海南岛西海岸红树林软体动物多样性

为了掌握海南岛西海岸红树林软体动物多样性状况, 本文于2015-2016年对海南岛西海岸6个主要红树林分布区软体动物的种类组成、物种多样性和群落结构的时空变化进行了研究。共采集到软体动物57科201种, 主要优势种有珠带拟蟹守螺(Cerithidea cingulata)、绯拟沼螺(Assiminea latericea)、圆胖樱蛤(Pinguitellina cycladiformis)和斜肋齿蜷(Sermyla riqueti)等。年平均密度与平均生物量分别为324.13 ind./m²和142.88 g/m², 物种数、密度和生物量均高于北部湾沿岸的其他红树林。海南岛西海岸各红树林软体动物的密度和生物量均未呈现明显的季节变化, 软体动物密度存在空间上的显著差异。聚类分析结果显示, 在盐度、土壤结构和红树林群落存在差异的不同红树林, 软体动物种类组成相似度低。多因子AZTI海洋生物指数(M-AMBI)结果表明海南岛西海岸红树林软体动物群落未受明显扰动, 生态环境质量介于一般和优良之间, 但仍受到人类活动与外来植物入侵威胁, 因其在候鸟迁徙中的重要作用, 亟需加强管理与保护。     

Mid-Neolithic Exploitation of Mollusks in the Guanzhong Basin of Northwestern China: Preliminary Results

Mollusk remains are abundant in archaeological sites in the Guanzhong Basin of Northwestern China, providing good opportunities for investigations into the use of mollusks by prehistoric humans. Here we report on freshwater gastropod and bivalve mollusks covering the time interval from about 5600 to 4500 cal. yrs BP from sites of Mid-Late Neolithic age. They are identified as Cipangopaludina chinensis and Unio douglasiae, both of which are currently food for humans. The shells are well preserved and have no signs of abrasion. They are all freshwater gastropods and bivalves found in pits without water-reworked deposits and have modern representatives which can be observed in rivers, reservoirs, and paddy fields in the studied region. Mollusk shells were frequently recovered in association with mammal bones, lithic artifacts, and pottery. These lines of evidence indicate that the mollusks are the remains of prehistoric meals. The mollusk shells were likely discarded into the pits by prehistoric humans after the flesh was eaten. However, these mollusk remains may not have been staple food since they are not found in large quantities. Mollusk shell tools and ornaments are also observed. Shell tools include shell knives, shell reaphooks and arrowheads, whereas shell ornaments are composed of pendants and loops. All the shell tools and ornaments are made of bivalve mollusks and do not occur in large numbers. The finding of these freshwater mollusk remains supports the view that the middle Holocene climate in the Guanzhong Basin may have been warm and moist, which was probably favorable to freshwater mollusks growing and developing in the region.     

Topical groups of mollusks in the lakes of Bol’shoy Solovetskiy Island (Solovetskiy Archipelago, White Sea, Northwestern Russian)

Topical groups of mollusks were studied in 13 lakes of Bol’shoy Solovetsky Island. A total of 20 species and 14 genera of mollusks were found. Five classes of mollusk topical groups may be defined with a higher probability. These groups include 12 to 19 species. All these species inhabit the littoral zone at depths of up to 3.2 m. No mollusks were found within the lakes’ deepwater zone (maximal depths of 10–30 m and silty grounds). A specific set of one to three dominant species is a characteristic of each class of topical groups. This may be treated as an effect of compensating for island communities: low species diversity is compensated for by increasing the density of colonies of some species. Ten mollusk species are significantly confined to a specific type of habitat.     

Reaction of mollusk population to emissions from the Middle Ural Copper Smelter

A quantitative study of the mollusk population of the herbaceous layer has been carried out in the secondary upland meadows in a gradient of pollution with emissions from the Middle Ural Copper Smelter (MUCS) (city of Revda, Sverdlovsk oblast). The total abundance of mollusks is 1.3 times lower in a moderately polluted area than in reference areas. The mollusks disappear entirely from the grass cover in close proximity to the smelter. The reasons for the change in the mollusk population structure may be as follows: a heavy-metal toxic effect under conditions of environmental acidification, a lack of available Ca due to its depletion from the upper soil horizons, a reduction in species diversity, and a simplification of meadow grasscover architecture (which modifies the hydrothermal regime in the herbaceous layer). Apparently, a combination of these effects eliminates mollusks from the herbaceous layer, a trend which is not observed in the case of environmental pollution with only heavy metals.     

