藏羚集群产羔与其胃肠道寄生虫传播和感染的风险

食草动物集群有利于降低被捕食的风险,同时集群也会增加感染和传播寄生物的风险。可可西里卓乃湖地区是雌性藏羚的重要产羔地,集群时间主要集中在6月上旬至7月上旬,停留时间不足30 d。区域内温度、湿度等气候因子对其粪便中的寄生虫卵发育到感染期可能存在重要影响。本研究于2018年6月9日在卓乃湖产羔地建立微气候观测仪收集当地气象数据的同时,收集新鲜藏羚粪便在当地室外分别放置0 d、10 d、15 d、20 d、25 d、30 d、35 d和约300 d,应用漂浮法检测35 d内不同时间段虫卵发育状况和放置近一年的存活幼虫数量。初步研究了卓乃湖区域内集群藏羚粪便中的优势寄生虫卵的发育及其越冬存活,探讨藏羚产羔地是否会增加藏羚胃肠道寄生虫传播和感染的风险。结果表明：(1) 6月9日至7月14日,藏羚产羔地平均温度为5℃,平均相对湿度81%;(2) 藏羚在卓乃湖产羔地集群期间,其粪便中的优势寄生虫卵不能发育到感染期 (第三期幼虫),如粪便中的优势线虫卵毛园属线虫 (Trichostrongylus sp.)、马歇尔属线虫 (Marshallagia sp.) 和细颈属线虫 (Nematodirus sp.) 在30 d内发育仅停留在第一期幼虫;优势种藏羚艾美耳球虫 (Eimeria pantholopensis) 和五道梁艾美耳球虫 (E.wudaoliangensis) 卵在25 d、30 d、35 d的孢子化率分别是0、18.9%、54.0%和0、13.5%、30.4%;(3) 很少有寄生虫卵能够越冬存活至第二年,在卓乃湖产羔地放置近一年的粪便中仅发现极少的马歇尔属线虫和细颈属线虫幼虫。研究认为藏羚在卓乃湖集群时发生胃肠道寄生虫传播和感染的风险较低,藏羚对产羔地的短时利用和迅速回迁是其避免增加胃肠道寄生虫病感染风险的重要行为策略,且产羔地的低温等气候环境利于对寄生虫的自然净化。     

不同根系分隔方式对栗和茶幼苗生长的影响

研究不同根系分隔方式对栗(Castanea mollissima)/茶(Camellia sinensis)间作地下部分相互作用和植物种间互作动态的影响, 探究根系互作对植株株高、基径和根系生长的影响, 可为栗/茶复合经营模式的可持续发展提供科学指导。该研究以栗/茶间作和相应单作为研究对象, 运用盆栽实验的根系分隔技术(塑料膜分隔、尼龙网分隔和不分隔), 分别利用logistic生长模型模拟栗和茶株高与基径生长动态过程, 利用幂函数研究株高-基径的异速生长关系, 并从细根发育角度分析地下部分相互作用对植物生长发育的影响。结果显示: 与单作茶相比, 间作茶塑料膜分隔方式地上部分、地下部分和总的干生物量以及根长、根表面积、根体积、分形丰度和直径为0.2-1.0 mm根的根长分别显著增加了357.1%、281.8%和345.2%以及74.3%、273.9%、244.8%、42.0%和382.4%。间作茶塑料膜分隔方式的株高渐进值比单作茶显著增加了30.9%, 尼龙网分隔方式的间作栗株高渐进值和基径渐进值比单作栗分别显著增加了21.9%和28.2%; 塑料膜分隔方式下间作茶株高达到最大增长速率的时间和间作栗的基径达到最大增长速率的时间比相应单作模式分别显著延迟了14和15天。不同处理中栗和茶的株高-基径异速生长均呈显著线性正相关关系, 且不分隔方式下间作栗和间作茶的株高-基径异速生长模型的斜率均表现为最小, 且均<1。结果表明, 栗和茶间作时, 栗地上部分通过遮阴促进茶幼苗侧根分枝数、细根根长和株高的生长来增加其干生物量累积, 但地下部分则表现为竞争作用, 且随着地下部分竞争作用的强度增加会逐渐抵消地上部分的促进作用, 最终植物种间相互作用表现为中性作用。     

Laboratory rearing of Hydrochus japonicus (Coleoptera: Hydrochidae) suggests larvae live at the water bottom

The aquatic larvae of the family Hydrochidae (Coleoptera) have been considered ‘mystery larvae’, because ecological knowledge about them is lacking. We discovered that Hydrochidae larvae (Hydrochus japonicus Sharp) are benthic via laboratory rearing. The larvae have a terminal spiracular atrium, but we did not observe them breathing at the water surface. The larvae fed on Naididae worms that were collected from the same habitat.     

A comparison of nuclear and cytoplasmic genetic effects on sperm competitiveness and female remating in a seed beetle

It is widely assumed that male sperm competitiveness evolves adaptively. However, recent studies have found a cytoplasmic genetic component to phenotypic variation in some sperm traits presumed important in sperm competition. As cytoplasmic genes are maternally transmitted, they cannot respond to selection on sperm and this constraint may affect the scope in which sperm competitiveness can evolve adaptively. We examined nuclear and cytoplasmic genetic contributions to sperm competitiveness, using populations of Callosobruchus maculatus carrying orthogonal combinations of nuclear and cytoplasmic lineages. Our design also enabled us to examine genetic contributions to female remating. We found that sperm competitiveness and remating are primarily encoded by nuclear genes. In particular, a male's sperm competitiveness phenotype was contingent on an interaction between the competing male genotypes. Furthermore, cytoplasmic effects were detected on remating but not sperm competitiveness, suggesting that cytoplasmic genes do not generally play a profound evolutionary role in sperm competition.     

