Primary cell culture from embryos of the Japanese scallop Mizuchopecten yessoensis (Bivalvia)

Primary cell cultures obtained from embryos of Mizuchopecten yessoensis (Bivalvia) survived for four months. Although the number of cells progressively decreased during the cultivation, mitotic cells were observed both at the first stages and at the end. A possibility of growing marine invertebrates cells in long term primary culture is discussed.     

Cretaceous opine bivalves from the Pacific slope of North America and palaeobiogeography of subfamily Opinae Chavan, 1969

Abstract: Opines constitute a small subfamily of Mesozoic astartid bivalves that lived mostly in the Tethys Sea region. They first appeared in western Europe during the Middle Triassic, became most widespread during the Jurassic and had their first undoubted appearance in the New World during the Late Jurassic. Their Pacific slope of North America record is studied in detail for the first time. The earliest of the Pacific slope opines is Opis californica Stanton of Early Cretaceous (Hauterivian or Barremian) age. The other six opine species in the study area are of Late Cretaceous age (collectively Middle Turonian – early Late Maastrichtian), have hinges bearing two strong cardinal teeth in each valve, and are placed in the new subgenus Hesperopsis, which is the first astartid to have a partially internal ligament. These six species comprise two morphological lineages inferred to have evolved from O. (H.) popenoei sp. nov. The ‘holzana’ lineage includes O. (H.) holzana sp. nov. and O. (H.) rosarioensis Anderson and Hanna. The ‘anae’ lineage includes O. (H.) anae sp. nov., O. (H.) vancouverensis Whiteaves and O. (H.) triangulata (Cooper). Hesperopis lived in warm temperate waters in offshore shelfal areas. It had a vertical commissure and probably lived as an edgewise recliner. Through time, the species of both lineages became larger and either broader or more elongate. Neither Opis shastalis Anderson, of Aptian age, nor Opis virginalis Waring, of late Palaeocene age, are opines. A junior secondary homonym of Opis trigonalis (Sowerby) was detected and is renamed here as Opis tamurai nom nov.     

Comparison of the spermatozoan morphology of Isognomon bicolor and Isognomon alatus (Mollusca, Bivalvia, Isognomonidae)

In this study we used transmission and scanning electron microscopy to examine the spermatozoan structure of Isognomon bicolor and Isognomon alatus. The spermatozoa of both species were of the primitive or ect-aquasperm type. The acrosomal morphologies were essentially similar but the top of the acrosomal vesicle in I. bicolor sperm had a slightly flattened edge whereas the apex of the acrosomal vesicle of I. alatus sperm had a rounded outline. This difference suggested that acrosomal morphology could be an important character for taxonomic differentiation. In the present work, the results demonstrated that the gamete ultrastructure of the two distinct species I. alatus, from Panama, and I. bicolor, from the southeastern region of Brazil, were similar to the other studied species of the superfamily Pterioidea.     

Olenekian (Early Triassic) bivalves from the Salt Range and Surghar Range,Pakistan

Abstract: Based on newly collected material from the uppermost Smithian and lower to middle Spathian (Olenekian, Lower Triassic) of the Salt Range and Surghar Range (Pakistan), 15 bivalve species belonging to 11 genera are described, including two new genera, Eobuchia and Dimorphoconcha, and one new species, Palaeoneilo? fortistriata. Eobuchia gen. nov. is placed in a new subfamily, the Eobuchiinae, which differs from the Buchiinae in having an almost planar and only moderately inclined or offset right anterior auricle. Inclination of the right anterior auricle is proposed as a synapomorphy of the revised suborder Monotidina, which includes the Buchiidae, Monotidae, Oxytomidae and, tentatively, the Dolponellidae. The Pseudomonotidae, Chaenocardiidae and Claraiidae are discussed as candidate ancestors of the Monotidina. Dimorphoconcha gen. nov., provisionally placed in the Limidae, is a morphologically unusual genus characterized by a globose shell centre and a strongly plicate fringe. Permophorus costatus, which was previously known exclusively from Permian strata, is reported from the Spathian of the Surghar Range. This record extends the range of P. costatus for at least 8 Myr and makes it the first reported Lazarus species, with an outage of more than 2 Myr after the end‐Permian mass extinction. Ten of 15 species recognized in this study have not been reported from other regions, which may indicate increasing provincialism towards the end of the Early Triassic, or, alternatively, reflect the still insufficient knowledge of benthic faunas from the epoch that followed the greatest crisis in the history of life.     

The effect of environmental conditions on distribution,growth and life span of <Emphasis Type="Italic">Protothaca euglypta</Emphasis> (Mollusca: Bivalvia)

The distribution and growth of the bivalve mollusk Protothaca euglypta in Peter the Great Bay and at the northern boundary of its area were investigated. It is shown that in some biotopes P. euglypta biomass reaches 1–2 kg/m², which exceeds the estimated values of abundance obtained for most associated species of mollusks. It has been established that local variability of P. euglypta growth rates can be compared with latitudinal variability, and the life span increases from the southern part of the area towards its northern boundary. It has been concluded that P. euglypta occupies a more prominent position in the malacofauna of shallow waters in its abundance, than it was considered earlier.     

