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311.
Lepidophagous (scale-eating) blue-striped fangblennies (Plagiotremus rhinorhynchus Bleeker 1852) are often found sympatrically with the bluestreak cleaner wrasse (Labroides dimidiatus Valenciennes 1839). They have some resemblance to the juvenile L. dimidiatus and have previously been reported as aggressive cleaner wrasse mimics. We observed 14 P. rhinorhynchus on a small area in the barrier reef near Hoga Island, Indonesia to assess the effects of client size on the behaviour and
attack success of fangblennies: our results suggest that fangblennies are selective with regard to victim size; fish avoided
by the fangblennies are significantly larger than those not avoided and attack success is significantly higher at intermediate
victim size classes. The behaviour of the victims also has a significant direct effect on the foraging success of the fangblennies;
where the potential victim posed, 63.6% were ignored by the fangblenny and only 7.4% of attacks were successful on posing
fish as opposed to a surprise attack success rate of 71.6%. Overall, victims which exhibited the pose behaviour were significantly
smaller in size. It appears likely that the predatory strategy of these fangblennies varies with victim size and that mimicry
plays a minor role in attracting potential victims. We suggest that in common with other mimetic fish the resemblance of fangblennies
to juvenile bluestreak cleaner wrasse allows them to actively hunt in areas where adult cleaners are common thus, indirectly
improving their feeding opportunities. 相似文献
312.
To explore potentially selective growth conditions for fetal cells in cultures from the blood of pregnant women, we investigated if fetal and adult erythroid progenitors with different hemoglobin expression programs are differentially responsive to erythropoietin (EPO). Co-cultures of clonogenic cells from 12-week fetal and adult peripheral blood were established, and the development of erythropoietic cells was monitored using flow cytometric profiles of correlated cellular contents of fetal and adult hemoglobin (HbF and HbA, respectively). Adult nucleated red cells were classified as F+A−, F+A+ or F−A+. All fetal cells were F+A−. The population of F+A− cells was flow-sorted and fetal cells were identified by fluorescence in situ hybridization (FISH) using chromosome-specific probes. Delayed EPO addition revealed that all types of erythroid cells entered the EPO-dependent phase with similar kinetics, beginning at about Day 4. The data suggest that fetal and adult erythroid stem/progenitor cells have the same initial maturation kinetics in culture independent of their hemoglobin chain expression program. Fetal and adult cells with different hemoglobin profiles also showed similar EPO dose–response curves, determined for different intervals during the first 2 weeks of culture. Thus, the kinetics of entry into the phase of EPO dependence, as well as the sensitivity to EPO at various stages of development, are essentially the same for erythropoietic progenitor cells derived from adult and early fetal blood, which rules out the possibility of using the timing or concentration of EPO for the selective growth of fetal cells from the blood of pregnant women. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
313.
314.
Fobissie B. Kalame Johnson Nkem Monica Idinoba Markku Kanninen 《Mitigation and Adaptation Strategies for Global Change》2009,14(2):135-151
Many studies have suggested various kinds of forest policies, management planning and practices to help forests adapt to climate
change. These recommendations are often generic, based mostly on case studies from temperate countries and rarely from Africa.
We argue that policy and management recommendations aimed at integrating adaptation into national forest policies and practices
in Africa should start with an inventory and careful examination of existing policies and practices in order to understand
the nature and extent of intervention required to influence the adaptation of forest ecosystems to climate change. This paper
aims to contribute to closing this gap in knowledge detrimental to decision making through the review and analysis of current
forest policies and practices in Burkina Faso and Ghana and highlighting elements that have the potential to influence the
adaptation of forest ecosystems to climate change. The analysis revealed that adaptation (and mitigation) are not part of
current forest policies in Burkina Faso and Ghana, but instead policies contain elements of risk management practices which
are also relevant to the adaptation of forest ecosystems. Some of these elements are found in policies on the management of
forest fires, forest genetic resources, non-timber resources, tree regeneration and silvicultural practices. To facilitate
and enhance the management of these elements, a number of recommendations are suggested. Their implementation will require
experienced and well-trained forestry personnel, financial resources, socio-cultural and political dimensions, and the political
will of decision makers to act appropriately by formulating necessary policies and mainstreaming adaptation into forest policy
and management planning. 相似文献
315.
Jeffery?S.?PettisEmail author Dennis?vanEngelsdorp Josephine?Johnson Galen?Dively 《Die Naturwissenschaften》2012,99(2):153-158
Global pollinator declines have been attributed to habitat destruction, pesticide use, and climate change or some combination
of these factors, and managed honey bees, Apis mellifera, are part of worldwide pollinator declines. Here we exposed honey bee colonies during three brood generations to sub-lethal
doses of a widely used pesticide, imidacloprid, and then subsequently challenged newly emerged bees with the gut parasite,
Nosema spp. The pesticide dosages used were below levels demonstrated to cause effects on longevity or foraging in adult honey bees.
