Veliger larvae of dreissenids (Bivalvia,Dreissenidae) in the plankton foodweb of Rybinsk Reservoir

The abundance dynamics of adult dreissenids (Dreissena polymorpha (Pallas) and D. bugensis Andrusov) and of their larvae and the spatial distribution of the abundance of veligers and their role in the functioning of the plankton community have been analyzed on the basis of the data of original long-term monitoring (2004–2013) in Rybinsk Reservoir. The dreissenid veligers are most abundant in the summer time (July to August) when their number is comparable to that of the filter-feeding crustaceans and their biomass is close to that of rotifers. Before 2010 the production of veligers during the vegetation season comprised about 5% of the production of metazooplankton and the food consumption was about 1% of the primary production of phytoplankton. Pelagic invertebrate predators consumed about 90% of the production of veligers for the vegetation period. After 2010, the abundance of dreissenid larvae and their functional characteristics decreased by a factor of 5–6. Trophic relationships between zooplankton and veligers are discussed.     

Characterization of intracytoplasmic prokaryote infections in Dreissena sp. (Bivalvia: Dreissenidae)

This study characterizes intracytoplasmic infections with prokaryote microorganisms in Dreissena sp. (near Dreissena polymorpha) from northeastern Greece and represents the first report of such infections in freshwater bivalves. Light microscope observations of stained tissues revealed basophilic, cytoplasmic inclusion bodies in 87.5% (28/32) of the mussels sectioned. Inclusions in epithelial cells and connective tissues were noted, respectively, in 34.4 and 71.9% of the sample, with 5 mussels (15.6%) having both tissue types infected. Epithelial cell infections were observed in histological sections only in digestive gland tubules and ducts; within tubules, inclusions were present more often in secretory than digestive cells. Connective tissue infections, however, were systemic; among the 32 mussels sectioned, inclusions were found in the gills (65.6%), foot (12.5%), mantle (9.4%), labial palps (6.3%), digestive gland (6.3%), stomach (6.3%), and gonads (3.1%). Cytoplasmic inclusions (maximum dimension, 138 microm) were prominent enough in the gills to be visible in 17.0% of the 247 mussels dissected. Ultrastructurally, prokaryote cells in gill connective tissues were clearly characteristic of Chlamydiales-like organisms, with each intracytoplasmic inclusion containing a loosely packed mixture of elementary, reticulate, intermediate bodies, and blebs. Prokaryote colonies in digestive gland epithelial cells exclusively contained 1 of 4 morphological cell types and were considered Rickettsiales-like. Hexagonal, virus-like particles were present in the cytoplasm of the largest of these Rickettsiales-like prokaryotes. Although host stress was evident from localized cell necrosis and dense hemocyte infiltration, overall infection was fairly benign, with no major, adverse impact on body condition evident among sectioned or dissected mussels. A possible negative effect was partial constriction of gill water tubes, but at the infection intensity observed (typical range 1 to 7 inclusion bodies per section), significant interference with respiration and other metabolic functions of the gills was highly unlikely.     

Field and laboratory studies of Ophryoglena sp. (Ciliata: Ophryoglenidae) infection in zebra mussels,Dreissena polymorpha (Bivalvia: Dreissenidae)

This study, conducted in the Dnieper-Bug Canal in Belarus, is the first to monitor the seasonal (June-November) dynamics of infection with the parasitic ciliate Ophryoglena sp. in a zebra mussel (Dreissena polymorpha) population. Mean population prevalence and intensity of infection varied, respectively, from 11 to 62% and from 0.9 to 24.1 ciliates/mussel. Mean prevalence was highly correlated with mussel length in mussels <20 mm (R(2)=0.97) and was lower in larger mussels. Mean infection intensity in mussels 1-25 mm long was similarly correlated with their size (R=0.98), reached a maximum in the 20-25 mm size-class, and then sharply decreased, thus providing evidence, albeit limited, that high intensity of infection might be lethal. Transinfection of zebra mussels by Ophryoglena sp. was achieved in the laboratory-a first for a protozoan parasite of D. polymorpha; from an initial complete lack of infection, mean prevalence and intensity rose, respectively, to 86.7% and 8.3 ciliates/mussel.     

