Growth Biorhythms of the Freshwater Pearl Mussel Margaritifera margaritifera (Bivalvia,Margaritiferidae), Nemina River Population (Karelia)

Biology Bulletin - Individual linear growth was studied in 23 specimens of the freshwater pearl mussel Margaritifera margaritifera by measuring successive annual growth rings on the shell surface....     

Pearl mussels of the genus Dahurinaia (Bivalvia,Margaritiferidae): Differently sized groups of Margaritifera dahurica Middendorff, 1850

Molecular and genetic studies have revealed that all five species of pearl mussels of the genus Dahurinaia (Bivalvia, Margaritiferidae) inhabiting the upper basin of the Amur River on the territory of Transbaikalia belong to Margaritifera dahurica Middendorff, 1850. Based on the statistical analysis, it has been shown that morphometric shell ratios form continuous variation series without differentiation on discrete groups. It has been found that changes in these ratios are caused by the shell growth of pearl mussels and their morphological variations reflects the high level of polymorphism. The so-called “comparator” species of the genus Dahurinaia are differently sized groups of one polymorphic biological species M. dahurica.     

Diel variation of the RNA/DNA ratios in Crassostrea angulata (Lamarck) and Ruditapes decussatus (Linnaeus 1758) (Mollusca: Bivalvia)

The aim of this study was to investigate the effect of time of day on RNA/DNA ratios among fed and starved Crassostrea angulata and Ruditapes decussatus juveniles. Sampling to investigate the day and night condition of juveniles was carried out for 48 h. A highly sensitive method for nucleic acid quantification was applied to bivalves. The results suggest that there is some variation in nucleic acid quantities with the time of the day. For the two species analysed, the RNA/DNA ratio was particularly high during the night and was higher in the fed animals. The results seem to indicate that there is some endogenous rhythm in the production of RNA. If there are diel changes in RNA/DNA ratios, it follows that average RNA/DNA ratios can be unrepresentative if there is any day or night bias in sampling.     

A lengthy discussion concerning the composition of the genus Margaritifera Schum., 1915 (Mollusca, Bivalvia)

The arguments given by Bolotov et al. (Ivz. Ross. Akad. Nauk, Ser. Biol., 2013, no. 2, pp. 245–256) were shown to be invalid because the allometric growth of mollusks was not taken into account.     

Electrophoretic study of gene-enzyme systems in oysters classified as Crassostrea gigas (Thunberg, 1793) and Crassostrea angulata (Lamarck, 1819) (Mollusca: Ostreidae)

As a further contribution to the systematics of species belonging to the genus Crassostrea, electrophoretic studies of gene-enzyme system have been carried out on five populations of oysters regarded as either Crassostrea gigas or Crassostrea angulata species. Two populations of C. gigas from Japan (Karakawa and Hiroshima), one of C. gigas from France (Fouras), one of C. angulata from Portugal (Sado) and one of Crassostrea sp. from Italy (Chioggia) have been examined. The electrophoretic study of 20 enzyme loci and the genetic distance value showed no significant genetic divergence among the Crassostrea sp. populations. Thus the results of this study seem to confirm and extend to other populations what obtained by Buroker et al. (1979), that is a remarkable genetical identity between the two species Crassostrea gigas and Crassostrea angulata.     

Effect of zinc and benzene on respiration and excretion of mussel larvae (Perna perna) (Linnaeus, 1758) (Mollusca; Bivalvia).

The presence of pollutants in the ocean may affect different physiological parameters of animals. Oxygen consumption and ammonia excretion were evaluated in D-shaped larvae of mussels (Perna perna) exposed to zinc sulphate (ZnSO(4)) and benzene (C(6)H(6)). When compared to the control group, both pollutants presented a significant reduction in oxygen consumption. A reduction in the ammonia excretion was also observed, both for ZnSO(4) and C(6)H(6) and also in the oxygen consumption. The results indicate that anaerobic metabolism may occur at the beginning of P. perna mussels development, as observed in veliger larvae. The O:N ratio under experimental conditions showed low values indicating that catabolism in veliger larvae was predominantly proteic.     

Biorhythms of <Emphasis Type="Italic">Margaritifera margaritifera</Emphasis> (Bivalvia,Margaritiferidae) Freshwater Pearl Mussel Growth: Population of Syuskyuyanioki River (Karelia)

It was demonstrated that individual linear growth of the Margaritifera margaritifera freshwater bivalve mollusk in Syuskyuyanioki River is accompanied by natural biorhythms. The periods of biorhythms, as well as growth retardation coefficients, vary widely and differ in different individuals. The periods of biorhythms in individual ontogenesis are approximately constant. Mean values of the growth retardation coefficients and periods do not depend on the biotope and are 0.114 ± 0.003 year^–1 and 3.88 ± 0.06 years, respectively. The possibility of thermodynamic nature of biorhythms is discussed.     

