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1.
The results of an 11-month field study of the feeding behavior of adult yellow baboons (Papio cynocephalus)are presented. Although catholic feeders, the baboons are not unselective in their choice of foods, and a small number of foods account for the bulk of their feeding time and are significant determinants of their home-range utilization patterns. These preferred foods are consumed throughout the year, a response, perhaps, to relatively minor fluctuations in their availability. Seasonal changes in food abundance are, however, reflected in other aspects of the baboons’ feeding behavior, including a tendency to show greater day- to- day dietary variability during periods of higher rainfall and greater overall food availability. It is suggested that this, and other, aspects of baboon feeding behavior can be understood only in the context of the extremely “patchy” distribution of their food supplies.  相似文献   

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3.
北京地区蕨类植物区系分析   总被引:10,自引:3,他引:10  
葛源  于明  刘全儒 《西北植物学报》2006,26(8):1657-1662
对北京地区蕨类植物区系进行了初步分析,研究表明,北京共有蕨类植物77种,隶属于19科34属,以蹄盖蕨科、岩蕨科、鳞毛蕨科、卷柏科等为优势科,以岩蕨属、卷柏属、铁角蕨属等为优势属,科内及属内分化程度较低,种类组成贫乏;地理成分以温带成分占优势,有11属为温带分布属,占非世界分布属总数的61.11%,除世界种和中国特有种外,全为温带性质的种;生境特点以石生为主,大多数种类分布在北京西部和北部的山区;与河北的关系最为密切,其次为山西、内蒙、辽宁、山东,与秦岭也有一定的联系,与西藏的关系疏远。  相似文献   

4.
Colicin Biology   总被引:3,自引:0,他引:3       下载免费PDF全文
Colicins are proteins produced by and toxic for some strains of Escherichia coli. They are produced by strains of E. coli carrying a colicinogenic plasmid that bears the genetic determinants for colicin synthesis, immunity, and release. Insights gained into each fundamental aspect of their biology are presented: their synthesis, which is under SOS regulation; their release into the extracellular medium, which involves the colicin lysis protein; and their uptake mechanisms and modes of action. Colicins are organized into three domains, each one involved in a different step of the process of killing sensitive bacteria. The structures of some colicins are known at the atomic level and are discussed. Colicins exert their lethal action by first binding to specific receptors, which are outer membrane proteins used for the entry of specific nutrients. They are then translocated through the outer membrane and transit through the periplasm by either the Tol or the TonB system. The components of each system are known, and their implication in the functioning of the system is described. Colicins then reach their lethal target and act either by forming a voltage-dependent channel into the inner membrane or by using their endonuclease activity on DNA, rRNA, or tRNA. The mechanisms of inhibition by specific and cognate immunity proteins are presented. Finally, the use of colicins as laboratory or biotechnological tools and their mode of evolution are discussed.  相似文献   

5.
Females of the hump earwig, Anechura harmandi, are completely consumed by their offspring at the end of their care (matriphagy). The effect of this matriphagy was assessed by manipulative experiments. Matriphagy led to a delay in the dispersal of the nymphs and an increase in their survival rate. The same results were obtained when mothers were removed and the nymphs were given sufficient food. Females separated from their offspring after larval hatching failed to produce a second clutch, and three-quarters of them did not develop their ovaries. These results suggest that the survival of nymphs and their stay in the nest are dependent on food availability and that A. harmandi females are strictly semelparous.  相似文献   

6.
In many vernal pools, visibility is very poor because of the turbidity from suspended clay particles. For predatory species like Branchinecta gigas, these conditions can be detrimental to successful prey capture. In vernal lakes in central California, B. gigashave developed specialized hunting modes to capture anostracan prey in pools of low visibility. The position of their body, the kinematics of their locomotion, and their reduced eye size suggested the possibility of novel sensory structures on their antennae and/or their cercopods designed to enhance their prey capture abilities. Using Scanning Electron Microscopy, we investigated the presence and design of sensory setae on the antennae and cercopods of B. gigas. On both males and females, there are dense patches of sensilla along the length of the antennae. They are oriented ventrally and slightly anteriorly. These antennal setae appear to be chemosensory in structure and position; they resemble antennal setae of other branchiopods. However, the setae of the cercopods are unusual in their morphology and location on the appendage. The cercopods, which are bent over the head in the hunting position, have a linear arrangement of specialized setae on their ventral side. They are jointed setae with an anterior crown of protective spines. The setal joint only permits limited abduction either toward the head in the hunting position or ventrally when swimming. These setae appear to be mechanosensory in function and may be adaptations to a raptorial lifestyle. They correlate well with the behavioral components of hunting in B. gigasand their complex prey capture mechanism.  相似文献   

