Mollusc Species Research Articles

Monthly distribution of lipophilic marine biotoxins and associated microalgae in the South Sea Coast of Korea throughout 2021

Aquaculture farms have been established along the South Sea Coast of Korea, supplying most of the seafood consumed domestically. However, annual harmful algal blooms pose a potential threat to seafood safety. This study aimed to determine the spatial and seasonal distributions of 12 lipophilic marine biotoxins (LMTs) in phytoplankton and mussels in the region in 2021. Solid-phase adsorption toxin tracking (SPATT) was used to monitor the cumulative compositions of LMTs in seawater. LMT concentrations were also determined in twelve commercially available species of domestic shellfish to evaluate the potential risks to human health. Gonyaulux spinifera and Dinophysis acuminata, causative microalgae of yessotoxins (YTXs) and pectenotoxins (PTXs), respectively, showed high densities in the region from May to July. This period corresponded to high LMT concentrations in phytoplankton and mussels. Phytoplankton mainly contained PTX-2 and homo-YTX, with a maximum concentration of 2300 ng g−1 wet weight (ww) in May. In contrast, mussels mainly contained homo-YTX and YTX, with a maximum concentration of 1300 ng g−1 ww in July. LMTs-producing microalgae showed low densities and concentrations after July, whereas mussels accumulated toxins until September. In the SPATT sampler, more diverse LMTs were detected than in seawater, phytoplankton, and mussels. For example, dinophysistoxin-1 and azaspiracid-2 were detected only in SPATT. YTXs were detected in domestic seafood samples, including mussels, red scallops, and pen shells, but the concentrations were below the European Food Safety Agency recommended standard of 3.75 mg YTX-eq. kg−1. Moreover, the hazard quotient was less than 100 in all scenarios, indicating that the human health risk was not significant. This study provides valuable data on monthly distribution patterns of LMTs in the South Sea Coast of Korea and can serve as baseline data for future management policies of marine biotoxins.

The impact of climate changes on the ranges of invertebrates (Diptera, Molluska) in Tavush province of Armenia

Aim. The work’s aim is to study the species composition of invertebrates (Insecta, Molluska) of the Tavush province of Armenia and changes of their ranges due to climatic conditions.Material and Methods. Our own collections of 2021–2022 from different areas of the Tavush province and the collections of invertebrates of the Scientific Centre of Zoology and Hydroecology served as study material. The collection and identification of dipterous insects and mollusks was carried out according to generally accepted methods. The work was performed at the Scientific Centre of Zoology and Hydroecology The scientific material is stored in the collection fund of the Scientific Centre.Results. As a result of our studies of invertebrate species composition, 28 species of horseflies (Tabanidae) are currently listed for the Tavush region: 27 species of phytophagous gall midges (Cecidomyiidae) and 10 species of mollusks. As a result of warming climate change new changes of locality have been registered for: 6 horsefly species S. (N.) caucasicus, Ch. (H.) f. flavipes, Ch. ludens, T. unifasciatus, T. indrae vappa, T. miki; 4 phytophagous gall midge species A. verbasci, D. tortrix, S. euphorbiae, R. terminalis; For one species of mollusk, H. buchi, there are new localities. All these species have expanded their habitat: in horseflies, changes in the range along vertical zonality are observed.Conclusions. As a result of this research, it was revealed that as a consequences of climate change, the ranges of some species of invertebrates – horseflies, gall midges‐phytophages and mollusks – have expanded compared to the data of previous years. All species in which there is a direct dependence of range change on climatic conditions can be further considered as bioindicators of climate change.

Polychlorinated biphenyls residues in bivalve shellfish from Niger Delta: distribution pattern, tissue burden and food safety assessment

ABSTRACT This study investigated the distribution pattern, tissue burden, and safety of bivalve shellfish for human consumption. Edible species of bivalve shellfish harvested from Niger delta were screened for polychlorinated biphenyl (PCB) contaminants. Instrumental analysis and quantification of PCB congeners were performed using gas chromatography fitted with electron capture detector (GC-ECD). Results indicated an accumulation of PCB concentration of 0.36 ng/g, 0.89 ng/g, 0.98 ng/g, and 1.73 ng/g at Andoni, Iko Town, Ibeno, and Bonny, respectively. The PCB burden showed bloody cockle at Bonny location recorded the highest concentration of PCB congeners (2.37 ng/g), closely followed by mangrove oyster (2.13 ng/g) at Iko Town location, while Donax clam at Ibeno (0.09 ng/g) has the least PCB burden. The results obtained were lower in relation to food regulatory threshold. However, PCB tissue burden of bivalve shellfish harvested at the study locations indicated an environment impacted by anthropogenic activities that could negatively affect human health which depends on these shellfish for food.

