麻雀幼鸟和成鸟逃逸距离的比较

逃逸是鸟类常用的反捕食手段。自然选择会优化鸟类的逃逸距离,以便在躲避被捕食风险和保持能量之间做出权衡。理论模型预测动物个体可依据期望寿命来调整自身的行为：期望寿命短的个体倾向于风险偏好,即逃逸距离短;而期望寿命长的个体倾向于风险回避,即逃逸距离长。同时,逃逸距离还受到外部因素（如人为干扰强度、鸟类群体大小）的影响。本研究在北京城区收集了麻雀（Passer montanus）145只成鸟和75只幼鸟的逃逸距离数据,发现麻雀成鸟比幼鸟有着更长的逃逸距离,且成鸟更可能是群体中首先逃逸的个体。此外,研究发现麻雀的逃逸距离随着人为干扰强度的增加而降低,随着群体大小增加而增加。本研究结果符合理论预期：存活率高的类群（成鸟）有着更长的逃逸距离。     

Responses of the saucer scallop Amusium balloti to potential predators

A high natural mortality rate has been documented for the saucer scallop Amusium balloti, an Australian scallop found on sediment bottoms at 30–60 m deep, but little is known about the causes of mortality. We studied escape responses of A. balloti to five consumers common in the bycatch of the scallop fishery as a means of identifying potential predators. The scallop showed a negligible to weak response when touched with the sea star Pentaceraster regulus and the red portunid crab Portunus rubromarginatus. The response was similar to that observed when the scallop was touched with a plastic object. In contrast, A. balloti showed a consistent and vigorous swimming response to contact with the slipper lobster Thenus orientalis, the blue swimmer crab Portunus pelagicus and the coral crab Charybdis cruciata. This was not a generalized response to crustaceans, given the scallop's weak response to the red portunid crab. This is the first report of a scallop that has a strong swimming escape response to contact with decapod crustacean predators.     

粤东地区野生杜鹃花资源及其开发利用

经调查统计,粤东地区野生杜鹃花有11种．其中．该区特产2种．模式植物2种,主要分布在该区北部山区。在调查的基础上就粤东地区野生杜鹃花资源的开发利用提出建议。     

关于HCMV 潜伏感染与激活感染研究的新进展

人巨细胞病毒(HCMV)是疱疹病毒科中最大的病毒,结构复杂,其感染在人群中非常普遍,近年来免疫妥协(immunocompromised)群体尤其是移植群体中的HCMV潜伏感染和激活感染越来越受到临床重视。本文就HCMV的感染与免疫、HCMV的致病机制、宿主的抗感染与免疫、HCMV的免疫逃逸、HCMV的潜伏与激活及HCMV相关研究的困境与展望近年来此方面研究新进展作一简要综述。     

Behavioural and endocrine fear responses in Japanese quail upon presentation of a novel object in the home cage

Most tests used to study fear in birds involve transferring them to a novel environment, which constitutes a bias in studies aiming at identifying the neural correlates of a specific fear-inducing situation. In order to investigate fear in birds with minimum interference by humans, behavioural and endocrine responses to the presentation of a novel object in the home cage were investigated in two lines of Japanese quail divergently selected for long or short duration of tonic immobility, a behavioural index of fear. Presentation of the novel object induced typical fear responses (avoidance of the object, increased pacing and increased plasma corticosterone levels) that were similar in the two lines of quail. Presentation of a novel object in the home cage thus appears to be a suitable stimulus to induce fear reactions in quail, with minimum interference from other motivational systems. The fact that quail of both lines reacted similarly in this test, while they are known to differ greatly in their behavioural responses to other fear-inducing tests, illustrates the multidimensional nature of fear.     

Tumor escape mechanisms in prostate cancer

Numerous immunotherapy trials have been carried out in prostate cancer (PC) patients, with induction of antigen-specific T cells in some cases. Despite this capability, limited success is seen in terms of tumor regression or survival. In this review, we discuss the evidence for tumor escape strategies that may contribute to vaccine failure in the setting of PC. These include defects in antigen presentation, production of immunosuppressive substances, induction of T cell death, T cell receptor dysfunction, and the presence of tolerogenic dendritic cells and regulatory T cells inside prostate tumors. It is clear that novel strategies aimed at preventing tumor escape, such as small molecular weight inhibitors of immunosuppressive molecules, adoptive transfer of TCR transgenic T cells, removal of Tregs, combined with anti-androgen therapy and prostate-specific vaccines, need to be examined further in PC patients.This article is a symposium paper from the conference Progress in Vaccination against Cancer 2005 (PIVAC 5), held in Athens, Greece, on 20–21 September 2005.     

