华南重要人工林及地带性森林凋落物酸碱缓冲能力

植物残体可以修正土壤酸度,但其作用机理还有很大争议,本研究评估森林凋落物作为酸碱缓冲体系的能力,它可能是调节土壤酸度的重要机理之一.凋落物材料取自华南重要的人工林类型及一个地带性顶极森林群落,将材料用不同pH酸溶液提取,并用酸碱进行滴定.结果表明,凋落物本身是一个极强的酸碱缓冲体系,它使浸提液酸度保持不变,并对添加的酸碱起显著的缓冲作用.首次发现两个豆科树种凋落物马占相思(Acacia mangiumWilld)与大叶相思(Acacia auriculaiformis A.Cunn)具有很高的pH值(约pH6.0),约高于土壤酸度2个pH单位,每年凋落于地表的枯落物层通过缓冲机理可以提高雨水0.1至0.4pH单位.其它人工林凋落物酸度约为pH4.0,与它们生长的土壤酸度相似.溶液中无机离子组成上的差异不能完全解释凋落物pH格局,但高钠低硝态氮可能是两个豆科树种高pH的一个重要原因.地带性顶极群落12个树种加权酸度为pH3.90,明显低于土壤酸度(pH4.19),因而,凋落物是林下土壤进一步变酸的驱动因素;发现一个种凋落物(山竹子(Garcinia oblongifolia))酸度极低(pH 3.19)并且缓冲力极强,该种植物生长的土壤将难于通过施用石灰等措施对酸度进行调节,它影响下的土壤环境将影响其它植物的入侵.观光木(Tsoongiodendron odorum Chun)凋落物酸度碱向最远离土壤酸度,这种凋落物酸度与环境酸度间的不一致可能对植物形成某种长期生态压力,并成为该种致濒危的一个因素.因而,植物残体是一个极强的酸碱缓冲体系,它以化学缓冲机理可以影响环境酸度,但可能只有少数种通过这一机理使土壤致酸或致碱,因为多数植物残体与土壤酸度基本相似.     

浦东滩涂中型土壤动物群落结构及土质酸碱度生物评价分析

1999年,对上海浦东滩涂4类不同酸碱度土壤中的中型土壤动物进行了调查。应用物种丰富度,个体数多度,多样性指数和均匀度4个群落参数,并结合种类研究,讨论了土壤动物群落结构与不同酸碱度土壤的关系。结果表明,土壤中弹尾目和蜱螨目对不同酸碱度土壤反应敏感。弹尾目的3个群落参数和蜱螨目的4个参数均很好地反映与土壤反应敏感。弹尾目的3个群落参数和蜱螨目的4个参数均很好地反映与土壤pH的关系,相关系数分别在0．9以上和0．85左右,在pH相差较大的情况下,可以区分不同酸碱度的土壤。弹尾目的符Tao(Paranura sp.)可用于评价酸碱度较接近的土壤,球角Tao(Hypogastrura sp.）可用于评价酸碱度相差较大,高pH或环境条件较恶劣的土壤。     

DIATOM COMMUNITY DYNAMICS IN STREAMS OF CHRONIC AND EPISODIC ACIDIFICATION: THE ROLES OF ENVIRONMENT AND TIME1

Community dynamics of epiphytic diatoms were studied for 3 years in a chronically and an episodically acidified tributary of Buck Creek, Adirondacks. Both streams experienced pulses of acidity during hydrologic events but these pulses were more pronounced in the episodically acidified stream, where pH decreased over two units (between 4.53 and 6.62) and the acid‐neutralizing capacity (ANC) became negative. In the chronically acidified stream, pH was below 4.9 and the ANC was negative 94% of the time. In this stream, high inorganic acidity following SO₄^2? enrichment from snowmelt or rainstorms alternated with high organic acidity derived from a headwaters wetland during base flow. The fluctuating water chemistry generated shifts in diatom community composition: from exclusive dominance of Eunotia bilunaris (Ehrenberg) Mills during periods of high inorganic acidity to proliferation of several subdominant species during periods of high organic acidity. In the episodically acidified stream, the pulses of acidity were associated with high NO₃^? concentrations and the corresponding high ratios of inorganic monomeric Al (Al_im) to organic monomeric Al (Al_om). Diatom communities there were dominated exclusively by E. exigua (Brébisson) Rabenhorst year round; however, this species peaked during periods of low acidity. Periods of high acidity and Al_im:Al_om ratios were marked by a decline in E. exigua and a concomitant increase in the subdominant species. Variance partitioning into terms of environmental and temporal variance, and their covariance, suggested that diatom communities in the chronically acidic stream were governed primarily by environmental factors while in the episodically acidic stream environmental and temporal factors had equal contributions.     

