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排序方式: 共有542条查询结果,搜索用时 31 毫秒
481.
Martinez-Jeronimo F Ventura-Lopez C 《Journal of environmental biology / Academy of Environmental Biology, India》2011,32(4):513-521
The knowledge of population effects of food on tropical, filter-feeding cladocerans is scarce because a reduced number of species has been extensively studied. Ceriodaphnia rigaudi Richard 1894, a small-sized cladoceran distributed mainly in tropical and subtropical regions of the world, was studied. The aim of this study was to contribute to the knowledge of the reproductive biology of a poor-known Cladoceran; for this we assessed the effect of feeding and temperature on the reproduction and life cycle of this species. Three microalga species (Pseudokirchneriella subcapitata, Ankistrodesmus falcatus, and Chlorella vulgaris) were supplied as food each at a concentration of 12 mg l(-1) (dry weight, equivalent to 1.3 x 10(6), 0.4 x 10(6) and 1.35 x 10(6) cell m1(-1), respectively, and equivalent to 7.8 microg C ml(-1), at two temperatures (20 and 25 degrees C). We evaluated, among other responses, longevity, total progeny, survival, life expectancy at birth and fecundity. Organisms fed with the microalgae A. falcatus and P subcapitata presented both higher longevity (30.7 +/- 5.91, 26.6 +/- 3.59 days, respectively) and total progeny (45 +/- 13.80, 40.7 +/- 0.66 neonates female (-1) values than those organisms fed C. vulgaris (13.5 +/- 4.63 days and 17.6 +/- 6.19 neonates female (-1), respectively). On the other hand, temperature affected significantly the population parameters of C. rigaudi, recording maximal longevity values (56.1 +/- 9.41 days) at 20 degrees C in organisms fed A. falcatus; however, age at first reproduction and total progeny were negatively affected by this temperature: sexual maturation of the females was delayed until the age of 16 days and the number of neonates produced was smaller (9.8 +/- 3.45 with C. vulgaris; 24.7 +/- 6.01 with P subcapitata, and 35.5 +/- 8.59 neonates female(-1) with A. falcatus). The best reproductive responses for C. rigaudi in this study were obtained with A. falcatus at degrees 25 degrees C. 相似文献
482.
David Bierbach Claudia Kronmarck Carmen Hennige-Schulz Stefan Stadler Martin Plath 《Behavioral ecology and sociobiology》2011,65(9):1699-1707
Mate choice copying was mostly described as a strategy employed by females to assess the quality of potential mates, but also
males can copy other males’ mate choice. An open question in this context is whether and how copying males evaluate sperm
competition risk, as mating with a female that has already copulated with another male obviously sets the stage for intense
sperm competition (i.e., in species with internal fertilization). Using the livebearing Atlantic molly (Poecilia mexicana) as a model, we asked (a) whether males of that species indeed copy other males’ choices, and if they do so, (b) whether
copying males strategically adjust their behavior to sperm competition risk. We used an approach where focal males could first
choose to associate with a large or a small stimulus female. Mate choice tests were then repeated after an “observation phase”
during which either no model male was present (treatment 1, control) or the previously non-preferred female could be seen
associating (treatment 2) or physically interacting (treatment 3) with a model male. We found that, after the observation
phase, males spent considerably more time with the previously non-preferred female in treatment (2), i.e., they copied the
model male’s choice. This effect was much weaker during treatment (3) where sexual interactions between the model male and
the formerly non-preferred female were allowed. Males, therefore, seem to adjust their copying behavior strategically to the
perceived risk of sperm competition. 相似文献
483.
