Molluscan Diversity Research Articles

Historical changes in mollusc communities from a temperate chenier ridge system (Mont-Saint-Michel Bay, France)

Abstract Coarse-grained chenier ridges contain abundant mollusc shells that help to reconstruct the evolution of marine ecosystems throughout the Holocene, but few temperate environments have been studied. Historical surveys of the mollusc death assemblages sampled in a chenier ridge system from the southern English Channel were compared. Present-day active ridges provide a regional-scale, time-averaged signal of the subtidal mollusc diversity. Back-barrier fossil ridges dated to the Early Medieval Period document pre-industrial baseline conditions. Shellfish farming and invasive species had little impact on mollusc death assemblages recovered from active ridges so far. However, detection of these recent changes is delayed due to taphonomic inertia as shell ages can span more than 1000 years, even in active ridges. Differences in taxonomic and functional composition between fossil and present-day ridges show a decline in grazing and carnivorous species related to macrophytobenthic habitats (seagrass beds and macroalgal belts) and a shift towards a suspensivore-dominated community. The study confirms water temperature as a major driver of ecological change in the English Channel, as warm-water species are more common in present-day ridges. Shelly chenier ridges are useful records of ecological changes in coastal environments that offer a temporal coverage far exceeding that of long-term ecosystem monitoring studies.

Molluscan Diversity Present in Tawarja River at Peth in Latur District of Maharashtra

Latur district is a part of Maharashtra's Marathwada region in the southern part, which is geographically located in the Deccan plateau between 17°52′ and 18°50′ North and 76°18′ and 79°12′ east. It is typically 631 meters (2,070 feet) above mean sea level on the Balaghat plateau. Manjara is the main river which flows on the Balaghat plateau along with its tributaries: Terna, Tawarja and Gharni. The other three tributaries of Manjara are Manyad, Teru and Lendi which flow on the northern plains. Tawarja originates near Murud in Latur taluka and joins the Manjara river at Shivani on the Latur-Ausa boundary. The study was necessary for evaluating the ecological state of water bodies with the help of freshwater molluscs with studies focusing on variety, distribution, and ecology. Two sampling sites were chosen along the Tawarja River in Peth Village for mollusk collection, and these locations were carefully organized from the river's source to its confluence point following various land use/cover patterns. Throughout the course of the research, a total of 13 taxa were noted from all sample sites. The molluscan community was represented by two classes, namely Bivalvia and Gastropoda, with three species belonging to the former and ten to the latter. Three species and one family—the Unionidae—belong to the class Bivalvia. Gastropoda class had three orders, including Mesogastropoda, three families, and seven species. The study's crucial conclusions, which demonstrated that gastropods outnumbered bivalves, were taken. These species can be utilized as bioindicators of pollution and ecosystem health. The findings of this study might contribute to better molluscan fauna management and conservation in the area.

DIVERSITY AND IMPACT OF SEASONAL VARIATION IN THE DISTRIBUTION OF MOLLUSCS IN MANAPADU COASTAL AREA, THOOTHUKUDI DISTRICT, TAMIL NADU, INDIA

Molluscs are economically and ecologically important components of aquatic ecosystems. In addition to supporting valuable aquaculture and wild-harvest industries, their populations determine the structure of benthic communities, cycling nutrients and they serve as prey resources for higher trophic levels. This study aims at identifying the diversity of Molluscs in the coastal area of Manapadu, Thoothukudi District, Tamil Nadu. The result of the study shows that a total of 61 species of molluscs belonging to 35 families were identified. Maximum numbers of species were identified during the post-monsoon season. Minimum species were identified during the summer season. ANOVA was carried out to test the level of significance. Significant results were observed only during the monsoon season. Biodiversity indices were calculated in which maximum species diversity of Shannon(H) Weiner index was noted as 4.107ng during the monsoon season, and minimum species diversity was recorded as 4.037 ng during the post-monsoon season. Alpha index and Margalf’s index were also used in the study which showed varied diversity throughout different seasons. The study shows that molluscan species fluctuated seasonally throughout the year. Suggestions to update the checklist and distribution of Molluscs from the Manapadu region located on the southeast coast of India were presented in this study.

