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51.
Using published records and original data from recent field work and revision of Iranian material of certain species deposited in the collections of the Natural History Museum Basel, the Zoological Museum Berlin, and Natural History Museum Vienna, a checklist of the freshwater gastropod fauna of Iran was compiled. This checklist contains 73 species from 34 genera and 14 families of freshwater snails; 27 of these species (37%) are endemic to Iran. Two new genera, Kaskakia and Sarkhia, and eight species, i.e., Bithynia forcarti, Bithynia starmuehlneri, Bithynia mazandaranensis, Pseudamnicola georgievi, Kaskakia khorrasanensis, Sarkhia sarabensis, Valvata nowsharensis and Acroloxus pseudolacustris are described as new to science; Ecrobia grimmi (Clessin & Dybowski, 1888), Heleobia dalmatica (Radoman, 1974) and Hippeutis complanatus (Linnaeus, 1758) are reported for the first time from Iran. Additional field work is highly desirable for a more appropriate evaluation of the extant freshwater snail biodiversity in Iran. 相似文献
52.
During the RNA World, organisms experienced high rates of genetic errors, which implies that there was strong evolutionary
pressure to reduce the errors’ phenotypical impact by suitably structuring the still-evolving genetic code. Therefore, the
relative rates of the various types of genetic errors should have left characteristic imprints in the structure of the genetic
code. Here, we show that, therefore, it is possible to some extent to reconstruct those error rates, as well as the nucleotide
frequencies, for the time when the code was fixed. We find evidence indicating that the frequencies of G and C in the genome
were not elevated. Since, for thermodynamic reasons, RNA in thermophiles tends to possess elevated G+C content, this result
indicates that the fixation of the genetic code occurred in organisms which were either not thermophiles or that the code’s
fixation occurred after the rise of DNA.
Supplementary Materials Original data and programs are available at the author’s web site: . 相似文献
53.
GNRA tetraloops, found in high frequency in natural RNAs, make loop-receptor interactions, stabilizing the tertiary structure of Group I introns, a class of small RNAs. Analyzing 230 Group I introns, to study the distribution and sequence pattern of the GNRA tetraloops, we suggest that these features reflect the ancestral nature of these catalytic molecules, in a prebiotic RNA world. The adenosine rich GNRA tetraloops would have interacted with each other through long range RNA-RNA interactions to form higher order structures forming potential sites that render the propensity for the short RNAs to bind to metal ions from the prebiotic pool, aiding them to act as metalloenzymes. 相似文献
54.
Overpopulation and deficient management of the worlds coastlines have seriously degraded beaches and coastal dunes, which are environments that provide valuable ecosystem services to society. The need to restore these ecosystems is increasingly urgent; however, this is a complex task since variables that differ widely (i.e. ecological, geomorphological and socio-economic) must all be taken into consideration. The present study proposes an index in the form of a weighted checklist named the “ReDune” Index (Restoration of coastal Dunes). This index allows decision makers and non-specialized professionals with some level of understanding of coastal dynamics to decide whether coastal dunes (foredunes) require and can be restored. Furthermore, in cases where more than one coastal dune system is to be evaluated, the index can distinguish which are in the most urgent need of restoration. The index consists of four sections: the first evaluates the degree of perturbation. The second determines the presence of endogenous and exogenous stress factors that may compromise the long-term stability of the restoration. The third section is focused on highlighting the abiotic and biotic elements that may facilitate restoration. Finally, the fourth section contributes to the identification of interests related to the conservation of the site and the provision of ecosystem services. The index was tested on 31 locations along the Gulf of Mexico, with differing sedimentary, ecological and human pressure characteristics and clearly distinguished between locations where restoration is urgent from those where it is not. This index can be applied on any foredune. 相似文献
55.
Franco Mason 《ZooKeys》2013,(336):61-78
An updated checklist for Stratiomyidae of Italy is presented. Previous knowledge and information are put together in a comprehensive way, integrated also with results obtained by sampling with Malaise traps in some of the test areas of the LIFE+ project ManFor C.BD.At the time of writing, with 91 known species, the Italian fauna of Stratiomyidae is the richest in Europe. Neopachygaster meromelas (Dufour, 1841) and Zabrachia minutissima (Zetterstedt, 1838) are new to the Italian fauna. A comprehensive key to the European species of Chorisops Rondani, 1856 is given. 相似文献
56.
