Predation induced changes in behavior and growth rate in three populations of the intertidal snail, Littorina sitkana (Philippi)

We investigated the sublethal effects of a predatory crab, Cancer productus (Randall), on the behavior and growth of its snail prey, Littorina sitkana, by setting up controlled rearing and prey-size selection experiments. L. sitkana were collected from three sites on San Juan Island, WA, USA. These sites varied in snail size, abundance, and vertical distribution, and in the abundance of the crab predator C. productus. Snails from all three populations were raised for 34 days under the following treatments: no-crab control, a non-feeding C. productus encased in mesh box, and an encased C. productus feeding on L. sitkana. The non-feeding crab treatment did not affect snail foraging behavior or growth rate in comparison with the no-crab control. In contrast, the presence of a feeding crab elicited escape behavior in the snails, halted grazing, and consequently reduced growth rates. A population difference in escape behavior was observed: upward migration in snails from rocky shores and hiding in crevices in snails from a mud flat. It thus appears that chemicals leaching from crushed conspecific snails, rather than the presence of the crab predator, act as the “alarm substance” to which L. sitkana react. The magnitude of the growth depression in the presence of feeding crabs was 85%, with no difference among the three populations. Once the feeding crab stimulus was removed, snails in all populations resumed normal growth, suggesting that this response to feeding predators is reversible with changing environmental conditions. Laboratory experiments were set up to determine if all size classes of L. sitkana are equally susceptible to C. productus predation. C. productus consistently selected the largest of three size classes of L. sitkana. These results suggest that slow growth rate and small size in L. sitkana may actually be an adaptation for coexisting with high C. productus abundance, rather than simply a cost of escape behavior.     

Comparison of the physiological responses of Phaseolus vulgaris and Vigna unguiculata cultivars when submitted to drought conditions

Three cultivars differing in their susceptibility to water stress were compared—Phaseolus vulgaris cv. Carioca (susceptible), Vigna unguiculata cv. IT83D (intermediately tolerant) and V. unguiculata cv. EPACE-1 (tolerant)—during an imposed water stress treatment. Variation in leaf gas exchange (i.e. assimilation and stomatal conductance) and leaf relative water content in response to progressive substrate water depletion were investigated. To verify the extent of the injury caused by the drought treatment, leaf gas exchange was measured after rehydration. In the three cultivars, stomatal conductance declined before leaf relative water content was affected. P. vulgaris showed the largest decrease in the rate of stomatal conductance with decreasing substrate water content compared to both V. unguiculata cultivars. Photosynthetic assimilation rates were largely dependent on stomatal aperture, but there was evidence of the participation of non-stomatal factors in the reduction of CO₂ fixation. The response of leaf gas exchange parameters to severe water stress conditions differed significantly between P. vulgaris and V. unguiculata cultivars. After rehydration, cultivars can be characterised according to the degree of injury induced by the drought treatment: V. unguiculata cv. EPACE-1 as the least affected, V. unguiculata cv. IT83D slightly affected and P. vulgaris cv. Carioca strongly affected. Similar ranking was obtained with experiments previously performed at a cellular and subcellular level. Our results confirm the utility of physiological parameters as early screening tools for drought resistance in bean cultivars.     

Oil emulsions increase efficacy of Phoma herbarum to control dandelion but are phytotoxic

Paraffinic-vegetable and vegetable oil emulsions were investigated for their ability to increase efficacy of the fungal pathogen Phoma herbarum as a bioherbicide to control dandelion (Taraxacum officinale) under sub-optimal leaf wetness durations (LWDs) in controlled environments. Mycelia of P. herbarum (20%, v/v) were formulated in 10 oil emulsions; two based on paraffinic-vegetable (soybean) oil mixtures, and eight based on vegetable (canola, coconut and soybean) oil emulsions alone. Emulsions were applied to dandelions using an automatic track sprayer and plants were exposed to sub-optimal LWDs simulating dew periods in field conditions. An aqueous formulation of P. herbarum was included as a standard treatment and formulations without P. herbarum were included as controls. Eight of 10 oil emulsions (two paraffinic-vegetable and six vegetable) significantly increased damage ratings caused by P. herbarum compared to the standard treatment under certain sub-optimal LWDs (P=0.05). However, all oil emulsions caused at least some phytotoxicity when applied alone under most LWDs. Also, the high viscosity of nine oil emulsions caused mixing and application problems. These results indicate that oil emulsions increase damage ratings caused by P. herbarum on dandelion under sub-optimal LWDs, but may not be suitable formulations due to their phytotoxicity and high viscosity.     

