Abundance Of Molluscs Research Articles

Optimizing mangrove afforestation: Mollusc biodiversity comparisons reveal optimal mudflat-mangrove area ratio.

In recent decades, mangrove wetlands globally have suffered from human activities and climate change, leading to issues like area reduction, degraded ecological functions and declining biodiversity. Restoration efforts, primarily through mangrove afforestation (i.e. mangrove plantation in mudflats), have been widespread, yet they often overlook the significance of unvegetated mudflats. In addition, under the condition that the total area of suitable mudflats is limited, the problem of what is the threshold of mangrove forests and unvegetated mudflats to better protect mangrove biodiversity has not been solved. Therefore, this study conducted a field survey of molluscs in mangrove wetlands in Hainan Island in China and explored the relative importance of mangroves and unvegetated mudflats through taxonomic alpha diversity and functional diversity. The results showed that (1) mollusc abundance of unvegetated mudflats was notably higher than this of mangrove forests, and the species richness, functional richness and functional vulnerability were significantly lower than those of mangrove forests; (2) the abundance and functional vulnerability of molluscs were mainly affected by sediment properties (pH, interstitial water salinity, median diameter, total nitrogen, C/N ratio), while the species richness and functional richness of molluscs were primarily influenced by vegetation structure (plant density); and (3) retaining at least 20% of the unvegetated mudflat area could well protect the biodiversity of mangrove wetlands. To our knowledge, our study is the first to propose the proportion of mangrove forests and unvegetated mudflats on the basis of benthic biodiversity, providing theoretical support and decision-making reference for mangrove protection and restoration.

Paleodepositional Environment of Kaliwangu Formation based on Mollusc Fossils Assemblage in Ciwaringin River, Leuwimunding Area, Majalengka, West Java, Indonesia

Abstract The Kaliwangu Formation in the Leuwimunding area, Majalengka Regency, West Java Province, Indonesia is exposed in the Ciwaringin River and its tributaries. This location contains abundant mollusc fossils. However, it has not been mentioned in the Javan Mollusk Neogen Stages. The exposed rocks are Pliocene sandstones and claystones layers. The purpose of this study was to determine changes in the paleodepositional environment at the study site based on the mollusc fossils content. Data was collected from fieldwork by measured section in 8 observation locations containing mollusc fossils along the Ciwaringin River. The mollusc fossils of the rework results were separated, then an association was made for the molluscs based on the abundant fossils found in each layer. The results of the preparation of fossils on 11 rock samples obtained 309 individuals from 63 specimens of molluscs. From these samples, there are 11 mollusc association were determined. The sequence from bottom to top are: Marginella ventricosa sangiranensis association, Arca nodosa association, Paphia sp. association, Turritella simplex – Placuna sp. associations, Natica zebra – Bicorbula tjiguhanensis association, Timoclea bataviana – Turritella bantamensis association, Nassaria suturalis tjemoroensis association, Ostrea sp. association, Timoclea bataviana association, Arca nodosa – Columbella sp. association, and Turritella djadjariensis – Turritella javana association. The mollusc fossils association shows 3 paleodepositional environments and there are 6 changes in the paleodepositional environment, namely from intertidal – subtidal to intertidal, shallow marine, subtidal, shallow marine, subtidal, and returning to shallow marine. In general, there was a rise in sea level at this location.

Hubungan komunitas moluska dengan parameter lingkungan di kawasan mangrove Pulau Penyu, Tanjung Benoa, Bali

