Asymptotic prey profitability drives star-nosed moles to the foraging speed limit

Foraging theory provides models for predicting predator diet choices assuming natural selection has favoured predators that maximize their rate of energy intake during foraging. Prey profitability (energy gained divided by prey handling time) is an essential variable for estimating the optimal diet. Time constraints of capturing and consuming prey generally result in handling times ranging from minutes to seconds, yet profitability increases dramatically as handling time approaches zero, providing the potential for strong directional selection for increasing predator speed at high encounter rates (tiny increments in speed increase profitability markedly, allowing expanded diets of smaller prey). We provide evidence that the unusual anatomical and behavioural specializations characterizing star-nosed moles resulted from progressively stronger selection for speed, allowing the progressive addition of small prey to their diet. Here we report handling times as short as 120 ms (mean 227 ms) for moles identifying and eating prey. 'Double takes' during prey identification suggest that star-nosed moles have reached the speed limit for processing tactile information. The exceptional speed of star-nosed moles, coupled with unusual specializations for finding and eating tiny prey, provide new support for optimal foraging theory.     

Diet and prey consumption of breeding Common Kestrel （Falco tinnunculus） in Northeast China

The diet of Common Kestrels Falco tinnunculus was studied during the breeding seasons from 2004 to 2008 in Northeast China. Diet was determined by direct observation of the prey brought to nests, and analysis of prey remains collected from nests. Fifteen vertebrate species from three classes, and two groups of insects were identified as prey items. Rodents were the main prey items, comprising 93.9% of the total prey items (TPI) and 97.0% of total prey biomass (TPB). Birds, frogs and insects were also eaten. The kestrels preferred to prey on small rodents (mean weight 20-40 g) and displayed density-dependent prey selection. Daily prey consumption of an adult and a nestling was 2.6 individual rodents or 87.6 g, and 1.7 individual vertebrates or 48.2 g, respectively. The estimated prey consumption of a breeding pair (adults and nestlings) during the breeding season was 520.1 individual vertebrates or 19.7 kg.     

Ecosystem remodelling among vertebrates at the Permian-Triassic boundary in Russia

The mass extinction at the Permian-Triassic boundary, 251 million years (Myr) ago, is accepted as the most profound loss of life on record. Global data compilations indicate a loss of 50% of families or more, both in the sea and on land, and these figures scale to a loss of 80-96% of species, based on rarefaction analyses. This level of loss is confirmed by local and regional-scale studies of marine sections, but the terrestrial record has been harder to analyse in such close detail. Here we document the nature of the event in Russia in a comprehensive survey of 675 specimens of amphibians and reptiles from 289 localities spanning 13 successive geological time zones in the South Urals basin. These changes in diversity and turnover cannot be explained simply by sampling effects. There was a profound loss of genera and families, and simplification of ecosystems, with the loss of small fish-eaters and insect-eaters, medium and large herbivores and large carnivores. Faunal dynamics also changed, from high rates of turnover through the Late Permian period to greater stability at low diversity through the Early Triassic period. Even after 15 Myr of ecosystem rebuilding, some guilds were apparently still absent-small fish-eaters, small insect-eaters, large herbivores and top carnivores.     

Innate defence: evidence for memory in invertebrate immunity

Acquired immunity in vertebrates is characterized by immunological memory and specificity, whereas the innate defence systems of invertebrates are assumed to have no specific memory. Here we use a model system of a copepod, which is a minute crustacean, and a parasitic tapeworm to show that the success of reinfection depends on the antigenic resemblance between the consecutively encountered parasites. This finding indicates that an invertebrate defence system may be capable of specific memory.     

Group formation stabilizes predator-prey dynamics

Theoretical ecology is largely founded on the principle of mass action, in which uncoordinated populations of predators and prey move in a random and well-mixed fashion across a featureless landscape. The conceptual core of this body of theory is the functional response, predicting the rate of prey consumption by individual predators as a function of predator and/or prey densities. This assumption is seriously violated in many ecosystems in which predators and/or prey form social groups. Here we develop a new set of group-dependent functional responses to consider the ecological implications of sociality and apply the model to the Serengeti ecosystem. All of the prey species typically captured by Serengeti lions (Panthera leo) are gregarious, exhibiting nonlinear relationships between prey-group density and population density. The observed patterns of group formation profoundly reduce food intake rates below the levels expected under random mixing, having as strong an impact on intake rates as the seasonal migratory behaviour of the herbivores. A dynamical system model parameterized for the Serengeti ecosystem (using wildebeest (Connochaetes taurinus) as a well-studied example) shows that grouping strongly stabilizes interactions between lions and wildebeest. Our results suggest that social groups rather than individuals are the basic building blocks around which predator-prey interactions should be modelled and that group formation may provide the underlying stability of many ecosystems.     

