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161.
Summary. Arion lusitanicus and other slugs are able to feed on a variety of plants, even those containing toxic secondary metabolites, such as alkaloids. Alkaloids, like sparteine, lupanine, quinidine and atropine are avoided in no-choice feeding experiments only when they are present in concentrations above 1 mg/g food pellet. Alkaloids (sparteine, lupanine, cytisine, quinidine, atropine, senecionine, eserine, and harmaline) are toxic to Arion lusitanicus when injected. LD50 values are 10 to 20 fold higher than in vertebrates indicating that slugs have a high tolerance towards food toxins. The tolerance is higher in young animals than in adult slugs. Injected alkaloids are rapidly detoxified within 72 h. Tolerance and detoxification can be induced by feeding slugs on non-lethal doses of lupin alkaloids. Using isolated microsomal preparations from the digestive gland, active detoxification was observed in vitro. Evidence is presented that cytochrome p450 plays an important role in detoxification of the applied alkaloids. A powerful and inducible detoxification systems appears to be the main mechanism that allows slugs to feed on plants rich in secondary metabolites (when no other food is available), that are usually avoided by other herbivores. 相似文献
162.
Recovery of Faunal Communities During Tropical Forest Regeneration 总被引:14,自引:0,他引:14
ROBERT R. DUNN 《Conservation biology》2004,18(2):302-309
Abstract: As mature tropical forests are cleared, secondary forests may play an important role in the conservation of animal species, depending on how fast animal communities recover during forest regeneration. I reviewed published studies on the recovery of animal species richness and composition during tropical forest regeneration. In 38 of the 39 data sets I examined, conversion of forest to agriculture or pasture substantially reduced species richness. Given suitable conditions for forest recovery, the species richness of the animal taxa considered can be predicted to resemble that of mature forests roughly 20–40 years after land abandonment. At least for ants and birds, however, recovery of species composition appears to take substantially longer than recovery of species richness. Because species richness for many taxa appears to recover relatively rapidly in secondary forests, conservation of secondary forests may be an effective investment in future diversity. The slower recovery of species composition indicates, however, that some species will require stands of mature forest to persist. 相似文献
163.
对环太湖丘陵地区农田氮素随地表径流的输出特征进行了研究,结果表明,地表径流中TN浓度随径流量而变化,浓度峰值出现时间滞后于径流量峰值;径流发生前期,NH3 N和NO-3 N浓度水平相当,后期NO-3 N浓度缓慢抬升,而NH3 N含量缓慢下降;NO-2 N浓度相对较低,随时间快速下降;对于TN和NO-3 N而言,溶解态含量高于悬浮态,而溶解态和悬浮态NH3 N的浓度相当;无机氮平均浓度高于有机氮,有机氮尤其是悬浮态有机氮浓度表现出随径流量而变化的特点。 相似文献
164.
Summary. Pyrrolizidine alkaloids (PAs) present a model system in the investigation of tritrophic interactions mediated by plant secondary compounds. However, their toxicity for insect herbivores has never been experimentally proven. Here, we demonstrate the toxic effects of a PA on growth and survival of the eri silk moth Philosamia ricini. In a feeding experiment, larvae of this generalist herbivore fed with an artificial PA diet gained weight significantly slower than control animals, and died as pupae. We suggest that derivatives of the ingested PA N-oxide damage developmental functions during metamorphosis. A tracer test with [14C]senecionine N-oxide revealed that the caterpillars lack adaptations that would prevent conversion of the chemical into the pro-toxic free base. In contrast, the PA adapted leaf beetle Longitarsus anchusae accumulates PAs as N-oxides. We tested the purpose of sequestration in this species as defence against predators. Through a series of prey choice experiments with three carabid predator species, chemically non-protected bark beetle pupae were chosen almost uniformly over L. anchusae pupae. In a following choice test with one of these predators, artificially PA-treated mealworm segments deterred the predator from feeding. Overall the study corroborates the immediate toxic effect of PAs on non-adapted herbivores and the protective effect that adapted insects may gain by sequestering them. It thereby underlines the potential for PAs to play a central role in multitrophic interactions between plants, phytophages and their predators. 相似文献
165.