Mangroves are plants in coastal and estuary areas that are influenced by tides. Mangroves provide essential habitats as spawning, nursery and food sources for various biota, including mollusks. Mollusks have a reciprocal relationship with mangrove plants, play an important role in maintaining the balance of the food chain in mangrove ecosystems. The objective of the research is to establish the structure of the mollusk community and its correlation with environmental conditions in the Pulau Penyu mangroves. The study was carried out in September 2023. The method employed the 1x1m quadrat transect with 15 points per station. Salinity, pH, temperature and substrate type are all measurements of environmental conditions. The research revealed 24 species, including 20 gastropod species and 4 bivalvia species from 12 mollusk families. Families found include Potamididae, Cerithiidae, Batillariidae, Ellobiidae, Mitridae, Neritidae, Littorinidae, Naticidae, Muricidae, Veneridae, Cyrenidae and Corbulidae. Mollusk abundance ranged from 0,07 to 13,07 ind/m2 at the research site, with Cerithium coralium being the most abundant species and Corbula macgillivrayi being the least abundant. The results of diversity index is 1,90 to 2,25; evenness index is 0,68 to 0,78; dominance index is 0,18 to 0,25; indicating moderate species diversity, high individual numbers each species, and no dominant species. The range of environmental parameter values obtained were; temperature ranges from 34,1 to 35,37 oC; pH ranges from 6,43 to 6,68; and salinity ranges from 35,2 to 36,3 ppt. The substrate type at the research site was sandy clay and clayey sand. PCA analysis results indicate a strong relationship between mollusk abundance and pH, salinity and sand fraction, but very weak relationship with temperature, dust and clay fraction.

Effects of different hydrological conditions on the taxonomic structure and functional traits of mollusk communities in a large floodplain wetland.

Floodplain wetlands are critical to the conservation of aquatic biodiversity and the ecological integrity of river networks. However, increasing drought severity and frequency caused by climate change can reduce floodplain wetlands' resistance and recovery capacities. Mollusks, which are common inhabitants of floodplain wetlands, are among the most vulnerable species to drought. However, the response of mollusk communities to drought has received little attention. Here, we investigated how the structure and functional traits of mollusk communities changed in response to varying hydrological conditions, including a flash drought (FD) in the Poyang Lake floodplain wetland. Our findings showed that FD strongly reduced mollusk abundance and biomass, decreased both α- and β-diversity, and resulted in the extinction of bivalve taxa. A sudden shift in community trait structure was discovered due to the extinction of many species. These traits, which include deposit feeding, crawling, scraping, aerial respiration, and dormancy, help mollusks survive in FD and tolerate completely dry out of their Changhuchi habitat. Finally, we discovered that dissolved oxygen was an important controlling variable for mollusk communities during drought. Our findings provide a scientific basis for the management and conservation of floodplain wetland biodiversity in the context of increasing drought frequency and intensity.

MOLLUSKS DIVERSITY IN THE PROTECTED COASTLINE OF BERBAK-SEMBILANG NATIONAL PARK INDONESIA

Mollusk has a role as a food source in benthic ecosystems. Presumably, there has been a decrease in its diversity on the protected coastline of Berbak-Sembilang National Park (BSNP) due to fluctuations in water quality parameters that threaten the sustainability of another biota in the web food system. The purpose of this study was to describe the diversity of mollusks and their correlation with water quality in the protected coastline area. The research methodology was carried out, namely: water quality data collection, mollusk sampling, diversity analysis, and correlation analysis. Principal component analysis and similarity analysis were used. The results showed that there were 28 species of mollusks, which were classified into two classes: Bivalvia (79%), and Gatropoda (49%), with 21 species. The mollusk abundance means 263.25 ind.m-2, and the diversity is categorized as low H'1 except stations 2 and 4. It is supported by the dominant species, namely Anadara granosa (36.61%), and Nutricola sp. (35.47%. There are two clusters of mollusks: open coastal areas are characterized by higher temperatures, nutrients, salinity, pH, currents, and brightness, and estuary clusters are characterized by higher dissolved oxygen and mollusk abundance.

Abundance, Distribution, and Diversity of Freshwater Snail and Prevalences of Their Infection by Cercaria of Fasciola gigantica and Schistosoma spp at Mayo-Vreck River, Far North Region of Cameroon.

