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1.
We analysed monthly samples collected in Guanabara Bay, with a conical net of 200 m mesh during 1985. The bay was divided into three areas: an outer region (area A), influenced by oceanic waters; an inner region (area C), influenced by fluvial inflow; and a transition region (area B) with intermediate features. Penilia avirostris and Evadne tergestina were observed in the three areas, with greatest densities, however, in the outermost region, which had the highest salinities and lowest temperatures. Penilia avirostris was more abundant in summer (March), a period with the greatest relative densities of nanoplankton. Evadne tergestina was also abundant in summer, but its peak fell in November, a period with a relative increase in microphytoplankton density in the bay. The two species disappeared in winter: Penilia avirostris was absent from May to August, whereas Evadne tergestina disappeared in August and September. 相似文献
2.
Jena R. Hickey Janet Nackoney Nathan P. Nibbelink Stephen Blake Aime Bonyenge Sally Coxe Jef Dupain Maurice Emetshu Takeshi Furuichi Falk Grossmann Patrick Guislain John Hart Chie Hashimoto Bernard Ikembelo Omari Ilambu Bila-Isia Inogwabini Innocent Liengola Albert Lotana Lokasola Alain Lushimba Fiona Maisels Joel Masselink Valentin Mbenzo Norbert Mbangia Mulavwa Pascal Naky Nicolas Mwanza Ndunda Pele Nkumu Valentin Omasombo Gay Edwards Reinartz Robert Rose Tetsuya Sakamaki Samantha Strindberg Hiroyuki Takemoto Ashley Vosper Hjalmar S. Kühl 《Biodiversity and Conservation》2013,22(13-14):3085-3104
Habitat loss and hunting threaten bonobos (Pan paniscus), Endangered (IUCN) great apes endemic to lowland rainforests of the Democratic Republic of Congo. Conservation planning requires a current, data-driven, rangewide map of probable bonobo distribution and an understanding of key attributes of areas used by bonobos. We present a rangewide suitability model for bonobos based on a maximum entropy algorithm in which data associated with locations of bonobo nests helped predict suitable conditions across the species’ entire range. We systematically evaluated available biotic and abiotic factors, including a bonobo-specific forest fragmentation layer (forest edge density), and produced a final model revealing the importance of simple threat-based factors in a data poor environment. We confronted the issue of survey bias in presence-only models and devised a novel evaluation approach applicable to other taxa by comparing models built with data from geographically distinct sub-regions that had higher survey effort. The model’s classification accuracy was high (AUC = 0.82). Distance from agriculture and forest edge density best predicted bonobo occurrence with bonobo nests more likely to occur farther from agriculture and in areas of lower edge density. These results suggest that bonobos either avoid areas of higher human activity, fragmented forests, or both, and that humans reduce the effective habitat of bonobos. The model results contribute to an increased understanding of threats to bonobo populations, as well as help identify priority areas for future surveys and determine core bonobo protection areas. 相似文献
3.
In animal communication, elaborate signals have been shown to be under sexual selection and often to reliably indicate a signaler's quality, condition, or motivation. For instance, the performance of physically challenging signals such as trills – i.e. rapidly repeated elements of broad frequency bandwidth – is considered to reflect signaler quality. Nightingales Luscinia megarhynchos are renowned for their outstanding song repertoire sizes, and most songs include a variety of complex trills. In the present study, we examined whether performance of trills can reliably reflect male quality. We show that vocal performance of trills predicts the age of a male. Older males sang trills that were closer to the performance limit than did younger males. Moreover, males with narrower beaks sang more consistent trills than did males with wider beaks. Vocal performance of trills, however, did not significantly predict other measures of biometric quality such as body size or body condition of the males. The findings suggest that receivers could benefit from the predictive value of physically demanding song traits in assessing age as an important quality component of potential mates or rivals. Particularly in species with high singing versatility, signaler assessment based on readily assessable structures may be adaptive, as this will allow receivers to quickly gather relevant information about the singer without attending to the full song repertoire. 相似文献
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Active state of sensory rhodopsin II: structural determinants for signal transfer and proton pumping
Gushchin I Reshetnyak A Borshchevskiy V Ishchenko A Round E Grudinin S Engelhard M Büldt G Gordeliy V 《Journal of molecular biology》2011,412(4):591-600
The molecular mechanism of transmembrane signal transduction is still a pertinent question in cellular biology. Generally, a receptor can transfer an external signal via its cytoplasmic surface, as found for G-protein-coupled receptors such as rhodopsin, or via the membrane domain, such as that in sensory rhodopsin II (SRII) in complex with its transducer, HtrII. In the absence of HtrII, SRII functions as a proton pump. Here, we report on the crystal structure of the active state of uncomplexed SRII from Natronomonas pharaonis, NpSRII. The problem with a dramatic loss of diffraction quality upon loading of the active state was overcome by growing better crystals and by reducing the occupancy of the state. The conformational changes in the region comprising helices F and G are similar to those observed for the NpSRII-transducer complex but are much more pronounced. The meaning of these differences for the understanding of proton pumping and signal transduction by NpSRII is discussed. 相似文献
9.
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10.
Lévesque B Gagnon F Valentin A Cartier JF Chevalier P Cardinal P Cantin P Gingras S 《Canadian journal of microbiology》2006,52(10):984-991
The aims of the present study were to assess the microbial quality of Mya arenaria clams from the north shore of the St. Lawrence River estuary and to validate various microbial indicator microorganisms of bivalve mollusks contamination. Clams were collected from nine sites, including four harvesting sites closed by virtue of the Canadian Shellfish Sanitation Program (CSSP). Six contamination indicators (fecal coliforms, somatic coliphages, F-specific coliphages, fecal streptococci, Clostridium perfringens, and Escherichia coli) and four pathogens (Campylobacter sp., Cryptosporidium parvum, Giardia sp., and Salmonella sp.) were identified in the clams. Indicators sensibility, specificity and predictive values with respect to the presence of pathogens were calculated. Pathogenic microorganisms detection frequency in clams was important (92%). Globally, pathogens tend to be less frequently detected in opened harvesting sites (p = 0.086). Although the assessed indicators were not perfect, when F-specific coliphages are associated with E. coli or fecal coliforms, a good sensibility (62%-64%) and good positive predictive value (88%) with respect to the investigated pathogens are obtained. 相似文献