北京山区侧柏-荆条系统水分来源对降雨事件的响应

分析了北京鹫峰山区侧柏、荆条枝条水及其潜在水分来源的氢氧同位素特征,运用IsoSource模型解析侧柏、荆条系统水分利用来源的季节变化及其对降雨事件的响应.结果表明:旱季初期(4月)研究区0～20 cm土层富集土壤水¹⁸O值,20 cm以下该值则随着土层深度增加逐渐减小,侧柏主要利用前2～3 d降雨补充的0～30 cm层土壤水;旱季末期(6月)侧柏和荆条分别利用当天雨水补充的0～10和10～30 cm层土壤水;雨季(7月)侧柏利用前期降水补给的0～40 cm层土壤水(59.3%)和近期降水(12.5%),荆条则利用近期降雨供给的0～30 cm层土壤水;侧柏的土壤水分来源逐月加深,至生长季末(11月)其主要利用60～80 cm层土壤水(前2～3 d降雨补给),而荆条枝条水δ¹⁸O值远离各水分来源δ¹⁸O值.两物种对水分的竞争压力小,适应本区域气候特征,尤其在应对特大暴雨等极端天气时,植物系统垂直分布的水分来源能够有效分流洪峰,减小暴雨瞬时破坏力.     

Effects of competition on an endangered limpet Patella ferruginea (Gastropoda: Patellidae): Implications for conservation

Spatial and trophic competitive interactions were analysed for the seldom-studied limpet Patella ferruginea (which is considered as an “extinction risk”). Spatial patterns of distribution of P. ferruginea were studied using quadrats of 1 × 1 m² at several transects along the coastline, whereas trophic interactions were studied through manipulations of densities of P. ferruginea and Patella caerulea in experimental plots located at the mid-shore. Physical parameters were measured inside each plot to determine the microenvironmental differences between fenced and unfenced plots. Fenced plots of 50 × 50 cm² were used with six different treatments. Mortality was recorded every 15 days and length was measured monthly during the 3.5 months of the experiment. At the beginning and end of the experiment, lengths and weights of limpets were recorded and chlorophyll concentration was measured by spectrophotometric analysis of rock surface. Both species showed increased mortality and reduced size and weight in treatments with greater densities. High intraspecific competition was detected in P. caerulea compared with P. ferruginea whereas asymmetrical interspecific competition was observed. The results suggest that P. caerulea is the superior competitor, possibly due to differences in radular morphology and mobility between the two species. Microalgal food assessment showed that it is probably a limiting resource, especially for P. caerulea, although this species has a lower biomass than P. ferruginea. The high intraspecific competition observed in P. caerulea could be responsible for the coexistence of both species. The present study may be useful in helping to conserve P. ferruginea, which is presently under serious threat of extinction, because the results show that experimental fences are a viable means of concentrating breeding individuals.     

热带、亚热带典型森林-土壤系统植硅体碳演变规律

分别选取中国亚热带毛竹林、马尾松林、青冈林、杉木林和热带青梅林、芭蕉林、橡胶林、马占相思林8种森林类型,采集其鲜叶、凋落叶以及0～10和10～30 cm土层土壤,通过微波消解法提取其中的植硅体,并采用碱溶法测定植硅体中碳含量.结果表明: 4种亚热带森林类型鲜叶、凋落叶和0～10 cm土层中植硅体碳含量均以马尾松林(230.24、229.17、20.87 g·kg^-1)最高,毛竹林(30.55、37.37、3.38 g·kg^-1)最低,10～30 cm土层则以青冈林(18.54 g·kg^-1)最高,毛竹林(2.90 g·kg^-1)最低.热带森林鲜叶中植硅体碳含量以马占相思林(377.66 g·kg^-1)最高,青梅林(46.83 g·kg^-1)最低,凋落叶中则是橡胶林(218.23 g·kg^-1)最高,芭蕉林(27.66 g·kg^-1)最低,而0～10和10～30 cm土层土壤中均以马占相思林(23.84、24.90 g·kg^-1)最高,芭蕉林(3.89、3.93 g·kg^-1)最低.与0～10 cm表层土相比,杉木林、青冈林、马尾松林、毛竹林、橡胶林、马占相思林、芭蕉林和青梅林鲜叶植硅体碳含量分别下降97.4%、94.9%、90.9%、88.9%、95.9%、93.7%、93.3%和63.7%.青冈林、芭蕉林和马占相思林鲜叶植硅体碳含量显著高于凋落叶,而毛竹林、马尾松林、杉木林、青梅林和橡胶林之间无显著差异.8种森林类型土壤植硅体碳含量均显著低于鲜叶和凋落叶,表明植硅体在通过凋落物释放到土壤的过程中是不稳定的.     

