Spatio-temporal co-occurrence of alien and native molluscs : a modelling approach using physical-chemical predictors

The invasion of alien species can have serious economic and ecological impacts. Ecologically, invasions often lead to an increased rate of native species replacement and decreased biodiversity. A critical step in the dominance of alien species is their successful co-occurrence with native species. In this study, we assessed the occurrence of alien molluscs and their co-occurrence with native molluscs and identified the determining physical-chemical variables. We expected that a combination of some key variables of water quality could provide suitable conditions promoting alien molluscs to occur and to co-occur with native molluscs. The analyses were based on 20-year data, collected from river systems across Flanders (Belgium). Classification Trees (CTs) were used to perform the analyses and to develop the predictive models. Based on CT models, the co-occurrence of alien and native molluscs could be reliably predicted based on physical-chemical variables. However, there was insufficient data to determine the environmental conditions in which alien taxa dominate. From the past to the present, spatial co-occurrence significantly increased. Sinuosity, ammonium and nitrate concentrations, chemical oxygen demand, pH and conductivity were the key determining variables. Our findings suggest that the co-occurrence of alien and native molluscs mainly occurs in straight rivers with good chemical water quality. These results provide insights into the ecology and behaviour of alien species which could support management practices and priority setting for conservation planning in surface waters of Flanders and Europe

Results of a study of bivalve molluscs of central Asia = Итоги исследования двустворчатых моллюсков Центральной Азии

The article is devoted to many years’ research (1972 - 2001) of bivalve mollusks of Central Asia. It is established that it is inhabited by 51 species of molluscs belonging to 16 genera, 8 families and three orders. Among them 13 species and 1 subgenus are described as new for science. Their ecology, distribution by basin types, byotopes, life forms and economic significance have been studied

The food of coarse fish

Remarkably little has been published on the feeding habits of the non-salmonid fishes of British fresh waters. The following report briefly summarizes the results obtained from the examination of the stomach contents of some 2,700 fish, belonging to 19 species, which were obtained during 1939. The results of all examinations of gut contents were analysed, species by species, upon a simple basis of the presence of different types of food. Foodstuffs were divided up into six main categories— fish, molluscs, insects, crustaceans, higher plants together with filamentous algae, and diatoms—and the occurrence of members of any of these categories was recorded for each fish

The Population Status of Cardііdae (Bіvalvіa) as a Bioindicator for Water Quality in the North-western Part of the Sea of Azov

An attempt was made to evaluate the suitability of using mollusc populations from the family Cardiidae as a biological indicator to monitor ecological water quality in the north-western part of the Sea of Azov. It is known that some qualitative indices of mollusc populations reflect large-scale changes occurring in benthos communities of the region. In this research, the monitoring of aquatic organisms was carried out using such indices as population density, age distribution dynamics, characteristics of behaviour, etc. Temporal and spatial dynamics of these indices allow the detection of changes in environmental factors which in their turn determine basic and crucial functions of water bodies. Among other molluscs, representatives of the family Cardiidae stand out for their ability of rapid occupation of new locations (due to the presence of a pelagic larval stage), and their adult individuals are rather tolerant to fluctuations in salinity and other factors. The aim of this research was to reveal the variability range for basic qualitative characteristics of bivalve populations in the north-western part of the Sea of Azov and to estimate if these molluscs are suitable to be bioindicators of the environmental status of the region

The nuclear receptors of Biomphalaria glabrata and Lottia gigantea: Implications for developing new model organisms

© 2015 Kaur et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are creditedNuclear receptors (NRs) are transcription regulators involved in an array of diverse physiological functions including key roles in endocrine and metabolic function. The aim of this study was to identify nuclear receptors in the fully sequenced genome of the gastropod snail, Biomphalaria glabrata, intermediate host for Schistosoma mansoni and compare these to known vertebrate NRs, with a view to assessing the snail's potential as a invertebrate model organism for endocrine function, both as a prospective new test organism and to elucidate the fundamental genetic and mechanistic causes of disease. For comparative purposes, the genome of a second gastropod, the owl limpet, Lottia gigantea was also investigated for nuclear receptors. Thirty-nine and thirty-three putative NRs were identified from the B. glabrata and L. gigantea genomes respectively, based on the presence of a conserved DNA-binding domain and/or ligand-binding domain. Nuclear receptor transcript expression was confirmed and sequences were subjected to a comparative phylogenetic analysis, which demonstrated that these molluscs have representatives of all the major NR subfamilies (1-6). Many of the identified NRs are conserved between vertebrates and invertebrates, however differences exist, most notably, the absence of receptors of Group 3C, which includes some of the vertebrate endocrine hormone targets. The mollusc genomes also contain NR homologues that are present in insects and nematodes but not in vertebrates, such as Group 1J (HR48/DAF12/HR96). The identification of many shared receptors between humans and molluscs indicates the potential for molluscs as model organisms; however the absence of several steroid hormone receptors indicates snail endocrine systems are fundamentally different.The National Centre for the Replacement, Refinement and Reduction of Animals in Research, Grant Ref:G0900802 to CSJ, LRN, SJ & EJR [www.nc3rs.org.uk]

Analysis of proteins from marine molluscs

Application of the two-dimensional gel electrophoresis (2DE) protocols which were developed for samples of mammalian origin gives unsatisfactory results when used in samples from marine molluscs. This chapter describes a detailed protocol of 2DE that can be applied to these organisms, especially for Ruditapes decussatus and Bathymodiolus azoricus.info:eu-repo/semantics/publishedVersio