Malacological and parasitological studies were conducted from April 2020 to March 2021 to determine the abundance and distribution of molluscs and cercariae of Schistosoma spp and Fasciola gigantica. Collected molluscs are exposed to strong light to induce cercarial release. Mollusc densities were higher at station 1 (Gamak) than in station 8 (Patakai), with Bellamya unicolor and Biomphalaria pfeifferi more abundant and Bulinus truncatus, B. tropicus, and B. globosus less abundant. The overall prevalence of cercariae (19.87%) is higher in station 3 (Yaye orchard), station 9 (Gougni), station 4 (Madiogo), station 5 (Madiogo pasture), and station 6 (Ziam 3). It varies significantly between 15.76% in station 8 and 25.77% in station 3, between 8.48% in B. truncatus and 25.53% in B. globosus, and between 19.27% for cercariae of Schistosoma spp and 21.60% for those of F. gigantica. Cercarial emissions in L. natalensis and B. pfeifferi were higher in hot and cold dry seasons; on the other hand, cercarial emissions in B. globosus were higher in hot dry seasons (31.48%) and rainy seasons (23.38%). Emissions of cercariae from S. haematobium are related to areas of human activity and defecation, while those of F. gigantica in L. natalensis, Schistosoma haematobium in B. tropicus, and S. mansoni in B. pfeifferi are related to grazing areas. Mayo-Vreck is a site that favors the endemicity of fascioliasis and human schistosomiasis.

Diversity and species richness of land snails inhabiting an impacted macro-zone-Mfamosing limestone hill in Sub-Saharan Region

The land snail diversity and abundance and some ecological aspects of the fauna in a threatened limestone hill in Mfamosing, Cross Rivers state, Nigeria was investigated between May 2017 and June 2018. Twelve plots of 10 m x 10 m each using a combination of leaf litter in the forest floor (litter and topsoil in a total of ninety sample bags) were sampled from which shells were extracted by handpicking. A total of 289 (two hundred and eighty-nine) specimens representing twenty-three species in seven molluscan families were recorded. The carnivorous Streptaxidae family dominated the fauna regarding species richness while the family Urocyclidae dominated species abundance. The families Eucolinidae and Aillyidae accounted for the least dominant species. The family Streptaxidae with seven species accounted for over 30% of the mollusk abundance, while Urocyclidae had the highest number of individual specimens. True estimates of diversity using Chao2 and second-order Jack-Knife estimators yielded 25 and 24 species respectively. The Land Snail diversity in Mfamosing limestone hill when compared with those from other parts of Nigeria (Okomu in Edo State) and some other parts of the world (Sabah, Malaysia) is relatively high, with moderate levels of species abundance, showing relatively high differentiation, local dominance and endemism by few species. This reveals that Mfamosing limestone hill is one of the biodiversity hotspots for terrestrial mollusks and requires urgent conservation measures, given the current rate of Limestone quarrying in the region.

Tergomyan molluscs from the Early Ordovician of the Llangynog Inlier, South Wales, UK

A low abundance but diverse fauna of tergomyan molluscs is described from the Llangynog Inlier, Carmarthenshire, South Wales. The specimens originate from a single quarry exposing shallow-water siltstone and mudstone beds of the Early Arenig (early Floian) Bolahaul Member of the Ogof Hên Formation. The fauna includes Proplina areniga sp. nov., Proplina? obtusa sp. nov., Celtopileus calvapex gen. et sp. nov. with preserved muscle scars, Costulaconus mirificus gen. et sp. nov., and Hypseloconus? sp. Comparable tryblidiid taxa are mainly found in the Lower Ordovician of Midwestern USA among species of Proplina Kobayashi, 1933 and Gasconadeoconus Stinchcomb, 1986. The tentative assignment of the predominantly late Cambrian Hypseloconus is symptomatic of the many uncertainties regarding the phylogeny of the tryblidiids. The diverse assemblage of organisms preserved at the single locality represents one of the most remarkable faunas of this age worldwide.