Non-Susceptibility of Earthworm Eisenia fetida to the Rhabditid Nematode Phasmarhabditis hermaphrodita, a Biocontrol Agent of Slugs

The rhabditid nematode Phasmarhabditis hermaphrodita is a lethal parasite for slugs that is sold commercially in Europe under the trade name Nemaslug™. We evaluated the effects of P. hermaphrodita on the earthworm Eisenia fetida (Savigny). Adults of E. fetida were exposed in one-liter glass beakers to P. hermaphrodita at three concentrations (1×, 10× and 50× of the field recommended rate of 3×10⁹ billion nematodes/ha) during a 14-day period in an artificial soil substrate. The average body weight, burrowing behavior, mortality and other clinical signals of the earthworms were recorded at 0, 7, and 14 days after exposure to the treatments. In addition, injured earthworms (posterior ends removed) were exposed to the 10× field recommended rate of the commercial formulation. Neither intact nor injured E. fetida showed susceptibility to the slug-parasitic nematode P. hermaphrodita during the 14 days of exposure even at concentrations 10 and 50 times higher than the label dose. However, the worms in the attenuated control (autoclaved formulation) had higher mortality and lost less weight compared to the other treatments. Under the conditions of the test, we conclude that the use of the commercially available strain of P. hermaphrodita is safe to E. fetida.     

基于DNA条形码技术对浙江省外来入侵福寿螺进行分子鉴定

外来入侵福寿螺对我国农业生产和水生生态系统平衡等造成严重危害。2010年, 种类鉴定研究首次揭示我国外来入侵福寿螺包括Pomacea canaliculata和P. maculata两个种, 而浙江省仅见P. canaliculata一种报道。P. canaliculata和P. maculata种间形态近似, 且受环境、食物源等因素影响, 同种内外壳形态特征多样, 因而基于形态特征进行种类的准确鉴定极为困难。本研究在采集浙江省7个区县的福寿螺样本的基础上, 利用DNA条形码技术扩增了101个不同个体的COI序列, 并从BOLD数据库下载了“P. canaliculata种团”的5个近缘种的55条COI序列用于分析, 其中包括P. lineata, P. dolioides和P. paludosa所有已发表序列, 以及P. canaliculata和P. maculata的南美洲样品的序列等。序列相似度比对、DNA条形码间隙和系统发育树等分析表明, COI序列可以实现近缘福寿螺的有效鉴别。待测的浙江省福寿螺样品中, 杭州江干区检测到P. canaliculata和P. maculata两种, 而舟山普陀区、绍兴上虞区和新昌县、温州瓯海区及杭州西湖区仅检测到P. canaliculata, 表明P. canaliculata在浙江省具有更广的分布范围。P. canaliculata和P. maculata分别形成4种和2种单倍型, 各区县样点分别包含1-3种单倍型, 浙江省各发生地呈现较低的遗传多样性。依据系统发育关系推测, 浙江省分布的P. canaliculata和P. maculata分别可能来源于阿根廷和巴西。     

Is the social parasite Vespa dybowskii using chemical transparency to get her eggs accepted?