Responses of insects,especially Chironomidae (Diptera), and mites to 130 years of acidification in a Scottish lake

About 130 years of anthropogenic acidification of Round Loch of Glenhead, SW Scotland, has resulted in successively decreased stability, diversity, productivity and survival rate of the non-biting midge (Diptera: Chironomidae) fauna. Similar trends have also been observed among mayflies, caddis-flies and water mites. The first effects of anthropogenic acidification on the insect and mite fauna, as evidenced by palaeolimnological analyses of²¹⁰Pb-dated sediment cores, occurred as early as around 1850, i.e. earlier than in any other lake hitherto studied. The drop in the lake's pH was first indicated by decreased stability and changes in species composition of chironomids and mayflies in the littoral zone. Major changes in the profundal chironomid fauna did not take place until about 1950, when mean lake pH dropped below 5.0. At the same time, the littoral insect fauna became even more unstable and the first significant elimination of species occurred. Comparison with insect fauna of other lakes suggests that a pH of less than 5 might be critical for the ecological conditions in many acidified lakes. None of the twelve most common chironomid species present prior to the acidification of the lake had disappeared after 120–130 years of considerable acidification, and they are all common in oligotrophic lakes with a pH of 6.5–7.0. This is in contrast to the effects of heavy acidification on other aquatic animal groups. Chironomids are probably more sensitive to lake trophic status than lake acidity.     

Response of Picea rubens seedlings to intermittent mist varying in acidity, and in concentrations of sulfur-, and nitrogen-containing pollutants

Two-year-old red spruce seedlings ( Picea rubens Sarg .) growing in. field chambers were repeatedly exposed to acidic mist with a factorial combination of 3 fluctuating levels of acidity: median pH values of 3.0 (range of 2.5 to 3.5), 3.5 (range of 3.0 to 4.0), and 4.0 (range of 3.5 to 4.5). and 3 ion compositions: sulfate. nitrate and ammonium, and a combination of all 3 ions. The experiment was performed during the growing season over a period of 3.5 months. Mist exposures were intermittent with 5 wet-dry cycles for each 16-h overnight exposure period, Foliar necrosis occurred on seedlings treated with the most acidic mist and was most severe when the mist contained sulfate. At a median pH of 3.5, a value close to that of cloud water occurring in the eastern United States, injury developed with sulfuric acid mist, but not. when the mist contained nitric acid. The combination of high acidity and sulfate significantly decreased volume of aboveground tissues, while high acidity and nitrate increased volume. Root and needle dry weights were not affected. However, high acidity of mist was associated with increased leader shoot length. These results indicate, that there is a risk of foliar injury and changes in growth of red spruce with cloud water at a median acidity of pH 3.5 or below, especially when there are high concentrations of sulfate and low concentrations of nitrate.     

Stream acidification in South Germany – chemical and biological assessment methods and trends*