INVENTORY OF AQUATIC MOLLUSCS IN THE SOUBRE RIVER-LAKE DAM AREA TO ASSESS THE BIOLOGICAL STATUS OF THIS AQUATIC ECOSYSTEM (SASSANDRA RIVER, COTE DIVOIRE, WEST AFRICA)

The aim was to study the population dynamics of aquatic molluscs in relation to abiotic variables in the fluvio-lacustrine zone of the Soubre hydroelectric dam, in order to determine its bioecological status. The Mollusc class and physico-chemical parameters were sampled monthly in two periods, the first from July 2019 to February 2020 and the second from March 2021 to June 2021 at six (06) sampling stations. The total abundance was 16,885 individuals divided into 16 taxa belonging to two (02) classes, five (05) orders and ten (10) families were identified. The stations located in the lake recorded the highest number of individuals, while the TIE station (Tieme, 13 taxa) located in the fluvial environment was the most diverse of all the sampling sites. Taxa such as Melanoïdes tuberculata, Indoplanorbis exustus and Viviparus sp. appeared frequently in all the sampling stations. Focused Principal Correspondence Analysis (FPCA) revealed that turbidity, TDS and dissolved oxygen had a strong influence on the abundance of molluscs at the sites studied. Several species studied in our environment are important intermediate hosts of parasites, in particular Planorbidae (Indoplanorbis exustus), which represents a potential risk to public health. However, three invasive taxa, Aplexa marmorata, Indoplanorbis exustus and Melanoïdes tuberculatawere collected. The biological condition of the sampling sites was generally good. Assuming that the ecological state of the sediments in the lake environment is not yet damaged.

Benthic mollusc communities across space and through time in a hypersaline coastal lagoon, Mexico

The coast of the Yucatan Peninsula (Mexico) has undergone numerous changes over the last century as a result of population growth, shifts in land use, establishment of industries, and storm impacts. To understand how the mollusc fauna responded to these changes over time, paleoecological studies were conducted to compare historical and modern data, and to reveal information on past environmental conditions. We analyzed mollusc assemblages in sediment cores from Río Lagartos coastal lagoon, which span the last ∼70 years. Mollusc assemblages in the sediment cores were compared to a modern inventory of Mollusca fauna, which was compiled to assess species distributions associated with multiple environmental variables. Mollusc assemblages from the sediment cores (17,089 specimens), which represent 19 bivalve and 43 gastropod species, and modern inventory datasets possess the same ubiquitous species and the same feeding guilds, i.e., groups that exploit the same food resources. Nearly twice as many species were identified in the sediment cores as in the modern inventory. This finding probably reflects the fact that the mollusc community changed through time at the core sites in response to shifting environmental conditions. Nevertheless, we encountered a number of taxa in the modern survey samples, which were absent from the sediment cores. This was probably a consequence of the limited spatial coverage of the cores and small diameter of the core barrels, which precluded sampling of large taxa. We report differences in mollusc abundance and taxonomic composition in the cores across space and time, which may be related to salinity changes in the lagoon and modifications of the nearby terrestrial environment.

Patterns of rock pool molluscs in differing shore exposures

Rock pools are understudied systems of extreme importance due to their proven vulnerability to climate change. Rock pool molluscs play essential ecological roles therein, directly by acting both as prey and predator and, indirectly by influencing the macroalgal canopy/vegetation topography via grazing. However, the environmental factors driving their rock pool occupation remain largely unknown. Our study is one of the few to focus on community patterns in rock pool molluscs, particularly at a large scale between shores of differing exposure to wave action, being the first focused assessment of rock pool molluscs in Portugal. Overall, 32 intertidal rock pools on four rocky shores were studied during the summer spring tide of 2015. We used multivariate analysis to evaluate the potential impact of sheltered versus exposed wave action, physical pool structure (length, width, and depth), and relationships within the pool community on the abundance and diversity of molluscs. Wave exposure significantly influenced mollusc abundance and diversity. The majority of the 37 different taxa identified were grazing gastropods (62.2%), followed by bivalves (27.0%) and chitons (10.8%). We suggest that mollusc taxa may have preferences for particular rock pool habitats depending on the type of algae present rather than pool size. We also suggest that species-specific mollusc presence in rock pools can be related to their shell size, aperture, and foot size due to corresponding variation in musculature needed to hold the snail to the substrate in hydrodynamic conditions. Further investigation would benefit from disentangling the potential role of algal pool coverage as a refuge for molluscs.

