Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 6

Liczba wyników na stronie
first rewind previous Strona / 1 next fast forward last
Wyniki wyszukiwania
Wyszukiwano:
w słowach kluczowych:  Mollusca
help Sortuj według:

help Ogranicz wyniki do:
first rewind previous Strona / 1 next fast forward last
EN
Mollusk species associated with Cystoseira barbata were examined in the Sea of Marmara in 2012 at 14 sampling sites with a depth ranging from 0.2 to 0.5 m. A total of 18 468 specimens belonging to three classes (Polyplacophora, Gastropoda and Bivalvia) and 30 species were identified. Alvania mamillata Risso, 1826 is a new record for the marine mollusk fauna of the Sea of Marmara. The number of species at the sampling sites varied from 2 to 11 (400 cm–2), the density ranged between 758 and 63 083 ind. m–2, and wet weight between 0.4 and 34.3 g m–2. Gastropoda were the richest class, represented by 22 species and 7611 individuals. The families Rissoidae, Mytilidae and Pyramidellidae were represented by the largest number of species. The most dominant mollusk species in C. barbata facies were Mytilaster minimus (Poli, 1795) (37.77%), Rissoa splendida Eichwald, 1830 (27.20%), Mytilaster lineatus (Gmelin, 1791) (18.69%) and Bittium reticulatum (da Costa, 1778) (6.89%). However, the mollusks R. splendida (86%), M. lineatus (71%), M. minimus (69%) and Steromphala adansonii (Payraudeau, 1826) (67%) were characterized by the highest values of the frequency index. Canonical correspondence analysis showed that the main factors affecting the assemblages of mollusks were the content of total nitrogen, the maximum thallus height, algal wet weight and temperature.
EN
The present study was performed to follow temporal variation of the soft-bottom molluscan fauna in north-western Iskenderun Bay. The benthic material was collected at a depth ranging from 3 to 37 m at 12 sampling locations by the van Veen grab sampler in the summer season of 2012, 2013 and 2014. A total of 133 species were identified in the study area through the examination of the collected material. Among the identified species, Corbula gibba (Olivi, 1792), Bittium reticulatum (da Costa, 1778), Nassarius pygmaeus (Lamarck, 1822), Cerithidium diplax (Watson, 1886) and Finella pupoides Adams, A., 1860 have the highest values of the frequency index. According to the Bray-Curtis similarity index, these species also have an important effect on the similarity between the stations. Furthermore, C. diplax and F. pupoides are alien species to the Mediterranean.
3
Content available remote Diversity of Mollusca in lowland river-lake system: lentic versus lotic patches
EN
Longitudinal organisation of macroinvertebrate fauna along river is one of the most important problem commonly used to explain the functioning of flowing water ecosystems. The river system can be treated as a mosaic of landscapes patches and riverine macroinvertebrates’ community structure is a function of longitudinal changes in its key abiotic patterns. The aims of the study was to analyse the taxonomic structure of molluscs in the river-lake system, to compare river and lake malacofauna and to determine the factors responsible for its diversity in lakes and river stretches. The study based on comprehensive analysis of malakofauna sampled at 10 sites in the Krutynia River and in all 19 lakes it flows through were performed in the years 2008–1011. River Krutynia is one of the most important rivers in Masurian Lakeland (north-eastern Poland) with length of 100 km and mean annual discharge of 10.6 m3 h-1. It forms a characteristic river-lake system typical for the lakeland landscape in Central Europe. The density and taxonomic composition of molluscs were found as strongly dissimilar in a local scale – between closely located lakes and between particular parts of flowing waters, divided by the lakes. Multivariate methods were used to demonstrate a clear dissimilarity of lake and river malakofauna and to show that the mean content of phosphorus, nitrogen and organic matter in bottom sediments were correlated with each other in lakes but not in the river. The most important species differentiating river sites into larger groups with respect to the similarity was Theodoxus fluviatilis while Stagnicola corvus and Anisus vortex were such species differentiating lakes. The numbers and percentages of Dreissena polymorpha and Unionidae were negatively correlated with nutrients in river sediments. There was a strong positive relationship between nutrients’ concentrations in sediments and the percentages of Viviparus, Obtained results of multiple regression indicate a strong effect of nutrient and organic matter concentrations in the sediments and the distance from the site to the lake on the domination structure of molluscs.
EN
During 2004 and 2005 research on the malacocenoses existing in oxbow lakes differ in terms of hydrological connectivity was conducted in the valley of the Łyna River. The results showed that the connection of an oxbow lake with the river is the key factor influencing the abundance and biomass of molluscs in the lake. Three types of oxbow lakes representing lentic, semi-lotic and lotic environments were considered. In the lentic oxbow lake Mollusca was dominated by Potamapyrgus antipodarum Gray, the semi-lotic by Viviparus viviparus L., and the lotic by Pisidium sp. The most hospitable conditions for the molluscs’ development were found in the semi-lotic reservoir where contact with the river was maintained by backwater in the downstream arm. The separation of the reservoir from the river caused a total reduction of the Bivalvia representatives. Diversity of the malacocenoses resulted mainly from different abilities to adapt to temporary oxygen deficits. Each type of oxbow lake is characterized by an individual pattern of oxygen distribution. To avoid anaerobic conditions and enable the development of biodiversity in floodplains, water bodies should be supplied by well-aerated river water.
EN
A holoplanktonic mollusc assemblage from Neogene sediments of the Azorean island Santa Maria is described and analysed to determine the age of the sediments. Sixteen taxa are documented (three heteropods, thirteen pteropods), fourteen of which are new records for the fossil fauna of Santa Maria Island. The composition of the heteropod and pteropod assemblage indicates a Zanclean age, which contrasts with earlier age assignments to the Early, Middle or Late Miocene based on benthic molluscs, but is in good agreement with more recent data based on foraminiferal and geochemical evidence. The pteropod Cavolinia marginata (BRONN, 1862) is re-described based on abundant topotypic material and a neotype is designated. The species Cavolinia vendryesiana (GUPPY, 1873) is considered to be a junior subjective synonym of C. marginata. The temporal range of the pteropod Limacina trochiformis (D.ORBIGNY, 1836) is extended to the Zanclean.
EN
This article presents results of multidisciplinary research which has been carried out in order to determine changes in the vegetation cover as well as changes in the structure of the Karaśne lake-mire complex in the Late Glacial and Holocene. In addition, human impact on the formation of the vegetation cover and the bio- and chronostratigraphy of the Late Glacial sediments is discussed.
first rewind previous Strona / 1 next fast forward last
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.