7.
Johnson et al. (2013) found that morphometric measurements of dragonfly wings taken from actual specimens and measurements taken from whole-drawer images of those specimens were equally accurate. We do not believe that their conclusions are justified by their data and analysis. Our reasons are, first, that their study was constrained in ways that restrict the generalisability of their results, but second, and of far greater significance, their statistical approach was entirely unsuited to their data and their results misled them to erroneous conclusions. We offer an alternative analysis of their data as published. Our reanalysis demonstrates, contra Johnson et al., that measurements from scanned images are not a reliable substitute for direct measurement.  相似文献   

8.
The Freckled Nightjar Caprimulgus tristigma and the Blackish Nightjar C. nigrescens are widespread and common within their rupicolous habitat, in the Afrotropics and Neotropics respectively, and may therefore be considered as successful in their adaptation to this habitat, a niche that has not been exploited by any other nightjar species. However, apart from a plumage pattern that matches a rocky substrate, their known life histories provide no common factors to explain this adaptive success. The factors that they do share are common to most other nightjars. While they nest and roost on rocks, their breeding biology is remarkably different. The contrasts and lack of convergence are surprising, and suggest that these two species are not as closely related as their current congeneric status implies. This is supported by recent molecular studies that place the African and South American Caprimulgus species in different well-supported clades.  相似文献   

9.
ABSTRACT

Since early 2016, part of the Malian urban refugees living in Bobo-Dioulasso, Burkina Faso, have to “capitalize” on their refugee status to make ends meet. By examining when, why, and how the refugee status transmutes into an economic asset, this article shows how the possibilities to negotiate with the refugee category vary significantly within this group of forced migrants. Indeed, categories are not only imposed on people, but are negotiated by the actors themselves in their interactions and within their social and political economies. My article shows how the refugees’ ability or possibility to participate in the co-construction of their category is shaped by both the social and political context in which they are, as well as by wider intersectional and structural dynamics in which their lives are situated, such as socio-economic class, gender and race.  相似文献   

10.
《MABS-AUSTIN》2013,5(1):29-30
Apart from the nifty science behind their development, are monoclonal antibodies (mAbs) different than other new technologies? As highlighted by Cohen and Wilson in their interesting new paper, mAbs are distinctive from most traditional pharmaceuticals in some ways: their relatively high prices; their high costs of development; their mode of administration; the fact that, unlike many other drugs, they offer disease modification not simply symptomatic relief; the frequency of supplemental indications and off-label use – much of it recognized in drug compendia and reimbursable; and the lack of a clear pathway for their generic substitution.  相似文献   

11.
Book Reviews     
《Anthrozo?s》2013,26(3):206-226
Abstract

A study of the attitudes and actions of 281 dog owners towards neutering their animals is reported from New Providence, The Bahamas. Owner attitudes towards neutering are associated with different sterilization rates of dogs. While owners' gender is associated with differences in attitudes, these differences are not necessarily associated with owner behavior with respect to neutering their animals. Men, more than women, want to have animals for long-term breeding. No evidence is found to support the belief that men are less likely to neuter their dogs than women, but younger owners are less likely than older owners to neuter their dogs. A comparison with a study from Australia suggests that Bahamians are more likely to project human traits on to their animals and so appear more reluctant to have their dogs neutered.  相似文献   

12.

Background  

It has been understood that biological networks have modular organizations which are the sources of their observed complexity. Analysis of networks and motifs has shown that two types of hubs, party hubs and date hubs, are responsible for this complexity. Party hubs are local coordinators because of their high co-expressions with their partners, whereas date hubs display low co-expressions and are assumed as global connectors. However there is no mutual agreement on these concepts in related literature with different studies reporting their results on different data sets. We investigated whether there is a relation between the biological features of Saccharomyces Cerevisiae 's proteins and their roles as non-hubs, intermediately connected, party hubs, and date hubs. We propose a classifier that separates these four classes.  相似文献   