Eemian paleoenvironment based on the freshwater malacofauna and isotope record (Piła site; north-western Poland)

This article presents the results of malacological and isotope studies on lacustrine sediments from the Eemian interglacial site in the Piła (north-western Poland). Twenty species of molluscs were found in the analysed sediments. Changes in the taxonomic composition and the quantitative structure of malacofauna in the profile allowed distinguishing five types of assemblages corresponding to different phases of the lake's evolution. Ratios of oxygen and carbon isotopes (δ18O and δ13C) reflecting changes in the lake water composition were measured in shells of two predominating snail species, Valvata piscinalis (Müller, 1774) and Bithynia tentaculata (Linnaeus, 1758), and in opercula of Bithynia tentaculata. Significant variability in isotope contents was noted for shells in individual profile sections and between analysed taxa. The results of malacological and isotope studies were supplemented with lithological, stratigraphical and palynological data. On this basis, the sediments age was determined (optimal and suboptimal phases of the Eemian interglacial). Environmental changes of paleolake have been also reconstructed. The analysed sediments were initially deposited in the coastal, periodically drained zone of the reservoir. The younger part of the sequence represents the shallow part of the littoral zone of the permanent water body. The malacological and isotope data also allowed distinguishing two phases of increased water level in the reservoir, and changes in its trophic state probably generated by climatic factors.

The molluscan fauna of Chella Bank and surroundings (Western Mediterranean Sea)

Molluscs of Chella Bank and its surroundings were studied from 21 samples collected with a van Veen grab in the depth range 95-729 m. A total of 299 taxa were identified (77 live-taken), thus increasing by more than 95% the species of molluscs reported in the recently declared site of community importance “Sur de Almería-Seco de los Olivos”. Two of the species are new records to Spanish waters and one to the Alboran Sea. The high species richness observed could be related to the location, the hydrological characteristics and the topographical heterogeneity of the area within the Alboran Sea. Four significant groups of samples were discriminated through multivariate analysis of quantitative data of live-taken molluscs: (I) bathyal muddy bottoms with buried rhodoliths; (II) bathyal muddy bottoms with coral rubble; (III) bathyal hemipelagic muddy bottoms and (IV) bathyal sandy bottoms. Molluscs were more diverse on coral framework bottoms than on sedimentary bottoms around Chella Bank. Most of the live-taken species are widely distributed along the Atlantic and Mediterranean Sea, and a few are strictly Mediterranean. The most striking feature was the occurrence of two species with planktotrophic larval development for which Chella Bank is the sole recorded locality in the Mediterranean (Episcomitra angelesae and Mitrella templadoi) and which elsewhere extremely rare (Mathilda spp.).

Climate change projections of commercial fish distribution and suitable habitat around north western Europe

AbstractUnder future climate change, modification of temperature and salinity are expected to result in distribution shifts of marine organisms, including commercial fish and shellfish. Changes are anticipated everywhere, including in the seas of many important fishing nations. Species turnover will in turn result in both opportunities and threats to fishing industries. To determine the impacts for northwest European shelf fisheries, we project changes for 49 commercially important fish and shellfish species using an ensemble of five ecological niche models and three different downscaled climate change projections. The habitat suitability and latitudinal shifts projected from the recent past (1997–2016) to two futures (2030–2050; 2050–2070) were calculated for waters around the United Kingdom. Of the species examined, around half were projected to have consistently more suitable habitat in the future, including European seabass (Dicentrarchus labrax, Moronidae), sardine (Sardina pilchardus, Alosidae) and anchovy (Engraulis encrasicolus, Engraulidae). Conversely, it is suggested that UK waters will become less suitable for species including Atlantic cod (Gadus morhua, Gadidae) and saithe (Pollachius virens, Gadidae). Our comprehensive approach using a number of models and climate change scenarios shows that while there are differences in the magnitude of change between models, and while some models perform better for certain species compared with others, overall, the general trends in habitat suitability and abundance are robust across models and climate scenarios. This emphasises the value in using more than one modelling technique with different climate scenarios (i.e., an ensemble approach) to capture the uncertainty or agreement around climate change projections.

