Dynamics of skeleton formation in the Lake Baikal sponge Lubomirskia baicalensis. Part II. Molecular biological studies

In a preceding study it has been reported that the freshwater sponge Lubomirskia baicalensis, living in Lake Baikal (East Siberia), is composed of spicules forming a characteristic pattern which follows radiate accretive growth. Here we report that the spicules are synthesized by the enzyme silicatein, a protein which is related to cathepsin L. The cDNAs for silicatein and the related cathepsin L were isolated and used as probes to show that the mRNA levels of silicatein in the bases of the spicule skeleton of the animals are low, while the mRNA level of cathepsin L in this region exceeds that of the growing zone. This is the first comprehensive study on the importance of the axial filament/silicatein as an essential structural and functional component determining the growth and stability of demosponge spicules.Note: Sequences from Lubomirskia baicalensis have been deposited in the EMBL/GenBank; cDNAs for the putative silicatein (LBSILICA) are deposited under the accession no. AJ786771 and for cathepsin L (LBCATL) under the accession no. AJ786770.     

Earthworm resources of Benghazi, Libya

This study presents the first survey of earthworm species (Oligochaeta) from Benghazi, a Mediterranean coastal city in Libya. A total of three peregrine species were recorded: Allolobophora caliginosa trapezoides, Allolobophora rosea (Family: Lumbricidae), Microscolex dubius (Family: Microscolecidae). Their distribution and density in six habitats (vegetable garden, flower garden, green house, farmland, grassland, plain barren landscape) are discussed in relation to some of the physico-chemical parameters and composition of the soil.     

Toxicological study of plant extracts on termite and laboratory animals

Toxic activity of leaf extracts of Polygonum hydropiper L. and Pogostemon parviflorus Benth. were tested in the laboratory against tea termite, Odontotermes assamensis Holm. Both the tested extracts caused mortality of the termite. The highest toxic activity (100%) was found in the 2.0% chloroform extracts of P. hydropiper. The chloroform extract of P. hydropiper was explored for possible mammalian toxicological effects. The LD50 was 758.58 mg/kg in male albino mice. Subcutaneous injection of sub-lethal dose of extract into male mice once a week for 6 weeks failed to express any significant influence on WBC, RBC count and blood cholesterol.     

Geochemistry and bioavailability of metals in sediments from northern San Francisco Bay

In this study, metals (Be, Cr, Mn, Fe, Ni, Cu, Zn, Ag, Cd, Pb and Hg) in the fine-grained fraction (<63 microm) from 12 sites at different locations in northern San Francisco Bay over a year period from March 2000 to March 2001 were analyzed after acid extraction. The results showed that metal concentrations in the sediments varied from site to site, whereas some of them were found elevated with respect to the sediment of Tomales Bay, CA, which has little contamination history, indicating an enrichment of the metals in the sediment samples analyzed. Sediment toxicity and bioaccumulation evaluation by a clam species, Macoma nasuta, exposed to the sediment samples collected from the six sampling sites was carried out. The results showed that the sediment samples tested significantly reduced clam survival. Toxicity of the sediments to the clam was, in part, related to elevated metal concentrations in the sediments. In order to examine geochemistry of the metals and to understand potential correlations between metal concentrations and geochemical matrix elements of the sediments, bioavailability and toxicity of the metals, detailed analysis of metal concentrations associated with total organic carbon and the Fe-oxy-hydroxides in the sediment samples was performed. The analysis showed that sediment geochemistry appeared to influence metal bioavailability and may have important impacts on the toxicity of these metals to the clam.     

Radioactivity of the soil in Vojvodina (northern province of Serbia and Montenegro)

The widespread public belief that during the bombardment of Vojvodina (Yugoslavia) this region was contaminated by depleted uranium has recently raised public concern with respect to the potential contamination of agricultural products due to soil radioactivity. Based on the gamma-spectrometric analysis of 50 soil samples taken from the region of Vojvodina we concluded that there is no increase of radioactivity that could endanger the food production. Taking into account the transfer factors of 137Cs to plants, the measured activity concentrations of this isotope should not endanger the health safety of the produced food. No traces of depleted uranium have been found. The natural radioactivity levels are compared with the results form other countries.     