Middle Cambrian pterobranchs and the Question: What is a graptolite?

The presence of distinct fusellar structure is taken as evidence to include a number of fossils from the Middle Cambrian to the Lower Ordovician of North America and Europe with the Pterobranchia. The dome of the pterobranchs and the prosicula of the planktic graptolites are contrasted and evidence is given for the re‐assignment of a number of well known dendroid graptolites to the pterobranchs. A non‐destructive method is described to reveal fusellar development of delicate hemichordate exoskeletons from shales. Rhabdotubus robustus n. sp. from the Czech Republic and ? Cephalodiscus sp. from the Wheeler Shale of North America are described as new Middle Cambrian pterobranchs.     

Diversity protects plant communities against generalist molluscan herbivores

Wildflower strips are used to increase natural enemies of crop pests and to conserve insect diversity on farmland. Mollusks, especially slugs, can affect the vegetation development in these strips considerably. Although recent theoretical work suggests that more diverse plant communities will exhibit greater resistance against herbivore pressure, empirical studies are scarce. We conducted a semi‐natural experiment in wildflower strips, manipulating trophic structure (reduction in herbivorous mollusks and reduction in major predators) and plant diversity (2, 6, 12, 20 and 24 sown species). This design allowed us to assess the effect of plant diversity, biomass and composition on mollusks, and vice versa, the effect of mollusc abundance on vegetation. Seven species of mollusks were found in the strips, with the slugs Arion lusitanicus, Deroceras reticulatum and Deroceras panormitanum being most frequent. We found a negative relationship between plant diversity and mollusk abundance, which was due predominantly to a decrease in the agricultural pest species A. lusitanicus. These results are consistent with the hypothesis that plant diversity can reduce the impact of herbivores. However, plant identity also had an effect on mollusks, and accounted for a much larger fraction of the variation in mollusk communities than biodiversity effects. While overall plant diversity decreased during the 3 years of the study, in the final year the highest plant diversity was found in the plots where mollusk populations were experimentally reduced. We conclude that selective feeding by generalist herbivores leads to changes in plant community composition and hence reduced plant diversity. Our results highlight the importance of plant biodiversity as protection against generalist herbivores, which if abundant can in the long term negatively impact plant diversity, driving the system along a “low plant diversity – high mollusk abundance” trajectory.     

Origin and the Early Evolution of the Phylum Mollusca

The paper gives an overview of the modern hypotheses on the origin of the phylum Mollusca and the formation of its main classes. The Cambrian stage of molluscan evolution is characterized based on the paleontological material. The doubtfulness of assignment of the Precambrian (Vendian) soft-bodied fossil Kimberella to mollusks is argued. Judging from the interpretation of the morphologically diverse Cambrian fossils, it is suggested that the classes Polyplacophora, Monoplacophora, Gastropoda and Bivalvia formed already near the Precambrian–Cambrian boundary, i.e., from the beginning of the paleontologically documented evolutionary history of the phylum, whereas the assumption of the later origin of these taxa is unconvincing. The remaining classes of mollusks arose later, i.e., Cephalopoda, in the Late Cambrian; Scaphopoda, in the Ordovician; and Aplacophora, in the Silurian.     