Predator diversity dampens trophic cascades

Food web complexity is thought to weaken the strength of terrestrial trophic cascades in which strong impacts of natural enemies on herbivores cascade to influence primary production indirectly. Predator diversity can enhance food web complexity because predators may feed on each other and on shared prey. In such cases, theory suggests that the impact of predation on herbivores relaxes and cascading effects on basal resources are dampened. Despite this view, no empirical studies have explicitly investigated the role of predator diversity in mediating primary productivity in a natural terrestrial system. Here we compare, in a coastal marsh community, impacts of arthropod predators on herbivores and plant productivity between a simple food web with a single predator species and a complex food web with a diverse predator assemblage. We show that enhancing predator diversity dampens enemy effects on herbivores and weakens trophic cascades. Consequently, changes in diversity at higher trophic levels can significantly alter ecosystem function in natural systems.     

Tracking apex marine predator movements in a dynamic ocean

Pelagic marine predators face unprecedented challenges and uncertain futures. Overexploitation and climate variability impact the abundance and distribution of top predators in ocean ecosystems. Improved understanding of ecological patterns, evolutionary constraints and ecosystem function is critical for preventing extinctions, loss of biodiversity and disruption of ecosystem services. Recent advances in electronic tagging techniques have provided the capacity to observe the movements and long-distance migrations of animals in relation to ocean processes across a range of ecological scales. Tagging of Pacific Predators, a field programme of the Census of Marine Life, deployed 4,306 tags on 23 species in the North Pacific Ocean, resulting in a tracking data set of unprecedented scale and species diversity that covers 265,386 tracking days from 2000 to 2009. Here we report migration pathways, link ocean features to multispecies hotspots and illustrate niche partitioning within and among congener guilds. Our results indicate that the California Current large marine ecosystem and the North Pacific transition zone attract and retain a diverse assemblage of marine vertebrates. Within the California Current large marine ecosystem, several predator guilds seasonally undertake north-south migrations that may be driven by oceanic processes, species-specific thermal tolerances and shifts in prey distributions. We identify critical habitats across multinational boundaries and show that top predators exploit their environment in predictable ways, providing the foundation for spatial management of large marine ecosystems.     

具有避难所的非自治差分修正Leslie-Gower捕食-食饵系统的动力学行为研究

研究一类具有避难所的非自治差分修正Leslie-Gower捕食-食饵系统,通过对系统动力学行为的详细分析,得到保证系统持久和全局渐近稳定的充分性条件,发现只要避难所足够大就可以保证食饵种群持久生存.借助差分不等式获得一组保证食饵种群绝灭而捕食者种群持久的充分性条件,发现当避难所较小时,食饵种群会由于捕食者的捕食而最终绝灭,但此时捕食者由于拥有其他的食物来源仍可持久生存.     

Raptorial jaws in the throat help moray eels swallow large prey

Most bony fishes rely on suction mechanisms to capture and transport prey. Once captured, prey are carried by water movement inside the oral cavity to a second set of jaws in the throat, the pharyngeal jaws, which manipulate the prey and assist in swallowing. Moray eels display much less effective suction-feeding abilities. Given this reduction in a feeding mechanism that is widespread and highly conserved in aquatic vertebrates, it is not known how moray eels swallow large fish and cephalopods. Here we show that the moray eel (Muraena retifera) overcomes reduced suction capacity by launching raptorial pharyngeal jaws out of its throat and into its oral cavity, where the jaws grasp the struggling prey animal and transport it back to the throat and into the oesophagus. This is the first described case of a vertebrate using a second set of jaws to both restrain and transport prey, and is the only alternative to the hydraulic prey transport reported in teleost fishes. The extreme mobility of the moray pharyngeal jaws is made possible by elongation of the muscles that control the jaws, coupled with reduction of adjacent gill-arch structures. The discovery that pharyngeal jaws can reach up from behind the skull to grasp prey in the oral jaws reveals a major innovation that may have contributed to the success of moray eels as apex predators hunting within the complex matrix of coral reefs. This alternative prey transport mode is mechanically similar to the ratcheting mechanisms used in snakes--a group of terrestrial vertebrates that share striking morphological, behavioural and ecological convergence with moray eels.     