Biodiversity of Mollusca in Dalmaj Marsh, Southern Marshland, Al-Diwaniya City, Iraq

One of nature’s most valuable resources, biodiversity plays a critical role in meeting many of human requirements and protecting from environmental extremism conditions. Mollusca benthic invertebrates are important biota in aquatic ecosystems and need further investigation. The current study highlights some species recorded in Al-Delmage Marsh in Iraq. The current study points out six species of Mollusca. These species are Melanoides tuberculate, Physa acuta, Viviparus bengalensis, Lymnaea radix, Corbicula fluminalis and Corbicula fluminea. Ecological indices reveal decrease in the values of Shannon (H’), Evenness (E), Margalef (R). This result reflects the ecological disturbance that the world faces over time and Iraq is the fifth country in this regard.

The utility of transcriptomics in the conservation of sensitive and economically important species

The utility of transcriptomics in the conservation of sensitive and economically important species

Study of the Mullusca Community in the Reclamation Beach of Manado Beach

Purpose: This study aims to inventory the types of molluscs and community structure and to know their activities on the reclamation beach of Manado Bay. The types of molluscs encountered in the first phase of the study totaled 15 species from 7 families while in the second phase there were 21 species from 10 families. Method: Based on the methods observations were made using the observation method or direct observation of mollusc species that were affected by environmental factors. The research was conducted from July to August on the reclamation beach of Manado Bay, North Sulawesi. Method of this study is based on the Preliminary Research, Mollusca Sampling, Data analysis. Results and conclusion: Based on the results of data analysis in phase I research in the intertidal zone showed that the mollusk density value was 58.30 Ind/m2. The damage index obtained from the analysis results is low, namely H' = 1.684. The dominance value obtained from the results of data analysis is low, namely C = 0.27-0.44. The highest species frequency value was found in the Cellana radiata species with a value of 0.60 and the lowest in the species Menathais tuberosa, Drupa rubusidae, Drupa ricinus, Nerita polita, with a value of 0.03. The domination value obtained from the results of data analysis is C = 0.06, which means that the value is classified as low. The activity of molluscs in terms of their ability to respond and adapt to the molluscs in the intertidal zone varies according to the species observed based on the size of the species and their preferred adaptability. Research implications: The relatively high importance value index was found in the species Saccostrea cucullata with a value of 106.28% while the lowest value was in the species Menathais tuberosa and Drupa ricinus with a value of 1.24%. In phase II research in the subtidal zone showed that the mollusk density value was 1.86 Ind/m2. The damage index obtained from the analysis results is classified as moderate, namely H' = 2.950. Originality/value: Molluscs are one of the many potential biological resources found in an ecosystem, and have an important role for the balance of the ecosystem.

Распространение раковинных брюхоногих моллюсков с длительной и короткой пелагической стадиями в открытых районах Баренцева моря

The duration of the pelagic stage in different species of gastropod molluscs affects their ability to disperse by marine currents. We counted the number of species with long (planktotrophic larva) and short or absent (lecitotrophic larva) pelagic stages in development in shell gastropods from 8 areas of the open part of the Barents Sea. A total of 66 species were identified in the study area, of which 25 were true micromolluscs, and 41 species were represented mainly by juvenile individuals of larger molluscsby larger macrofaunal species. The predominant type of development is lecithotrophic (57 species) and partially pelagic planktotrophic (9 species). According to our data, the shares proportions of species with lecithotrophic and planktotrophic types of development are approximately the same in all investigated areas of the Barents Sea. But in the southern part of the Barents Sea the share of species with a long pelagic stage are sligthlyis slightly higher than in more numerous than in its northern part.

THE LONG-TERM DYNAMICS OF ZOOBENTHOS COMMUNITIES IN THE LAKE UNDER CONDITIONS OF WASTEWATER POLLUTION FROM APATITE- NEPHELINE PRODUCTION

The changes in the composition and structure of zoobenthos of Bolshoi Vudyavr Lake were analyzed in the long-term dynamics. Benthic fauna is characterized by low taxonomic diversity. Zoocenosis consists of eurybiont species of oligochaetes (Tubifi cinae), chironomids (Chironiminae, Tanypodinae), and mollusks (Pisidiidae) in the deep-water zone. Chironomids Orthocladiina dominated in the littoral zone. Communities are complemented by bivalves, oligochaetes and invertebrates typical for the littoral zone of the lakes (gastropods, caddisfl y, beetles, mayfl ies, stonefl ies). In the structure of deep-water biocenoses there is a tendency of increasing of mollusks Pisidiidae. Their share in the total number of invertebrates increased from 30 % in 2001 to 66 % in 2022. Zoobenthos are characterized by relatively high values of abundance number and biomass. The average level of biomass of zoobenthos in the lake varies from “moderate” (5,0–10,0 g/m2) to “elevated” class (10–20 g/m2).

