Patches of barnacles and ascidians in soft bottoms: Associated motile fauna in relation to the surrounding assemblage

Epibenthic patches dominated by barnacles Balanus crenatus Bruguiere and solitary ascidians Styela spp., Bolthenia echinata (L.) and Molgula spp. in the White Sea shallow subtidal develop on bivalve shells and small stones surrounded with muddy sand. The space between barnacles and ascidians is filled with muddy sediment inhabited by motile taxa. We hypothesized that (i) epibenthic patches and unstructured sediment would attract different motile fauna and (ii) motile fauna of the patches would be affected by local abundances of epibenthic foundation species. Most dominant motile species demonstrated a significant difference in abundance between the two microhabitats. In contrast to the fauna of the sediment, species composition observed in aggregations of barnacles and ascidians was stable across different locations. In the field experiment initially clear bivalve shells after 5 years of exposure developed barnacle clusters with motile fauna similar to that observed in natural aggregations. Amphipods, isopods and bivalves, capitellid polychaets, Cirratulus cirratus (Müller) and Pholoe minuta Fabricius (Polychaeta) dominated in the sediment inside epibenthic patches. The proportion of capitellids, known to be sensitive to organic enrichment, was much higher within the patches than outside. The abundances of motile taxa found in aggregations were mostly determined by the number of barnacles of different size and of their empty shells, the biomass of ascidians, and the effect of location. Different dominant species demonstrated sensitivity to different parameters.Physical structure of the habitat, provided by barnacles and ascidians, as well as their biodeposition activity are regarded as the main factors structuring the motile fauna in the community studied. The spatial pattern observed seems to imply a range of pattern-generating biogenic processes, similar to those previously revealed in patches of filter-feeding bivalves, tube-building worms and seagrass.     

Early Jurassic shell beds from marginal marine environments in southern Mendoza, Argentina

External estuarine facies in Late Sinemurian beds from the base of the Puesto Araya Formation in the Atuel river region, Mendoza Province, Argentina, contain concentrations of a new species of Cardinioides (a shallow burrowing suspension-feeding Pachycardiidae bivalve) and a low diversity benthic fauna. These bivalves appear in tidal inlet facies of a wave-dominated estuary (environment similar to lagoon-barrier island systems), forming bioclastic lags at the channel bases. The taphonomic attributes (such as shell articulation, degree of fragmentation and abrasion, bioclast size, orientation) change from North to South, from monospecific concentrations of nearly complete large Cardinioides shells with low degree of fragmentation and abrasion, through beds with smaller Cardinioides shells associated with a few bivalves from marine environments, to only isolated fragmented specimens associated with a fully marine biota including not only other bivalves but also brachiopods and ammonoids. This, together with different palaeoecologic, sedimentologic and stratigraphic attributes at the studied localities are evidence of southwards changing environmental conditions from marginal marine (brackish) to fully marine on the eastern margin of the Neuquén basin at that time. From detailed analysis of taphonomic features, size distribution of shells, and the associated fauna at the different localities, the new species is regarded as a brackish water endemic, possibly a low salinity euryhaline species, which inhabited well oxygenated waters. Salinity, turbulence levels and food supply were the main limiting factors in the distribution of the species.     

Isotopic signatures (δO and δC) of bivalve shells from cold seeps and hydrothermal vents

The oxygen and carbon isotopic compositions of 108 modern shells of various bivalve species collected from cold seeps and hydrothermal vents were investigated in order to evaluate whether these parameters can provide information on environmental geochemical variability as well as on bivalve species and on the type of symbiotic bacteria present in their gills. The results show that the carbonate of bivalve shells from hydrothermal vents is characterized by abnormal positive δ¹³C values due to kinetic isotope effects, whereas the carbonate of bivalve shells from cold seeps exhibits positive as well as negative δ¹³C values suggesting that oxidized methane emitted by the seeping fluids may be incorporated in the shell. Comparison of the δ¹⁸O and δ¹³C values of bivalve shells hosting different chemosymbiotic bacteria suggests that each type of symbiosis is associated with a specific environment and bivalve species, indicating that there is a strong physiological/metabolic control on the incorporation of stable isotopes during the biomineralization process.     