Review of investigation on the feeding of the European grayling [Translation from: Flora Slodkowodna Polski. Tom 2. Cyanophyta, Glaucophyta (ed. K. Starmach) p350-352. Warsaw, Polska Academia Nauk, 1966]

The composition of the food of the European grayling and the character of its feeding has been studied fully enough, but this knowledge is scattered in the literature and often contradictory. rare exceptions, analysis of the results of different investigations. Therefore the proposed short outline of the history of the study of the problem with a description of the basic data on the feeding of the grayling in different geographical areas is presented as expedient and opportune, primarily in relation to the determination of immediate problems and the trend of research

Benthic macrofauna and habitat monitoring on the Continental Shelf of the northeastern United States: I. Biomass

Information on long-term temporal variability of and trends in benthic community-structure variables, such as biomass, is needed to estimate the range of normal variability in comparison with the effects of environmental change or disturbance. Fishery resource distribution and population growth will be influenced by such variability. This study examines benthic macrofaunal biomass and related data collected annually between 1978 and 1985 at 27 sites on the continental shelf of the northwestern Atlantic, from North Carolina to the southern Gulf of Maine. The study was expanded at several sites with data from other studies collected at the same sites prior to 1978. Results indicate that although there was interannual and seasonal variability, as expected, biomass levels over the study period showed few clear trends. Sites exhibiting trends were either in pollution-stressed coastal areas or influenced by the population dynamics of one or a few species, especially echinoderms. (PDF file contains 34 pages.

Toxic Effects of Copper, Cadmium, and Methoxychlor Shown by Neutral Red Retention Assay in Two Species of Freshwater Molluscs

We used neutral red retention assay in lysosomes of digestive gland cells as an indicator for stress effects by the environmental contaminants Cu, Cd, and the pesticide methoxychlor in two freshwater molluscs, the unionid mussel, Elliptio complanata (Lightfoot) and the ramshorn snail Helisoma trivolvis (Say). Mussels and snails were exposed for 7 and 14 days to Cu and Cd each at nominal concentrations of 2.5 μg/L, 5.0 μg/L, and 10.0 μg/L, and to methoxychlor concentrations of 1.0 μg/L, 10.0μg/L, and 100.0 μg/L. Both mussels and snails exposed to Cu showed a significant increase in the percent of destabilized lysosomes compared with lab control and freshly-collected (field control) mussels at both 7 and 14 days exposure for all concentrations. Cd-exposed mussels did not show a significant difference with either of the controls at 7 days, but at 14 days exposure, Cd significantly increased the percent of destabilized lysosomes at all concentrations compared to field control mussels. Compared to laboratory controls, Cd increased lysosomal destabilization at 5.0 μg/L and 10.0 μg/L. Snails exposed to Cd for 7 days had a significantly higher percentage of lysosomal destabilization than both lab and field controls but at 14 days, significant differences were only seen at the two highest Cd concentrations. Methoxychlor-exposed mussels showed no significant lysosomal destabilization at 7 days compared to controls. But at 14 days exposure, the pesticide increased the percentage of lysosomal destabilization at 10.0μg/L compared to lab controls, and increased at both 10.0μg/L and 100.0μg/L compared to field control mussels. Methoxychlor-exposed snails had a higher percentage of lysosomal destabilization at 7 and 14 days at all concentrations compared to both controls with the exception of the 1.0 μg/L -7 day exposure group. Snails were more sensitive to Cd and to methoxychlor than were mussels possibly because they lack an operculum and are thus completely exposed to the environment. The lowest observed effect concentration (LOEC) for Cd was 2.5 μg/L (14 days) for Elliptio and 2.5 μg/L (7 and 14 days) for Helisoma. For methoxychlor, the LOEC was 10.0 μg/L (14 days) for Elliptio and 10.0 and 1.0 μg/L (7 and 14 days, respectively) for Helisoma. The LOEC for Cu was 2.5 μg/L (7 and 14 day exposure) for both Elliptio and Helisoma. These results show that lysosomal destabilization as indicated by neutral red retention is a reliable indicator of stress from heavy metals and a pesticide in freshwater molluscs, including a taxon that is endangered or threatened in North America

Lacustrine mollusc radiations in the Lake Malawi Basin : experiments in a natural laboratory for evolution

In terminal Pliocene-early Pleistocene times, part of the Malawi Basin was occupied by paleo-lake Chiwondo. Molluscan biostratigraphy situates this freshwater lake either in the East African wet phase between 2.7-2.4 Ma or that of 2.0-1.8 Ma. In-lake divergent evolution remained restricted to a few molluscan taxa and was very modest. The lacustrine Chiwondo fauna went extinct at the beginning of the Pleistocene. The modern Lake Malawi malacofauna is depauperate and descends from ubiquistic southeast African taxa and some Malawi basin endemics that invaded the present lake after the Late Pleistocene mega-droughts. The Pleistocene aridity crises caused dramatic changes, affecting the malacofauna of all East African lakes. All lacustrine endemic faunas that had evolved in the Pliocene rift lakes, such as paleo-lake Chiwondo, became extinct. In Lake Tanganyika, the freshwater ecosystem did not crash as in other lakes, but the environmental changes were sufficiently important to trigger a vast radiation. All African endemic lacustrine molluscan clades that are the result of in-lake divergence are hence geologically young, including the vast Lavigeria clade in Lake Tanganyika (ca. 43 species)