Dictyonema Hall and its importance for the evolutionary history of the Graptoloidea

Dictyonema retiforme has been regarded as the benthic ancestor to the planktic Graptoloidea, represented by the earliest planktic Rhabdinopora flabelliformis and its descendants. The revision of the type material of Dictyonema retiforme, the type species of the genus Dictyonema, from the Silurian of New York State shows compound stipes formed by the complexly growing and overlapping tubular thecae of acanthograptid type. The connections between adjacent stipes are formed by thecal tubes or thecal bridges and not by dissepiments. Thus, the species has to be transferred to the Acanthograptidae and cannot be regarded as being related to the early planktic Graptoloidea. The tubarium meshwork of Dictyonema is phylogenetically unrelated to the meshwork of the planktic Rhabdinopora, and represents a case of convergent evolution. The origins of the planktic graptoloids lie among members of middle to upper Cambrian Dendrograpidae, as can be seen from the thecal style and the triad budding patterns with regularly developed bithecae in this group.     

Centrocestus formosanus (Opisthorchiida: Heterophyidae) as a cause of death in gray tilapia fry Oreochromis niloticus (Perciforme: Cichlidae) in the dry Pacific of Costa Rica

Centrocestusformosanus is a zoonotic trematode from Asia and has been mainly associated as cause of death of cultured fish. To identify pathogen trematode species in tilapia fry (Oreochromis niloticus) and to determine mollusks hosting these parasites, freshwater mollusks were collected from tilapia cultured ponds and experimental infections were carried out with tilapia fries and different mollusk species. A total of 907 freshwater mollusks were obtained from tilapia ponds and were identified to species level, four gastropods and one bivalve were determined: Melania tuberculata, Melanoides turricula, Pomacea flagellata, Haitia cubensis and Anodontiles luteola. For the first time, the presence of M. turricula and H. cubensis are reported in Costa Rica. Seven morphotypes of cercariae (Xifiodiocercaria, Equinostoma, Oftalmocercaria, Parapleurolofocercus, Cistocerca, Furcocercaria and Leptocercaria) parasitizing all five species of mollusks were found, all of distome type. Experimental exposure of tilapia fry to M. tuberculata demonstrated that the parapleurolofocercus morphotype found in the mollusk is in accordance with the finding of C. formosanus in tilapia fry. An abundance and mean intensity of 1018-1027 digeneans per gill in each exposed fish was determined. Centrocestus formosanus is reported for the first time in Costa Rica, for which the primary and secondary intermediate hosts were also determined.     

Differences in the number of hemocytes in the snail host Biomphalaria tenagophila, resistant and susceptible to Schistosoma mansoni infection

The relationships between schistosomiasis and its intermediate host, mollusks of the genus Biomphalaria, have been a concern for decades. It is known that the vector mollusk shows different susceptibility against parasite infection, whose occurrence depends on the interaction between the forms of trematode larvae and the host defense cells. These cells are called amebocytes or hemocytes and are responsible for the recognition of foreign bodies and for phagocytosis and cytotoxic reactions. The defense cells mediate the modulation of the resistant and susceptible phenotypes of the mollusk. Two main types of hemocytes are found in the Biomphalaria hemolymph: the granulocytes and the hyalinocytes. We studied the variation in the number (kinetics) of hemocytes for 24 h after exposing the parasite to genetically selected and non-selected strains of Biomphalaria tenagophila, susceptible or not to infection by Schistosoma mansoni. The differences were analyzed referred to the variations in the number of hemocytes in mollusks susceptible or not to infection by S. mansoni. The hemolymph of the selected and non-selected snails was collected, and hemocytes were counted using a Neubauer chamber at six designated periods: 0 h (control, non-exposed individuals), 2 h, 6 h, 12 h, 18 h and, 24 h after parasite exposure. Samples of hemolymph of five selected mollusks and five non-selected mollusks were separately used at each counting time. There was a significant variation in the number of hemocytes between the strains, which indicates that defense cells have different behaviors in resistant and susceptible mollusks.     

A review of the world marine gastropod fishery: evolution of catches,management and the Chilean experience

Reviews in Fish Biology and Fisheries - Marine mollusks are among the most importantinvertebrate fisheries in the world. The mainclasses of mollusk fished are Cephalopoda,Bivalvia and Gastropoda....     