Microsatellite loci for dreissenid mussels (Mollusca: Bivalvia: Dreissenidae) and relatives: markers for assessing exotic and native populations

We developed and tested 14 new polymorphic microsatellite loci for dreissenid mussels, including the two species that have invaded many freshwater habitats in Eurasia and North America, where they cause serious industrial fouling damage and ecological alterations. These new loci will aid our understanding of their genetic patterns in invasive populations as well as throughout their native Ponto-Caspian distributions. Eight new loci for the zebra mussel Dreissena polymorpha polymorpha and six for the quagga mussel D. rostriformis bugensis were compared with new results from six previously published loci to generate a robust molecular toolkit for dreissenid mussels and their relatives. Taxa tested include D. p. polymorpha, D. r. bugensis, D. r. grimmi, D. presbensis, the 'living fossil'Congeria kusceri, and the dark false mussel Mytilopsis leucophaeata (the latter also is invasive). Overall, most of the 24 zebra mussel (N = 583) and 13 quagga mussel (N = 269) population samples conformed to Hardy-Weinberg equilibrium expectations for the new loci following sequential Bonferroni correction. The 11 loci (eight new, three previously published) evaluated for D. p. polymorpha averaged 35.1 alleles and 0.72 mean observed heterozygosity per locus, and 25.3 and 0.75 for the nine loci (six new, three previously published) developed for D. r. bugensis. All but three of these loci successfully amplified the other species of Dreissena, and all but one also amplified Congeria and Mytilopsis. All species and populations tested were significantly divergent using the microsatellite data, with neighbour-joining trees reflecting their evolutionary relationships; our results reveal broad utility for resolving their biogeographic, evolutionary, population and ecological patterns.     

Underyearlings of dreissenid mussels (Dreissenidae,Bivalvia) in the phytophylic communities in the mouth area of the Rybinsk Reservoir tributary

The data on the abundance and biomass of dreissenid underyearlings in macrophyte stands in different zones of the mouth part of a small tributary of Rybinsk Reservoir are presented. The highest density and biomass of underyearlings are recorded in the transient zone of the reservoir and the river mouth cross section. It is shown that the number of dreissenid underyearlings inhabiting the mouth area has not changed considerably in the years with unfavorable meteorological conditions.     

Dreissenid species (Mollusca,Dreissenidae) in the Upper Volga reservoirs

The results of our long-term studies of populations of two dreissenid species (Dreisena polymorpha Pallas, 1771 and D. bugensis Andrusov, 1897) in Rybinsk and Gorkii reservoirs have been analyzed. New habitats of D. bugensis have been found in Rybinsk Reservoir.     

Wide tolerance to environmental conditions and substrate colonization mediates the invasion of false mussels (Bivalvia: Dreissenidae) in brackish systems

Biological Invasions - False mussels are recognized as the brackish water equivalent of zebra mussels, although the abiotic and habitat conditions that mediate these invaders’ success are...     

Molecular resolution of the family Dreissenidae (Mollusca: Bivalvia) with emphasis on Ponto-Caspian species, including first report of Mytilopsis leucophaeata in the Black Sea basin