Chemical measurements are designed to classify acid sensitive streams in Baden-Württemberg (South West Germany) as a basis on which a biological indication method for stream acidity is worked out. Sampling of macrozoobenthos is carried out as a basis for the biological classification of the degree of acidity in acid sensitive silicate streams. Interlinking of the chemical and biological data is made with, among others, statistical methods aiming to describe the pH values and other parameters relevant to acidification which effect the presence of the organisms. The sensitivity levels of the benthic macroinvertebrates are related to the pH values and the corresponding indicator values for the bioindication are assigned to the current acidification level of the calcium-poor streams. Relevant data, information, and procedures from literature were hereby taken into account. Computer-aided assessment of the acidity status of the slightly-buffered streams based on the macrobenthic cenosis following the principle of maximum biological sensitivity of the individual taxa has been carried out. This has been done by successive examination of the values of all observed indicator species, beginning with the most acid sensitive ones. Cartographic presentation of the biological results – obtained between 1992 and 1998 – reveals a slight improvement of the degree of acidity in streams of the Black Forest. This can also be observed in the chemical data. Most sampling sites show an increasing trend in pH-values as well as in buffer capacity. On the other hand most of the streams in poorly buffered areas show a declining trend in their aluminium concentrations and their content of sulphate-ions, which is a consequence of the decreasing sulphur-dioxide concentrations in the air during the last 15 years.     

Fungi from Geothermal Soils in Yellowstone National Park

Geothermal soils near Amphitheater Springs in Yellowstone National Park were characterized by high temperatures (up to 70°C), high heavy metal content, low pH values (down to pH 2.7), sparse vegetation, and limited organic carbon. From these soils we cultured 16 fungal species. Two of these species were thermophilic, and six were thermotolerant. We cultured only three of these species from nearby cool (0 to 22°C) soils. Transect studies revealed that higher numbers of CFUs occurred in and below the root zone of the perennial plant Dichanthelium lanuginosum (hot springs panic grass). The dynamics of fungal CFUs in geothermal soil and nearby nongeothermal soil were investigated for 12 months by examining soil cores and in situ mesocosms. For all of the fungal species studied, the temperature of the soil from which the organisms were cultured corresponded with their optimum axenic growth temperature.     

Factors influencing Clostridium botulinum spore germination, outgrowth, and toxin formation in acidified media

Clostridium botulinum type A spores were inoculated at a level of 10(7) spores per ml into sterile beef media with protein concentrations of 1, 2, 3, 4, or 6% and acidified to pH values of 2.01 to 4.75 with hydrochloric acid or 4.19 to 4.60 with citric acid. All experimental manipulations, including blending, acidification, inoculation, incubation (30 degrees C), and analyses, were conducted in an anaerobic chamber-incubator in which atmospheric oxygen levels were maintained below 2 ppm (2 microliters/liter). Under these strict anaerobic conditions (oxidation-reduction values in media ranging from -370 to -391 mV), C. botulinum spores were consistently found to germinate, grow, and produce toxin below pH 4.6. The boundary between toxic and atoxic samples in HC1-acidified beef media was mediated by titratable acidity, pH, and protein concentration. A limiting acidity was not established for the citrate-acidified samples; all blends tested (1, 2, 3, and 4% protein and titratable acidities of 0.091 to 0.453%) became toxic within 5 weeks. At the same pH and protein concentration, citric acid was less effective than HC1 in preventing the germination of C. botulinum spores. Higher levels of cell proliferation in the beef protein, as well as enhanced gas production and putrefactive degradation, indicated that beef was a better substrate than soy for C. botulinum spores under these conditions. Reducing the inoculum to 10(4) delayed but did not prevent spore outgrowth and toxin release at pH levels below 4.6.     

Factors influencing Clostridium botulinum spore germination, outgrowth, and toxin formation in acidified media.

Clostridium botulinum type A spores were inoculated at a level of 10(7) spores per ml into sterile beef media with protein concentrations of 1, 2, 3, 4, or 6% and acidified to pH values of 2.01 to 4.75 with hydrochloric acid or 4.19 to 4.60 with citric acid. All experimental manipulations, including blending, acidification, inoculation, incubation (30 degrees C), and analyses, were conducted in an anaerobic chamber-incubator in which atmospheric oxygen levels were maintained below 2 ppm (2 microliters/liter). Under these strict anaerobic conditions (oxidation-reduction values in media ranging from -370 to -391 mV), C. botulinum spores were consistently found to germinate, grow, and produce toxin below pH 4.6. The boundary between toxic and atoxic samples in HC1-acidified beef media was mediated by titratable acidity, pH, and protein concentration. A limiting acidity was not established for the citrate-acidified samples; all blends tested (1, 2, 3, and 4% protein and titratable acidities of 0.091 to 0.453%) became toxic within 5 weeks. At the same pH and protein concentration, citric acid was less effective than HC1 in preventing the germination of C. botulinum spores. Higher levels of cell proliferation in the beef protein, as well as enhanced gas production and putrefactive degradation, indicated that beef was a better substrate than soy for C. botulinum spores under these conditions. Reducing the inoculum to 10(4) delayed but did not prevent spore outgrowth and toxin release at pH levels below 4.6.     