Derivation of ecotoxicity thresholds for uranium

Assessment of the risk of impact from most radionuclides is based on the total radiological dose rate to the organism of concern. However, for uranium (U) there can be greater risk from chemical toxicity than radiological toxicity (depending on the isotopic composition). Chemical ecotoxicity of U is dependent on several environmental parameters. The most important are carbonate content, because of the formation of soluble carbonate complexes, and divalent cation content (Ca++ and Mg++), because of their competitive interaction with the uranyl ion (UO2++). This study summarizes the literature available to set PNECs (predicted no-effect concentrations) for chemical toxicity of U to non-human biota. The corresponding radiological doses were estimated, and as expected chemical toxicity proved to be the greater concern. There were limited data from some types of biota; however, PNECs for the types of biota of interest were as follows: terrestrial plants--250 mg U kg(-1) dry soil; other soil biota--100 mg U kg(-1) dry soil; freshwater plants--0.005 mg U L(-1) water; freshwater invertebrates--0.005 mg U L(-1) water; freshwater benthos--100 mg U kg(-1) dry sediment; freshwater fish at water hardnesses of: <10 mg CaCO3 L(-1) (very soft water)--0.4 mg U L(-1) water; 10-100 mg CaCO3 L(-1) (soft water)--2.8 mg U L(-1) water; and >100 mg CaCO3 L(-1) (hard water)--23 mg U L(-1) water; or as a function of hardness--0.26 (hardness as mg CaCO3 L(-1); mammals--0.1 mg U kg(-1) body weight d(-1).     

Modelling and experimental studies on the transfer of radionuclides to fruit

Although fruit is an important component of the diet, the extent to which it contributes to radiological exposure remains unclear, partially as a consequence of uncertainties in models and data used to assess transfer of radionuclides in the food chain. A Fruits Working Group operated as part of the IAEA BIOMASS (BIOsphere Modelling and ASSessment) programme from 1997 to 2000, with the aim of improving the robustness of the models that are used for radiological assessment. The Group completed a number of modelling and experimental activities including: (i) a review of experimental, field and modelling information on the transfer of radionuclides to fruit; (ii) discussion of recently completed or ongoing experimental studies; (iii) development of a database on the transfer of radionuclides to fruit; (iv) development of a conceptual model for fruit and (v) two model intercomparison studies and a model validation study. The Group achieved significant advances in understanding the processes involved in transfer of radionuclides to fruit. The work demonstrated that further experimental and modelling studies are required to ensure that the current generation of models can be applied to a wide range of scenarios.     

Transformation of ecological conditions of soil and humus substance formation in the urban environment

Ecological conditions of soil formation and specific features of humus substance formation are considered with regard to urban soils of different types formed in the following functional zones: the park zone, residential area, and sanitary protective zone of the Middle Ural Copper-Smelting Plant. The specificity of soil formation in Revda, a typical industrial city of the Middle Urals, is determined by the combined effect of urban and technogenic factors (urbogenesis and technogenesis), with the former being of primary importance. At a constant period of biological activity, the depth of humification is primarily a function of granulometric and chemical composition of urban soils.Translated from Ekologiya, No. 1, 2005, pp. 11–19.Original Russian Text Copyright © 2005 by Meshcheryakov, Prokopovich, Korkina.     

Gradient Genogeographic Analysis of <Emphasis Type="Italic">Pinus sylvestris</Emphasis> L. Populations in Europe

Gradients of Nei's genetic distances between 15 samples of Pinus sylvestris L. trees were analyzed along three submeridional transects, from Scandinavia to the Mediterranean and Transcaucasia. As a result, distinct chorogenetic differentiation was revealed between the populations of this species growing in climatically specific regions of northern and southern Europe. Considerable Nei's distances (DN = 0.045–0.056) and their gradients, combined with differences in stable phenotypic characters (the composition of monoterpenes and morphological parameters of cones) determined at the Pyrenean and Caucasian mountain borders, suggest that the P. sylvestris species structure includes two South Eurasian subspecies, the Pyrenean P. sylvestris L., ssp. iberica Svoboda and the Transcaucasian P. sylvestris L., ssp. hamata (Stev.) Fomin.     

Ecological Mechanisms of the Formation of Biological Rhythms in Hibernators of the Family Sciuridae in Northeastern Siberia

A mechanism of the formation of biological rhythms in hibernators at cold temperatures is proposed. Certain ecophysiological characteristics have been studied in three hibernating species: the ground squirrels Citellus undulatus Pallas, 1778 and C. parryi Richardson, 1825 and the chipmunk Tamias sibiricus Laxmann, 1769. The changes in body temperature and the temperature of litter in wintering nests during hibernation seasons have been studied. The dependences of metabolic rate on ambient temperature and the size and species of animals have been studied.