Both avian and insect cuckoos must trick their hosts into accepting foreign eggs. In birds this is achieved through egg mimicry. Within the hornets the only known social parasite is the rare Vespa dybowskii. We investigated how the V. dybowskii queen induces tens or hundreds of host workers to accept her eggs and offspring. Since hydrocarbons function as recognition cues in social insects, we investigated these compounds from the surface of eggs and workers of V. dybowskii, both host species (V. simillima and V. crabro) and an additional four non-host species. We found that chemical mimicry of the hosts’ colony odour and their eggs normally associated with wasps was not being employed by V. dybowskii. Chemical insignificance is also unlikely as the amounts of hydrocarbons extracted from parasite, host and non-host eggs were similar. Eggs of V. dybowskii may survive in part due to being chemically transparent, as methyl-branched compounds only represent a tiny proportion (<1%) of the parasites hydrocarbon profile but a large proportion (26–41%) in both host species. However, the functions of various hydrocarbon groups need to be investigated in the hornets before this new acceptance mechanism of parasite eggs and adults is understood.     

Evaluation of an Inoculum Production and Delivery Technique for Valdensinia heterodoxa, a Potential Biological Control Agent for Salal

Inoculum production of Valdensinia heterodoxa Peyr. (isolate PFC 3027), a foliar pathogen of salal (Gaultheria shallon Pursh.), was evaluated on various solid substrates. Incubation on salal leaf pieces resulted in the greatest number of discharged conidia, which is deemed a suitable indicator for sporulation and inoculum dispersal of V. heterodoxa. Subsequently, V. heterodoxa inoculum of two isolates (PFC 2761 and PFC 3027) was produced on salal leaf pieces using four different growth periods (0, 4, 8, or 12 days) and three different cold storage treatments (0, 4, or 8 weeks) following harvest of colonised leaf pieces. Overall, the maximum number of discharged conidia was obtained with a growth period of 4 or 8 days, whereas the effect of a cold storage treatment was inconclusive between the fungal isolates and various growth periods. Conidia discharge from salal leaf piece inoculum of V. heterodoxa (PFC 2761 and PFC 3027) applied on pot soil level resulted in 8-41% leaf damage of intact salal plants. Results from this study indicate the potential of salal plant tissue as both a growth substrate and a suitable delivery technique for V. heterodoxa to control salal.     

风车草和香根草在人工湿地中迁移养分能力的比较研究

为研究风车草(Cyperus alternifolius)和香根草(Vetiveria zizanioides)迁移养分的能力,建立17.0m²风车草潜流式人工湿地和13.3 m²香根草潜流式人工湿地处理猪场废水,在四个季节末测定植物生物量和组织氮、磷、铜、锌含量.结果表明,香根草地下部生物量大于风车草,地上部生物量则是风车草大于香根草.风车草年地上部收获量为3406.47 g·m^-2,比香根草的1483.88 g·m^-2高2.3倍;风车草的氮含量为22.69 mg·g^-1,比香根草的15.44 mg·g^-1高7.25 mg·g^-1;风车草的磷含量为6.09 mg·g^-1,比香根草的5.47 mg·g^-1高0.62 mg·g^-1.植株含铜、锌量风车草略比香根草高.风车草每年迁移N 68.72 g·m^-2和P18.49 g·m^-2,香根草迁移N 8.93 g·m^-2和P 3.69 g·m^-2.风车草人工湿地每年由植物迁移的氮、磷、铜、锌比香根草高4～7倍.     

基于ITS和matK基因对牡丹组序列分析及其亲缘关系的研究

以芍药属牡丹组全部9个野生种、5个紫斑牡丹栽培品种及3个中原牡丹品种为试材,进行核糖体内转录间隔区（ITS）和叶绿体成熟酶K （matK）基因片段测序分析,探讨ITS和matK序列为牡丹组所有野生种种间关系提供分子证据。从GeneBank中选取了1个牡丹及3个外类群芍药、川赤芍和草芍药的ITS及matK序列。对试验样品进行DNA提取、PCR扩增并双向测序得到44条序列,人工校正后将所得44条序列进行比对;计算碱基组成频率、变异位点、简约信息位点数、转换/颠换比率、种内及种间遗传距离,以邻接法进行系统发育分析。结果表明,牡丹组所有个体ITS序列长度在750~800 bp,含有86个多态位点,74个简约信息位点,转换/颠换比率（R）为1.2;而matK序列含有20个简约信息位点,转换/颠换比率（R）为1.7。ITS序列分析将牡丹组野生种分为两大枝,稷山牡丹、紫斑牡丹、卵叶牡丹和杨山牡丹聚为一枝,狭叶牡丹、滇牡丹、黄牡丹和大花黄牡丹聚为另一枝,这两枝分别与革质花盘亚组和肉质花盘亚组相对应,而四川牡丹位于革质花盘亚组最底端,支持前人研究将四川牡丹归为革质花盘亚组。matK序列分析的牡丹组野生种间遗传距离结果不理想,未能清晰的表明野生种之间的亲缘关系。由此说明,ITS序列更适合牡丹组野生种间亲缘关系的研究分析。     

