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611.
This study analyses the temporal and spatial changes in abundance and distribution of the warm water species round sardinella (Sardinella aurita) in the western Mediterranean over the last decades in relation to sea water temperature. In the western Mediterranean basin (1950–2003), a significant positive relationship was found between round sardinella landings and temperature anomalies. Along a latitudinal gradient off the Mediterranean Iberian coast (1989–2004), a gradual increase in species abundance was observed from south to north, with a certain time lag going northwards, associated with the increase in sea water temperature. The abundance of round sardinella in the two warmest and southernmost areas was positively and significantly correlated with sea surface temperature registered during the start of gonad maturation the previous year. In addition, the positive relationship established between water temperature and abundance of round sardinella in the coldest and northernmost study area demonstrates that there is a temperature limit for the distribution of this species in the western Mediterranean. In addition, this study analyses round sardinella larvae distribution and abundance in the summers of 2003 and 2004, and conducts a comparison with the situation 20 years ago (summer 1983). Results show a marked increase in larval abundance during the last decades and the present appearance of larvae in the northernmost study areas, where they did not occur 20 years ago. This indicates the successful reproduction of round sardinella in the northern part of the Mediterranean, where the species has expanded, confirming its establishment in the area. 相似文献
612.
ZISSIS MAMURIS MARIA TH. STOUMBOUDI COSTAS STAMATIS ROBERTA BARBIERI KATERINA A. MOUTOU 《Freshwater Biology》2005,50(9):1441-1453
1. The genetic variation of the endangered freshwater fish Ladigesocypris ghigii, endemic to the island of Rhodes (Greece), was investigated for nine populations, originating from seven different stream systems and a reservoir, both at the mtDNA and nuclear level, in order to suggest conservation actions. 2. Both restriction fragment length polymorphism analysis of five segments of mitochondrial DNA (ND‐5/6, COI and 12S‐16S rRNA) amplified by polymerase chain reaction, and random amplified polymorphic DNA analysis, revealed extremely low levels of intra‐population polymorphism. It is highly likely that the low intra‐population variability is the result of successive bottleneck events evident in shrinkage and expansion of the populations year after year, which may have led to a complete loss of several genotypes and haplotypes, and an increased degree of inbreeding. 3. Inter‐population genetic structuring was high, with fixation of haplotypes within six of the nine populations and fixation of alleles within populations originating from different waterbodies. It is probable that all haplotypes and/or alleles found were initially represented in all populations. However, because of the long time of isolation coupled with successive bottleneck and subsequent genetic drift, common mtDNA haplotypes and alleles among the populations may have become rare or extinct through stochastic lineage loss. 4. Although nucleotide divergence among haplotypes was very shallow, half of the haplotypes recorded (three of six), resulted from nucleotide changes on the 12S–16S rRNA segments, which are the most conserved part of the mitochondrial genome. This fact may indicate that the observed genetic variation did not necessarily result only from the retention of ancestral polymorphism, but may have arisen through mutation and complete lineage sorting over a relatively small number of generations, once the populations had become isolated from one another. 5. Our data suggest that two of the L. ghigii populations may be on independent evolutionary trajectories. Considering that each population appears so far well adapted within each site, all populations should be managed and conserved separately. 相似文献
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614.
ANA RODRIGO‐MORENO NURIA ANDRÉS‐COLÁS CHARLOTTE POSCHENRIEDER BENET GUNSÉ LOLA PEÑARRUBIA SERGEY SHABALA 《Plant, cell & environment》2013,36(4):844-855
Transition metals such as copper can interact with ascorbate or hydrogen peroxide to form highly reactive hydroxyl radicals (OH?), with numerous implications to membrane transport activity and cell metabolism. So far, such interaction was described for extracellular (apoplastic) space but not cytosol. Here, a range of advanced electrophysiological and imaging techniques were applied to Arabidopsis thaliana plants differing in their copper‐transport activity: Col‐0, high‐affinity copper transporter COPT1‐overexpressing (C1OE) seedlings, and T‐DNA COPT1 insertion mutant (copt1). Low Cu concentrations (10 µm ) stimulated a dose‐dependent Gd3+ and verapamil sensitive net Ca2+ influx in the root apex but not in mature zone. C1OE also showed a fivefold higher Cu‐induced K+ efflux at the root tip level compared with Col‐0, and a reduction in basal peroxide accumulation at the root tip after copper exposure. Copper caused membrane disruptions of the root apex in C1OE seedlings but not in copt1 plants; this damage was prevented by pretreatment with Gd3+. Our results suggest that copper transport into cytosol in root apex results in hydroxyl radical generation at the cytosolic side, with a consequent regulation of plasma membrane OH?‐sensitive Ca2+ and K+ transport systems. 相似文献
615.