This study investigated geochemical characteristics of the acid mine drainage (AMD) discharged from the abandoned mine adits in the vicinity of the Dogye coal mine in Korea. Acid mine drainage discharged from Jeoncha pit adit of the Dogye coal mine, which is the main source of the AMD in the study area, had a pH value of 3.0 and concentrations of 2148mg SO4
2– L–1, 229mg Fe L–1, 71mg A1 L–1 and 11mg Mn L–1. The reduction of some metal concentrations downstream from the discharge point could be explained on the basis of dilution and precipitation. The order of removal of metal ions downstream from the discharge point was Fe>A1, Cu>Zn, Mn. Acidity could be used as a good determining factor offering comprehensive and quantitative values for the polluting extent of acid mine drainage. The acidities existing in all acidic water samples in the Gunahan district originated primarily from mineral acidity, especially in the upper Nahan Creek from dissolved Fe and Al and in the middle and down Nahan Creek from dissolved Al. From the application of the WATEQ4F program, it was determined that predominant species of dissolved Fe in all water samples was Fe2+, and those of dissolved Al were AlSO4
+ and Al3+ except for IW2 sample which was associated with white precipitates. The species of dissolved Al in IW2 sample include also AlOH2+ and Al(OH)2
+. The saturation indices of goethite and haematite were positive in the water samples associated with ochrous precipitates (usually called Yellow Boy), therefore these solids might be precipitated. For the IW2 sample, the saturation indices of amorphous Al(OH)3 and gibbsite were positive, so theoretically these solids might also be precipitated. By XRD analysis, it was found that goethite occurs in ochrous precipitates, and gibbsite in white precipitates. 相似文献
166.
167.
研究了UV/H2O2工艺对2,4-二氯酚(2,4-DCP)的去除效果和水中阴离子、腐殖酸对该工艺降解2,4-DCP的影响。结果表明:UV/H2O2工艺可以有效的去除水中2,4-DCP,光降解过程符合一级反应动力学模型;在H2O2投加量为8mg/L,1个30W低压汞灯照射下,2,4-DCP在蒸馏水和自来水中光降解速率常数分别为0.0232/min和0.0162/min;NO3-、Cl-、HCO3-对2,4-DCP光降解有抑制作用;当3种离子浓度为0.5mmol/L、10mmol/L、20mmol/L时,对2,4-DCP光降解的抑制程度为HCO3->NO3->Cl-;随着离子浓度增大,抑制作用增强;自来水中的光降解速率常数低于蒸馏水中的光降解速率常数是由于水中多种离子影响的结果;腐殖酸在低浓度时,促进光降解反应的进行,在高浓度时,2,4-DCP的光降解氧化受到抑制。 相似文献
168.
高分子壳聚糖对微量金属离子的螯合作用研究 总被引:5,自引:0,他引:5
研究了壳聚糖对溶液中Mn2 + 、Fe2 + 、Cu2 + 、Zn2 + 4种常见微量金属离子的吸附作用 ,通过吸附率、溶液pH等参数 ,表征了壳聚糖的吸附能力及其对离子的选择性吸附 ,其选择性次序为 :Cu+ 2 >Zn2 + >Fe+ 2 >Mn+ 2 ,为壳聚糖处理污水中的微量金属离子作了探索。 相似文献
169.
为探索新型生物吸附剂,以乌贼墨黑色素(SIM)为吸附剂,研究Pb2+、Cu2+单组分溶液及Pb2+-Cu2+二元混合体系中SIM对Pb2+和Cu2+的吸附效果并构建等温吸附模型.结果表明,pH值、SIM添加量、吸附时间对SIM吸附Pb2+和Cu2+的吸附量影响较大,而吸附温度对吸附效果影响较小;单组分吸附与二元混合体系吸附对比表明,二元混合体系中Pb2+和Cu2+存在竞争吸附.应用L (Langmuir)和F (Freundlich)等温吸附模型拟合了SIM对Pb2+、Cu2+单组分金属离子的吸附过程,其中L模型与试验结果拟合度更高;应用Non-modified Langmuir、Modified Langmuir isotherm、Extended Langmuir、Extended Freundlich和SRS模型5种模型对Pb2+-Cu2+二元混合体系的等温吸附过程进行拟合,其中Extended Langmuir模型与试验结果拟合度最佳.应用红外光谱(FTIR)分析SIM吸附金属离子的原理时发现,SIM上羟基、-NH和不饱和键是金属离子的吸附位点,且SIM对Pb2+的吸附能力优于对Cu2+的吸附. 相似文献
170.