Considerable uncertainty exists in determination of the phylogeny among extant members of the Dreissenidae, especially those inhabiting the Ponto-Caspian basin, as multiple systematic revisions based on morphological characteristics have failed to resolve relationships within this group of bivalves. In this study we use DNA sequence analyses of two mitochondrial gene fragments, 16S rRNA and cytochrome c oxidase subunit I (COI), to determine phylogenetic relationships among Dreissena rostriformis, D. bugensis, D. polymorpha, D. stankovici, Congeria kusceri, and Mytilopsis leucophaeata. Dreissena stankovici was determined to represent a sister taxa to D. polymorpha and both are more closely related to other extant Dreissena species than Congeria or Mytilopsis. Sequence divergence between D. rostriformis and D. bugensis was relatively low (0.3-0.4%), suggesting that these two taxa constitute a single species. However, environmental differences suggest two races of D. rostriformis, a brackish water race (rostriformis) and a freshwater race (bugensis). Spread of bugensis-type individuals into habitats in the Caspian Sea that are occupied by rostriformis-type individuals may create novel hybridization opportunities. Species-specific molecular markers also were developed in this study since significant intraspecific variation in morphological features complicates dreissenid identification. Using two gene fragments (nuclear 28S and 16S), we identified restriction fragment length polymorphisms (RFLPs) that distinguish among D. rostriformis/bugensis, D. polymorpha, and D. stankovici and revealed the presence of a cryptic invader to the Black Sea basin, Mytilopsis leucophaeata. This is the first report of this North American native in southern Europe.     

Genetic studies on the Asmat population (Irian-Jaya, Indonesia)

The Asmat are a population of about 35,000 people living on the South-West coast of Irian-Jaya (Indonesia; New Guinea). This paper presents the results of enzyme group and serum protein group typings in a sample of Asmats living in the coastal region around Agats. Red cell enzyme polymorphisms (EaP, PGM1, 6-PGD, EsD, ADA and AK) could be typed in 154 blood samples, serum protein polymorphisms (Ge, alpha 1-AT, PLG, Tf and Hp) in 160 blood samples. The results of this study are discussed in detail.     

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...     

Genetic studies of blood markers in Przewalski's horses

Ninety-six Przewalski's horses (Equus przewalskii) were blood typed using systems of inherited blood variants known to be highly effective for parentage testing of domestic horses (E. caballus). Sixteen red cell antigenic factors detected using sera prepared by alloimmunization of domestic horses were shown to be inherited in six systems (A, C, D, P, Q, and U) and in the same patterns as domestic horses. Family data confirmed autosomal, codominant inheritance at five loci of serum protein variants (Al, Tf, Xk, Pi, and Es) and three loci of red cell proteins (PGM, PHI, and Hb). One serum protein locus (Gc) and two red cell protein loci (PGD and CA) appeared to be monomorphic. Despite the narrow genetic base and high inbreeding coefficients of captive Przewalski's horses, average heterozygosity calculated over 18 loci was estimated to be 0.320 +/- 0.05, which was similar to that found in five breeds of domestic horses.     

Genetic studies in the Garfagnana population (Tuscany, Italy)

The relationship between geographic isolation and historical-demographic features and genetic structure and pattern of variation of genetic markers was analyzed in the population of Garfagnana, a semi-isolated mountainous area in the province of Lucca (Italy), taking into account hierarchical subdivisions. A random sample of unrelated individuals, whose parents were both born in this area, was typed for AB0, MN, Kell, Rh, AK, EsD, 6-PGD, AcP and ABH secretor status. The village samples were aggregated into larger population units: Two districts and six subdistricts. Comparisons were performed with population samples of the plain and the coastal area of the same province (Lucca). Phenotype and genetic differentiations among and within subdivisions were studied using G2, R statistic, Nei's method, Harpending & Ward's method and analysis of genetic distance and similarity matrices. The various parameters consistently show significant heterogeneity among the subdivisions, both at district and at subdistrict level. As expected, the gene diversity between and within subdivisions varies according to their distinctive features of isolation.     

mtDNA analysis of <Emphasis Type="Italic">Mytilopsis</Emphasis> (Bivalvia,Dreissenidae) invasion in Brazil reveals the existence of two species

The present study sought to identify general patterns of genetic variability and structure of fish stocks (migratory and non-migratory species) along one of the largest Brazilian rivers, the São Francisco. Given that genetic variability of populations of all organisms is governed by both present and past influences, herein we investigate both these aspects by evaluating the current genetic differences between populations of five species (Leporinus piau, Megaleporinus reinhardti, Pimelodus maculatus, Prochilodus argenteus, and Pygocentrus piraya) along the entire extension of the river, as well as their demographic history. Analyses were done through sequences of two mitochondrial fragments and microsatellite data. In general, the data showed no support for recent fragmentation of stocks by the dams present in this river, and that all species show signs of past population expansion. We discuss the possible reasons for the common patterns found between these species, including the influence of the river’s topography and history.     