华南重要人工林及地带性森林凋落物酸碱缓冲能力

植物残体可以修止土壤酸度,但其作用机理还有很大争议,本研究评估森林凋落物作为酸碱缓冲体系的能力,它可能是调节土壤酸度的重要机理之一。凋落物材料取自华南重要的人工林类型及一个地带性顶极森林群落,将材料用不同pH酸溶液提取,并用酸碱进行滴定。结果表明,凋落物本身是一个极强的酸碱缓冲体系,它使浸提液酸度保持不变,并对添加的酸碱起显著的缓冲作用。首次发现两个豆科树种凋落物马占相思（Acacia mangium Willd)与大叶相思(Acacia auriculaiformis A.Cunn)具有很高的pH值(约pH6．0),约高于土壤酸度2个pH单位,每年凋落于地表的枯落物层通过缓冲机理可以提高雨水0．1至0．4pH单位。其它人工林凋落物酸度约为pH4．0,与它们生长的土壤酸度相似。溶液中无机离子组成上的差异不能完全解释凋落物pH格局,但高钠低硝态氮可能是两个豆科树种高pH的一个重要原因。地带性顶极群落12个树种加权酸度为pH3．90,明显低于土壤酸度(pH4．19),因而,凋落物是林下土壤进一步变酸的驱动因素;发现一个种凋落物(山竹子(Garcinia oblongifolia))酸度极低(pH3．19)并且缓冲力极强,该种植物生长的土壤将难于通过施用石灰等措施对酸度进行调节,它影响下的土壤环境将影响其它植物的入侵。观光木(Tsoongiodendron odorum Chun)凋落物酸度碱向最远离土壤酸度,这种凋落物酸度与环境酸度间的不一致可能对植物形成某种长期生态压力,并成为该种致濒危的一个因素。因而,植物残体是一个极强的酸碱缓冲体系,它以化学缓冲机理可以影响环境酸度,但可能只有少数种通过这一机理使土壤致酸或致碱,因为多数植物残体与土壤酸度基本相似。     

Macroinvertebrate species and assemblages in the headwater streams of the River Tyne,northern England in relation to land cover and other environmental variables

The macroinvertebrate species and assemblages of headwater streams of the River Tyne catchment in northern England were classified and their relationship with environmental variables based on stream structure, water acidity, distance from source and land cover investigated using constrained ordination and logistic regression. Fuzzy classification of data from 322 stream sites generated five assemblages. Stream structure, quantified as an exposure index, was found to be the most important environmental variable, with water acidity also important. Distance from source and land cover had less influence on species and assemblage distribution. A considerable amount of variation in assemblage distribution was explained using a two-variable logistic regression with stream structure (exposure index) and water acidity (pH) in a template. Site structure and water acidity appeared to be related to drift, geology and topography with little anthropogenic influence. The applicability of the habitat template concept for explaining the distribution of stream macroinvertebrates is discussed.     