13.
Saccharomyces species, which are mostly used in the food and beverage industries, are known to differ in their fermentation efficiency and tolerance of adverse fermentation conditions. However, the basis of their difference has not been fully elucidated, although their genomes have been sequenced and analyzed. Five strains of four Saccharomyces species (S. cerevisiae, S. kudriavzevii, S. bayanus, and S. paradoxus), when grown in parallel in laboratory conditions, exhibit very similar basic physiological parameters such as membrane potential, intracellular pH, and the degree to which they are able to quickly activate their Pma1 H+-ATPase upon glucose addition. On the other hand, they differ in their ability to proliferate in media with a very low concentration of potassium, in their osmotolerance and tolerance to toxic cations and cationic drugs in a growth-medium specific manner, and in their capacity to survive anhydrobiosis. Overall, S. cerevisiae (T73 more than FL100) and S. paradoxus are the most robust, and S. kudriavzevii the most sensitive species. Our results suggest that the difference in stress survival is based on their ability to quickly accommodate their cell size and metabolism to changing environmental conditions and to adjust their portfolio of available detoxifying transporters.  相似文献   

14.
Hydroxycinnamates including p-coumaric acid, caffeic acid, ferulic acid, sinapic acid, and their esterified/etherified conjugates such as chlorogenic acids are abundant in cereals, coffee, fruit and vegetables. Studies have shown their potential in the prevention of chronic diseases such as cardiovascular disease and cancer. The impact of these dietary hydroxycinnamates on health depends on their bioavailability. In this article, in vivo and in vitro studies pertaining to bioavailability of hydroxycinnamates are reviewed and discussed. The chemical structures, existing forms, and/or doses of hydroxycinnamates may affect their metabolic fate. Limited studies suggest that the relative bioavailability of hydroxycinnamates may be in the following order: chlorogenic acid < rosmarinic acid < caffeic acid < ferulic acid < p-coumaric acid. Bound hydroxycinnamates generally have lower bioavailability than their monomer counterparts. Further pharmacokinetic and phamacodynamic studies are required to characterize the metabolism of hydroxycinnamates and their potential health impact in humans.  相似文献   

15.
Interactions among species, which range from competition to facilitation, have profound effects on ecosystem functioning. Large carnivores are of particular importance in shaping community structure since they are at the top of the food chain, and many efforts are made to conserve such keystone species. Despite this, the mechanisms of carnivore interactions are far from understood, yet they are key to enabling or hindering their coexistence and hence are highly relevant for their conservation. The goal of this review is thus to provide detailed information on the extents of competition and facilitation between large carnivores and their impact in shaping their life histories. Here, we use the example of spotted hyaenas (Crocuta crocuta) and lions (Panthera leo) and provide a comprehensive knowledge of their interactions based on meta‐analyses from available literature (148 publications). Despite their strong potential for both exploitation and interference competition (range and diet overlap, intraguild predation and kleptoparasitism), we underline some mechanisms facilitating their coexistence (different prey‐age selection and scavenging opportunities). We stress the fact that prey abundance is key to their coexistence and that hyaenas forming very large groups in rich ecosystems could have a negative impact on lions. We show that the coexistence of spotted hyaenas and lions is a complex balance between competition and facilitation, and that prey availability within the ecosystem determines which predator is dominant. However, there are still many gaps in our knowledge such as the spatio‐temporal dynamics of their interactions. As both species' survival becomes increasingly dependent on protected areas, where their densities can be high, it is critical to understand their interactions to inform both reintroduction programs and protected area management.  相似文献   

16.
Parasites can induce alterations in host phenotypes in order to enhance their own survival and transmission. Parasites of social insects might not only benefit from altering their individual hosts, but also from inducing changes in uninfected group members. Temnothorax nylanderi ant workers infected with the tapeworm Anomotaenia brevis are known to be chemically distinct from nest-mates and do not contribute to colony fitness, but are tolerated in their colonies and well cared for. Here, we investigated how tapeworm- infected workers affect colony aggression by manipulating their presence in ant colonies and analysing whether their absence or presence resulted in behavioural alterations in their nest-mates. We report a parasite-induced shift in colony aggression, shown by lower aggression of uninfected nest-mates from parasitized colonies towards conspecifics, potentially explaining the tolerance towards infected ants. We also demonstrate that tapeworm-infected workers showed a reduced flight response and higher survival, while their presence caused a decrease in survival of uninfected nest-mates. This anomalous behaviour of infected ants, coupled with their increased survival, could facilitate the parasites'' transmission to its definitive hosts, woodpeckers. We conclude that parasites exploiting individuals that are part of a society not only induce phenotypic changes within their individual hosts, but in uninfected group members as well.  相似文献   