Modelling the behaviour of Listeria monocytogenes in ground pork as a function of pH, water activity, nature and concentration of organic acid salts

AIMS: to study and model the effect of sodium acetate, sodium lactate, potassium sorbate and combination of acid salts on the behaviour of Listeria monocytogenes in ground pork. METHODS AND RESULTS: Water activity (a(w)), pH and concentration of acid salt of the meat were adjusted. The behaviour of inoculated L. monocytogenes was studied and modelled according to physicochemical parameters values. Whatever the acid salt concentration used, we observed an inhibition of the growth of L. monocytogenes at pH 5.6 and a(w) 0.95. At pH 6.2 and a(w) 0.97, addition of 402 mmol l(-1) of sodium lactate or 60 mmol l(-1) of potassium sorbate was required to observe a slower growth. CONCLUSIONS: The inhibitory effect of acid salts was a function of pH, a(w), as well as of the nature and concentration of acid salts added. When one acid salt was added, the Augustin's model (Augustin et al. 2005) yielded generally correct predictions of either the survival or growth of L. monocytogenes. SIGNIFICANCE AND IMPACT OF THE STUDY: The suggested model can be used for risk assessment concerning L. monocytogenes in pork products.     

Occurrence of moulds in drinking water

AIMS: In order to determine the occurrence of filamentous fungi in public drinking water systems in Norway, water from 14 water supply networks from all over the country was sampled and analysed. Networks with both ground and surface water sources were included in this study. METHODS AND RESULTS: During a one-year period, 273 water samples were collected. Frequencies of fungi in samples from raw water, treated water and from home and hospital installations were determined on the basis of incubation of 100 ml membrane-filtered samples on dichloran 18% glycerol agar media. Filamentous fungi were recovered from 62% of all samples. In ground water 42.3% of the samples were positive for mould growth, while surface waters yielded 69.7% positive samples. CONCLUSIONS: The risk to recover moulds from surface water is three times higher compared with ground water. It is more likely to detect moulds in cold waters and showers than in hot waters. SIGNIFICANCE AND IMPACT OF THE STUDY: By analysing the water reaching the consumers, the results reported in present study indicate that filamentous fungi in drinking water is not negligible, and that moulds should be considered as part of the microbiological analysis parameters in drinking water.     

Species of two paleoendemic sap beetle genera of the Tribe Nitidulini (Nitidulidae: Coleoptera) from the Baltic and Dominican amber

Omositoidea gigantea Schaufuss, 1892 is redescribed; O. pubescens sp. nov. from the Baltic amber, Palaeometopia dominicana gen. et sp. nov. and P. colorata gen. et sp. nov. from the Dominican amber are described. The taxonomic position of the two genera and their probable bionomy are discussed.     

Brain energy metabolism and neurotransmission at near-freezing temperatures: in vivo (1)H MRS study of a hibernating mammal

The brain of a hibernating mammal withstands physiological extremes that would result in cerebral damage and death in a non-hibernating species such as humans. To examine the possibility that this neuroprotection results from alterations in cerebral metabolism, we used in vivo(1)H NMR spectroscopy at high field (9.4 T) to measure the concentration of 18 metabolites (neurochemical profile) in the brain of 13-lined ground squirrels (Spermophilus tridecemlineatus) before, during, and after hibernation. Resolved in vivo(1)H NMR spectra were obtained even at low temperature in torpid hibernators ( approximately 7 degrees C). The phosphocreatine-to-creatine ratio was increased during torpor (+143%) indicating energy storage, and remained increased to a lesser extent during interbout arousal (IBA) (+83%). The total gamma-aminobutyric acid concentration was increased during torpor (+135%) and quickly returned to baseline during IBA. Glutamine (Gln) was decreased (-54%) during torpor but quickly returned to normal levels during IBA and after terminal arousal in the spring. Glutamate (Glu) was also decreased during torpor (-17%), but remained decreased during IBA (-20% compared with fall), and returned to normal level in the spring. Our observation that Glu and Gln levels are depressed in the brain of hibernators suggests that the balance between anaplerosis and loss of Glu and Gln (because of glutamatergic neurotransmission or other mechanisms) is altered in hibernation.     

Environmental effects on sexual size dimorphism of a seed-feeding beetle

Sexual size dimorphism is widespread in animals but varies considerably among species and among populations within species. Much of this variation is assumed to be due to variance in selection on males versus females. However, environmental variables could affect the development of females and males differently, generating variation in dimorphism. Here we use a factorial experimental design to simultaneously examine the effects of rearing host and temperature on sexual dimorphism of the seed beetle, Callosobruchus maculatus. We found that the sexes differed in phenotypic plasticity of body size in response to rearing temperature but not rearing host, creating substantial temperature-induced variation in sexual dimorphism; females were larger than males at all temperatures, but the degree of this dimorphism was smallest at the lowest temperature. This change in dimorphism was due to a gender difference in the effect of temperature on growth rate and not due to sexual differences in plasticity of development time. Furthermore, the sex ratio (proportion males) decreased with decreasing temperature and became female-biased at the lowest temperature. This suggests that the temperature-induced change in dimorphism is potentially due to a change in non-random larval mortality of males versus females. This most important implication of this study is that rearing temperature can generate considerable intraspecific variation in the degree of sexual size dimorphism, though most studies assume that dimorphism varies little within species. Future studies should focus on whether sexual differences in phenotypic plasticity of body size are a consequence of adaptive canalization of one sex against environmental variation in temperature or whether they simply reflect a consequence of non-adaptive developmental differences between males and females.