Long-term relationships between the abundance of pest molluscs and weather in agricultural fields in South Australia

ABSTRACT Invasive snails, Cernuella virgata, Theba pisana and Cochlicella acuta, infest grain crops prior to harvest in early summer in southern Australia. They breed in autumn–early winter and peak in abundance in spring following the recruitment of young snails. Long-term studies (20 years) were established on three farms in South Australia (two practicing pasture–cereal rotations and one continuous cropping) to better understand the role of prevailing weather in driving the population dynamics of the three snail species and to develop predictive models that might assist farmers and off-farm grain handlers to anticipate future peaks in snail abundance and tailor their management practices accordingly. The three species are asynchronous in their population dynamics; they peak in numbers in different years. The abundance of C. virgata in late spring (preharvest) was most closely associated with, and could be broadly predicted by, the previous autumn to spring rainfall, but no significant associations were found between the rainfall and the abundance of C. acuta and T. pisana. Local air temperatures had little apparent association with the abundance of all three species. Broader scale weather, exemplified by the El Niño Southern Oscillation Index, was only occasionally, and weakly, related to the spring abundance of C. virgata.

Assessing benthic reef assemblages: A comparison between no-take artificial reefs and partially protected natural reefs

The marine protected area (MPA) of the Espiritu Santo Archipelago (ESA; Gulf of California), is exposed to a high level of anthropogenic disturbances, consequently, the local authorities have deployed artificial reefs (shipwrecks) in the ESA area to increase fishing refuges, breeding sites, and tourist attractions. To explore the potential contribution of these artificial reefs as a conservation tool, we compared their benthic community structures (i.e. diversity and live cover categories) to those of the natural reefs. Our results indicate a higher abundance of mollusks on the artificial reefs compared to the natural reefs; a higher echinoderm abundance on the natural reefs; and a very similar species richness of hexacorals between the natural and artificial reefs, with 10 and 9 species recorded respectively. The natural reefs hosted a four-fold higher live cover of hexacorals than the artificial reefs, while the artificial reefs had a higher number of octocoral species, 8 versus 5 on the natural reefs. In addition, the artificial reefs had a 4.6 fold higher octocoral cover than the natural reefs. Overall findings indicate that the benthic community assemblages significantly differ between the natural and artificial reefs, which may be related to their location, structural composition, material, and morphology. These results suggest that shipwrecks have the potential to enhance local reef diversity by increasing the cover and abundance of certain benthic-associated species. Although the shipwrecks do not function as surrogate habitats for the adjacent natural rocky reefs, as no-take areas they provide suitable refuges for several target species (e.g. black coral and mollusks).

Contributions of climate andBrassica oleraceacultivar to gastropod abundance and assemblage in southeastern Brazil

AbstractTerrestrial gastropods (slugs and snails, Mollusca: Eupulmonata) are destructive pests of brassica crops. These organisms defoliate plants and contaminate the harvest, leading to reduced crop yield and marketability. Losses caused by molluscs have escalated in recent years in Brazil.We aimed to determine the seasonal activity of gastropods in brassica fields and unravel the environmental variables associated with these dynamics. Gastropod abundance, assemblage and within‐plant distribution were also compared amongBrassica oleraceacultivars (broccoli, cabbage and cauliflower).Mild temperatures and rainy periods were found to coincide with gastropod peaks. Regression analyses confirmed a positive association of rainfall and humidity with gastropod abundance, whereas gastropod abundance increased with decreasing temperature.Deroceras laeve(Müller) (Agriolimacidae) andBradybaena similaris(Férussac) (Bradybaenidae) were the most constant species. Mollusc abundance and assemblage differed amidB. oleraceacultivar; cabbage had the highest abundance and its species composition differed from broccoli and cauliflower. Slugs and snails were more concentrated on lower plant portions, regardless of the cultivar.Management efforts should be reinforced in mild‐temperature and rainy periods to reduce damage by gastropods, and cabbage should be monitored more closely than other cultivars.

