The efficiency of adaptive search tactics for different prey distribution patterns: a simulation model based on the behaviour of juvenile plaice

Juvenile plaice Pleuronectes platessa are particularly useful for studying forager search behaviour because their search paths are essentially two dimensional, and punctuated by natural stops. Their prey occur in a range of natural distributions from highly aggregated to over‐dispersed. Juvenile plaice use area‐restricted search near aggregated prey and extensive search, consisting of longer moves and fewer turns, between aggregations and when searching for dispersed prey. They search for less conspicuous prey items mainly in the pauses between movements. This saltatory search behaviour contrasts with the continuous search that is usually assumed in search models. A simulation model of saltatory search behaviour showed that a strategy combining extensive and intensive search allows the efficient exploitation of a range of natural prey distribution patterns, and that it is particularly effective when the search behaviour is controlled by perceived prey density. This allows the predator to respond to the localized aggregations which often occur in nature. The selective use of intensive search was more efficient than the continuous use of extensive search even in prey distribution patterns that were statistically over‐dispersed.     

A Study of Changes in Uterine Leucocytes During Early Pregnancy in the Mouse-vole Interspesific Pregnancies

Mouse and vole embryos were allogeneically and xenogeneically transferred into pseudopregnant CD-1 and immunodeficient （scid） female mice, and we investigated the distribution of uterine leucocytes cells in the implantation sites on days 5,6,and 7 of pregnancy. Macrophages were evenly distributed in the endometrium on days 5 N 7. Neutrophils were rarely seen on days 5 ~ 7, but lymphoeytes were found throughout the endometrium,often in groups associated with glands or the luminal epithelium. The number of uNK cells increased markedly at the mesometrial triangle and the outer decidual area in the CD-1 uteri containing vole embryos; by contrast, scid uteri having vole embryos showed almost the same number as those having mouse embryos. Mast cells were present in large numbers at the myometrium,but rarely in the decidua in all types of pregnant uteri. Cells at the myometrium were more numerous in xenogeneic than in allogeneic transfer. Many mast cells appeared in the inner decidua where xenogeneically transferred vole embryos were dead and aborted. These results suggest the possibility that uterine leucocytes mediate various immunological events in the mouse-vole interspesific pregnancies.     

Loss of preferred mates forces female satin bowerbirds (Ptilonorhynchus violaceus) to increase mate searching

Variation in mate choice among females can have important consequences for the operation of sexual selection, and can result from differences in the way females search for mates. Our previous work indicates that female satin bowerbirds Ptilonorhynchus violaceus alter their mate-searching patterns according to long-term experience. Females which mate with very attractive males mate with the same males in the following year, thereby reducing their search. In contrast, females which fail to encounter very attractive males typically reject their previous mates and search for more attractive males in the following year, thereby increasing their search. Here we report results from a natural experiment consistent with these observations. Five males, including the most attractive male of 1997, failed to re-establish display sites in 1998, most probably dying over winter. We monitored the mate-searching behaviour of females which mated with these males in 1997 to determine how the loss of attractive mates affects subsequent mate-searching patterns. Females which lost their mates sampled more males compared with their own search patterns in 1997 and with faithful females in 1998. Results from this natural experiment indicate that the loss of attractive and preferred mates forces females to increase their search and provide evidence that long-term experience with males shapes mate-searching behaviour.     

Natural levels of colour polymorphism reduce performance of visual predators searching for camouflaged prey

Polymorphism, the coexistence of two or more variants within a population, has served as a classic model system to address questions about the evolution and maintenance of intraspecific variation. It has been hypothesized that a natural level of colour polymorphism may impair the search efficiency of visually orientated predators. To test this polymorphism protects hypothesis, we asked human participants to search for images of natural black, striped or grey Tetrix subulata grasshopper colour morphs presented against photographs of their natural habitat on computer screens. Fewer grasshoppers were detected when morphs were presented in mixed than in uniform sequences. All three morphs benefited to comparable degrees, in terms of reduced detection, from being presented in polymorphic sequences. Our findings demonstrate that natural levels of polymorphic variation can impede the efficiency of visually orientated predators and increase survival of prey. This protective effect supports the limited attention hypothesis, explains why predators develop ‘search images’, may account for the spread and establishment of novel colour variants, and contributes to maintenance of polymorphisms. © 2014 The Authors. Biological Journal of the Linnean Society published by John Wiley & Sons Ltd on behalf of The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 112 , 546–555.     