Tissue Hemoglobins in Bivalvia (Mollusca)

Distribution and properties of tissue hemoglobins in bivalves are reviewed. The mollusk gills are given particular attention; data on their functions, relative weight, and surface area as well as the content, properties, and functional importance of gill hemoglobin are reviewed.     

Genetic diversity studies of Kherigarh cattle based on microsatellite markers

We report a genetic diversity study of Kherigarh cattle, a utility draught-purpose breed of India, currently declining at a startling rate, by use of microsatellite markers recommended by the Food and Agriculture Organization. Microsatellite genotypes were derived, and allelic and genotypic frequencies, heterozygosities and gene diversity were estimated. A total of 131 alleles were distinguished by the 21 microsatellite markers used. All the microsatellites were highly polymorphic, with mean (±s.e.) allelic number of 6.24 ±1.7, ranging 4–10 per locus. The observed heterozygosity in the population ranged between 0.261 and 0.809, with mean (±s.e.) of 0.574 ±0.131, indicating considerable genetic variation in this population. Genetic bottleneck hypotheses were also explored. Our data suggest that the Kherigarh breed has not experienced a genetic bottleneck in the recent past.     

The invasive dark falsemussel <Emphasis Type=Italic>Mytilopsis leucophaeata</Emphasis> (Bivalvia: Dreissenidae): a literature review

This paper reviews literature from the Americas and Europe on the dark falsemussel Mytilopsis leucophaeata (Conrad in J Acad Nat Sci Phila 6(2):256–268, 1831), including data collected in its native habitat in the Americas that appear as incidental information in published reports. Mytilopsis leucophaeata is a poorly studied dreissenid bivalve that is native to mainly oligohaline–mesohaline regions of estuaries in North America. In its native habitat, it usually occurs in very low numbers and has rarely been mentioned in field survey reports. However, occasionally in its native habitat and often in habitats where it has been introduced (as in Europe and Brazil), it may undergo population irruptions for no clear reason. This review describes habitat characteristics, environmental tolerances, and biological and ecological attributes of the species. The assembled information reveals the species to be euryhaline and eurythermal, with an unexplained ability to persist in its native estuaries even though it is relatively short-lived and usually uncommon.     

Genetic studies on human thyroxine-binding globulin (TBG)

Summary An enzyme immunoassay technique combined with Western blotting is described to demonstrate thyroxine-binding globulin (TBG) by isoelectric focusing in thin-layer polyacrylamide gels with 8mol/l urea. Quantitative evaluation was by laser densitometry. No genetic charge variants of TBG were encountered in a sample of 840 unrelated individuals from southwestern Germany. There was no correlation between structural and quantitative variations in the TBG protein. Results from a family with quantitative TBG deficiency strongly support the postulated X-linked mode of inheritance. The method described can be considered as an additional diagnostic tool in thyroid evaluation.     

Reproduction and sperm structure in Galeommatidae (Bivalvia, Galeommatoidea)

Reproduction and/or sperm structure was studied in 18 species belonging to five genera of Galeommatidae from Phuket Island, Andaman Sea, Thailand, and Hong Kong. Incubation of the ova occurs in the inner and outer demibranchs of both gills, and sperm is most probably transferred to the ctenidial brood chamber as masses of agglutinated and non-encapsulated spermatozoa. The smallest specimens are males, but change into the female sex and there is a strong indication that some of the species are alternate hermaphrodites. Dwarf males occur in one species (Galeomma layardi). The sperm of all 18 species studied are of the ent-aquasperm type with a more or less hemispherical acrosome that is tilted with respect to the long axis of the moderately elongated nucleus. It is suggested that this type of sperm affords the best autapomorphy for the family Galeommatidae.