Bacillary necrosis, a disease of larval and juvenile bivalve mollusks. I. Etiology and epizootiology

Tubiash, Haskell S. (U.S. Bureau of Commercial Fisheries, Milford, Conn.), Paul E. Chanley, and Einar Leifson. Bacillary necrosis, a disease of larval and juvenile bivalve mollusks. I. Etiology and epizootiology. J. Bacteriol. 90:1036-1044. 1965.-Lethal bacterial infections of a variety of hatchery-spawned bivalve mollusk larvae and juveniles have been studied. The symptoms of the disease and the course of the infection are described. Four biotypes and five antigenic types of bacteria, pathogenic for the larvae of five species of bivalve mollusks, were isolated and described in some detail. All are gram-negative motile rods. Comparative studies were made of a fairly large number of similar bacteria isolated from presumably normal marine fauna. None of these was pathogenic for the bivalve larvae nor did they have antigens in common with the pathogenic group. The four biotypes had a number of characteristics in common that rarely were present in other cultures from marine fauna. Several antibiotic preparations proved to be of value in the treatment and control of the infection.     

Bivalve borings in Lower Jurassic Lithiotis fauna from northeastern Italy and its palaeoecological interpretation

Random shell sections of the Pliensbachian (Early Jurassic) larger bivalve Opisoma from columns within the Main Post Office building of Ferrara, northern Italy, have been discovered to bear neat clavate-shape boreholes. These boreholes belong to the ichnogenus Gastrochaenolites Leymerie and represent bivalve borings. Opisoma is a subordinate component of the Lithiotis fauna characterised by aberrant shells thriving in tropical lagoonal settings which were widespread throughout the Tethyan and Panthalassa coasts. Although the Lithiotis fauna is well known in the palaeontological literature, no bivalve boring have been so far been formally described. The uniqueness of the morphology, size and substrate of these borings merits the designation of the new species Gastrochaenolites messisbugi ichnosp. nov. which thereby represents the first ichnospecies described from this fauna. The morphology of the boreholes and the included bivalves allows the boring activity to be ascribed to a mytilid bivalve. Palaeoecological and taphonomic analyses allowed the presence of the boreholes to be correlated to the Opisoma mode of life (epifaunal, free-living form) as well as to generally low sedimentation rates and seasonal mesotrophic conditions during an overall oligotrophic regime.

http://zoobank.org/urn:lsid:zoobank.org:act:CCF77B32-D459-4305-BC86-93F228852E50     

长江中下游湖泊软体动物的多样性及分布现状

长江中下游流域是我国淡水贝类多样性最为集中的地区,然而由于人类活动的影响,淡水贝类已成为高度濒危的类群。为有效保护淡水贝类的多样性,我们于2003年6月-2005年5月对长江中下游流域13个水体软体动物的多样性及分布进行了调查。共采集到软体动物69种(中国特有种42种),隶属于腹足类9科14属29种和瓣鳃类5科17属40种。其中,蚌科和田螺科是种类数最多的两个科,分别占总种类数的50.7%和14.5%。不同类型湖泊软体动物种类数的差别较大。通江湖泊所占种类数相对丰富,尤其是适应流水的种类,如河螺属、短沟蜷属及蚌科的种类。大型通江湖泊鄱阳湖和洞庭湖软体动物的种类数和特有种数分别66种和40种,分别占总种类数和总特有种数的95.7%和95.2%。阻隔水体所占种类数相对较少,种类数为4-19种。与历史资料相比,长江中下游湖泊软体动物的种类数和特有种数均减少50%左右,且多数种类的分布范围也明显缩小。造成贝类资源衰退的可能原因主要是江湖阻隔所引起的整个江湖复合系统栖息地和水文情势的改变,其他的人为活动如过度捕捞、围垦及废污水的过度排放等也可能是其中的重要原因。     

New data on mollusks from the Miocene (Tarkhanian-Chokrakian) of northern Sinop Province,Turkey

An insufficiently known bivalve and gastropod assemblage from the Early-Middle Miocene (Tarkhanian-Chokrakian) of northern Sinop Province (Turkey), is analyzed. Environments of the assemblage are reconstructed for the Chokrakian as subtidal, with prevailing lime and sandy bottom and good aeration, and partially well vegetated. Impoverishment of the mollusk biocoenose in this part of the marine basin (only 18 bivalve and 22 gastropod species recorded) compared to other areas, including the closest regions, Bulgaria on the west and Georgia on the east, is emphasized. The relatively low diversity of the fauna is probably connected not only with insufficient collecting, but with special hydrological conditions. A special aspect of the fauna is highlighted by the presence of the bivalve Circomphalus foliaceolamellosus subplicatus (Orb.), which is rare in the Chokrakian.     