Impact of natural products in modern drug development

Usage of natural substances as therapeutic agents in modern medicine has sharply declined from the predominant position held in the early decades of last century, but search for bioactive molecules from nature (plants, animals, microflora) continues to play an important role in fashioning new medicinal agents. With the advent of modern techniques, instrumentation and automation in isolation and structural characterisation, we have on hand an enormous repository of natural compounds. In parallel to this, biology has also made tremendous progress in expanding its frontiers of knowledge. An interplay of these two disciplines constitutes the modern thrust in research in the realm of compounds elaborated by nature. The purpose of this article is to underline how natural products research continues to make significant contributions in the domain of discovery and development of new medicinal products. It is proposed to present the material under several heads, each of which has made natural products research relevant in the search for new and better medication.     

Diversity and biogeography of marine actinobacteria

The actinomycetes, although not all the Actinobacteria, are easy to isolate from the marine environment. However, their ecological role in the marine ecosystem is largely neglected and various assumptions meant there was little incentive to isolate strains for search and discovery of new drugs. However, the marine environment has become a prime resource in search and discovery for novel natural products and biological diversity, and marine actinomycetes turn out to be important contributors. Similarly, striking advances have been made in marine microbial ecology using molecular techniques and metagenomics, and actinobacteria emerge as an often significant, sometimes even dominant, environmental clade. Both approaches - cultivation methods and molecular techniques - are leading to new insights into marine actinobacterial biodiversity and biogeography. Very different views of actinobacterial diversity emerge from these, however, and the true extent and biogeography of this are still not clear. These are important for developing natural product search and discovery strategies, and biogeography is a hot topic for microbial ecologists.     

Genetic and non-genetic control of search duration in adults of two morphs of Drosophila melanogaster

Phenotypic plasticity in search duration of two lines of Drosophila melanogaster selected for short and long search duration (rover/sitter) was demonstrated by altering the sucrose concentration of the feeding stimulus and the period of starvation prior to testing. Although the inherited traits were apparent over a wide range of resource quality and deprivation periods, either variable, within natural environmental variation, could equalize the search duration scores of individuals from the high and low selected lines.     

Eye Movements,Visual Search and Scene Memory,in an Immersive Virtual Environment

Visual memory has been demonstrated to play a role in both visual search and attentional prioritization in natural scenes. However, it has been studied predominantly in experimental paradigms using multiple two-dimensional images. Natural experience, however, entails prolonged immersion in a limited number of three-dimensional environments. The goal of the present experiment was to recreate circumstances comparable to natural visual experience in order to evaluate the role of scene memory in guiding eye movements in a natural environment. Subjects performed a continuous visual-search task within an immersive virtual-reality environment over three days. We found that, similar to two-dimensional contexts, viewers rapidly learn the location of objects in the environment over time, and use spatial memory to guide search. Incidental fixations did not provide obvious benefit to subsequent search, suggesting that semantic contextual cues may often be just as efficient, or that many incidentally fixated items are not held in memory in the absence of a specific task. On the third day of the experience in the environment, previous search items changed in color. These items were fixated upon with increased probability relative to control objects, suggesting that memory-guided prioritization (or Surprise) may be a robust mechanisms for attracting gaze to novel features of natural environments, in addition to task factors and simple spatial saliency.     