De Luca E Novelli C Barbato F Menegoni P Iannetta M Nascetti G 《Environmental monitoring and assessment》2011,183(1-4):437-450
This study describes the conservation status of dune systems in relation to disturbance factors in the coastal stretch of the Viterbo province, Latium Region, Italy. Particular emphasis was given to the bioindication value of plant communities and their sequence. Each plant community was considered as a "habitat" in accordance with Annex I of the Directive 92/43/EU. Stress factors, such as sand dynamic and erosion, and anthropogenic pressures, such as trampling and bathing settlements, influence the sequence of habitats and weaken the system of relations that makes these coenoses to occur in extreme conditions. The choice to carry out surveys along wide transects, recording different data, allowed to explore the use of habitats as bioindicators. Comparing sites characterized by the same extension in a homogeneous area, it was possible to expand the use of canonical correspondence analysis (CCA) as a tool to correlate habitat composition and disturbance factors. The application of CCA showed a high correlation of degradation and habitat loss with coastal erosion, trampling and presence of waste. Furthermore, floristic surveys allowed the application of different biodiversity indices to quantify species richness of sampled areas. The conservation status of the sites investigated was found to be diverse, from the total disappearance of the mobile dune habitats to their complete sequence. The proposed methodology has been useful to fulfill the objective of the work and is applicable to other case studies in the Mediterranean. 相似文献
484.
Oscar Amin Laura Comoglio Carla Spetter Claudia Duarte Ra��l Asteasuain Rub��n Hugo Freije Jorge Marcovecchio 《Environmental monitoring and assessment》2011,175(1-4):63-73
The study deals with the determination of physico-chemical parameters, inorganic nutrients, particulate organic matter, and photosynthetic pigments on a monthly basis during an annual cycle from nine sampling sites of the coastal zone of a high-latitude ecosystem (Tierra del Fuego, Argentina). Nitrites and phosphates concentrations were similar to other systems of the south Atlantic coast (median, 0.30 and 1.02 ??M, respectively), while nitrates were higher in all sampling periods (median, 45.37 ??M), and silicates were significantly smaller (median, 7.76 ??M). Chlorophyll a and phaeopigments have shown median values of 0.38 and 0.85 mg m???3, respectively, while saturated values of dissolved oxygen were recorded throughout the study. The analysis reflected that nutrient enrichment seems to be linked to an anthropogenic source, the presence of peatlands areas, and a sink of Nothofagus pumilio woods. The area could be characterized in three zones related to (1) high urban influence, (2) natural inputs of freshwater, and (3) mixed inputs coming from moderate urban impacts. 相似文献
485.
McDonald LT Rasmussen PE Chénier M Levesque C 《Journal of environmental monitoring : JEM》2011,13(2):377-383
Wipe sampling is the USA regulatory protocol for determination of "dust lead loadings" in residential environments. Few studies have applied the wipe sampling method to metals other than lead (Pb) for the purpose of residential exposure assessments. This study was undertaken to develop and expand the wipe method for quantifying additional metal(loid)s including arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), and antimony (Sb); and to provide information on typical background loadings for these metals in urban Canadian homes. A total of 932 wipe samples, 220 field blanks, and 220 duplicate wipes were collected from 222 homes located in three cities in Ontario, Canada using the ASTM 1728 standard. The wipes were digested using a modified version of the ASTM 1644 standard for Pb, which prescribes a hot nitric acid/hydrogen peroxide digestion. The key modification was the addition of hydrofluoric acid to improve recoveries of the target elements, and determination using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). Generally, a large proportion of the results fell below the limits of detection (LOD) and quantification (LOQ). To distinguish "elevated" metal loadings from loadings characterized as "urban background", an upper background threshold for each element was derived using a normality (Q-Q) plot. LOQ was determined to be the appropriate minimum threshold based on quality assurance criteria. It is concluded that wipes are a useful sampling option to investigate multi-element loadings in residential environments. 相似文献
486.
Chávez-Sánchez María-Cristina Abad-Rosales Selene Lozano-Olvera Rodolfo Montoya-Rodríguez Leobardo Franco-Nava Miguel Ángel Mejía-Ruíz Claudio Humberto Pestryakov Alexey Bogdanchikova Nina 《Environmental science and pollution research international》2021,28(7):8224-8234
Environmental Science and Pollution Research - The objective of this study was to evaluate the histopathological alterations in juvenile Penaeus vannamei caused by silver nanoparticles (AgNPs) for... 相似文献
487.
