antidepressant, amitriptyline, affect feeding and reproduction in a freshwater mollusc

Antidepressant drugs (ADDs) are one of the most extensively used pharmaceuticals globally. They act at particularly low therapeutic concentrations to modulate monoamine neurotransmission, which is one of the most evolutionary conserved pathways in both humans and animal species including invertebrates. As ADDs are widely detected in the aquatic environment at low concentrations (ng/L to low µg/L), their potential to exert drug-target mediated effects in aquatic species has raised serious concerns. Amitriptyline (AMI) is the most widely used tricyclic ADD, while monoamines, the target of ADDs, are major bioregulators of multiple key physiological processes including feeding, reproduction and behaviour in molluscs. However, the effects of AMI on feeding, reproduction and mating behaviour are unknown in molluscs despite their ecological importance, diversity and reported sensitivity to ADDs. To address this knowledge gap, we investigated the effects of environmentally relevant concentrations of AMI (0, 10, 100, 500 and 1000 ng/L) on feeding, reproduction and key locomotor behaviours, including mating, in the freshwater gastropod, Biomphalaria glabrata over a period of 28 days. To further provide insight into the sensitivity of molluscs to ADDs, AMI concentrations (exposure water and hemolymph) were determined using a novel extraction method. The Fish Plasma Model (FPM), a critical tool for prioritization assessment of pharmaceuticals with potential to cause drug target-mediated effects in fish, was then evaluated for its applicability to molluscs for the first time. Disruption of food intake (1000 ng/L) and reproductive output (500 and 1000 ng/L) were observed at particularly low hemolymph levels of AMI, whereas locomotor behaviours were unaffected. Importantly, the predicted hemolymph levels of AMI using the FPM agreed closely with the measured levels. The findings suggest that hemolymph levels of AMI may be a useful indicator of feeding and reproductive disruptions in wild population of freshwater gastropods, and confirm the applicability of the FPM to molluscs for comparative pharmaceutical hazard identification.

Molluscophagy in North East India: Assessment of Nutritive Value of Four Edible Freshwater Molluscs

ABSTRACT Since time immemorial, molluscs have been a popular source of food in North East India. Given the historical importance of snail consumption in the region, the current investigation was carried out to assess the nutritional properties of mollusc meat/tissue and shell. Three species of freshwater snails (Cipangopaludina sp. Brotia costula, Filopaludina bengalensis) and the bivalve Lamellidens sp. were identified from five states of North East India. Proximate and elemental analyses of mollusc meat revealed high amounts of nutrients (more crude protein (range 26.75–22.83%) and low fat (3.82–2.70%)) and minerals (especially calcium). Additionally, high levels of polyunsaturated fatty acids were observed (maximum 1.95% in B. costula).

Влияние фосфорсодержащих пестицидов на ферментативную активность и множественные формы кислой фосфатазы живородки речной (Viviparus viviparus L.)

Organophosphate pesticides are used in agriculture and for treating landscape and park areas due to their high efficiency and economic availability, and therefore they are potential toxicants in water bodies. Broad-spectrum systemic herbicide (Glyphosate) and an organophosphorus insecticide (Malathion) have been studied against the freshwater mollusks (Viviparus viviparus L.), widespread in permanent water bodies of the European part of Russia and Siberia. Changes in the activity and composition of multiple forms of acid phosphatase (AcP) were revealed in the hepatopan creas of mollusks under the influence of high doses of glyphosate and malathion in an acute toxicological experiment (96 hours). In both cases, an increase in enzyme activity is observed, but the cholinomimetic malathion is significantly more active than glyphosate, the neurotropic activity of which is unknown. It was shown that the increase in activity in the experimental groups of mollusks is associated with the appearance of new multiple forms of acid phosphatase, which persist throughout the experiment. Multiple form of AсP with low relative electrophoretic mobility revealed as an effect of glyphosate and malathion. In addition, in mollusks exposed to malathion, a multiple form of the enzyme with an average electrophoretic mobility was detected. The composition of multiple forms of acid phosphatase in mollusks of the control group did not change during the exposure. The results indicate the formation of nonspecific adaptations in response to organophosphate pesticides and confirm that acid phosphatase can be an indicator of toxic effects in environmental and biochemical monitoring of freshwater pollution.