Algae-associated marine molluscs in the Azores

The raolluscan fauna of a special habitat, the high intertidal algal turf, was studied at four stations on the island of Sao Miguel, Azores. The number of species found ranged from 13 to 23. However, a small group of only six species (the bivalve Lasaea adansoni and the gastropods Pisinna punctulum, Omalogyra atomus, Fossarus ambiguus, Skeneopsis planorbis and Alvania postrema) accounted for more than 80% of all the specimens collected. Mollusc density reached values of 20000 specimens per 100 g algal dry weight. The abundance and number of species of molluscs was comparable with those reported for algal zones lower on the Azorean shores.
Wave exposure and seasonality effects were found to be small, presumably because of the relatively mild abiotic conditions and the protective role of the turf. The algal substrata influenced the phytal molluscan community in two ways. First, the abundance of molluscs was significantly correlated with algal dry weight. Secondly, molluscan abundance and diversity were influenced by the algal composition of the turf. A rich algal composition, with several species of branched fleshy and coralline algae, was associated with a rich molluscan fauna. The dominance of coralline algae resulted in a abundant but species-poor fauna, while an almost monospecific turf of Gigartina was poor in both species and number of molluscan fauna.     

Species composition,richness, and distribution of marine bivalve molluscs in Bahía de Mazatlán,México

We describe the composition and distribution of bivalve molluscs from the sandy and rocky intertidal and the shallow subtidal environments of Bahía de Mazatlán, México. The bivalve fauna of the bay is represented by 89 living species in 28 families, including 37 new records and four range extensions: Lithophaga hastasia, Adula soleniformis, Mactrellona subalata, and Strigilla ervilia. The number of species increases from the upper (44) and lower intertidal (53) to the shallow subtidal (76), but only 11 (17%) have a wide distribution in the bay (i.e., found in all sampling sites and environments). The bivalve assemblages are composed of four main life forms: 27 epifaunal species, 26 infaunal, 16 semi-infaunal, and 20 endolithic. A taxonomic distinctness analysis identified the sampling sites and environments that contribute the most to the taxonomic diversity (species to suborder categories) of the bay. The present work increased significantly (31%) to 132 species previous inventories of bivalves of Bahía de Mazatlán. These species represent 34% of the bivalve diversity of the southern Golfo de California and approximately 15% of the Eastern Tropical Pacific region.     

The functional role of burrowing bivalves in freshwater ecosystems

1. Freshwater systems are losing biodiversity at a rapid rate, yet we know little about the functional role of most of this biodiversity. The ecosystem roles of freshwater burrowing bivalves have been particularly understudied. Here we summarize what is known about the functional role of burrowing bivalves in the orders Unionoida and Veneroida in lakes and streams globally. 2. Bivalves filter phytoplankton, bacteria and particulate organic matter from the water column. Corbicula and sphaeriids also remove organic matter from the sediment by deposit feeding, as may some unionids. Filtration rate varies with bivalve species and size, temperature, particle size and concentration, and flow regime. 3. Bivalves affect nutrient dynamics in freshwater systems, through excretion as well as biodeposition of faeces and pseudofaeces. Excretion rates are both size and species dependent, are influenced by reproductive stage, and vary greatly with temperature and food availability. 4. Bioturbation of sediments through bivalve movements increases sediment water and oxygen content and releases nutrients from the sediment to the water column. The physical presence of bivalve shells creates habitat for epiphytic and epizoic organisms, and stabilizes sediment and provides refugia for benthic fauna. Biodeposition of faeces and pseudofaeces can alter the composition of benthic communities. 5. There is conflicting evidence concerning the role of resource limitation in structuring bivalve communities. Control by bivalves of primary production is most likely when their biomass is large relative to the water volume and where hydrologic residence time is long. Future studies should consider exactly what bivalves feed upon, whether feeding varies seasonally and with habitat, and whether significant overlap in diet occurs. In particular, we need a clearer picture of the importance of suspension versus deposit feeding and the potential advantages and tradeoffs between these two feeding modes. 6. In North America, native burrowing bivalves (Unionidae) are declining at a catastrophic rate. This significant loss of benthic biomass, coupled with the invasion of an exotic burrowing bivalve (Corbicula), may result in large alterations of ecosystem processes and functions.     