Natural Variation in OsPRR37 Regulates Heading Date and Contributes to Rice Cultivation at a Wide Range of Latitudes

Heading date and photoperiod sensitivity are fundamental traits that determine rice adaptation to a wide range of geographic environments. By quantitative trait locus （QTL） mapping and candidate gene analysis using whole- genome re-sequencing, we found that Oryza sativa Pseudo-Response Regulator37 （OsPRR37; hereafter PRR37） is respon- sible for the Early heading7-2 （EH7-2）/Heading date2 （Hd2） QTL which was identified from a cross of late-heading rice ＇Milyang23 （M23）＇ and early-heading rice ＇H143＇. H143 contains a missense mutation of an invariantly conserved amino acid in the CCT （CONSTANS, CO-like, and TOC1） domain of PRR37 protein. In the world rice collection, different types of nonfunctional PRR37 alleles were found in many European and Asian rice cultivars. Notably, the japonica varieties harboring nonfunctional alleles of both Ghd7/Hd4 and PRR37/Hd2 flower extremely early under natural long-day condi- tions, and are adapted to the northernmost regions of rice cultivation, up to 53~ N latitude. Genetic analysis revealed that the effects of PRR37 and Ghd7 alleles on heading date are additive, and PRR37 down-regulates Hd3a expression to suppress flowering under long-day conditions. Our results demonstrate that natural variations in PRR37/Hd2 and GhdT/ Hd4 have contributed to the expansion of rice cultivation to temperate and cooler regions.     

Demonstrating the suitability of genetic algorithms for driving microbial ecosystems in desirable directions

The functioning of natural microbial ecosystems is determined by biotic interactions, which are in turn influenced by abiotic environmental conditions. Direct experimental manipulation of such conditions can be used to purposefully drive ecosystems toward exhibiting desirable functions. When a set of environmental conditions can be manipulated to be present at a discrete number of levels, finding the right combination of conditions to obtain the optimal desired effect becomes a typical combinatorial optimisation problem. Genetic algorithms are a class of robust and flexible search and optimisation techniques from the field of computer science that may be very suitable for such a task. To verify this idea, datasets containing growth levels of the total microbial community of four different natural microbial ecosystems in response to all possible combinations of a set of five chemical supplements were obtained. Subsequently, the ability of a genetic algorithm to search this parameter space for combinations of supplements driving the microbial communities to high levels of growth was compared to that of a random search, a local search, and a hill-climbing algorithm, three intuitive alternative optimisation approaches. The results indicate that a genetic algorithm is very suitable for driving microbial ecosystems in desirable directions, which opens opportunities for both fundamental ecological research and industrial applications.     

Pre- and post-zygotic reproductive isolation between co-occurring Mussaenda pubescens var. alba and A/I. shikokiana （Rubiaceae）

Reproductive isolation is a fundamental require- ment for speciation and includes several sequential stages. Few studies have determined the relative contributions of pre- and post-zygotic reproductive isolation in plants, especially between relative species with clear differentiation in flower form. To investigate the mechanisms responsible for repro- ductive isolation in sympatric A4ussaenda pubescens var. alba and Mussaenda shikokiana （Rubiaceae） in Guangxi Province, China, we made observations of flowering phenology, patterns of insect visitation, and conducted pollination experiments, including artificial hybridization. The two species had over- lapping flowering times and were pollinated by overlapping pollinators; however, their relative importance differed significantly with M. pubescens visited more commonly by bees and M. shikokiana more frequently by butterflies. Using vegetative and floral characters and molecular evidence based on nuclear ribosomal internal and external transcribed spacer regions we detected seven naturally occurring hybrids among a sample of approximately 125 individuals. Hybrids were characterized by morphologies that most closely resembled their maternal parents based on chloroplast evidence. Studies of artificially synthesized and natural hybrids demonstrated that hybrid seed had very low germination rates and naturally occurring hybrids exhibited pollen sterility. Post-zygotic reproductive isolating mechanisms play a primary role in limiting gene exchange between co-occurring species and maintaining species integrity in areas of sympatry.     