Struktur Komunitas Moluska: Gastropoda dan Bivalvia di Vegetasi Perairan Danau Sentani Papua

Community structure of bivalvia and gastropods nearby water vegetation in Sentani Lake, Papua. Line’s transect and plot methods were used to determining the structure of mollusks and vegetation by using index, diversity, and dominance as parameters. Intentional measurement were carried out on several biological parameters of the waters at 10 sampling points. From the observation and measurments, we obtained seven types of mollusk with 5644 individuals, where six types are belong to gastropods and one type is a member of bivalves. The highest level of mollusk diversity was in Kwadeware, the highest at the inlet of the lake, and were dominated by Melanoides tuberculata and Pomacea canaliculata. In addition, vegetation found in the area observation were water hyacinth (Eichhornia crassipes), water spinach (Ipomoea aquatica), apu wood (Pistia stratiotes), genjer (Limnocharis flava), Hydrilla verticillata, seagrass (Potomogeton malainus), Nymphaea alba, Ceratophyllum demersum, and Nymphoides indica.Key words: gastropods; molluscs; vegetation; Sentani lake

Functional and taxonomic diversity of macroinvertebrates present opposite patterns in tropical estuarine ecosystems

The determination of the processes that act in the assembly of the communities is a theme of growing interest among ecologists. Different processes (e.g., environmental filtering and biotic interactions) can shape the structure of communities depending on the spatial scale analyzed. In this study, we partitioned the functional and taxonomic diversity of polychaete and molluscs communities of tropical estuaries from the hot and humid region, named as typical, and from the semi-arid region into the alpha, beta, and gamma components. The biological communities were sampled in three typical tropical estuaries (Paraíba do Norte, Mamanguape and Passos) and three semi-arid estuaries (Galinhos, Tubarão and Casqueira) once in each dry and rainy period. We used Rao's quadratic entropy and Simpson's index, respectively, to partition the functional and taxonomic diversity. Our results showed that when functional diversity was considered, the alpha component (diversity within sites) presented higher proportions in relation to beta diversity. For taxonomic diversity, the opposite occurred, with higher proportions of beta diversity (diversity between sites). This trend was observed in both seasonal periods. Our results indicate that different processes act in the assembly of the functional and taxonomic diversity of molluscs and polychaetes at different spatial scales. More specifically, biotic interactions seem to be more important in the assembly of functional diversity, while environmental filtering and dispersal limitation seems to have a greater effect on taxonomic diversity. Therefore, functional and taxonomic approaches provided complementary results on the distribution patterns of estuarine communities at different spatial scales.

Diversity of mollusc communities in some aquatic habitats of Shatsk Lake Area

Background. The paper presents the results of an original research on groups of freshwater molluscs in some water habitats of Shatsk Lake Area. The Shatsk National Nature Park belongs to the Volynian Polissia according to physical and geographical zoning. Aesthetic appeal, clear water, clean sandy lake bottoms, pine forests, etc., are attracting more visitors to the park every year. The recreational value of the Shatsk National Nature Park in the summer season is significant. The high anthropogenic load accelerates the intensity of eutrophication of lakes and promotes the overgrowth of the shores with macrophytes, which eventually leads to an increase in the density of the macrobenthos, in particular the malacofauna of the lakes. Material and Methods. Research was conducted in the summer period of 2013–2014 and 2018–2020 on some water bodies of the Shatsk National Nature Park with different trophic state including Lakes Svityaz, Pisochne, Lyutsymer, Krymne, Ostrivyanske and Somynets. Results. Freshwater molluscs are convenient subjects for water pollution stu­dies because they are good indicators of habitat quality. Svityaz and Pisochne Lakes belong to slightly mesotrophic water bodies, which are actively used for recreational purposes. Among water bodies under study, Lake Svityaz is characterized by the most significant species diversity of molluscs (23 species). Lakes Lyutsymer and Krymne are mesotrophic water bodies exposed to a high anthropogenic load. The largest number of bivalve molluscs of the genera Unio and Anodonta is characteristic of Lake Lyutsymer, while in Lake Krymne, the lowest species diversity of malacofauna (13 species) was observed. Lakes Ostrivyanske and Somynets are mesotrophic shallow water bodies. We detected a significant increase in the species composition of molluscs in these lakes during the research period. Conclusions. The research of the qualitative and quantitative composition of the malacofauna revealed an increase in the number and species diversity of molluscs. In addition, the spread of an invasive New Zealand snail Potamopyrgus antipodarum to new water bodies on the territory of Shatsk Lake Area has been recorded.