Characters used in the taxonomy of the genus Lepidonella Yosii, 1960 (Collembola: Paronellidae) are listed and discussed. Several new ones are introduced. An overview of pseudopore patterns across Collembola is presented, with several new locations of these structures across Entomobryomorpha. Their interest at different taxonomic level is underlined. The genus Lepidonella is redefined. The American species L. marimuti Soto Adames &; Bellini, 2015 is placed in incertae sedis among Lepidonella. Lepidonella species of the world are listed with synonymies and combinations. The Malaysian troglobitic species Pseudoparonella doveri Carpenter, 1933 is redescribed in detail, with emphasis on its pattern of antennal chaetae, and transferred to the genus Lepidonella. Its close similarity with L. lecongkieti Deharveng &; Bedos, 1995 from southwestern Vietnam caves is underlined. This disjunct distribution is briefly discussed. 相似文献
57.
Yaroslav Staroseletz Sergey Nechaev Elena Bichenkova Richard A. Bryce Catherine Watson Valentin Vlassov Marina Zenkova 《Biochimica et Biophysica Acta (BBA)/General Subjects》2018,1862(3):705-725
Background
While the RNA world hypothesis is widely accepted, it is still far from complete: the existence of self-replicating ribozyme, consisting of potentially hundreds of nucleotides, is a core assumption for the majority of RNA world models. The appearance of such long RNA molecules under prebiotic conditions is not self-evident. Recombination seems to be a plausible way of creating RNA diversity, resulting in the appearance of functional RNAs, capable of self-replicating.Methods
We report here on the study of recombination process modelled with two 96 nts RNA fragments. Detection of recombination products was performed with RT-PCR followed by TA-cloning and Sanger sequencing.Results
A wide range of recombinant products was detected. We found that (i) the most efficient ligation was observed for RNA species forming bulges or internal loops, with ligation partners located within the loop; (ii) a strong preference was observed for formation of a few types of major products with a large variety of minor products; (iii) ligation could occur with participation of either 2′,3′-cyclophosphate or 5′-ppp; (iv) the presence of key reaction components, i.e. 5′ppp-RNAs, enabled the formation of additional types of product; (v) molecular dynamics simulations of one of the most abundant products suggests that the ligation results in a preferable formation of 2′-5′- rather than 3′-5′-linkages.Conclusions
The study demonstrates regularities of new RNA molecules formation with non-enzymatic recombination process.General significance
Our findings provide new data supporting the RNA World hypothesis and show the way of new RNA sequences emergence under prebiotic conditions. 相似文献58.
59.
《Journal of Industrial Ecology》2005,9(1-2):99-114
This article describes the integration of life-cycle assessment methods with a new input-output model of the world economy to analyze the environmental and economic implications of alternative future diets. The article reviews findings by industrial ecologists about the energy and land required for the production and consumption of alternative foods and diets in several European countries. It also reviews attributes of foods and diets identified by nutritionists as reducing the risks of obesity and major chronic diseases related to the diets of the affluent. The predominantly plant-based Mediterranean-type diet emerges as a dietary scenario that could satisfy both sets of concerns. The likely implications for agriculture and for farm policies of a shift toward this diet from the current average diet in the United States are discussed and shown to be substantial. The one-country studies reviewed in the article provide substantial insights into the potential ramifications of dietary change. Many of the limitations of these studies could be overcome by conducting the analysis in a global framework that represented the relationships among consumption, production, and trade and the physical constraints within which they operate. Analysis of the environmental and economic implications of alternative scenarios describing healthy diets can help stimulate more intensive dialogue, debate, and action among the interested parties; such analysis can both benefit from and contribute to initiatives such as the World Health Organization's global strategy on diet and health, which intends to enlist the support of governments, corporations, and civil society. 相似文献
60.
Two Issini genera, Sarima Melichar, 1903 and Sarimodes Matsumura, 1916, are examined. One new Sarima species: Sarima
bifurcus
sp. n. and two new Sarimodes species Sarimodes
clavatus
sp. n. and Sarimodes
parallelus
sp. n. are added from South China. A checklist of species in the genus Sarima with data on distribution is provided. The distribution and morphological peculiarities of the genera Sarima and Sarimodes are briefly discussed. 相似文献