DNA Barcoding and Phylogenetic Analysis of Some Gastropod Molluscs (Class-gastropoda) from Three Ecological Habitats of Bangladesh

An attempt has been made for molecular characterization of gastropods from three different ecological habitats (marine, freshwater and terrestrial) in Bangladesh. A total of eight species of gastropod (Lissachatina fulica, Pila globosa, Pila virens, Brotia costula, Nerita articulata, Nerita balteata, Macrochlamys indica and Telescopium telescopium) were identified belongs to seven genera and six families. These species were confirmed through morphological studies and by adopting DNA barcoding using mitochondrial cytochrome c oxidase subunit I (COI) and 16S ribosomal RNA (16S rRNA) gene. The average GC content 39.53% and 33.40% were found for COI and 16S rRNA, respectively. Genetic divergence increased as predicted with higher taxonomic rank, ranging from 0% to 2.84% with an average 1.45% within species and 3.57% to 35.23% between species with a DNA barcoding gap of 0.73 for 16S. This study revealed that gastropod species can be discriminated using both COI and 16S rRNA gene. Phylogenetic relationships among identified species were established where individuals belonging to the same species were grouped under the same clade. Molecular characterization of remaining molluscan species of Bangladesh remains to be completed.
 Bioresearch Commu. 9(2): 1305-1309, 2023 (July)

Geo-spatial distribution and trends of trawl catch and bycatch off the south Konkan coast, Maharashtra, India

Trawl fishing is well-known for its high catch rate, but due to its non-selective nature, it is now widely acknowledged to have an impact on biodiversity and habitat. The geographical and temporal aspects of trawl catch, bycatch, discard, and ichthyofaunal trawl diversity along the south Konkan coast of Maharashtra, India, are contemplated in the current study. The data of 177 georeferenced trawl hauls, towed between 15°53’38”N to 17°34’52”N latitude and 72°54’29”E to 73°25’48”E longitude, revealed that maximum bycatch (70–110 kg/haul) and discard (60–110 kg/haul) regions were found towards the southern direction, near ecologically sensitive estuarine areas off the south Konkan coast, Maharashtra. The post and pre-monsoon seasons were found to be much more productive in terms of catches, while the post-monsoon and winter seasons had the highest species diversity 38.15% and 33.86%, respectively, with the winter season having higher discard rates. In the present study, bycatch contributed nearly 49% of the total catch, with the maximum catch per hour recorded in October (62.20 kg) and the discard per hour in January (14.59 kg). There were 134 different species of fish and shellfish recorded, and the family Carangidae (8.21%) was prominent in terms of species richness, followed by Penaeidae (6.72%), Clupeidae (5.22%), Engraulidae (5.22%), and Sciaenidae (4.48%). The results of various biodiversity indices confirmed that the studied region is blessed with rich and evenly distributed biodiversity. The mapped predictive values of trawl fishing showed a high fishing pressure zone towards the south off the Maharashtra coast, and it highlighted the need for suitable strategies for the conservation and management of fisheries resources to achieve long-term sustainability in that region.

Synthase-selected sorting approach identifies a beta-lactone synthase in a nudibranch symbiotic bacterium

BackgroundNudibranchs comprise a group of > 6000 marine soft-bodied mollusk species known to use secondary metabolites (natural products) for chemical defense. The full diversity of these metabolites and whether symbiotic microbes are responsible for their synthesis remains unexplored. Another issue in searching for undiscovered natural products is that computational analysis of genomes of uncultured microbes can result in detection of novel biosynthetic gene clusters; however, their in vivo functionality is not guaranteed which limits further exploration of their pharmaceutical or industrial potential. To overcome these challenges, we used a fluorescent pantetheine probe, which produces a fluorescent CoA-analog employed in biosynthesis of secondary metabolites, to label and capture bacterial symbionts actively producing these compounds in the mantle of the nudibranch Doriopsilla fulva.ResultsWe recovered the genome of Candidatus Doriopsillibacter californiensis from the Ca. Tethybacterales order, an uncultured lineage of sponge symbionts not found in nudibranchs previously. It forms part of the core skin microbiome of D. fulva and is nearly absent in its internal organs. We showed that crude extracts of D. fulva contained secondary metabolites that were consistent with the presence of a beta-lactone encoded in Ca. D. californiensis genome. Beta-lactones represent an underexplored group of secondary metabolites with pharmaceutical potential that have not been reported in nudibranchs previously.ConclusionsAltogether, this study shows how probe-based, targeted sorting approaches can capture bacterial symbionts producing secondary metabolites in vivo.8entVVL2Hhkfc-ejj4sDuQVideo