具无限时滞和非单调功能性反应捕食系统的多周期解

利用重合度理论中的延拓定理,研究一类具有无限时滞和非单调功能性反应的捕食者-食饵系统正周期解的存在性,得到了两个有界开集和至少存在两个周期正解的充分条件.结果表明,当食饵群负载容纳量和捕食者种群增长率均足够大时,系统将产生生物性多周期振荡。     

依赖比率的捕食被捕食系统的全局分析:捕食与被捕食者均有密度制约的情况

近年来依赖比率的捕食与被捕食模型已引起了生态学者和生物数学研究者的密切注意，这是因为它们比传统的模型更加接近实际情形．本文研究了依赖比率的捕食与被捕食系统的全局定性性态，这里捕食与被捕食者均为密度制约的．     

一类食饵-捕食扩散模型分析

在两种群相互作用的Lotka-Voherra模型的基础上考虑了一类食饵种群分布在2个斑块：一个斑块上食饵和捕食者相互作用且对捕食者种群进行捕获；而另—个斑块属于食饵保护区．没有捕食者进入且不允许对食饵种群进行捕获．并且食饵种群可以在2个斑块间进行扩散的食饵—捕食模型。讨论了平衡点的存在性，利用Hurwitz判别法证明了平衡点的局部渐近稳定性和通过构造李雅普诺夫函数，得到了平衡点全局渐近稳定的结论。     

Double cones as a basis for a new type of polarization vision in vertebrates

Many invertebrates and vertebrates are sensitive to the polarization of light. The biophysical basis of invertebrate polarization sensitivity is an intrinsic dichroism, the alignment of chromophores along the photoreceptor microvilli. But such dichroism to axially propagating light is not present in vertebrate photoreceptors, whose chromophores are free to rotate in the plane of the outer-segment disc membranes, and a biophysical mechanism responsible for vertebrate polarization sensitivity has not been established. We hypothesize that the roughly elliptical cross-sectioned double-cone inner segment acts as a birefringent, polarization-sensitive dielectric waveguide, and that the double cone mosaic generates a 'polarization contrast' neural image. Here we confirm three predictions derived from these hypotheses: (1) 90 degrees periodicity for polarization sensitivity; (2) polarization sensitivity maxima corresponding to the absolute orientation of the axes of the double-cone inner-segment cross-sections; and (3) action spectrum for polarization sensitivity corresponding to the absorption spectrum of the double cones. We also present evidence for a polarization-opponent neural encoding in vertebrates.     

浙江北部海区口虾蛄繁殖和摄食习性的初步研究

本文是浙江北部海区口虾站Ｏｒａｔｏｓｑｕｉｌｌａｏｒａｔｏｒｉａ（ＤｅＨｕａｎ）繁殖与摄食习性的研究结果。根据卵巢成熟系数、食物种类组成、摄食强度等的周年变化规律，结果认为：每年的３－５月是口虾蛄的成熟期；６－７月为产卵期。一年性成熟一次，卵巢成熟系数４月份最高；最小性成熟个体８０ｍｍ左右。口虾蛄为肉食性捕食动物，食性组成较杂，以鱼虾类为主。６月和１２月摄食强度最大，８月份摄食强度最小。     

捕食者追捕与食饵逃逸对共位捕食系统中物种共存的影响

基于元胞自动机模型,探讨捕食者追捕和食饵逃逸两种行为对共位捕食系统中物种共存动态的影响.结果表明:捕食者追捕能够扩大物种共存区域,但食饵逃逸能否提高共位捕食系统中物种的共存取决于两物种竞争与捕食能力的相互权衡关系.在捕食者占绝对优势以及竞争与捕食之间存在弱权衡关系时,食饵逃逸能够促进两物种的共存;而在食饵占有绝对优势以及两物种间强权衡关系时,食饵逃逸则使得物种共存变得更加困难.另外,模拟结果显示,捕食者追捕与食饵逃逸对物种共存与种群密度产生不对称性效应:捕食者追捕对系统产生的影响较食饵逃逸行为更为显著.     