Martin Claussen Victor Brovkin Andrey Ganopolski Claudia Kubatzki Vladimir Petoukhov Stefan Rahmstorf 《Environmental Modeling and Assessment》1999,4(4):209-216
We present a new reduced-form model for climate system analysis. This model, called CLIMBER-2 (for CLIMate and BiosphERe, level 2), fills the current gap between simple, highly parameterized climate models and computationally expensive coupled models of global atmospheric and oceanic circulation. We outline the basic assumptions implicit in CLIMBER-2 and we present examples of climate system analysis including a study of atmosphere–ocean interaction during the last glacial maximum, an analysis of synergism between various components of the climate system during the mid-Holocene around 6000 years ago, and a transient simulation of climate change during the last 8000 years. These studies demonstrate the feasibility of a computationally efficient analysis of climate system dynamics which is a prerequisite for future climate impact research and, more generally, Earth system analysis, i.e., the analysis of feedbacks between our environment and human activities. 相似文献
488.
Claudia J. K. Engelmann Andy D. Ward Ann D. Christy E. Scott Bair 《Journal of the American Water Resources Association》2002,38(1):289-300
ABSTRACT: The purpose of this study was to evaluate the Better Assessment Science Integrating Point and Nonpoint Sources (BASINS) watershed management system. BASINS data were used with the NPSM model to predict discharge and sediment concentrations at the outlet of a 103 km2 Ohio watershed. It was concluded that the NPSM model should always be calibrated but only a few of the parameters provided with BASINS needed to be calibrated. For a three‐year study period, there was a 2 percent underestimation of discharge using area weighted precipitation values and a 25 percent overestimation using the single station data in BASINS. A comparison of observed and predicted monthly discharge resulted in an r2 of 0.86 with area‐weighted precipitation and an r2 of 0.74 with the single station data. Calibrating the model to substantially improve sediment predictions was unsuccessful and we concluded that a calibration period of one year was too short. For the three‐year study period, the r2 for sediment was 0.36 with a slope of 0.37 and an intercept of 18.8 mg/l. The mean observed and predicted sediment concentrations were 27.1 mg/l and 22.6 mg/l, respectively. 相似文献
489.
Cerda IA Paulina Carabajal A Salgado L Coria RA Reguero MA Tambussi CP Moly JJ 《Die Naturwissenschaften》2012,99(1):83-87
Sauropoda is one of the most diverse and geographically widespread clades of herbivorous dinosaurs, and until now, their remains
have now been recovered from all continental landmasses except Antarctica. We report the first record of a sauropod dinosaur
from Antarctica, represented by an incomplete caudal vertebra from the Late Cretaceous of James Ross Island. The size and
morphology of the specimen allows its identification as a lithostrotian titanosaur. Our finding indicates that advanced titanosaurs
achieved a global distribution at least by the Late Cretaceous. 相似文献
490.
Timing matters when assessing dominance and chemical signatures in the paper wasp Polistes dominulus
Leonardo Dapporto Claudia Bruschini Rita Cervo Francesca R. Dani Duncan E Jackson Stefano Turillazzi 《Behavioral ecology and sociobiology》2010,64(8):1363-1365
A recent study (Izzo et al., Behav Ecol Sociobiol 64: 857–864, 2010) reported that cuticular hydrocarbons (CHCs) correlate with fertility, not dominance, in the paper wasp Polistes dominulus thus contradicting the results of recent investigations which concluded that social dominance is the main determinant for
CHC signatures in this species. We suggest here that different forms of dominance in the pre-nesting and post-nesting phases
caused the apparently contradictory results. Thus the assumption that dominance behaviour in the pre-nesting stage is synonymous
with dominance after colony foundation is incorrect. We provide standardised definitions for forms of “dominance” observed
in the P. dominulus life cycle to avoid apparent discrepancies in the future among studies dealing with the same topics in different annual stages. 相似文献