Diversity and distribution of molluscs (Gastropoda and Bivalvia) in the seagrass beds at Pulau Gazumbo, Penang, Malaysia

Diversity and distribution of molluscs (Gastropoda and Bivalvia) in the seagrass beds at Pulau Gazumbo, Penang, Malaysia

Mollusk death assemblages from the deep slope off northwestern Cuba (Gulf of Mexico)

We evaluated the mollusk death assemblages along seven sites in a deepsea expedition off northwestern (NW) Cuba. We aimed to (1) provide the first baseline of mollusk diversity in sediments of the NW region, and (2) test if there were west-east gradients of α- and β-diversities. We found 141 species in sediments: 68 deepsea benthic, 43 shelf benthic, and 30 pelagic species. The richness of pelagic species was similar along the NW region indicating significant settlement of pteropod shells to the seabed. The occurrence of shelf species in the deepsea suggested a downslope transport of shells enhanced by the slope steepness and dredging in two ports. β-diversity of deepsea benthic mollusks showed a high turnover at local scales explained by habitat heterogeneity. β-diversity of pelagic species was extremely low suggesting that the planktonic assemblage was evenly distributed. In contrast, high β-diversity of shelf benthic species occurred likely due to downslope transportation of materials. Deepsea gastropods were mostly detritivores, while bivalves were mostly suspension feeders. These dominant biological traits indicated oligotrophic conditions in sediments likely coupled with an intense hydrodynamic regime in the deepsea. The NW Cuban region seems to be a hotspot for mollusk diversity because of the discovery in a single expedition of seven new species, 12 new records, and 36% endemism relative to the entire Gulf of Mexico. Our findings revealed a complex and diverse mix of deep/pelagic/shelf species but did not indicate a west-east gradient in the mollusk assemblage structure.

Mollusk Diversity in Percut Sei Tuan Silvofishery Ponds, North Sumatra, Indonesia

Highlight Research We found 16 species of mollusks with a total of 15 species from the gastropod class and 1 species from the Bivalvia class bivalves in the silvofishery ponds, recording a total of 369 individuals. The density of mollusks in July in pond I was 3.6 ind/m2, while it was 10.66 ind/m2 in pond II. The mollusk diversity index in October after rehabilitation was included in the high diversity category because the value of H' was 1.6 - 3.0. Pond I has a diversity index value of 1.89 and pond II 1.82. The value of C-organic concentration in both ponds ranged from 3.00% to 5.72%, which is the optimum level for mollusk growth. Abstract Silvofishery is a system that combines mangrove and fishery to protect mangrove ecosystems and restore their functions, one of which is as a habitat for macrozoobenthos. Investigate the mollusks and mangrove density. Mollusk sampling was carried out on sub-plots measuring 1 x 1 m² in the mangrove vegetation transect, and mangrove density was measured by counting the number of trees directly on all of the mangrove species at two silvofishery ponds. A total of 16 species of mollusks were found at the observation site, consisting of gastropods and bivalves. The density of mollusks in July was 20 ind/m2 in pond I, while it recorded 9 ind/m2 in pond II. In October, after pond II rehabilitation, the density was inversely proportional to July, and the highest density was found in pond I at 10 ind/m2, while pond II measured 9 ind/m2. After rehabilitation, the index value H’ decreased in pond I and pond II from 2.82 and 2.98 to 2.52 and 2.68, respectively. The mangrove density was 887 ind/ha in pond I and 686 ind/ha in pond II. The substrate in both ponds was clay. Nitrate concentration values ​​in the substrate in both ponds ranged from 0.27% to 0.29%, phosphate recorded a percentage of 0.07–0.09%, and C-organic ranged from 3.00% to 5.72%. The water's physicochemical parameters and the type and content of the substrate were still suitable for mollusk life.

Species diversity and DNA barcode library of freshwater Molluscs of South Caucasus.