Design of Array-Type Compound Libraries that Combine Information from Natural Products and Synthetic Molecules

A new approach to the design of compound libraries, named MetaFocus (Metabolite-Focused library), is presented that exploits information encoded in natural molecules and combines naturally occurring and synthetic compounds. An important goal of the MF approach is the identification of synthetic compounds that mimic properties of natural molecules that are difficult to obtain in sufficient quantities or to synthesize. Compounds in MetaFocus (MF) arrays are focused on natural molecules with attractive therapeutic effects. Similarity search and diversity design techniques are employed to generate compound arrays that start from a selected natural molecule, add similar molecules, either from natural or synthetic sources, and diversify scaffolds derived from these molecules. Since the identification of similar molecules from natural and synthetic sources plays a significant role in our library design efforts, the performance of fingerprint-type search tools was systematically assessed in a newly assembled test database consisting of 16 biological activity classes. MF arrays are organized as an easily expandable and searchable data structure and serve as a knowledge base for drug discovery applications. Here we introduce the design principles and organization of MF arrays and present example applications.     

The evolution of colour polymorphism in British winter‐active Lepidoptera in response to search image use by avian predators

Phenotypic polymorphism in cryptic species is widespread. This may evolve in response to search image use by predators exerting negative frequency‐dependent selection on intraspecific colour morphs, ‘apostatic selection’. Evidence exists to indicate search image formation by predators and apostatic selection operating on wild prey populations, though not to demonstrate search image use directly resulting in apostatic selection. The present study attempted to address this deficiency, using British Lepidoptera active in winter as a model system. It has been proposed that the typically polymorphic wing colouration of these species represents an anti‐search image adaptation against birds. To test (a) for search image‐driven apostatic selection, dimorphic populations of artificial moth‐like models were established in woodland at varying relative morph frequencies and exposed to predation by natural populations of birds. In addition, to test (b) whether abundance and degree of polymorphism are correlated across British winter‐active moths, as predicted where search image use drives apostatic selection, a series of phylogenetic comparative analyses were conducted. There was a positive relationship between artificial morph frequency and probability of predation, consistent with birds utilizing search images and exerting apostatic selection. Abundance and degree of polymorphism were found to be positively correlated across British Lepidoptera active in winter, though not across all taxonomic groups analysed. This evidence is consistent with polymorphism in this group having evolved in response to search image‐driven apostatic selection and supports the viability of this mechanism as a means by which phenotypic and genetic variation may be maintained in natural populations.     

Evolution and Optimality of Similar Neural Mechanisms for Perception and Action during Search

A prevailing theory proposes that the brain''s two visual pathways, the ventral and dorsal, lead to differing visual processing and world representations for conscious perception than those for action. Others have claimed that perception and action share much of their visual processing. But which of these two neural architectures is favored by evolution? Successful visual search is life-critical and here we investigate the evolution and optimality of neural mechanisms mediating perception and eye movement actions for visual search in natural images. We implement an approximation to the ideal Bayesian searcher with two separate processing streams, one controlling the eye movements and the other stream determining the perceptual search decisions. We virtually evolved the neural mechanisms of the searchers'' two separate pathways built from linear combinations of primary visual cortex receptive fields (V1) by making the simulated individuals'' probability of survival depend on the perceptual accuracy finding targets in cluttered backgrounds. We find that for a variety of targets, backgrounds, and dependence of target detectability on retinal eccentricity, the mechanisms of the searchers'' two processing streams converge to similar representations showing that mismatches in the mechanisms for perception and eye movements lead to suboptimal search. Three exceptions which resulted in partial or no convergence were a case of an organism for which the targets are equally detectable across the retina, an organism with sufficient time to foveate all possible target locations, and a strict two-pathway model with no interconnections and differential pre-filtering based on parvocellular and magnocellular lateral geniculate cell properties. Thus, similar neural mechanisms for perception and eye movement actions during search are optimal and should be expected from the effects of natural selection on an organism with limited time to search for food that is not equi-detectable across its retina and interconnected perception and action neural pathways.     

Testing the efficiency of sensory coding with optimal stimulus ensembles

According to Barlow's seminal "efficient coding hypothesis," the coding strategy of sensory neurons should be matched to the statistics of stimuli that occur in an animal's natural habitat. Using an automatic search technique, we here test this hypothesis and identify stimulus ensembles that sensory neurons are optimized for. Focusing on grasshopper auditory receptor neurons, we find that their optimal stimulus ensembles differ from the natural environment, but largely overlap with a behaviorally important sub-ensemble of the natural sounds. This indicates that the receptors are optimized for peak rather than average performance. More generally, our results suggest that the coding strategies of sensory neurons are heavily influenced by differences in behavioral relevance among natural stimuli.     