Freshwater Molluscs in the Gangetic Riverine System: Present Status of Diversity and Emerging Threats

Freshwater Molluscs in the Gangetic Riverine System: Present Status of Diversity and Emerging Threats

Pathological and ultrastructural changes of Bellamya bengalensis under chronic carboxylic acid exposure at environmentally relevant levels: Inferences from general unified threshold model for survival (GUTS) predictions and hepatopancreatic integrity assessment

This study aimed to understand the effects of freshwater acidification, driven by industrial runoff, agricultural activities, and atmospheric deposition, on the freshwater mollusk Bellamya bengalensis. By systematically investigating the impact of two common carboxylic acids, acetic acid (AA) and benzoic acid (BA), this research employed diverse toxicological, pathological, and ecological assessments. We explored survival predictions through the generic unified threshold model of survival (GUTS-SD), examined oxidative stress responses, and investigated hepatopancreatic alterations. In the experimental design, Bellamya bengalensis were subjected to environmentally relevant sublethal concentrations (10%, 20% LC50) of AA (39.77 and 79.54 mg/l) and BA (31.41 and 62.82 mg/l) over 28 days. Acute toxicity tests revealed increased LC50 values, indicating heightened toxicity with prolonged exposure, particularly due to the greater potency of benzoic acid compared to acetic acid. The GUTS-SD model provided accurate predictions of time-specific effects on populations, presenting long-term exposure (100 days) LC50 values for AA (263.7 mg/l) and BA (330.9 mg/l). Sequentially, the integrated biomarker response (IBR) analysis across study intervals highlighted the 28-day interval as the most sensitive, with GST emerging as the most responsive enzyme to oxidative stress induced by AA and BA. Histopathological and ultrastructural assessments of the hepatopancreas showed severe alterations, including necrosis, vacuolation and disrupted micro-villi, which were especially pronounced in higher BA exposure concentrations. These findings highlight the health and survival impacts of carboxylic acid toxicity on Bellamya bengalensis, emphasizing the need for proactive measures to mitigate acidification in aquatic ecosystems. The broader ecological implications underscore the importance of effective management and conservation strategies to address ongoing environmental challenges

Morphological and molecular data establishes Clinostomum dolichorchum n. sp. (Digenea: Clinostomidae) in the great blue heron Ardea herodias L. and American bullfrog Rana catesbeiana Shaw.

Clinostomum is a cosmopolitan genus of trematodes that infect piscivorous birds, freshwater molluscs, freshwater fish and amphibians. Herein, a novel species of Clinostomum is described based on morphological and molecular data from an adult in the oral cavity of the great blue heron Ardea herodias and metacercariae collected from the gills and skin of American bullfrog tadpoles Rana catesbeiana. The novel species shares similar qualitative and quantitative morphological features with a congener, Clinostomum marginatum, which has overlap in host and geographic distribution. The most notable morphological difference when compared to C. marginatum is the greater posterior testis length of the novel species. Molecular data resolved similarities with morphological comparisons to nominal species and supports the establishment of a novel species. Molecular data include partial small ribosomal subunit (18S rRNA gene), ribosomal internal transcribed spacer regions (ITS1, 5.8S rRNA gene, and ITS2), partial large ribosomal subunit (28S rRNA gene), cytochrome c oxidase subunit 1 gene (cox1), and nicotinamide adenine dinucleotide dehydrogenase subunit 1 gene (nad1) sequences. Phylogenetic analyses place the novel species in a sister clade to C. marginatum. Morphological and molecular data, combined with phylogenetic analyses support the establishment of Clinostomum dolichorchum n. sp.

Findings on three endocommensal scuticociliates (Protista, Ciliophora) from freshwater mollusks, including their morphology and molecular phylogeny with descriptions of two new species

Species of the ciliate genera Myxophyllum and Conchophthirus are found as endocommensals of terrestrial and freshwater mollusks, respectively. So far, there have been few studies of these genera and morphological data for most members are often incomplete. In the present work, two new species, Myxophyllum weishanense sp. nov. and Conchophthirus paracurtus sp. nov., and a known species, Conchophthirus lamellidens, were isolated from hosts in Lake Weishan Wetland, China. Taxonomic studies indicate that M. weishanense sp. nov. can be recognized mainly by the combination of about 60 somatic kineties on both ventral and dorsal sides and the presence of caudal cilia. Conchophthirus paracurtus sp. nov. differs from congeners in its body shape and size, having a glabrous area on the posterior right side, and having fewer somatic kineties. In addition, differences in their ITS2 (Internally Transcribed Spacer 2) secondary structures support the discrimination of the two new species from their highly similar congeners. An improved diagnosis for the poorly known species, C. lamellidens is also provided. Phylogenetic analyses reveal that members of the genus Myxophyllum belong to a fully supported clade that is sister to a large, poorly supported clade consisting of Hemispeiridae, Ancistridae, and several lineages of the nonmonophyletic Cyclidiidae. The Myxophyllum clade also includes Protophyra ovicola JQ956552, a possible misidentification. Sequences of the two new Conchophthirus species cluster with other congeners in a fully supported clade that is unrelated to either the ‘typical’ thigmotrichs or to pleuronematids, thus conflicting with the traditional classification, and may represent an orphan scuticociliate lineage.