SPATIAL VARIATION IN THE FAUNA ASSOCIATED WITH MYTILUS EDULIS ON A WAVE-EXPOSED ROCKY SHORE

The fauna associated with Mytilus edulis at a rocky wave-exposedlocality in North Wales is reported. A total of fifty-nine taxawith representatives from most of the main invertebrate phylawas recorded. In terms of species richness the community wasdominated by crustaceans (25 taxa), molluscs (10 taxa) and cheliceratearthropods (9 taxa), mainly mites. Fora-miniferans and crustaceanswere the most abundant taxa, representing 25% and 23% of thetotal associated fauna respectively. Nemerteans and nema-todeswere also well represented. The mussel bed was broadly stratifiedinto three distinct layers each dominated by a single species.Thus, the foramini-feran Ammonia batavus was restricted to thesediment in the bottom layer, the barnacle Semibalanus balanoidesoccurred only on the outer exposed surfaces of the mussel shells,whilst the tiny brooding bivalve, Lasaea rubra, nestled mainlyamongst the complex matrix of byssal threads and shell fragmentsin the middle layer of the bed. Species richness and diversitydecreased systematically with tidal elevation and both theseindices were also signifocantly depressed amongst mussel communitiesfrom high-shore tide pools. Inclination of the rock surfacehad little or no effect on the mussel populations or their associatedfauna. Small mussel patches generally supported fewer taxa perunit area and had a lower diversity than larger, more extensivepatches. These marked, small-scale spatial variations exhibitedby the fauna associated with M. edulis appear to be relatedlargely to the degree of aerial and tidal exposure, mussel density,the amount of accumulated sediment and mussel patch size. (Received 2 August 1993; accepted 8 November 1993)     

云南石林石炭纪古盘虫类有孔虫及其沉积环境初探

本文报道云南石林地区石炭纪中间界线附近地层的有孔虫动物群古盘虫类4属8种。分析数据显示,这类具有独特壳壁类型和形态特征的小有孔虫类群分布,与碳酸盐岩中的亮晶、团块、海百合茎以及双壳瓣类等成分的相关系数较大。综合分析结果认为,该区古盘虫类有孔虫分布与较浅水、具中等搅动、温暖及盐度正常的潮间带环境关系密切。     

Endolithic micro-organisms silicification of a bivalve fauna from the Silurian of Gotland

The silicified Wenlockian bivalve shells at Möllbos have been fragmented to a considerable extent. Shells which were broken prior to silicification exhibit possible original shell layers while those which were fragmented during laboratory treatment show no primary structures. The fauna at Möllbos was attacked by endolithic micro-organisms. The borings of these were then coated with a carbonate envelope. After burial the unattacked original shell material was dissolved the envelope silicified. Later, empty moulds were subsequently filled with drusy calcite occasionally with quartz crystals. A third silicification went occurred at a later diagenetic stage when matrix had become lithified.     

Distribution of sponges on the Mauritanian continental shelf

Transect sampling on the continental shelf off the Banc d'Arguin, Mauritania, revealed a patchy distribution of sponge species and populations. Major sponge habitats are inshore coastal sandstone flats harbouring a diverse infaunal sponge fauna, and the moving substrate of shells of live gastropods or empty shells occupied by hermit crabs which harbour a numerically important but species-poor incrusting sponge fauna. The latter forms occur over most of the depth profile. Horizontal distribution of the sponges shows a distinct gap in species and numbers associated with a muddy bottom area where the sediment-rich Banc d'Arguin run-off is found. North and south of this gap the specific composition of the infaunal sponges is considerably different and this is explained as evidence for limitation of range extensions, notably of the southern sponge fauna, by the muddy area.     

海南岛东方早二叠世双壳类动物群及其古生物地理学研究──兼评南龙杂砾岩的冰川成因说

在海南岛东方县江边地区下二叠统南龙组中发现双壳类９属１０种，其中２新种。除新种外，这些双壳类常见于华南和日本的茅口期晚期地层，其它动、植物化石的研究也得出了相同结论，本区无疑是华夏生物区系的组成部分。海南岛的琼中地体不大可能在石炭一二叠纪仍位于冈瓦纳大陆北缘或其附近，南龙杂砾岩应属裂谷成因，与冰川无关。     