Nosema infections increased significantly in the bees from pesticide-treated hives when compared to bees from control hives demonstrating
an indirect effect of pesticides on pathogen growth in honey bees. We clearly demonstrate an increase in pathogen growth within
individual bees reared in colonies exposed to one of the most widely used pesticides worldwide, imidacloprid, at below levels
considered harmful to bees. The finding that individual bees with undetectable levels of the target pesticide, after being
reared in a sub-lethal pesticide environment within the colony, had higher Nosema is significant. Interactions between pesticides and pathogens could be a major contributor to increased mortality of honey
bee colonies, including colony collapse disorder, and other pollinator declines worldwide. 相似文献
316.
Carl E. Zipper Braven Beaty Gregory C. Johnson Jess W. Jones Jennifer Lynn Krstolic Brett J.K. Ostby William J. Wolfe Patricia Donovan 《Journal of the American Water Resources Association》2014,50(4):807-819
The Clinch River of southwestern Virginia and northeastern Tennessee is arguably the most important river for freshwater mussel conservation in the United States. This featured collection presents investigations of mussel population status and habitat quality in the Clinch River. Analyses of historic water‐ and sediment‐quality data suggest that water column ammonia and water column and sediment metals, including Cu and Zn, may have contributed historically to declining densities and extirpations of mussels in the river's Virginia sections. These studies also reveal increasing temporal trends for dissolved solids concentrations throughout much of the river's extent. Current mussel abundance patterns do not correspond spatially with physical habitat quality, but they do correspond with specific conductance, dissolved major ions, and water column metals, suggesting these and/or associated constituents as factors contributing to mussel declines. Mussels are sensitive to metals. Native mussels and hatchery‐raised mussels held in cages in situ accumulated metals in their body tissues in river sections where mussels are declining. Organic compound and bed‐sediment contaminant analyses did not reveal spatial correspondences with mussel status metrics, although potentially toxic levels were found. Collectively, these studies identify major ions and metals as water‐ and sediment‐quality concerns for mussel conservation in the Clinch River. 相似文献
317.
Matthew K. Landon Carmen A. Burton Tracy A. Davis Kenneth Belitz Tyler D. Johnson 《Journal of the American Water Resources Association》2014,50(1):179-195
The variables affecting the occurrence of hydrocarbons in aquifers used for public supply in California were assessed based on statistical evaluation of three large statewide datasets; gasoline oxygenates also were analyzed for comparison with hydrocarbons. Benzene is the most frequently detected (1.7%) compound among 17 hydrocarbons analyzed at generally low concentrations (median detected concentration 0.024 μg/l) in groundwater used for public supply in California; methyl tert‐butyl ether (MTBE) is the most frequently detected (5.8%) compound among seven oxygenates analyzed (median detected concentration 0.1 μg/l). At aquifer depths used for public supply, hydrocarbons and MTBE rarely co‐occur and are generally related to different variables; in shallower groundwater, co‐occurrence is more frequent and there are similar relations to the density or proximity of potential sources. Benzene concentrations are most strongly correlated with reducing conditions, regardless of groundwater age and depth. Multiple lines of evidence indicate that benzene and other hydrocarbons detected in old, deep, and/or brackish groundwater result from geogenic sources of oil and gas. However, in recently recharged (since ~1950), generally shallower groundwater, higher concentrations and detection frequencies of benzene and hydrocarbons were associated with a greater proportion of commercial land use surrounding the well, likely reflecting effects of anthropogenic sources, particularly in combination with reducing conditions. 相似文献
318.
Sheila M. Holmes Adam D. Gordon Edward E. Louis Steig E. Johnson 《Behavioral ecology and sociobiology》2016,70(11):1949-1960
319.
320.
V. R. Johnson C. Brownlee R. E. M. Rickaby M. Graziano M. Milazzo J. M. Hall-Spencer 《Marine Biology》2013,160(8):1813-1824
Increasing anthropogenic CO2 emissions to the atmosphere are causing a rise in pCO2 concentrations in the ocean surface and lowering pH. To predict the effects of these changes, we need to improve our understanding of the responses of marine primary producers since these drive biogeochemical cycles and profoundly affect the structure and function of benthic habitats. The effects of increasing CO2 levels on the colonisation of artificial substrata by microalgal assemblages (periphyton) were examined across a CO2 gradient off the volcanic island of Vulcano (NE Sicily). We show that periphyton communities altered significantly as CO2 concentrations increased. CO2 enrichment caused significant increases in chlorophyll a concentrations and in diatom abundance although we did not detect any changes in cyanobacteria. SEM analysis revealed major shifts in diatom assemblage composition as CO2 levels increased. The responses of benthic microalgae to rising anthropogenic CO2 emissions are likely to have significant ecological ramifications for coastal systems. 相似文献