Salt tolerance and survival of the freshwater bioinvasive gastropod Melanoides tuberculata (Thiariidae): when different methodologies tell us different stories

ABSTRACT The study of the ecophysiology of invasive species is one of the main steps in understanding the dynamics of territorial expansion of these species and establishing prevention, control, and combat measures and protocols. For freshwater molluscs, one of the main limiting factors is salinity. Laboratory tests closer to reality are needed to make more efficient models. Melanoides tuberculata is an invasive freshwater snail monitored worldwide, and it also has implications for human health. Recent studies supported that its rapid expansion has been enabled through its adaptation to both estuarine conditions and saline waters. The present study aims to determine the real tolerance range of M. tuberculata through a stepwise acclimation test as a more realistic model of a transitional gradient from a lentic to an estuarine environment and so determine the real potential for salinity adaptation. It also aims to check differences in the tolerance responses between age groups and life history, using two distinct populations subject to distinct ambient conditions. The stepwise acclimation test was effective in proving that M. tuberculata may be highly adaptable to salinity variation, contrasting with all previous tests. Thus, the results support the hypothesis of dispersion via estuaries by salinity-tolerant M. tuberculata juveniles.

Freshwater Malacofauna and Distribution of Trabzon, Türkiye

In this study, freshwater molluscs and their zoogeographical distributions in Trabzon were investigated. During the period of June-December 2021, samples were collected from 38 freshwater river localities. From the study area, Ancylus fluviatilis from Gastropoda class, Planorbidae family, non-native species Physella acuta from Physidae family, and Dreissena polymorpha from Bivalvia class and Dreissenidae family were identified. While A. fluviatilis specimens were found from all freshwater systems in Trabzon region, the non native P. acuta could be identified from Fol Stream, Yıldızlı Stream, Sera Lake and Manahoz River. Empty shells belonging to the D. polymorpha species were identified from the area where Çatalzeytin Stream joins the sea. P. acuta and D. polymorpha are new records for the freshwater streams of Trabzon region.

Surveys that prioritize site number over time per site will result in better gastropod status assessments: a case study on the rediscovery of Big Black Rocksnail

Freshwater gastropods are among the most imperiled organisms on Earth. Yet, they are among the most understudied freshwater taxa. Numerous freshwater gastropod species have gone extinct in the last 100 years, but recent rediscoveries indicate that some species were prematurely declared extinct. Such premature extinction declarations remove legal protections, which could facilitate actual extinction. Thus, research and policy recommendations are needed so surveys provide the best information possible for conservation. Here, we examined the case of Lithasia hubrichti, a freshwater gastropod endemic to the Big Black River in Mississippi that was last seen in 1965. In 2022, a freshwater mollusk survey resulted in finding L. hubrichti alive. An additional survey effort in 2023 that prioritized sampling as many sites as possible in a single day clarified the current range of L. hubrichti. Genomic analyses indicated that the species has persisted with a large population size for thousands of years, rather than ever falling below a survey detection limit. When considering the case of L. hubrichti and other recent freshwater gastropod rediscoveries, we conclude that freshwater gastropod surveys should emphasize sampling as many sites as possible under favorable sampling conditions when targeting rare species, rather than expending high sampling effort at a small number of sites or when stream conditions may impact ability to detect target species. We also advocate for policies that encourage partnerships with landowners, which was required to rediscover L. hubrichti.

Diversity of Freshwater Mollusks from Lake Pampulha, Municipality of Belo Horizonte, Minas Gerais, Brazil

The artificially created Lake Pampulha, within the metropolitan area of Belo Horizonte, Minas Gerais State, lacks detailed information about its freshwater mollusks, representing a challenge for the assessment and conservation of this ecosystem. In this study, conducted during June and August 2021, we collected specimens on four different occasions and at five sampling points around the lake, using different sampling equipment, such as a shovel and a scoop. During these collections, we identified, enumerated and measured 1538 species of mollusks and additionally examined the presence of trematode larvae. We identified twelve species of fresh water bivalves and gastropods: Biomphalaria straminea, Biomphalaria kuhniana, Biomphalaria occidentalis, Drepanotrema cimex, Pomacea maculata, Stenophysa marmorata, Physa acuta, Gundlachia ticaga, Melanoides tuberculata, Pseudosuccinea columella, Omalonyx matheroni and Corbicula largillierti. Echinostome and strigeocercaria types of larval trematodes were detected in B. straminea. Notably, some species of mollusks have not previously been recorded at Lake Pampulha. The analyses revealed differences in the composition and abundance of species, highlighting the higher number of mollusk species in areas more impacted by human actions. This study expands our understanding of mollusk diversity at Lake Pampulha, and provides valuable data for longitudinal comparisons of water quality and considerations of the conservation of native species. Furthermore, it highlights the importance of choosing appropriate sampling equipment, depending on the research objectives. The presence of invasive species of medical and veterinary relevance as intermediate hosts of parasites reinforces the need for efficient environmental protection strategies to preserve this artificial, aquatic environment widely used by the local population and by tourists.