17.
Biodiversity of freshwater fungi   总被引:5,自引:0,他引:5  
There are more than 600 species of freshwater fungi with more known from temperate, as compared to tropical regions. These includeca 340 ascomycetes, 300 deuteromycetes, and a number of lower fungi which are not discussed here.Aniptodera, Annulatascus, Massarina, Ophioceras andPseudohalonectria are common freshwater ascomycetes, which appear to be well adapted for this lifestyle either in their ascospore types or their competitive-degradative characters. The most common genera of wood-inhabiting deuteromycetes includeCancellidium, Dactylaria, Dictyosporium andHelicomyces. They are categorized into four groups depending on their form and life style: the ingoldian hyphomycetes; the aero-aquatic hyphomycetes; the terrestrial-aquatic hyphomycetes; and the submerged-aquatic hyphomycetes. The adaptations of aquatic fungi for their dispersal and subsequent attachment to new substrates are discussed.  相似文献   

18.
Lysozymes in the animal kingdom   总被引:11,自引:0,他引:11  
Lysozymes (EC 3.2.1.17) are hydrolytic enzymes, characterized by their ability to cleave the β-(1,4)-glycosidic bond between N-acetylmuramic acid and N-acetylglucosamine in peptidoglycan, the major bacterial cell wall polymer. In the animal kingdom, three major distinct lysozyme types have been identified — the c-type (chicken or conventional type), the g-type (goose-type) and the i-type (invertebrate type) lysozyme. Examination of the phylogenetic distribution of these lysozymes reveals that c-type lysozymes are predominantly present in the phylum of the Chordata and in different classes of the Arthropoda. Moreover, g-type lysozymes (or at least their corresponding genes) are found in members of the Chordata, as well as in some bivalve mollusks belonging to the invertebrates. In general, the latter animals are known to produce i-type lysozymes. Although the homology in primary structure for representatives of these three lysozyme types is limited, their three-dimensional structures show striking similarities. Nevertheless, some variation exists in their catalytic mechanisms and the genomic organization of their genes. Regarding their biological role, the widely recognized function of lysozymes is their contribution to antibacterial defence but, additionally, some lysozymes (belonging to different types) are known to function as digestive enzymes.  相似文献   

19.
Puroindolines, for years largely investigated for their involvement in wheat kernel hardness, have recently attracted attention thanks to their possible role as antimicrobial proteins. With the aim to enhance our knowledge of these proteins we studied their localization in the kernel, and their antimicrobial activity in vitro against six different bacterial strains. Immunolocalization showed that both the PINs are strongly concentrated in the aleurone layer, but also highly present in the endosperm. Interestingly we observed that puroindolines not only have the same spatial distribution in the kernel, they are also always found co-localized. Their co-localization suggests that they could cooperate in defending the plant against pathogens. We therefore tested antimicrobial activity of PINA and PINB, and a putative synergism between these proteins. The results showed that the two polypeptides can in vitro inhibit growth of all the bacteria tested; furthermore when combined together they are able to enhance each other’s toxicity. In view of their antimicrobial activity and of their natural presence in Triticum aestivum wheat flour, puroindolines look promising antibacterial agents and thus deserve further studies aimed at establishing their possible future applications in fields of food and health care. Since PINs were still detectable in bakery products, these proteins may be promising tools in investigating natural ways of food preservation.  相似文献   

20.
Guapira graciliflora and Neea theifera are taxonomically related species of the tribe Pisoneae. Both species are found in the same environment, the Brazilian Cerrado, and therefore, are subjected to similar selective pressures. These species occur in oligotrophic environments, yet contain high concentrations of nitrogen in their leaves. The present study was carried out to investigate the ecological role of nitrogen in herbivory on these species. The differences in the N content, compositions of secondary N-metabolites, mechanical resistance, and water content between their leaves indicate that these species have different adaptations as defense mechanisms. In both species, their high nitrogen content seems to promote herbivory. The presence of secondary nitrogen metabolites does not prevent the species from suffering intense damage by herbivores on their early leaves. The herbivory rates observed were lower for mature leaves of both species than for young leaves. In G. graciliflora, nutritional content and leaf hardness are the most important variables correlated with reduction of herbivory rates, whereas in N. theifera, N compounds are also correlated with herbivory rates. Despite the differences in the strategies of these two species, they exhibit a similar efficiency of protection against natural enemies because their total herbivory rates are similar. The difference in their N defense allocation may imply benefits for survival under Cerrado conditions. We briefly discuss the oligotrophic habitat conditions of the studied plants and possible advantages of their strategies of N accumulation and metabolic uses.  相似文献   

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