南洞庭湖区软体动物物种多样性评估及保护对策

洞庭湖孕育和维持了较高和独特的软体动物多样性。尽管有关该湖软体动物的调查较多, 但多分散于各文献中。本文结合文献调研和现场调查(2013-2018年), 系统评估了南洞庭湖区软体动物物种多样性, 解析驱动群落格局演变的关键因子, 并提出合理的保护对策。共记录2纲5目14科33属87种(腹足纲41种, 双壳纲46种), 其中本调查记录54种, 隶属于2纲5目12科31属, 包括腹足纲22种, 双壳纲32种。评估结果显示处于近危和受威胁等级物种21种, 包括腹足纲4种和双壳纲17种。调查区域软体动物平均密度和生物量分别为173.1 ind./m ²和279.3 g/m ²。优势种为河蚬(Corbicula fluminea)、大沼螺(Parafossarulus eximius)、铜锈环棱螺(Bellamya aeruginosa)、卵河螺(Rivularia ovum)。基于距离的冗余分析(distance-based redundancy analysis, dbRDA)结果显示, 局域环境因子(底质类型、水深、pH、总溶解固体和总磷)制约软体动物的群落变异。另外, 区域内的人类活动(如商业采砂、建坝和沿岸土地利用、过度捕捞和非法电捕等)亦深刻影响软体动物的生存。这些人类干扰已导致软体动物物种多样性显著下降, 可能造成一些特有物种的局域性灭绝。为了恢复和保护软体动物物种多样性和资源, 应采取一系列对策, 包括管控合法的挖沙业和取缔非法挖沙业、禁止过度捕捞和非法电捕、维持水文的自然节律、恢复沿岸自然湖滨带和控制点源和面源污染物排入等。我们呼吁尽快在南洞庭湖区建立软体动物国家级自然保护区, 以保护该湖区(可能是整个洞庭湖)残存的软体动物物种多样性和特有性。     

钱塘江流域的淡水贝类

报告了对钱塘江流域进行淡水贝类调查的结果。标本经鉴定计有67种,隶属于腹足纲有9科18属42种,瓣鳃纲有4科11属25种,内有29种属浙江省新记录。分析了该流域淡水贝类与栖息环境的关系及该流域的常见种和偶见种,并探讨了该流域淡水贝类的分布区划。     

Mollusks in Phanerozoic marine communities: Implications from the analysis of global paleontological databases

Evolutionary history of three mollusk classes (Bivalvia, Gastropoda, and Cephalopoda), regarded as components of the Phanerozoic marine biota, is discussed based on the comparison of dynamics of quantitative parameters obtained from the analysis of the global paleontological databases. The main trends in the evolution of the role of mollusks in Phanerozoic marine ecosystems and relationships between the diversification of this group and biodiversity of paleocommunities are considered. Certain parameters show similarity between the diversity dynamics of mollusks and the whole marine biota, including the paleolatitudinal distribution of diversity. At the same time, mollusk classes differ considerably in certain aspects. The evolutionary history of Bivalvia, Gastropoda, and Cephalopoda was different and determined presumably by deep ecological divergence which occurred as early as the Early Paleozoic adaptive radiation. Bivalves and gastropods followed the trend of a gradual and constant increase in their role in marine communities; they are characterized by high and constantly growing duration of genera, high (and also growing) frequency in paleontological collections. Cephalopods show more chaotic macroevolutionary dynamics, relatively low mean duration of genera and low relative frequency.     

Invasion of the Zebra Mussel Dreissena polymorpha (Pallas, 1771) (Dreissenidae) in Lake Ladoga

Biology Bulletin - In May 2019, the invasive mollusk Dreissena polymorpha (Pallas, 1771) was found in Volkhov Bay of Lake Ladoga by means of an unmanned underwater vehicle. The age of some mollusks...     

Shell structure of <Emphasis Type="Italic">Kutorgina</Emphasis> Billings (Brachiopoda,Kutorginida)

Shell structure in members of the genus Kutorgina, Lower Cambrian brachiopods with calcareous shells and primitive articulation, is described for the first time. This type of shell structure resembles that of the Lower Cambrian mollusks and hyoliths rather than of brachiopods.     