GABRIELE BIELLA GIANFAUSTO SALVADORI MARIA LUISA SOTGIU 《Somatosensory & motor research》2013,30(2):89-102
Using normal rats and rats with a chronic constriction injury of the sciatic nerve (injured, model of Bennett-Xie) we investigated the possibility of classifying, by statistical tools, the temporal sequences of neuronal discharges during different noxious and non-noxious stimuli. An analysis was made of both the distribution of the inter-spike intervals and the temporal density of spike trains, the latter being studied within the framework of stochastic universal multifractals, to allow the identification of different random processes involved in the discharge distributions through the Levy index alpha. The statistical analysis shows that the parametrization based on the Levy index seems able to discriminate between different noxious stimuli (mechanical pinching and thermal), both in normal and injured animals. Furthermore, comparing normal and injured animals, although the spontaneous basal and non-noxious stimuli (brushing) evoked activities presented different frequencies, these seem to have the same multifractal structure, while the corresponding statistics of the inter-spike intervals are quite different. This information might be relevant to the understanding of a code of neuronal firing and to the modelling of temporal patterns in acute and chronic noxious signals. 相似文献
616.
617.
PATRIZIA TRIFILÒ FABIO RAIMONDO MARIA A. LO GULLO PIERA M. BARBERA SEBASTIANO SALLEO ANDREA NARDINI 《Plant, cell & environment》2014,37(11):2491-2499
Diurnal changes in percentage loss of hydraulic conductivity (PLC), with recorded values being higher at midday than on the following morning, have been interpreted as evidence for the occurrence of cycles of xylem conduits' embolism and repair. Recent reports have suggested that diurnal PLC changes might arise as a consequence of an experimental artefact, that is, air entry into xylem conduits upon cutting stems, even if under water, while under substantial tension generated by transpiration. Rehydration procedures prior to hydraulic measurements have been recommended to avoid this artefact. In the present study, we show that xylem rehydration prior to hydraulic measurements might favour xylem refilling and embolism repair, thus leading to PLC values erroneously lower than those actually experienced by transpiring plants. When xylem tension relaxation procedures were performed on stems where refilling mechanisms had been previously inhibited by mechanical (girdling) or chemical (orthovanadate) treatment, PLC values measured in stems cut under native tension were the same as those measured after sample rehydration/relaxation. Our data call for renewed attention to the procedures of sample collection in the field and transport to the laboratory, and suggest that girdling might be a recommendable treatment prior to sample collection for PLC measurements. 相似文献
618.
619.
CARRIE S. THURBER MICHAEL REAGON BRIANA L. GROSS KENNETH M. OLSEN YULIN JIA ANA L. CAICEDO 《Molecular ecology》2010,19(16):3271-3284
Cultivated rice fields worldwide are plagued with weedy rice, a conspecific weed of cultivated rice (Oryza sativa L.). The persistence of weedy rice has been attributed, in part, to its ability to shatter (disperse) seed prior to crop harvesting. In the United States, separately evolved weedy rice groups have been shown to share genomic identity with exotic domesticated cultivars. Here, we investigate the shattering phenotype in a collection of U.S. weedy rice accessions, as well as wild and cultivated relatives. We find that all U.S. weedy rice groups shatter seeds easily, despite multiple origins, and in contrast to a decrease in shattering ability seen in cultivated groups. We assessed allelic identity and diversity at the major shattering locus, sh4, in weedy rice; we find that all cultivated and weedy rice, regardless of population, share similar haplotypes at sh4, and all contain a single derived mutation associated with decreased seed shattering. Our data constitute the strongest evidence to date of an evolution of weeds from domesticated backgrounds. The combination of a shared cultivar sh4 allele and a highly shattering phenotype, suggests that U.S. weedy rice have re‐acquired the shattering trait after divergence from their progenitors through alternative genetic mechanisms. 相似文献
620.
ANA M. IBARRA JESSICA L. PETERSEN THOMAS R. FAMULA BERNIE MAY 《Molecular ecology resources》2006,6(1):153-156
Four microsatellite‐enriched DNA libraries yielded 35 microsatellite loci from 100 primer pairs designed for Pacific lion‐paw scallop, Nodipecten subnodosus. The number of alleles ranged from four to 28. Three of the 35 loci were not in Hardy–Weinberg equilibrium and linkage disequilibrium was found for one pair of loci. These microsatellites will be used to analyse the population structure of the species in Mexico's Baja Peninsula to propose management strategies for scallop aquaculture development. Twenty‐six primer pairs cross‐amplified in Nodipecten nodosus, whereas none (Argopecten ventricosus) or few cross‐amplified in the Argopecten species. 相似文献