This study provides the first attempt to investigate the molecular diversity of South Caucasian freshwater molluscs (Mollusca, Gastropoda) and lay down the first bricks to build up a DNA-barcode library. In total, 289 COI barcode sequences were obtained from 33 morpho-species belonging to 24 molluscan genera and 10 families that represent nearly 30% of known freshwater molluscan diversity of the South Caucasus region. DNA barcodes were analysed by means of the Barcode Index Number (BIN) and the other tools available in BOLD Systems. Results showed that the knowledge of freshwater molluscs diversity in the South Caucasus is far from comprehensive. For the studied 33 morpho-species, 289 barcodes were clustered into 40 BINs, from which unique BINs were defined for 12 species and five species were characterised with more than a single BIN. From the studied taxa, 60% were characterised larger than 2.2% sequence divergence indicating high genetic variation or cryptic diversity. Within our limited taxonomic coverage, we found one new species for the Republic of Georgia (Galbaschirazensis) and at least three undescribed species belonging to the genera Stagnicola, Segmentina and Anisus. Uniqueness and high molecular diversity of the studied species emphasise the need for further intensive morphological and molecular investigations of the South Caucasian freshwater molluscan fauna.

Loss of lateral hydrological connectivity impacts multiple facets of molluscan biodiversity in floodplain lakes

Lateral hydrological connectivity (LHC) is a key process in maintaining aquatic biodiversity in river floodplain ecosystems. However, the effects of LHC loss on aquatic biodiversity are rarely studied. Here, we evaluated, for the first time, the responses of multiple facets (i.e., taxonomic, functional and phylogenetic) of alpha and beta diversity of freshwater molluscs to the LHC loss in 23 floodplain lakes in the Yangtze River Basin in China. Our results showed that taxonomic and functional alpha diversities were all significantly higher in connected lakes (CLs) than in disconnected lakes (DLs), whereas phylogenetic alpha diversity (Δ+) was lower in CLs than in DLs. For beta diversity facets, taxonomic (Tβsor) and phylogenetic (Pβsor) dissimilarities were slightly more contributed by the turnover component or equally contributed by the turnover and nestedness-resultant components both in CLs and DLs. Instead, functional beta diversity (Fβsor), generally showing much lower values than Tβsor and Pβsor, was mainly contributed by the nestedness-resultant component (76.6–84.0%), especially in DLs. We found that only functional dissimilarities were significantly higher in DLs than CLs, indicating a high level of functional diversity loss without replacement of species possessing traits sensitive to hydrological disconnection (i.e., large body size, lamellibranch body form, filter feeding, ovoviviparity and burrowing habits). In general, lake area, hydrological connectivity, aquatic vegetation coverage and nutrient levels (TN and TP) played important roles in structuring variation in molluscan alpha and beta diversities, although the three diversity facets responded to different environmental factors. Our results suggest that loss of connectivity to the mainstem river has negative impacts on molluscan assemblages in floodplain lakes. More importantly, as taxonomic, functional and phylogenetic diversities responded somewhat differently to the loss of hydrological connectivity, all of these biodiversity facets should be better incorporated into aquatic biodiversity assessment and conservation programs in large river floodplains.

Molluscs as bioindicators of tourism pressure on ecosystems of Dilijan National Park, Armenia

ABSTRACT Research on the impact of tourism on ecosystems in protected areas has grown in recent years as a part of the debate on how to efficiently combine the use and conservation of natural habitats. Various taxa have been used as indicators through the use of invertebrate animals that have remained modest. The impact of uncontrolled flow of tourism on indicator species richness and diversity in the Dilijan National Park was studied. Diversity, species richness, and abundance of terrestrial molluscs were used as response variables to analyze the impact of tourism on ecosystems for the first time. We found significant differences in the diversity, species richness, and abundance of terrestrial molluscs between the control and experimental plots. Species richness and abundance were not so different in spring but in the autumn almost twice higher total abundance and species richness were detected in control plots. Moreover, out of 31 detected species, the 5 rare ones were found in control plots with low human presence. We conclude that the high intensity of tourism harms the communities of land snails. We suggest that terrestrial molluscs show sensitivity to human presence and can be used to study the direct impact of tourism-related ecosystems in protected areas.