五种沉水植物对富营养化水体的净化效果

为达到净化水质的目的,采用移栽沉水植物控制富营养化水体中营养盐含量和浮游藻类生物量。本研究在夏季藻类密度较高的富营养化水体中移栽5种长江中下游流域常见沉水植物,比较不同沉水植物去除营养盐和控制藻类总量的能力。研究结果:5种沉水植物对水体总氮含量去除率的大小顺序为:竹叶眼子菜>黑藻>苦草>微齿眼子菜>菹草,对总磷去除率大小顺序为:竹叶眼子菜>黑藻>微齿眼子菜>苦草>菹草;竹叶眼子菜控制水体中藻类总量的效果最佳,苦草、微齿眼子菜及菹草次之,黑藻对水体总磷和浮游植物的去除效果均极显著(p≤0.01),而对总氮含量的作用影响不明显(p=0.209)。综合营养盐吸收作用和藻类控制效果来看,竹叶眼子菜在整个实验过程中生长状态良好并达到较为稳定的净化作用,是夏季治理浅型富营养化静水水体的理想物种之一。     

On the variation in chromosome number in Potamogeton pectinatus L.

To determine whether the large morphological differences that occur between populations of Potamogeton pectinatus L. have a genetic basis, the chromosome numbers of several populations were counted. Although several numbers were determined, no correlation between different numbers and populations could be established. The number was always close to 2n = 78, which is that most recorded for P. pectinatus in the literature. However, although some aberrant counts can probably be ascribed to incorrect interpretations of the preparations, some cells undoubtedly contain more than 78 chromosomes. Since the chromosomes of P. pectinatus are very small it is difficult to distinguish between “normal” and “B-chromosomes”, which may be the cause of the higher numbers.     

The effect of Trichoderma harzianum and T. koningii on the control of tan spot (Pyrenophora tritici-repentis) and leaf blotch (Mycosphaerella graminicola) of wheat under field conditions in Argentina

The effect of six isolates of Trichoderma harzianum and one isolate of T. koningii on the incidence and severity of tan spot (Pyrenophora tritici-repentis) and leaf blotch of wheat (Mycosphaerella graminicola) was evaluated under field conditions. Significant differences between wheat cultivars, inoculum types and growth stages were found. Three of the isolates tested (T2 for M. graminicola, T7 for P. tritici-repentis and T5 for both of them) showed the best performance in controlling leaf blotch and tan spot when coated onto seed or sprayed onto wheat leaves at different growth stages, with significant severity reduction up to 56%. At tillering, six of the isolates reduced the severity of P. tritici-repentis and M. graminicola compared to the control by up to 39% and 12-53%, respectively. In some experiments, the biocontrol preparation (T2 and T5) gave a level of disease control similar to that obtained with Tebuconazole (70 and 48%, respectively). The effect of Trichoderma against P. tritici-repentis was also observed at the heading stage, when six of the treatments reduced disease severity by 16-35%. This is the first report on the efficacy of Trichoderma spp. against wheat necrotrophic pathogens under field conditions in Argentina.     

Several pseudomonads,associated with the cultivated mushrooms Agaricus bisporus or Pleurotus sp., are hemolytic

Pseudomonas tolaasii, causing brown blotch disease on cultivated mushrooms, and yielding a white line precipitate towards P. “reactans”, has been shown to induce lysis of erythrocytes. Some Finnish strains isolated from diseased mushroom fruit bodies, although harboring the typical features of P. tolaasii, proved to be distinct, and have been allocated to a nov. sp. P. costantinii. We examined in these study whether all brown blotch causing agents were hemolytic. The induction of erythrocytes lysis seemed to be a rather common feature of mushroom associated-pseudomonads, especially for strains involved in the production of a white-line-in agar.     