Early Ordovician bivalves from Dali, West Yunnan, China

A bivalve fauna of Early Ordovician (late Arenig) age is described from the Hsiangyang Formation of the eastern part of West Yunnan, China. The fauna contains elements in common with Early Ordovician faunas of southern Gondwanan areas such as the Montagne Noire and Morocco and with those of Avalonia, together with several previously undescribed taxa. The following taxa are new: Biseriodonta simplex gen. et sp. nov.; Glyptarca sinensis sp. nov.; Trigonoglyptarca magna gen. et sp. nov.; Erhaiconcha xiangyangensis gen. et sp. nov.; Fasciculodonta impressa gen. et sp. nov.; Yunnanoredonia laevis gen. et sp. nov.; Daliella gen. nov.; Goniophorina ( Goniophorina ) contracta sp. nov.; Haidongoconcha radialis gen. et sp. nov.; Eopterinea aequiconcha gen. et sp. nov. The bivalve fauna includes the most diverse glyptarcid fauna and the earliest nuculanid and paracyclid known hitherto.   Eastern West Yunnan belonged to the Indochina terrane and it is concluded that the bivalve fauna represents a high-latitude assemblage and that the Indochina terrane should be considered a component part of the Peri-Gondwanan continent in the Ordovician; its bivalve faunas contrast with those of neighbouring terranes which have affinities with those of lower latitudes.     

Mitogenome sequence comparison in the endangered congeneric Pinna nobilis and Pinna rudis bivalves

Molecular Biology Reports - The pen shells Pinna nobilis and Pinna rudis are large wedge-shaped bivalve molluscs. Both species are threatened by different anthropogenic pressures. In the last few...     

Preliminary appraisal of an innovative hydraulic dredge with vibrating and sorting bottom on clam beds (Chamelea gallina)

To solve some of the efficiency and environmental problems related to the use of the hydraulic dredge in bivalve mollusc fishing, a new experimental gear with vibrating bottom grid and other technical changes has been tested on clam (Chamelea gallina) beds in the Adriatic Sea. Comparative fishing surveys indicate a significantly different selectivity of the vibrating dredge, with respect to a standard gear: in fact, undersize clams are sieved out during the fishing process, and almost no juveniles are hauled. Regarding the product quality, laboratory analyses show that the amount of intervalvar sediment is significantly lower in the catch from the modified dredge, due to a sort of `warning' device. Nevertheless, the larger number of damaged shells suggests that the vibrating grid subjects the clams to a greater mechanical stress than the standard gear. As for the environmental effects, the vibrating bottom is selective for the associated fauna too, as is shown by the higher mean weight of most the by-catch species in the experimental gear. Moreover, the riddling goes on continuously, allowing the immediate release of the sorted-out organisms, which are repositioned in the area of origin, thus avoiding a `contagious' distribution. In conclusion, these positive preliminary results suggest real benefits of this innovative modified dredge, with wide margins for further improvement.     

Mollusks of the Utlyuk Liman (Sea of Azov): A Review of Species Composition with Remarks on Distribution and Ecology

Summarized data on the fauna composition, distribution, and ecology of gastropod and bivalve mollusks of the Utlyuk Liman in the northwestern part of the Sea of Azov is presented. The total number of mollusk species identified was 63; 43 species belonged to the class Gastropoda, and 20 species, to the class Bivalvia. The distribution of mollusks in the liman has extremely irregular character, whereas the distribution of species along the marine shore of Biryuchii Ostrov spit is more homogeneous. Euryhaline Mediterranean species represent the core of liman malacofauna; some taxa of the Ponto-Caspian zoogeographical complex (Dreissena polymorpha and species of the genus Theodoxus) and invader species from distant sea basins (Mya arenaria and Anadara inaequivalvis) were also identified.     

Modern bivalve shell assemblages on three atolls offshore Belize (Central America,Caribbean Sea)

The Belize atolls—Glovers Reef, Lighthouse Reef and Turneffe Islands—show differences in geomorphology, lagoonal depth, bottom sediment, growth of mangroves and sea-grass, exposure to waves and currents as well as in their sedimentation rates and their age. Bivalve shell assemblages in lagoonal areas reflect these geomorphological differences. On each atoll, 32 to 44 recent sediment samples were taken (total number of samples 111) and bivalve shells subsequently identified. The resulting database (32,122 bivalve shells in total) was analysed using Q-mode cluster analyses. Both the distribution of species characteristic of different lagoonal habitats and the distribution of bivalves with different life and feeding habits were investigated. Epifaunal suspension feeders were found particularly on hard-bottom along the reef-crests or clinging to mangrove roots. Infaunal suspension feeders show a more diverse distribution. Deeper lagoonal parts and areas with mangrove growth are often inhabited by chemosymbiont-carrying bivalves, indicating locations of reduced sediment. Deep burrowing detritus feeders are very abundant in shallow-water areas with moderate to high water agitation and were seldom found in Halimeda-rich sediments.