Food utilization and niche overlap in three species of lake-dwelling leeches (Hirudinea)

The diets of Erpobdella octoculata, Glosiphonia complanata and Helobdella stagnalis on the stony littoral zone of eutrophic Crose Mere were examined over two years using the precipitin test. The abundances of food organisms were measured. For all leech species, juvenile mortality was greatest in locations where a low ratio of prey abundance to recruited leech abundance occurred, and the intensity of feeding by Erpobdella and Helobdella fell slightly in late summer when large numbers of juveniles of these species were present; these suggest the involvement of food in juvenile mortality, Seasonal changes in feeding intensity were similar for all leech species, with the exceptions outlined above and for Glossiphonia in April when feeding by brooding adults ceased, at which time the severity of any interspecific competition would have been reduced. Within a leech species, there was little change in the food spectrum as the leeches grew. Niche breadth was lowest for Erpobdella and highest for Helobdella. Niche overlap was greatest between Glossiphonia and Helobdella, and there was a trend for overlap values to be lower between Glossiphonia and Erpobdellu than between Helohdellu and Erpohdellu. Erpobdella fed mainly on chironomids and oligochaetes, Glossiphonia on molluscs, oligochaetes and chironomids, and Helobdella on oligochaetes, chironomids, Asellus, molluses and amphipods, all in decreasing order of importance. It is suggested that coexistence in the leech species may be due in part to Erpobdella and Glossiphonia having 'food refuges' in chironomids and molluscs, respectively, with Helobdellu being more of a general predator.     

Effects of Changes in Acidity on Aquatic Insects in Rocky Littoral Habitats of Lakes Near Sudbur y, Ontario

Benthic aquatic insects were collected from rocky nearshore areas (< 1 m deep) of 17 lakes near Sudbury, Ontario, with a pH range of 4.7–7.3 and a size range of less than 10 ha to over 10,000 ha. These insect communities were composed of taxa common to lake soft-sediments and streams. Direct and indirect effects of lake acidity appeared to be major controls on the structure of these communities, implying that several factors may be involved in restructuring during acidification or recovery. Declines in abundances of several taxa of Ephemeroptera at pH below 5.5 were attributable to acid toxicity, while increases in the abundances of Odonata and Diptera at pH below 5.5 were associated with the absence of fish predators and other indirect effects of acidity. The communities of two experimentally neutralized lakes restructured rapidly within 5 years, approaching but not achieving community structures typical of our near-neutral survey lakes. Neutralization led to recolonization or increased abundance of the acid-sensitive mayfly, Stenacron interpunctatum , and the dragonfly, Boyeria grafiana ; however, recolonization by other taxa expected to be present in near-neutral lakes ( Stenonema femoratum, Eurylophella, and Basiaeshna janata ) was not observed. Consistent with results for the survey lakes, declines in the abundances of the dragonflies Aeshna interrupta, Aeshna eremita , and Leucorrhinia glacialis in the neutralized lakes were associated with reintroductions of Salvelinus fontinalis (aurora trout) and increased fish predation pressure, while reduced abundances of the dipterans Ceratopogonidae, Psectrocladius , and Stackelbergina may be related to indirect effects of acidity other than fish predation. Although community composition varied greatly across the acidity gradient, total species richness and abundance were not correlated with lake chemistry or number of fish species.     

Bayesian classification of vegetation types with Gaussian mixture density fitting to indicator values

Question: Is it possible to mathematically classify relevés into vegetation types on the basis of their average indicator values, including the uncertainty of the classification? Location: The Netherlands. Method: A large relevé database was used to develop a method for predicting vegetation types based on indicator values. First, each relevé was classified into a phytosociological association on the basis of its species composition. Additionally, mean indicator values for moisture, nutrients and acidity were computed for each relevé. Thus, the position of each classified relevé was obtained in a three‐dimensional space of indicator values. Fitting the data to so called Gaussian Mixture Models yielded densities of associations as a function of indicator values. Finally, these density functions were used to predict the Bayesian occurrence probabilities of associations for known indicator values. Validation of predictions was performed by using a randomly chosen half of the database for the calibration of densities and the other half for the validation of predicted associations. Results and Conclusions: With indicator values, most reléves were classified correctly into vegetation types at the association level. This was shown using confusion matrices that relate (1) the number of relevés classified into associations based on species composition to (2) those based on indicator values. Misclassified relevés belonged to ecologically similar associations. The method seems very suitable for predictive vegetation models.     