Flavonoid data and populational observations in support of hybrid status for Populus acuminata

Flavonoid distribution and populational composition at the collection sites of several samples of Populus acuminata strongly suggest that this taxon is an inter-sectional hybrid between P. angustifolia, sect. Tacamahaca and any one of two or three different species of the section Aigeiros, when the entire range is considered. In the vicinity of the type locality, the Aigeiros parent is P. sargentii. Within any population, foliage of trees of P. acuminata is characterized by morphological intermediacy and an essentially additive flavonoid profile, as compared to the two parental taxa present. In habit the trees resemble those of P. sargentii, and habitats at the collection sites were found to be somewhat intermediate. Fifteen flavonoid compounds were consistently present in samples of the putative hybrid. Twelve of these had diagnostic value because they were absent in one of the parental species. One compound, apigenin 7-O-diglucoside, was found only in P. acuminata. In part, our identifications correspond to compounds reported by Crawford in a morphological and chemical study of P. acuminiata.     

Commensalism during submerged mixed culture of Geotrichum candidum and Penicillium camembertii on glutamate and lactate

Geotrichum candidum and Penicillium camembertii were cultivated in pure and mixed cultures on glutamate- and lactate-based medium. In pure culture, P. camembertii assimilated simultaneously glutamate, as a nitrogen and carbon source for biosynthesis, and lactate as an energy source. On the contrary, G. candidum grew on glutamate alone. The mixed culture led to higher growth rates and then higher rates of substrate consumption and metabolite production than each pure culture; however, the behaviour recorded was similar to that observed during G. candidum pure culture, in particular the absence of lactate assimilation during growth, illustrating a commensalism between both species. The presence of G. candidum induced a form of “competition” and then a better assimilation by P. camembertii of the sole nitrogen source, glutamate, which was therefore used as an energy source in addition to be a carbon (and nitrogen) source. Lactate was only used for energy supply during stationary state, as also recorded during G. candidum pure culture.     

Multiparasitism by the pupal parasitoids, Xanthopimpla stemmator (Hymenoptera: Ichneumonidae) and Pediobius furvus (Hymenoptera: Eulophidae) on two African cereal stemborers, Chilo partellus (Lepidoptera: Crambidae) and Busseola fusca (Lepidoptera: Noctuidae)

The outcome of multiparasitism by two pupal parasitoids, the exotic solitary ichneumonid Xanthopimpla stemmator and the indigenous gregarious eulophid Pediobius furvus, was studied using the invasive crambid stem borer Chilo partellus and the indigenous noctuid Busseola fusca as hosts. Two parasitism sequences were observed, where X. stemmator oviposited before P. furvus, and vice versa. In addition, the effect of time between first and second parasitism on parasitoid emergence, development, sex ratio, and number of offspring was assessed. For most treatments, time interval between parasitism had no significant effect on the percentage if pupae producing either P. furvus or X. stemmator. In general, X. stemmator outcompeted P. furvus irrespective of the order of oviposition, time interval between ovipositions and host species. Further studies, especially on host finding capacity of the two parasitoid species are required to determine the competitiveness of the two species under field conditions.     

Influence of chemical and visual stimuli in food-search behaviour of Procambarus clarkii under clear conditions

Chemical communication may play a major role in aquatic environments because of visibility limitations, but when turbidity is reduced do chemical and visual stimuli interact to elicit food-search behaviour by Procambarus clarkii? Does P. clarkii use visual cues to detect its prey? We conducted behavioural experiments in a Y maze, under non-turbid conditions. In the experiments P. clarkii was exposed to chemical plus visual (CV) and visual only (V) stimuli transmitted by Chironomus riparius. The results revealed that P. clarkii detected CV and V cues associated with the presence of C. riparius. In controls, with no prey, crayfish displayed only searching behaviour, whereas in treatments they exhibited searching, detection and attack behaviours. Further, there were no significant differences between CV and V stimuli in the mean number of attacks performed by crayfish. Thus, our findings indicate that under low turbidity, visual cues are sufficient to mediate prey detection by P. clarkii.