蛋白质骨架库的构建及其在功能蛋白质设计中的应用

利用活性位点嫁接设计新的功能蛋白质的方法需要功能模体和蛋白质骨架两种构件。出于活性位点嫁接的需要,我们构建了一个蛋白质骨架库,且提供搜索与功能模体相配骨架的工具及其评估方法。并用两个活性位点的嫁接进行了检验。     

Search mechanism of a stream grazer in patchy environments: the role of food abundance

Summary The search behavior of the grazing stream insect Baetis tricaudatus (Ephemeroptera: Baetidae) was examined in field and laboratory experiments. Regardless of food abundance in experimental habitats, nymphs spent significantly more time in food patches than predicted if they had moved randomly with respect to patches. A significant reduction in movement rate within patches relative to movement rate between patches largely accounted for these results. The movement pattern within patches was highly systematic and in agreement with predictions of optimal foraging theory since food was uniformly distributed within patches. Between-patch search movements were affected by food abundance in the most recently grazed patch. Search intensity after departure from a patch was positively related to food abundance in the patch while movement rate after patch departure was inversely related to patch food level. These effects produced between-patch movement patterns that were suboptimal in the experimental habitats because they resulted in revisitation of previously depleted patches. However, differences between experimental and natural habitats in the spatial occurrence of patch types suggest that Baetis between-patch search behavior may be adaptive in natural habitats.     

复合天然抗氧化制剂的抗氧化、抗运动疲劳、抗神经细胞氧化损伤作用研究

目的:观察复合天然抗氧化剂的抗氧化性能,抗运动疲劳及抗神经细胞氧化损伤的作用。方法:①采用光照核黄素生成O.2-,采用Fenton反应生成.OH,采用脂类过氧化反应生成L.,用顺磁波谱仪记录电子自旋共振ESR波谱。②建立力竭游泳运动模型,测定各组小鼠力竭性游泳的持续时间。③用氮蓝四唑NBT法测定肝脏和骨骼肌中SOD活力。④用硫代巴比妥酸TBA荧光比色法测定肝脏和骨骼肌中MDA的生成量。⑤测定经FeSo4处理后的脑细胞存活率和凋亡率。结果:①各实验组较对照组的电子自旋共振ESR波谱峰值显著降低,复合天然抗氧化制剂对O.-2和.OH有极强的清除作用,有效抑制脂质过氧化反应。②实验组较实验对照组游泳时间显著延长(P0.01);③实验组肝脏中SOD活力显著低于空白对照组(P0.01);实验组骨骼肌中SOD活力与空白对照组无显著差异(P0.05);实验对照组肝脏、骨骼肌中SOD活力显著低于空白对照组(P0.01,P0.05);实验组肝脏、骨骼肌中SOD活力显著高于实验对照组。④实验组肝脏和骨骼肌中MDA含量显著低于实验对照组(P0.01,P0.05);实验对照组肝脏和骨骼肌中MDA含量显著高于空白对照组(P0.01)。⑤实验组的细胞存活率明显高于实验对照组;空白对照组细胞的凋亡率低于实验组,实验组细胞的凋亡率低于实验对照组。结论:复合天然抗氧化制剂具有较强的抗氧化性能、抗运动疲劳及抗神经细胞氧化损伤作用。     

The crystal structure of AbsH3: A putative flavin adenine dinucleotide‐dependent reductase in the abyssomicin biosynthesis pathway

Natural products and natural product‐derived compounds have been widely used for pharmaceuticals for many years, and the search for new natural products that may have interesting activity is ongoing. Abyssomicins are natural product molecules that have antibiotic activity via inhibition of the folate synthesis pathway in microbiota. These compounds also appear to undergo a required [4 + 2] cycloaddition in their biosynthetic pathway. Here we report the structure of an flavin adenine dinucleotide‐dependent reductase, AbsH3, from the biosynthetic gene cluster of novel abyssomicins found in Streptomyces sp. LC‐6‐2.