Potential Toxic elements in shellfish from three rivers in Niger Delta, Nigeria: bioaccumulation, dietary intake, and human health risk assessment

Human health risks associated with the consumption of three shellfish (<i>Penaeus monodon, Crassostrea rhizophorae</i>, and <i>Tympanostomus fuscatus</i>) harvested from the Buguma, Krakrama, and Bonny Rivers in the Niger Delta region were evaluated in this study. The bioaccumulation of potential toxic elements (PTEs) [Arsenic (As), Cadmium (Cd), Chromium (Cr), Lead (Pb), and Nickel (Ni)] was analyzed using atomic absorption spectrophotometry (AAS). The pollution index (PPI), estimated daily intake (EDI), target hazard quotient (THQ), total hazard index (HI), target cancer risk (CR), and total cancer risk (TCR) were evaluated for potential human health risks. The bioaccumulation levels of PTEs in shellfish samples followed the order: Ni > Cr > Pb > Cd > As and were above standard recommended limits except for inorganic As levels observed in <i>T. fuscatus</i> and <i>P. monodon</i> samples from Krakrama and Bonny and <i>C. rhizophorae</i> from Bonny river. The EDI values for iAs, Cr, and Ni were lower than the tolerable daily intake (TDI), however, the EDI of Cd for children in <i>P. monodon</i> (4.6E-03 mg kg<sup>-1</sup>day<sup>-1</sup>), <i>T. fuscatus</i> (1.7E-03 mg kg-<sup>-1</sup>day<sup>-1</sup>) and C. rhizophorae (1.4E-03 mg kg<sup>-1</sup>day<sup>-1</sup>) from Buguma were higher than the TDI value (8.00E-04 mg kg<sup>-1</sup>day<sup>-1</sup>). The HI values were above 1. The total cancer risk (TCR) values of all analyzed PTEs for all the shellfish species from the rivers for children and adults ranged from 8.69E-04 to 2.47E-03 and 1.86E-03 to 5.30E-03 respectively and these were higher than the priority risk level (1E-04), hence, the need to monitor shellfish consumption in the study area.

Měkkýši NPR Špraněk: 140 let bádání v Javoříčském krasu (střední Morava, Česká republika) [Molluscs of Špraněk NNR: 140 years of malacological research in Javoříčský karst (Central Moravia, Czech Republic)

The Špraněk NNR, as a prominent part of the Javoříčko Karst, has long been a focus of malacological research. In this study, we have assembled all the information on the mollusc fauna regarding this area by compiling literature data, records from the Natural History Museum in Prague, and data from our own field research. Since the end of the 19th century, 86 species of molluscs have been recorded. The malacofauna is dominated by preserved forest communities with a significant proportion of xerophilous and calciphilous species. The three most represented ecological groups are strictly forest (31%), woodland (15%), and euryvalent (15%) species. European and Central European species comprise the largest portion of the species composition, but a significant component is also represented by Alpine and Carpathian species, as the area lies on the border between the Bohemian Massif and the Carpathians. Despite its small area, the Špraněk NNR hosts a rich mollusc community of both conservation and zoogeographical value.

IgE-Mediated Shellfish Allergy in Children.

Shellfish, including various species of mollusks (e.g., mussels, clams, and oysters) and crustaceans (e.g., shrimp, prawn, lobster, and crab), have been a keystone of healthy dietary recommendations due to their valuable protein content. In parallel with their consumption, allergic reactions related to shellfish may be increasing. Adverse reactions to shellfish are classified into different groups: (1) Immunological reactions, including IgE and non-IgE allergic reactions; (2) non-immunological reactions, including toxic reactions and food intolerance. The IgE-mediated reactions occur within about two hours after ingestion of the shellfish and range from urticaria, angioedema, nausea, and vomiting to respiratory signs and symptoms such as bronchospasm, laryngeal oedema, and anaphylaxis. The most common allergenic proteins involved in IgE-mediated allergic reactions to shellfish include tropomyosin, arginine kinase, myosin light chain, sarcoplasmic calcium-binding protein, troponin c, and triosephosphate isomerase. Over the past decades, the knowledge gained on the identification of the molecular features of different shellfish allergens improved the diagnosis and the potential design of allergen immunotherapy for shellfish allergy. Unfortunately, immunotherapeutic studies and some diagnostic tools are still restricted in a research context and need to be validated before being implemented into clinical practice. However, they seem promising for improving management strategies for shellfish allergy. In this review, epidemiology, pathogenesis, clinical features, diagnosis, and management of shellfish allergies in children are presented. The cross-reactivity among different forms of shellfish and immunotherapeutic approaches, including unmodified allergens, hypoallergens, peptide-based, and DNA-based vaccines, are also addressed.