Un nouveau Cycloconchide (Mollusca Bivalvia) du Llanvirn inférieur (Ordovicien) des Monts de Tolède (Espagne)

A new Cycloconchid, designated Ananterodontaoretanica, has been collected from the Lower Llanvirn (Montes de Toledo). The only known specimen is described and compared with several genera of Ordovician Cycloconchids, the validity of which is briefly discussed.     

中国西南地区淡水贝类八新种记述（腹足纲：瓣鳃纲）

本文报道中国西南地区淡水贝８个新种：Ｖｉｖｉｐａｒｕｓ ｔｒｉｃｉｎｃｔｕｓ Ｌｉｕ,Ｚｈａｎｇ ｅｔ Ｗａｎｇ,ｓｐ．ｎｏｖ．Ｐａｒａｆｏｓｓａｒｕｌｕｓ ｇｌｏｂｏｓｕｓ Ｌｉｕ,Ｚｈａｎｇ ｅｔ Ｗａｎｇ,ｓｐ．ｎｏｖ．,Ｌｉｔｈｏｇｌｙｐｈｏｐｓｉｓ ｈｙａｌｉｎｕｓ Ｌｉｕ,Ｗａｎｇ ｅｔ Ｄｕａｎ,ｓｐ．ｎｏｖ．,Ｓｅｍｉｓｕｌｃｏｓｐｉｒａ ｍａｒｉｃａ Ｌｉｕ,Ｗａｎｇ ｅｔ Ｚｈ     

Unravelling the systematics of Nodularia (Bivalvia,Unionidae) species from eastern Russia

Conservation efforts have been hindered by data deficient conservation status assessments, especially due to taxonomic problems. This is especially true for many eastern Russian species of freshwater mussels, where distinct classification systems have complicated their delimitation and identification. Nodularia is a widespread eastern Asian freshwater mussel genus, present from Vietnam in the south to the Magadan region in eastern Russia in the north. The number of recognized species in the genus Nodularia in eastern Russia has been inflated over the last several decades due to the use of a typological species concept, the so-called 'Comparatory Method'. This method uses a single diagnostic character for species delimitation, i.e., the arc of maximal convexity of the shell's outline. Using this classification system, 10 species were recognized for far eastern Russia under the genus Nodularia Conrad, 1853, divided into three subgenera: Nodularia s. str., Amurunio and Magadaninaia. Since it is not supported by any other classification methods, the current comparatory classification is rejected by many Russian and international scientists, who only recognize a single species for that region, i.e., Nodularia douglasiae. Therefore, the aim of the present study is to clarify the taxonomy and systematics of the Nodularia genus in far eastern Russia and adjacent territories, using a multiple dataset approach that combines distribution with detailed conchological and anatomical analyses with morphometry and COI barcoding molecular techniques. All analyses performed in this study support the existence of a single Nodularia species in eastern Russia, i.e., N. douglasiae.     

Salinity reduction of the end-Triassic sea from the Alpine region into northwestern Europe

A palaeoecological analysis of the Penarth Group (='Rhaetic') of southern England and Wales is undertaken in terms of a species-richness comparison with the Zlambach and Kössen Beds of the Austrian Alps. The three groups studied, bivalves, foraminifers and ostracodes, comprise the most important invertebrate faunas occurring in the deposits cited. All show significant diversity from the Alps into northwest Europe. Coupled with the disappearance of stenohaline elements including ammonites, and taking into account other facies information, the evidence suggests a transgression of a shallow epicontinental sea in northwest Europe at the end of the Triassic. The salinity of this sea (˜25–30%□) was appreciably below that of the Tethyan ocean.     

Developmental stability is not disrupted by extensive hybridization and introgression among populations of the marine bivalve molluscs Mytilus edulis (L.) and M. galloprovincialis (Lmk.) from south-west England

The effects of hybridization and introzgression were assessed among two naturally hybridizing bivalve molluscs (the mussels Mytilus edulis and M. galloprovincialis) from western Europe to estimate how disruptive these processes are to developmental stability (measured in terms of morphological variability). Ten shell traits were measured for 392 mussels from four allopatric populations (two each of At. edulis and At. galloprovincialis) and two hybrid populations. An index of variability (defined as Z_i= |y_i–y_i where y_; is the population mean of the length-standardized trait, and y_i is the individualcar;s length-standardized trait value) was constructed for each trait, and for the sum of the traits. The hybrid populations did not exhibit greater mean variability than the allopatric populations for any of the indices. Upon pooling, the hybrid populations had significantly lower variability than the pooled M. edulis populations and the pooled M. galloprovincialis populations in two analyses, and had similar means in the remaining nine analyses. Where significant differences existed, the pooled M. galloprovincialis had lower levels of mean trait variability than the pooled M. edulis. Among the two hybrid populations, the putative Fl hybrids and backcross individuals exhibited means of trait variability which were similar to those of the parental types. Thus, extensive hybridization and introgression do not adversely affect developmental stability among these mussel populations. There was a strong significant correlation between the ranking of indices (based on the amount of variability) across all six populations, indicating that a large genetic component determines the measured morphological variability. It is concluded that the genes or gene complexes which control morphological development in M. edulis and M. galloprovincialis arc very similar, providing further evidence of the close evolutionary relatedness of these mussel taxa.