Gut pH, redox conditions and oxygen levels in an aquatic caterpillar: potential effects on the fate of ingested tannins

Larvae of the freshwater moth Acentria ephemerella (Pyralidae, Lepidoptera) can fully develop on Myriophyllum spicatum, a submerged macrophyte containing 7-10% of its dry mass as tannins. We investigated the physicochemical gut parameters of larvae fed with M. spicatum or Potamogeton perfoliatus, a food plant lacking tannins, and the chemical fate of ingested polyphenols. Microelectrode studies revealed that larval midguts were slightly alkaline (pH 8) and had a positive redox potential. Whole guts were oxygen sinks owing to the oxygen demand of the gut contents. Oxygen penetrated the midgut up to 100 microm, but the centres of the foregut and midgut were always anoxic. The physicochemical parameters of the guts did not change with the food plant. The major tannin from M. spicatum, tellimagrandin II, was significantly depleted in the midgut and was not detected in faeces. In vitro studies indicated that tellimagrandin II is rapidly depleted mainly through oxidation, and hydrolysis might also occur. Our findings for A. ephemerella are compared with those for terrestrial Lepidoptera, and possible mechanisms for adaptations to tannin-rich food plants are discussed.     

Studies on a PMCA-like protein in the outer mantle epithelium of <Emphasis Type="Italic">Anodonta cygnea</Emphasis>: insights on calcium transcellular dynamics

Early studies on the outer mantle epithelium (OME) cells of the freshwater bivalve Anodonta cygnea (Linnaeus, 1758) revealed high ionic calcium concentrations by electrophysiological methods and subsequently a high tendency to reach an intracellular toxic condition. This toxicity could be neutralized by specific mechanisms in the cytosol of OME cells of A. cygnea. The present immunocytochemistry studies of OME cells by light and transmission electron microscopy (TEM) clearly showed a positive reaction of an antibody directed against the human plasma membrane Ca²⁺-ATPase 1 (PMCA-1) in the cytoplasm of OME cells. Also, western blot analysis of different fractions of OME cells with anti human PMCA-1 and C28R2 antibodies confirmed the presence of a PMCA-like protein with an unusual topographical localization and a molecular weight of only 70–80 kDa. These results lead us to speculate that this PMCA-like protein is distributed either in the plasma membrane or in the entire cytosol, where it eventually regulates intracellular calcium levels. Interestingly, the antibody reactions showed seasonal variations, being highest in OME samples prepared during summer when A. cygnea live under natural acidosis and absent in samples taken in winter conditions, which is in accordance with the seasonal variation of shell calcification rates. During winter, PMCA-1 antibody reaction was also detected in OME cells of animals kept only under experimentally induced acidosis conditions. Therefore, we assume that a functional role for this PMCA-like protein in the intracellular calcium regulation of OME cells during the mineralization of the shells of A. cygnea can be speculated.     

Phylogeography of the genus <Emphasis Type="Italic">Ulva</Emphasis> (Ulvophyceae,Chlorophyta), with special reference to the Japanese freshwater and brackish taxa

The nuclear-encoded ITS and associated 5.8S rDNA regions were sequenced for 72 specimens of Ulva collected from 44 rivers across Japan, including U. prolifera Müller from the Shimanto River, Kochi Prefecture, as well as 26 samples originally identified as U. linza L. from 20 coastal marine areas. Sequence data revealed that the samples fall into six distinct clades: the U. flexuosa Wulfen clade (2 samples), the Ulva linza-procera-prolifera (LPP) complex clade (75 samples), Ulva sp. 1 clade (3 samples), Ulva sp. 2 clade (7 samples), Ulva sp. 3 clade (4 samples) and Ulva sp. 4 clade (7 samples). The LPP complex contained a mixture of 26 samples collected from seashores and 49 samples obtained from rivers, including U. prolifera from the Shimanto River, and GenBank data for U. linza and U. procera Ahlner. The samples of the LPP complex differed by only 0–7 substitutions (0–1.149%). Subsequent phylogeographic analyses of the LPP complex based on the 5S rDNA spacer region revealed the presence of two further groupings: a group including 22 strictly marine littoral U. linza samples and a U. prolifera group composed of a mixture of 4 marine samples and all 49 river samples. The monophyly of all river samples indicates that adaptation to low salinity might have occurred only once in the evolutionary history of the LPP complex.     

Influence of soft rush (Juncus effusus) on phosphorus flux in grazed seasonal wetlands

Livestock significantly affect wetland soils and vegetation but their impacts on wetland nutrient dynamics are poorly understood. We set up a full factorial laboratory experiment to assess the effects of Juncus effusus, grazing exclusion, and flooding on P flux from intact cores collected from seasonal wetlands in cattle pastures in south Florida. We collected intact cores from Juncus tussocks and plant interspaces inside and outside 4-year grazing exclosures in five replicate wetlands. We incubated the cores for 50 days under continuous flooding or weekly 1-day flooding cycles and measured P concentrations in surface and pore water. Grazing exclosures had less Juncus (17%) and bare ground (2%) than adjacent grazed areas (Juncus, 48%; bare ground, 12%), but did not affect P fluxes. Initial fluxes of soluble reactive P (SRP) were much higher in cores with Juncus (242 ± 153 mg P m⁻² day⁻¹) than without Juncus (14 ± 20 mg P m⁻² day⁻¹). In weekly flooded cores P fluxes fell to 19.7 ± 13.4 mg P m⁻² day⁻¹ in cores with and 2.7 ± 2.6 in cores without Juncus. The strong effect of Juncus on P flux was an indirect effect of cattle grazing, but 4 years of grazing exclusion did not have a significant effect on P fluxes.     