Effects of sediment and water column acidification on growth, survival, burrowing behaviour, and GABAA receptor function of benthic invertebrates

In coastal regions, sediment-dwelling animals are exposed to a high degree of variability in seawater and sediment pH and pH is expected to decline due to anthropogenic effects. The impacts of 6-week exposure to reduced-pH seawater on length, weight, and survival of two species of molluscs that inhabit mudflats, juvenile soft-shell clams (Mya arenaria) and adult mud snails (Tritia obsoleta), were examined in two laboratory trials (2017 and 2018). The interactive effects of this prior exposure to water column acidification and subsequent sediment acidification on burrowing behaviour were then investigated for these mollusc species and adults of the amphipod Corophium volutator. In a separate experiment, the potential involvement of GABAA receptors in changes in burrowing behaviour in reduced-pH conditions was tested by exposing three species: C. volutator, T. obsoleta, and the Baltic clam Limecola balthica to sediment acidification and the neuroinhibitor gabazine. Reduced-pH water conditions only decreased the shell length of T. obsoleta in 2017 while all other morphometric metrics were not significantly impacted for this species in either year or for M. arenaria. The burrowing of T. obsoleta was reduced by 13% in acidified sediments in one of the two years but not by prior exposure to water column acidification. The burrowing of M. arenaria was not affected by either factor. The burrowing of C. volutator was impacted by the interaction of water column exposure and sediment acidification in 2017 with the acidified water, control sediment treatment having 14% higher burrowing then the remaining treatment combinations. In 2018, C. volutator burrowing was reduced in acidified sediment by 30%. The presence of gabazine only had an interactive effect on the burrowing of one species, C. volutator. The presence of gabazine increased the proportion of C. volutator individuals burrowed in the acidified water treatment by almost 30%, suggesting that GABAA neuroreceptors are involved in the mechanism for the impact of sediment acidification on burrowing in this species. The results of our experiments indicate that there is taxonomic variation in species' responses of benthic invertebrates to ocean and sediment acidification with respect to growth, survival, and burrowing behaviour.

Residue character of polycyclic aromatic hydrocarbons in river aquatic organisms coupled with geographic distribution, feeding behavior, and human edible risk

Polycyclic aromatic hydrocarbons (PAHs) residues in fish, shrimp and shellfish have attracted attention because they are major species in the aquatic food chain and an important food source for humans. These organisms have various feeding habits and different living environments, and through the food chain, they can directly or indirectly connect particulate organic matter and human consumption. However, little attention has been paid to the bioaccumulation of PAHs in aquatic organism groups representing varied conditions and feeding habits in the food chain. In this study, 17 species of aquatic organisms, comprising fish, shrimp, and shellfish, were captured from 15 locations distributed within the river network of the Pearl River Delta. The concentration of 16 PAHs was measured in the aquatic organisms. The sum of the 16 measured PAHs ranged from 57.39 to 696.07 ng/g, dry weight, while phenanthrene had the highest individual content. The linear mixed effect model was applied to estimate the random effects of PAH accumulation in aquatic organisms. The result showed that the contributed proportion of variance to feeding habits (58.1 %) was higher than that of geographic distribution (11.8 %). In addition, one-way analysis of variance (ANOVA) demonstrated that the concentrations of PAHs depended on the water layer inhabited by the organism and its species status. Specifically, shellfish and carnivorous bottom-dwelling fish showed significantly higher levels than other aquatic organisms.

Freshwater Molluscs of Konaseema District, Andhra Pradesh, India

Field surveys conducted in Konaseema district of Andhra Pradesh, especially from river Korangi and Coringa wildlife sanctuary area, revealed 21 species of molluscs belonging to 18 genera and 12 families. Of which 7 species viz., Tricula montana, Stenothyra woodmasoniana, Stenothyra deltae, Stenothyra ornata, Gangetia miliacea, Assiminea francessi and Sermyla riquetii recorded for the first time from the state. The shell characters, distribution and the current status of these species are discussed in this paper.