Current anthropogenic warming threatens shallow Lake ecosystems on the Tibetan plateau: A palaeolimnological study covering the past 1,600 years in Genggahai Lake

Abstract The Tibetan Plateau has ∼1,200 lakes larger than 1 km2 with a total area of ~46,000 km2. The annual mean air temperature of the Tibetan Plateau has increased 2.5°C over the past 60 years. Lakes in this region are extremely responsive to climate changes as a result of their low biodiversity and simple food webs. However, it is unclear whether the current anthropogenic warming will benefit or threaten the aquatic ecosystems in this region. We assessed patterns of change associated with climate change in a shallow, freshwater lake (Genggahai Lake) on the NE Tibetan Plateau over the past ~1,600 years based on diverse aquatic fossils (macrophytes, molluscs, cladocerans and diatoms), total organic carbon (TOC) and total nitrogen (TN) of a sediment core. The abundances of macrophytes, molluscs and cladocerans, and the concentrations of TOC and TN in the sediments were high during the Mediaeval Warm Period (MWP, ~940–1,410 CE) but low during the Dark Ages Cold Period (DACP, ~390–940 CE) and the Little Ice Age (LIA, ~1,410–1970 CE), suggesting that modest natural warming was associated with the biomass of macrophytes and consumers in the food web. By contrast, low abundance of macrophytes and high abundance of planktonic diatoms were recorded in the sediments during the Current Warm Period (CWP, ~1970–2020 CE). Current anthropogenic warming has resulted in significantly higher temperatures than during the MWP, associated with the development of planktonic algae rather than macrophytes. Our findings show that the current anthropogenic warming, coupled with increased atmospheric nitrogen deposition and activated nutrients from thawed permafrost, is associated with phytoplankton dominance in lakes on the Tibetan Plateau, and may lead to significant reductions in ecosystem services provided by the lakes.

Molluscs from Tidal Channels of the Gulf of Gabès (Tunisia): Quantitative Data and Comparison with Other Lagoons and Coastal Waters of the Mediterranean Sea

The present study analyses the spatio-temporal structuration of the molluscan fauna from four tidal channels of the Gulf of Gabès. A total of 26 stations were sampled at four seasons from March 2016 to January 2017, leading to the identification of 2695 individuals and 57 species. The species richness and abundances are higher in autumn than in other seasons. The fauna is dominated by seven species, three gastropods [Cerithium scabridum Philippi, 1848, Bittium reticulatum (da Costa, 1778) and Tricolia speciosa (Megerle von Mühfleld, 1824)] and four bivalves [Abra alba (W. Wood, 1802), Loripes orbiculatus Poli, 1791, Varicorbula gibba (Olivi, 1792) and Peronaea planata (Linnaeus, 1758)], which are characteristic of habitats with detritus accumulation and seagrass meadows. These dominant species are commonly recorded in lagoons and coastal shallow waters of the Mediterranean Sea. The structure of the molluscan fauna is linked to the location of tidal channels in the Gulf of Gabès. Abundances are lower in the Mimoun channel than in the other channels, especially the Maltine channel which shows a great accumulation of organic matter and high abundances of molluscs. Low abundances are found in high-energy hydrodynamic zones with gravel sediment; conversely, the presence of macrophytes (mainly in seagrass meadows) increases molluscan diversity. Comparisons with other sites in the shallow waters of the Tunisian coast and lagoons show that the taxonomic diversity of molluscs of the tidal channels of the Gulf of Gabès is equivalent to that reported elsewhere, but the abundance per m2 is among the lowest levels recorded here. Moreover, most of the dominant species found in the Gulf of Gabès tidal channel are reported as dominant in other studies covering the Mediterranean Sea. A distance-based redundancy analysis shows that depth, sediment type and the presence of marine phanerogams and filter-feeder bivalves on fine sands and gravels account for the structure of mollusc assemblages associated with each channel.