干旱区受水资源胁迫的下游绿洲动态变化趋势分析——以黑河流域额济纳绿洲为例

干旱内陆流域下游绿洲的形成与演变对流域地表径流变化响应强烈 .采用绿洲生态斑块动态模拟、植被与水盐状态相关分析、生态需水量估算等方法 ,分别对黑河流域下游额济纳绿洲在不同分水方案与水资源利用情景下的变化趋势进行了研究 .结果表明 ,维持现状绿洲面积不再萎缩 ,在考虑水资源利用合理化的前提下 ,其最低净需水量为 5 .7× 10 8m3 ,如果考虑下游地区人畜生活用水及工业用水 ,同时考虑水量在输送过程中的散失损耗 ,为在近期 (2 0 15年以前 )维持现状绿洲面积 ,狼心山断面入境流量需达到6 .0× 10 8m3 ;而要使绿洲面积恢复到 2 0世纪 80年代初的水平 ,狼心山断面过水量应不低于 8.9× 10 8m3 ,正义峡断面下泄水量要求达到 10 .9× 10 8～ 13.1× 10 8m3 .     

Phosphorus loss from land to water: integrating agricultural and environmental management

Phosphorus (P), an essential nutrient for crop and animal production, can accelerate freshwater eutrophication, now one of the most ubiquitous forms of water quality impairment in the developed world. Repeated outbreaks of harmful algal blooms (e.g., Cyanobacteria and Pfiesteria) have increased society's awareness of eutrophication, and the need for solutions. Agriculture is regarded as an important source of P in the environment. Specifically, the concentration of specialized farming systems has led to a transfer of P from areas of grain production to animal production. This has created regional surpluses in P inputs (mineral fertilizer and feed) over outputs (crop and animal produce), built up soil P in excess of crop needs, and increased the loss of P from land to water. Recent research has shown that this loss of P in both surface runoff and subsurface flow originates primarily from small areas within watersheds during a few storms. These areas occur where high soil P, or P application in mineral fertilizer or manure, coincide with high runoff or erosion potential. We argue that the overall goal of efforts to reduce P loss to water should involve balancing P inputs and outputs at farm and watershed levels by optimizing animal feed rations and land application of P as mineral fertilizer and manure. Also, conservation practices should be targeted to relatively small but critical watershed areas for P export.     

利用RAPD标记研究几种淡水腹足类的亲缘关系

以软体动物腹足纲、中腹足目的光滑狭口螺、长角涵螺、纹沼螺、赤豆螺、大沼螺几个形态分类的近缘种及梨形环棱螺(对照)作为研究对象,用随机扩增多态DNA技术对上述动物进行了20个引物的扩增,共获得117条扩增谱带,单个引物扩增的RAPD标记在3-12个之间,片段长度在30—3000bp之间。试验结果显示：淡水螺类的RAPD标记具有明显的多态性,而且种间的扩增标记及差异程度可以反映出物种间系统演化过程的亲缘关系。通过数值聚类制图后得到：长角涵螺、纹沼螺、大沼螺、赤豆螺之间的亲缘关系较近,而光滑狭口螺、梨形环棱螺与上述4个种的亲缘关系较远,其结果与新修订的淡水中腹足目科级分类方案相当吻合。     

海口地区集贸市场淡水鱼华枝睾吸虫囊蚴感染调查

用直接压片法和人工消化法检查了海口集贸市场上5种淡水色(鲫色、罗非鱼、鲤鱼、土鲮色、白鲳)感染华枝睾吸虫囊蚴情况。结果表明：5种淡水色的总感染率为53．66％。其中,鲤鱼、土鲮色、鲫鱼、罗非鱼、白鲳的感染率分别为68．75％、58．82％、58．06％、48．57％和36．67％;平均每克鱼肉含囊蚴数最高的是鲫鱼(9．47个／g),平均每尾阳性鱼含囊蚴数最高的是土鲮鱼(43个／尾)。     

钱塘江流域的淡水贝类

报告了对钱塘江流域进行淡水贝类调查的结果。标本经鉴定计有67种,隶属于腹足纲有9科18属42种,瓣鳃纲有4科11属25种,内有29种属浙江省新记录。分析了该流域淡水贝类与栖息环境的关系及该流域的常见种和偶见种,并探讨了该流域淡水贝类的分布区划。     

GIS-based distributed model for simulating runoff and sediment load in the Malian River Basin

GIS-based modeling is an effective approach for reflecting spatially-varied complexities in watershed systems. In this study, a GIS-aided distributive hydrological model was developed to simulate runoff and sediment transport in a loess-plateau context with semi-arid climate, sparse vegetation, and serious soil erosion. The model was then applied to a case study in the Malian River Basin, which is one of the largest catchments in the middle reach of the Yellow River. Based on the GIS technique, the DEM of the study basin was successfully used to delineate the stream network and extract information of catchment characteristics. The results show satisfactory accuracy for runoff simulation. Especially, the integrated soil-erosion and hydrological models can be used for simulating both runoff and sediment loads, which provide a useful decision-support tool for water resources management and pollution control. This study is an attempt to develop a distributed rainfall-runoff model for river basins in the loess plateau region. The developed model can also be extended to larger basins. Further works of field survey and investigation would be helpful for better calibrating critical parameters and thus improving performance of the developed model.