Marine mollusc (Mollusca: Gastropoda and Bivalvia) diversity of the Saya de Malha and Nazareth Banks, Mascarene Plateau

Marine molluscs are among the largest assemblages of the animal kingdom and inhabit the marine environment from the intertidal zone to the deep sea. This study reports the diversity of marine molluscs (Gastropoda and Bivalvia) collected from sediments at 19 stations (SS) at the Saya de Malha and Nazareth Banks during the EAFNansen expedition in May 2018. Sampling was carried out using the five hydraulic Van Veen grabs mounted on a Video-Assisted Multi-Sampler (VAMS). The mollusc shells were morphologically identified using established procedures and published guides. Shannon-Wiener diversity (H’) and Pielou’s evenness (J) indices were used to assess the diversity of the molluscs at each station. A total of 56 genera of marine gastropods belonging to 34 families, and 40 genera of bivalves from 16 families were recorded. The SS8 station at the Saya de Malha Bank had the highest diversity at a depth of 79 m for Gastropoda and Bivalvia, while SS1 harbored the highest overall molluscan diversity. At the Nazareth Bank, highest gastropod diversity was recorded at SS44, while SS43 had the highest bivalve and overall molluscan diversity. This study provides new information on the molluscan diversity at the Saya de Malha and Nazareth Banks.

Revisiting the Annandale malacological collection from Inle Lake, Myanmar kept in the Kyoto University Museum

ABSTRACT Inle Lake in central Myanmar is one of the hotspots of freshwater biodiversity in Southeast Asia. A small malacological collection from the lake made by Thomas Nelson Annandale and discovered at the Kyoto University Museum, Japan was examined here. In the collection comprised of thirty specimens, nine species in seven families were identified. The collection also included four species and one subspecies which were newly described by Annandale. Two subspecies, Hydrobioides nassa lacustris Annandale, 1918 and H. n. rivulicola Annandale, 1918, were identified in a single lot. The correspondence of the shell morphology of Lamellidens ferrugineus (Annandale, 1918) between the present study and the original description indicates that the specimen is a paratype of the species. The rediscovered collection provides us with insights into the species definition of Annandale and the molluscan diversity of the lake prior to recent environmental changes.

Increased information on biodiversity from the neglected part of the North Pacific contributes to the understanding of phylogeny and taxonomy of nudibranch molluscs

Understanding of the biological diversity, involving molecular phylogenetic methods, is a fundamental task for a broad array of evolutionary, taxonomic, and ecological studies, as well as a basis for conservation. Our hydrobiological survey during an expedition in 2021 to the coastal waters of the Kuril Islands (the northwestern Pacific) revealed the undocumented diversity of the nudibranch molluscs. Two new species of the genera Zelentia and Cuthonella are described here using analysis of fine-scale morphological and molecular data. Representatives of the genus Zelentia prior to this study were known only from the North Atlantic and from the Canadian and US northeastern Pacific. In addition, two new distributional records of the previously described species Cuthonella denbei Korshunova et al., 2020 and Cuthonella soboli Martynov, 1992 are presented here for the first time. The molecular phylogenetic framework for the majority of the species of the genera Cuthonella and Zelentia, including the two new species, confirmed the taxonomic distinctness of the genus Zelentia (family Trinchesiidae) and the genus Cuthonella (family Cuthonellidae), and represents another important result of this study.

Study of intertidal molluscan diversity of the Dakshina Kannada coast, India using remote sensing and GIS techniques

Study of intertidal molluscan diversity of the Dakshina Kannada coast, India using remote sensing and GIS techniques

Terrestrial molluscs species richness and diversity in Gashaka - Gumti National Park, Taraba State, Nigeria.