Diversity of wetland vegetation in the Bulgarian high mountains, main gradients and context-dependence of the pH role

We fill a gap in understanding wetland vegetation diversity and relationship with environmental determinants in Bulgarian high mountains. A total of 615 phytosociological samples were taken from springs, mires, wet meadows and tall-forb habitats throughout Bulgaria, of which 234 relevés are from mire and spring vegetation above timberline. The vegetation was classified by TWINSPAN and the resulting vegetation types were reproduced by the formal definitions using the combination of Cocktail species groups based on phi-coefficient of joint co-occurrence of the species. Nine vegetation types of springs and fens have been clearly delimited above the timberline. All vegetation types include Balkan endemic species, the representation of which varies. Fens generally harbour more Balkan endemics than do springs, with the exception of species-poor high-altitude Drepanocladetum exannulati. The gradient structure of the vegetation was revealed by DCA and by CCA with forward selection of environmental factors. The major determinants of vegetation variation strongly differ above and below the timberline and likewise between springs and fens. The base-richness gradient controls the floristic variation of Bulgarian submontane fens, whereas the complete data set including both submontane and subalpine fens is governed by the altitude gradient from lowland and basin fens to subalpine fens rich in Balkan endemics. When focusing on sites above the timberline only, the first DCA axis separates fens from springs without organic matter. The major species turnover in springs follows the variation in water pH and mineral content in water, whereas fen vegetation variation is primarily controlled by succession gradient of peat accumulation. Altitude remains an important factor in all cases. Weak correlation between water pH and conductivity was found. This correlation was even statistically insignificant in fens above the timberline. Water pH is not influenced by mineral richness in Bulgarian high mountains, since it is buffered by decomposition of organic matter in fens. In springs, pH reaches maximum values due to strong aeration caused by water flow. The plant species richness decreases significantly with increasing altitude. The increase of species richness towards circumneutral pH, often found in mires, was not confirmed in Bulgarian high mountains. The correlation between species richness and pH was significant only when arctic-alpine species and allied European high-mountain species were considered separately. The richness of boreal species was independent on pH. Some of them had their optima shifted to more acidic fens as compared to regions below the timberline. Our results suggest that subalpine spring and fen vegetation should be analysed separately with respect to vegetation-environment correlations. Separate analysis of fens below and above timberline is quite appropriate.     

Structure of chironomid assemblages along environmental and geographical gradients in the Bohemian Forest lakes (Central Europe): An exploratory analysis

Eight glacial lakes of the Bohemian Forest (Czech Republic and Germany) were characterised by the distribution of chironomids collected as pupal exuviae. Twenty-eight taxa were identified, including some faunistically interesting species of the region. Two-way indicator species analysis (TWINSPAN) was used to classify lakes according to their taxonomic composition. Canonical correspondence analysis (CCA) and multiple regression were used to relate the chironomid assemblages to two sets of explanatory variables: (i) local environmental variables, and (ii) broad-scale spatial variables. The TWINSPAN classified the lakes into four groups, whereas presence/absence of three taxa was indicative for this classification. The CCA of assemblage composition on environmental variables showed that chironomids respond significantly to altitude and alkalinity. The ordination of composition data on geographical variables revealed strong longitudinal gradient in chironomid distributions. Altitude and alkalinity accounted for 36.2% of the total variation, while the geographic gradient explained 20.5%. As revealed by the variation partitioning procedure, the significant effect of these variables was, in large part, independent of each other. Overall taxonomic richness appeared to be governed by altitude only. Causal ecological and historical factors underlying these results are discussed. This paper may provide a basis for hypothesis testing in future research of the Bohemian Forest lakes.     

The survival of larval perch, Perca fluviatilis L., under different combinations of acidity and duration of acid conditions, analysed with a generalized linear model

Naturally-occurring acidified water was used in a factorial experiment to study the effects of acidity and duration of acidic conditions on short-term survival of late larvae of perch. The analysis demonstrated that both factors influenced probability of survival. When the duration of acidic conditions exceeded 2 days, acidity alone could be used as a predictor of survival. At pH values below 4.5, and durations of 6–24 h, unexpectedly high survival rates were observed. Analyses of the concentration of total and soluble aluminium suggested that aluminium chemistry played a significant part in determining the observed survival pattern.     