Rapid evolution drives ecological dynamics in a predator-prey system

Ecological and evolutionary dynamics can occur on similar timescales. However, theoretical predictions of how rapid evolution can affect ecological dynamics are inconclusive and often depend on untested model assumptions. Here we report that rapid prey evolution in response to oscillating predator density affects predator-prey (rotifer-algal) cycles in laboratory microcosms. Our experiments tested explicit predictions from a model for our system that allows prey evolution. We verified the predicted existence of an evolutionary tradeoff between algal competitive ability and defence against consumption, and examined its effects on cycle dynamics by manipulating the evolutionary potential of the prey population. Single-clone algal cultures (lacking genetic variability) produced short cycle periods and typical quarter-period phase lags between prey and predator densities, whereas multi-clonal (genetically variable) algal cultures produced long cycles with prey and predator densities nearly out of phase, exactly as predicted. These results confirm that prey evolution can substantially alter predator-prey dynamics, and therefore that attempts to understand population oscillations in nature cannot neglect potential effects from ongoing rapid evolution.     

Strategy for rapid immobilization of prey by a fish-hunting marine snail

Some venomous animals capture prey with remarkable efficiency and speed. The purple cone, Conus purpurascens, uses two parallel physiological mechanisms requiring multiple neurotoxins to immobilize fish rapidly: neuromuscular block, and excitotoxic shock. The latter requires the newly characterized peptide kappa-conotoxin PVIIA, which inhibits the Shaker potassium channel 2-4, and beta-conotoxin PVIA5, which delays sodium-channel inactivation. Despite the extreme biochemical diversity in venoms, the number of effective strategic alternatives for prey capture are limited. How securely prey is initially tethered may strongly influence the venom strategy evolved by a predator.     

Evolution: a catfish that can strike its prey on land

An important step towards understanding the evolution of terrestriality in vertebrates is to identify how the aquatic ancestors of tetrapods were able to access ground-based prey. We have discovered that the 'eel catfish' Channallabes apus, an inhabitant of the muddy swamps of tropical Africa, has a remarkable ability to forage and capture prey on land. The animal's capacity to bend its head down towards the ground while feeding seems to be an essential feature that may have enabled fish to make the transition from an aquatic to a terrestrial mode.     

生命早期1000天的营养与肥胖

 生命早期1000天的营养暴露与儿童期乃至成年后肥胖及慢性疾病的发生风险关系密切。本文将生命早期1000天划分为3个营养阶段,即宫内营养期、母乳或婴儿配方食品期、辅食添加及早期饮食期,并对各阶段中可能暴露的多种营养相关危险因素进行了系统综述。其中,宫内营养期可能存在的主要危险因素是,母亲孕前体质指数过高、妊娠期体重增加量过高、孕期患有糖尿病、携带代谢性疾病易感基因;母乳或婴儿配方食品期可能存在的主要危险因素是,由于食用配方食品导致的婴儿生长速度过快、能量和蛋白质摄入过高、多不饱和脂肪酸摄入过低;而在辅食添加阶段可能存在的主要危险因素是,婴儿体重增加过快、固态食物添加过早、蛋白质摄入过高、肠道微生物。     

Deuterostome phylogeny reveals monophyletic chordates and the new phylum Xenoturbellida

Deuterostomes comprise vertebrates, the related invertebrate chordates (tunicates and cephalochordates) and three other invertebrate taxa: hemichordates, echinoderms and Xenoturbella. The relationships between invertebrate and vertebrate deuterostomes are clearly important for understanding our own distant origins. Recent phylogenetic studies of chordate classes and a sea urchin have indicated that urochordates might be the closest invertebrate sister group of vertebrates, rather than cephalochordates, as traditionally believed. More remarkable is the suggestion that cephalochordates are closer to echinoderms than to vertebrates and urochordates, meaning that chordates are paraphyletic. To study the relationships among all deuterostome groups, we have assembled an alignment of more than 35,000 homologous amino acids, including new data from a hemichordate, starfish and Xenoturbella. We have also sequenced the mitochondrial genome of Xenoturbella. We support the clades Olfactores (urochordates and vertebrates) and Ambulacraria (hemichordates and echinoderms). Analyses using our new data, however, do not support a cephalochordate and echinoderm grouping and we conclude that chordates are monophyletic. Finally, nuclear and mitochondrial data place Xenoturbella as the sister group of the two ambulacrarian phyla. As such, Xenoturbella is shown to be an independent phylum, Xenoturbellida, bringing the number of living deuterostome phyla to four.