To assess the biodiversity of terrestrial molluscs in Gashaka-Gumti National Park, a four plot (20 x 20m) each within the park were sampled by searching the forest floor, tree trunk, fallen logs, root facies, and vegetation for the presence of mollusks. The species found were collected by hand picking.A total of 819 specimens comprising 22 species belonging to six molluscan families were collected from four plots. Each plot yielded between 8 to14 species (Mean:10, Standard Deviation:2.71) and 33 to 683 individuals (Mean:204.75, Standard Deviation :319.09). The most abundant species in the park was Curvella sp. represented by 683 individuals (79.4%) of the total sampled species. The most abundant family is Streptaxidae represented by 8 species (36.4%) of the total sample.The sample intensity was 37.22 while the Inventory Completeness is 79.31%. Eleven (11) species occurred as singleton across plots while ten (10) species occurred as doubleton across the four plots sampled.The Whittaker Index is 4.00. The rarefaction curve nearly reached an asymptote as sampling stopped. The nonparametric estimator Chao 2 and jackknife 2 were 28.05 and 33.99 of all sample collected. The dendogram of similarity by plots using Bray-Curtis similarity of index show the close relationship of two plots in terms of species. It shows that there is no significant difference between plots. Plot 1 and 4(P=0.4329), Plot 2 and 3 (P=0.9595), Plot 1 and 3 (P=0.2390), Plot 2 and 4 (P= 0.78). In conclusion, the family Subulinidae has the most abundant individuals with 733 individuals representing 89.4% while Streptaxidae occur as the most abundant family with 8 species of the total sample.

Interaction among macrobenthic molluscan diversity of river Ganga and ecological variables by using multivariate indices

Interaction among macrobenthic molluscan diversity of river Ganga and ecological variables by using multivariate indices

Diversity and distribution of bivalve molluscs in the Central Cantabrian Sea and the Avilés Canyons System (Bay of Biscay)

Bivalve molluscs is one of the dominant benthic groups in soft-sediment communities off the Atlantic Ocean, including the European margin and the Bay of Biscay. The current knowledge of deep-sea Euro-Atlantic bivalves and their distribution is still far from comprehensive and has been the scope of several recent publications. We examined the collected bivalve samples from two oceanographic campaigns (COCACE and BIOCANT) carried out in the central Bay of Biscay, including the Avilés Canyons System (ACS), a Site of Community Importance within the Natura 2000 Network. Bivalve specimens were collected from the continental shelf, slope and bathyal zones, ranging in deep from 25 to 4700 m. This is the first study focused on bivalve diversity from the Cantabrian Sea that covers such a wide bathymetric range. Eighty-four live taxa in 36 families were identified; Cetomya neaeroides is reported for the first time in the area. We provide photographs showing the shell diagnostic features of all recorded species. The conducted Multivariate Analysis showed three species assemblages: i) samples from shallow waters (continental shelf); ii) intermediate depths (shelf and upper slope) and iii) deep water (slope and abyssal plain). Depth was the main structuring factor that influenced the distribution of the recorded species and the higher species richness was found on the continental shelf. The feeding strategy and the substrate preference appeared as not significant factors in the zonation patterns of the studied bivalves.

Factors Controlling the Distribution of Intermediate Host Snails of Schistosoma in Crater Lakes in Uganda: A Machine Learning Approach

Schistosomiasis affects over 700 million people globally. 90% of the infected live in sub-Saharan Africa, where the trematode species Schistosoma mansoni and S. haematobium transmitted by intermediate hosts (IH) of the gastropod genera Biomphalaria and Bulinus are the major cause of the human disease burden. Understanding the factors influencing the distribution of the IH is vital towards the control of human schistosomiasis. We explored the applicability of a machine learning algorithm, random forest, to determine significant predictors of IH distribution and their variation across different geographic scales in crater lakes in western Uganda. We found distinct variation in the potential controls of IH snail distribution among the two snail genera as well as across different geographic scales. On the larger scale, geography, diversity of the associated mollusk fauna and climate are important predictors for the presence of Biomphalaria, whereas mollusk diversity, water chemistry and geography mainly control the occurrence of Bulinus. Mollusk diversity and geography are relevant for the presence of both genera combined. On the scale of an individual crater lake field, Biomphalaria is solely controlled by geography, while mollusk diversity is most relevant for the presence of Bulinus. Our study demonstrates the importance of combining a comprehensive set of predictor variables, a method that allows for variable selection and a differentiated assessment of different host genera and geographic scale to reveal relevant predictors of distribution. The results of our study contribute to making realistic predictions of IH snail distribution and schistosomiasis prevalence and can help in supporting strategies towards controlling the disease.