Effects of epibiotic algae on the survival, biomass and recruitment of mussels, Mytilus L. (Bivalvia: Mollusca)

Habitats composed of living ‘ecosystem engineers’, such as mussels, are subject to direct and indirect interactions with organisms that live among them. These interactions may affect the presence and structure of habitat, and hence, the associated taxa. We examined the direct effects of epibiotic algae on the survival, biomass and recruitment of mussels (Mytilus L.) on the west coast of Ireland. A field experiment showed that the presence of epibiotic fucoid algae reduced the likelihood of survival of mussels during storms. We also found that the strength of attachment of mussels did not increase in the presence of epibionts. Another in situ experiment revealed that the presence of ephemeral epibiotic algal mats had no effect on the biomass of host mussels, suggesting no effect on mussel growth or production. The abundance of small mussels (< 5 mm) covaried with cover of epibiotic algae at one location, but experimental results suggest no direct effect of the algae on recruitment unless through the action of chemical cues which linger after the removal of algae. We have identified a negative direct interaction between epibiotic algae and mussels on exposed rocky shores, which may often be characterised by bottom-up regulation. It is thought that positive interactions may be more important on more sheltered or sedimentary shores where top-down processes are more likely to dominate.     

Comparison of the soluble organic matrices of healthy and diseased shells of Pinctada margaritifera (L.) and Pecten maximus L. (Mollusca, Bivalvia)

Pinctada margaritifera and Pecten maximus are among the mollusks of commercial value. Both are known to show abnormal calcification processes that strongly increase the mortality rate. Several parameters of the soluble organic matrices extracted from the shells of P. margaritifera and P. maximus are analyzed: bulk composition, molecular weights, and acidity. The composition of the matrices of healthy and diseased shells were compared, showing that the protein and the sugar contents are variously modified. Differences between healthy and diseased shells are dissimilar in the two species. This is in accordance with the previously described macroscopic and microscopic alterations (red color, numerous brown membranes). This study does not allow identification the origin of the disease, but provides new insights on the role of sugars in biomineralization processes.     

A population genetic study of the hybrid zone of Mytilus trossulus Gould, 1850 and an introduced species,M. galloprovincialis Lamarck, 1819, (Bivalvia: Mytilidae) in peter the great bay in the Sea of Japan

This paper examines the genetic variability of the Pacific mussel Mytilus trossulus and an introduced Atlantic species, M. galloprovincialis, in the northwestern Sea of Japan (Peter the Great Bay and Kievka Bay). The genotyping of individuals from eight populations was carried out using eight polymorphic enzyme loci and two nuclear DNA markers (Me-5 and ITS-1,2); the occurrence frequency of parent species and their hybrids was determined. The enzyme and nuclear markers demonstrated concordant genetic variation. The genotypes of the native species M. trossulus were predominant in the samples studied. The frequency of the introduced species M. galloprovincialis in the total material was relatively low; however, it reached 42 ± 2% in samples that were collected in Possjet Bay near the town of Zarubino in a zone of active international navigation. In this area the greatest number of hybrids was found as well. It is concluded that the invasion of M. galloprovincialis in the northwestern Sea of Japan is continuing; permanent populations of this mussel appeared in Possjet Bay that were not recorded here previously.     

On the synonymy of two species names of the genus <Emphasis Type="Italic">Aphodius</Emphasis> Ill. (Coleoptera,Scarabaeidae) described by S. M. Iablokoff-Khnzorian

Based on examination of the type material, names of two Aphodius species are placed in synonyms: A. edgardi Solsky, 1876 = A. sartus Iablokoff-Khnzorian, 1971, syn. n.; and A. putridus Geoffroy, 1785 = A. avetissiani Iablokoff-Khnzorian, 1964, syn. n.     

<Emphasis Type=Italic>Pycnoscelus surinamensis</Emphasis> (Linnaeus, 1758) (Blaberoidea: Blaberidae), a cockroach with a possible association with the ant <Emphasis Type=Italic>Brachymyrmex cordemoyi</Emphasis> Forel, 1895 (Hymenoptera: Formicidae) and which may be exhibiting a domiciliation trend.

In the present paper, we report on the occurrence of the cockroach Pycnoscelus surinamensis (Linnaeus, 1758) in Brachymyrmex cordemoyi Forel, 1895 nests, indicating a possible symbiosis between these two species. Also, the finding of intradomicile P. surinamensis nymphs may indicate this species is extending its habitat to human habitations, i.e. changing its ecological category from peridomestic to domestic.