Establishing mollusk colonization and assemblage patterns in planted mangrove stands of different ages in Lingayen Gulf,Philippines

We investigated the assemblage patterns and species composition of infaunal mollusks in different ages of planted mangroves (6-, 8-, 10-, 11- and 18-year old) in Lingayen Gulf, northwestern Philippines. The study aimed to determine if the mollusk assemblage was associated with the developing forest and if such patterns could provide evidence for restoration of habitat functionality. A total of 11 mollusk species were recorded. Only two species, Cerithidea cingulata (Gmelin, 1791) and Nerita polita (Linnaeus, 1758), consistently appeared in all stands where the former had increased biomass in maturing stands and the latter peaked in intermediate age stands. Vegetation structure and biomass, and sediment characteristics changed as plantations matured. Likewise, mollusk assemblages (based on species composition and biomass) significantly varied among different age stands. Such changes in assemblage patterns were correlated with vegetation and sediment characteristics. The groupings of mollusks species in the different stands can be categorized into: decreasing (species that have initially high biomass but disappeared in older stands); no detectable change (species that did not show any change in biomass); peaking (species that initially had low biomass, peaked at intermediate stands, and then diminished in mature stands; and, increasing (species that have increasing biomass with maturing stands). In summary, this study affirmed: (1) rehabilitated mangroves with increased forest structure and biomass can be effective in facilitating infaunal colonization; and (2) mollusk assemblage patterns changed as stands grow older.     

Evolutionary regularities of development of somatic polyploidy in salivary glands of gastropod mollusks: V. Subclasses Opisthobranchia and Pulmonata

Salivary glands of 25 species of Opisthobranchia and Pulmonata gastropod mollusks were studied with the use of histochemical methods and cytophotometry of DNA in cellular nuclei. In the secretory epithelium, cells of three main types are identified: granular cells (with granular glycoprotein inclusions), mucocytes-I (containing sulphatized acid mucopolysaccharides), and mucocytes-II (containing neutral and acid nonsulphatized polysaccharides and protein), as well as epithelial ciliated cells and cells of ducts. It is shown that the salivary gland secretory cells of all studied mollusk species are polyploidized, but to different degree. In most species, the maximal degree of polyploidy estimated by the DNA content amounts to 64–128c. Giant polyploidy—up to 4096c—is revealed in salivary gland cells of Tritonia diomedea. The functional properties due to the peculiarities of nutrition of different molluscan species and phylogenetic tendencies of development of somatic polyploidy in the class of Gastropoda are discussed. The high degree of obligatory polyploidization revealed in salivary gland cells of the opisthobranchian and pulmonate mollusks is considered as a peculiar cytological arogenesis as compared with allogenic, facultative, and slight manifestations of polyploidy in prosobranchian gastropod mollusks. The probable causes of such differences are due to the euthyneural type of organization of the central nervous system and to the giant neuronal polyploidy in opisthobranchian and pulmonate mollusks. The causes, mechanisms, and significance of such correlations are so far unclear.     

Correlating the global Cambrian–Ordovician boundary: Precise comparison of the Xiaoyangqiao section,Dayangcha, North China with the Green Point GSSP section,Newfoundland, Canada

The Cambrian–Ordovician boundary interval exposed at the Xiaoyangqiao section, North China is presented. The distribution of stratigraphically important fossils in the Xiaoyangqiao section revealed several nearly coeval graptolite, conodont, trilobite, and acritarch bioevents in the uppermost Cambrian–lowermost Ordovician carbonate-siliciclastic sedimentary sequence. The precise correlation to the Green Point GSSP section, western Newfoundland, Canada allows for the identification of the corresponding GSSP level in the Xiaoyangqiao section. The combined data from the Xiaoyangqiao section and the Green Point GSSP section provide a series of events that all can be applied as proxies for identification of the Cambrian–Ordovician boundary horizon outside the GSSP. Based on this, the Xiaoyangqiao section, Dayangcha, is here strongly recommended as a candidate for an Auxiliary Boundary Stratigraphic Section and Point section (ASSP) for the base of the Ordovician System, because it provides one of the best and most complete Cambrian–Ordovician transitions in the world and because the first planktic graptolites are from the Xiaoyangqiao section.