Risk assessment by crow phenotypes in a hybrid zone

Predation is one of the most selective forces in evolution and, thus, predation may select against hybrids in narrow hybrid zones. It may be possible that parental phenotypes and hybrids differ in their responses towards predators or humans. As predation is difficult to observe I used flight-initiation distance (FID) as a metric of risk assessment. FID is a measurable outcome of the trade-off between fleeing and remaining. Here, I tested whether hybrid and parent crow phenotypes (Corvus corone, Corvus cornix) from the hybrid zone in Eastern Germany differ in their FID. Further, I measured many environmental and social variables to control statistically for their influence on FID. I sampled 154 individuals (53 hooded crows, 54 carrion crows, and 48 hybrids) in the hybrid zone in eastern Germany. I calculated a general linear model using a stepwise backward procedure to establish a minimum model containing only significant variables that explained FID in crows. The variable phenotype (hooded, carrion, hybrid) was then added to the model. There were no differences in FID between hybrids and both parental phenotypes types, suggesting similar risk assessment. This suggests that hybrids may behave similarly in their decision to flee as their parent phenotypes, which, in turn, provides no evidence for a selective disadvantage. An additional analysis focusing on pure phenotypic flocks showed that hybrids in pure hybrid flocks had a lower FID than both parental species in pure flocks. This suggests that hybrids in pure hybrid flocks may be at a disadvantage.     

Predators and avian community organization: an experiment in a semi-desert grassland

Summary We provide experimental evidence that predators are a major factor organizing a community of granivorous grassland birds (mostly emberizid finches). Our focus is not on the lethal effects of predators, but on the simple idea that (i) birds will not settle where they perceive a high risk of predation, and (ii) species differ in their perception of the safety of woody vegetative cover due to differences in antipredator escape behavior. Consistent with this idea is the fact that the composition of this grassland community responds markedly to minor manipulations in the distribution of woody cover. In particular, with the addition of cover to open grasslands, species with cover-dependent escape tactics increase in abundance, while the abundance of cover-independent species decreases greatly; this decrease may reflect aggression from cover-dependent species, but evidence suggests that some cover-independent species may actively avoid cover-rich areas per se. Non-predatory effects of cover, most notably those concerning food resources and microclimate, appear unable to explain these results. Predators may influence many communities of terrestrial vertebrates via species-specific responses to cover.     

A visually evoked escape response of the housefly

Summary Flies (Musca domestica) avoid danger by initiating a rapid jump followed by flight. To identify the visual cues that trigger the escape response in the housefly, we measured the timing and probability of escapes when the fly was presented with a variety of visual stimuli created by moving targets toward it. Our results show that an escape response is triggered by an approaching dark disk, but not by a receding dark disk. On the other hand, a bright disk elicits escape only when it recedes. A disk with black and white rings is less effective at eliciting escape than is a dark solid disk of the same size. This indicates that the darkening contrast produced by an approaching stimulus is a more crucial parameter than expansion cues contained in the optical flow. Escape is also triggered by a horizontally moving dark edge, but not by a moving bright edge or by a grating. An examination of several visual parameters reveals that the darkening contrast, measured from the onset of stimulation to the start of escape is nearly constant for a variety of stimuli that trigger escape reliably. Thus darkening contrast, coupled with motion may be crucial in eliciting the visually evoked escape response. Other visual parameters such as time-to-contact or target angular velocity seem to be relatively unimportant to the timing of escapes.Abbreviations P _s Probability of successful escape - r _disk radius of disk target - r _arena radius of shielding arena - v _disk linear velocity of disk target - v _edge linear velocity of edge - d _disk angular velocity of disk target boundary - _edge angular velocity of edge - _escape target distance at escape - d _start target distance before onset of target movement - h _edge height of the edge above fly - x _start distance from corner of triangle to start position of edge (0 or 50 mm) - x _escape distance from corner of triangle to the position of the edge when the fly escapes - x _center distance from corner of triangle to point above the center of the pad - x _total distance from the corner of the triangle to the base (height of triangle = base of triangle)     

Habitat-specific sensory-exploitative signals in birds: propensity of dipteran prey to cause evolution of plumage variation in flush-pursuit insectivores

Sensory exploitation occurs when signals trigger behavioral reactions that diminish the receiver's fitness. Research in this area focuses on the match between the signal's form and the receiver's sensitivity, but the effect of habitat on interspecific sensory exploitation is rarely addressed. Myioborus redstarts use conspicuous wing and tail displays of contrasting black-and-white plumage patches to flush dipteran insects, which are then pursued and captured in flight. Previous studies have shown that by increasing the distance at which insects perform an escape response, conspicuous visual displays improve the birds' foraging performance. We tested the hypothesis that selection for a visual signal that maximizes prey escape distance under local habitat conditions can lead to the evolution of geographic variation in plumage pattern among Myioborus redstarts. Using models of foraging birds, we recorded the escape responses of Dipterous insects to a range of plumage patterns and background tones (from light to dark) to determine whether the plumage pattern that maximizes prey flushing is dependent upon that habitat (background) against which birds are viewed by their prey. Our results indicate that the effectiveness of a particular plumage pattern in flushing dipteran prey depends strongly on the background against which that plumage pattern is displayed, and darker habitat (background) conditions generally favor plumages with more extensive patches of white in the tail. However, the addition of white wing patches that imitate the plumage of the painted redstart (Myioborus pictus) generally increases insect escape responses but reduces the effect that tail pattern variation and background tone have on escape behavior. These experiments support the hypothesis that habitat-specific natural selection to enhance sensory exploitation of prey escape responses could produce geographic variation in plumage patterns of flush-pursuers.