The protective role of endogenous bacterial communities in chironomid egg masses and larvae

Insects of the family Chironomidae, also known as chironomids, are distributed worldwide in a variety of water habitats. These insects display a wide range of tolerance toward metals and organic pollutions. Bacterial species known for their ability to degrade toxicants were identified from chironomid egg masses, leading to the hypothesis that bacteria may contribute to the survival of chironomids in polluted environments. To gain a better understanding of the bacterial communities that inhabit chironomids, the endogenous bacteria of egg masses and larvae were studied by 454-pyrosequencing. The microbial community of the egg masses was distinct from that of the larval stage, most likely due to the presence of one dominant bacterial Firmicutes taxon, which consisted of 28% of the total sequence reads from the larvae. This taxon may be an insect symbiont. The bacterial communities of both the egg masses and the larvae were found to include operational taxonomic units, which were closely related to species known as toxicant degraders. Furthermore, various bacterial species with the ability to detoxify metals were isolated from egg masses and larvae. Koch-like postulates were applied to demonstrate that chironomid endogenous bacterial species protect the insect from toxic heavy metals. We conclude that chironomids, which are considered pollution tolerant, are inhabited by stable endogenous bacterial communities that have a role in protecting their hosts from toxicants. This phenomenon, in which bacteria enable the continued existence of their host in hostile environments, may not be restricted only to chironomids.     

Electrophysiological identification of antennal pH receptors in the ground beetle Pterostichus oblongopunctatus

Abstract. Electrophysiological responses of antennal taste bristles to 100 mm acetate and phosphate buffers were tested at pH 3–11 in the ground beetle Pterostichus oblongopunctatus (F.) (Coleoptera, Carabidae). Additionally, responses of these sensilla to 10 and 100 mm phosphate buffers were compared with each other. Generally, in response to these stimulating solutions, two sensory cells, classified as a salt cell (cation cell) and a pH cell, respectively, showed action potentials distinguished by differences in their amplitudes and polarity of spikes. The firing rate of the cation cell increased with increasing buffer concentration, and was influenced by buffer pH in a complicated way. The best stimulus for the second cell (pH cell) was pH of the stimulating buffer solution. As the pH of the stimulus solution increased, higher rates of firing were produced by the pH cell. For example, the number of action potentials elicited by 100 mm phosphate buffer at pH 11.1 was approximately 16-fold higher compared with that at pH 8.1, and firing rates during the first second of the response were 27.9 and 1.7 imp/s, respectively. The pH cell did not fire or fired at very low frequency (first second response below 5 imp/s) at pH 3–6. This level of acidity probably represents the pH preferences of this ground beetle in its forest habitat and hibernating sites. By contrast to the cation cell, the pH cell responded to increases in buffer concentration by decreasing its firing rate.     

The mechanism of bile salt-induced hemolysis.

The hemolytic activities of sodium deoxycholate (DChol) and its tauro-conjugate (TDChol) and glyco-conjugate (GDChol) were analysed. 50 % hemolysis occurred in 30 min at pH 7.3, at the concentrations of these detergents equal to 0.044, 0.042 and 0.040 % respectively. These values are below their critical micellar concentrations. Based on its kinetics, this hemolysis is classified as being of permeability type. The detergents increase the permeability of erythrocyte membranes to KCl, and colloid osmotic hemolysis occurs. The minimum of hemolytic activity of the three cholates is at about pH 7.5. A very high increase in hemolytic activity occurs at pHs below 6.8, 6.5 and 6.2 for DChol, TDChol, and GDChol, respectively. These values are close to the pK(a) for DChol (6.2), but much higher than the pK(a) for TDChol (1.9) and GDChol (4.8). It is therefore suggested that the increase in hemolytic activity is not a result of the protonation of the anionic groups of the cholates. At acidification below pH 6, the kinetics of DChol induced hemolysis change to the damage type characterised by nonselective membrane permeability. Such a transition is not observed in TDChol and GDChol induced hemolysis. It is therefore suggested that the change in the type of hemolysis depends on protonation of the anionic group of cholates.