Molluscs Across Space and Through Time in a Hypersaline Coastal Lagoon, Mexico

Biotic remains have been used in paleoecological studies to provide information on past environmental conditions. Death assemblages can be used to make inferences about past environmental conditions if modern optima and ranges of taxa are known. Gaps in knowledge about historical biotic changes often stem from a paucity of information regarding species distributions, community species richness and evenness, community structure, ecological interactions, and possible factors that caused past biotic shifts. We studied mollusc assemblages in sediment cores from Río Lagartos coastal lagoon (Mexico) and compared them to present-day mollusc communities to gain insights into environmental changes that occurred in the lagoon throughout the last century. A total of 18,779 mollusc specimens, representing 20 bivalve and 45 gastropod species, and belonging to 32 families and 48 genera, were identified in three short sediment cores collected from the coastal lagoon in 2017. Molluscs in the sediment cores were compared to an inventory of modern fauna from the lagoon, which was collected along a salinity gradient in 2017 and 2018 to link species distributions with environmental variables. Mollusc communities from the sediment cores and present-day datasets possess the same ubiquitous species and feeding guilds. Nearly twice as many species, however, were identified in the sediment cores as in the present-day inventory. We report differences in mollusc abundance and taxonomic composition in the cores across space and time, which may be related to the salinity gradient in the lagoon, temporal shift in salinity, and recent human-mediated modifications of the nearby terrestrial environment. Biotic changes driven by shifts in salinity could have been reduced salinity. Such inputs may have been driven by hurricanes, along with associated high wind velocities and geomorphologic transformations. This paleobiology study will be of use for future conservation efforts in the coastal lagoon.

Diversity and abundance of terrestrial molluscs and their associated nematode fauna in urban kitchen gardens in the city of Rio de Janeiro, Brazil

Terrestrial molluscs can become agricultural pests and transmit parasites, playing an important role in different biological communities. In the present study, we evaluated the diversity and abundance of this group in two horticultural areas in Rio de Janeiro (Manguinhos and Jacarepaguá neighborhoods), as well the presence of parasitic nematodes associated with these molluscs. We collected specimens in the austral spring and summer, with four sites being sampled within each study area, including malabar spinach, sweet potato, chicory greens, and cassava plantations, and one site in an adjacent, non-cultivated area. We collected a total of 522 live mollusc specimens and identified 16 species from 10 different families. The greatest abundance of molluscs was recorded in summer (363) and at Jacarepaguá (309). Overall, 174 (57%) of the 303 specimens analyzed parasitologically were positive for nematodes. Larvae of superfamily Metastrongyloidea, which includes nematodes that are a concern for public health and veterinary medicine, were found parasitizing the slug Sarasinula linguaeformis, in Manguinhos. Our results contribute to understanding of the diversity of terrestrial molluscs occurring in kitchen gardens in the city of Rio de Janeiro, and provide important insights for generating subsidies for health education actions and control of parasitic diseases transmitted by them.

Benthic Macroinvertebrates Structure of Two Agropastoral Dams, Nanan and Zatta: Yamoussoukro, Cote d’Ivoire

Aims: We are investigating benthic macroinvertebrates in two rice-growing dams and assessing their pollution levels.
 Place and Duration of Study: Nanan and Zatta Dams of Yamoussoukro in Côte d’Ivoire from April 2021 to March 2022.
 Methodology: Samples were collected monthly with a Van Veen bucket and a dip net and the environmental variables measured.
 Results: The values of the physico-chemical variables show that the waters are warm and more mineralized at Nanan than at Zatta. The species richness is higher at Zatta with 75 taxa present against 42 taxa at Nanan. The population is globally dominated by insects at Zatta, but a strong representation of Molluscs is observed at Nanan. The abundance of Molluscs indicates organic pollution in the Nanan dam. The water pollution tolerance index between the two dams showed a predominance at Zatta, of the Ephemeroptera group which are polluo-sensitive organisms against a predominance at Nanan, of the Diptera group which are polluo-resistant. The Shannon index and the others indexes of the two sites confirm a clear water pollution in Nanan compared to Zatta.
 Conclusion: These results suggest that the Zatta dam is in better condition than the Nanan dam. However, these two dams must be bio-monitored.

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.