The predatory behavior of Pheidole megacephala

We studied the foraging and predatory behaviors of the invasive African myrmicine ant, Pheidole megacephala (F.) in its native range. Workers can singly capture a wide range of insects, including relatively large prey items. For still larger prey, they recruit at short range those nestmates situated within reach of an alarm pheromone and together spread-eagle the insect. These behaviors are complimented by a long-range recruitment (of nestmates remaining in the nest) based on prey size. P. megacephala scouts also use long-range recruitment when they detect the landmarks of termites and competing ant species, thus permitting them to avoid confronting these termites and ants solitarily.     

Rippling is a predatory behavior in Myxococcus xanthus

Cells of Myxococcus xanthus will, at times, organize their movement such that macroscopic traveling waves, termed ripples, are formed as groups of cells glide together on a solid surface. The reason for this behavior has long been a mystery, but we demonstrate here that rippling is a feeding behavior which occurs when M. xanthus cells make direct contact with either prey or large macromolecules. Rippling has been observed during two fundamentally distinct environmental conditions: (i) starvation-induced fruiting body development and (ii) predation of other organisms. Our results indicate that case (i) does not occur in all wild-type strains and is dependent on the intrinsic level of autolysis. Analysis of predatory rippling indicates that rippling behavior is inducible during predation on proteobacteria, gram-positive bacteria, yeast (such as Saccharomyces cerevisiae), and phage. Predatory efficiency decreases under genetic and physiological conditions in which rippling is inhibited. Rippling will also occur in the presence of purified macromolecules such as peptidoglycan, protein, and nucleic acid but does not occur in the presence of the respective monomeric components and also does not occur when the macromolecules are physically separated from M. xanthus cells. We conclude that rippling behavior is a mechanism utilized to efficiently consume nondiffusing growth substrates and that developmental rippling is a result of scavenging lysed cell debris.     

In situ predatory behavior ofMysis relicta in Lake Michigan

Selectivity coefficients (W) and predation rates on Lake Michigan zooplankton were determined forMysis relicta during spring through fall using anin situ method. W values indicated the following ranked order of prey preference: Cladocera > copepod copepodites and copepod nauplii > adult diaptomids and cyclopoids. With few exceptions, W values for different prey categories remained fairly constant despite greatly changing relative abundances of prey. Predation rates and prey selectivity were similar in most cases to those determined in laboratory studies. Ingestion rates (percent dry body weight · day^–1) were correlated to total prey biomass (r = 0.38) and to effective prey biomass (r = 0.85), where the weighting factors were overall mean selectivity coefficients for the different prey categories. This result suggested that seasonally varying composition of prey caused much of the variation in ingestion rates among experiments. Feeding trials performed at the same depth with daytime and nighttime assemblages of zooplankton indicated that Cladocera may escape heavyMysis predation at night by migrating from the metalimnetic-hypolimnetic interface into the epilimnion.Contribution 333 from the Great Lakes Research Division, The University of Michigan and contribution 287 from the Great Lakes Environmental Research Laboratory, National Oceanic and Atmospheric Administration.Contribution 333 from the Great Lakes Research Division, The University of Michigan and contribution 287 from the Great Lakes Environmental Research Laboratory, National Oceanic and Atmospheric Administration.     

New record of predatory behavior by the mandrill in Cameroon

The predatory behavior of the mandrill (Mandrillus sphinx,Linnaeus 1758), a forestliving baboon, on the bay duiker (Cephalophus dorsalis,Gray 1864) was observed under natural conditions. In the predatory episode, at least two mandrills (one adult female and one adult male) attacked a bay duiker, but no overt aggressive interactions between the attackers occurred during consumption. The estimated predation pattern based on scars—intensive attacking of the head and pulling of the hind legs to eat the thigh muscles first—resembled the predation patterns of captive mandrills observed experimentally. The findings suggest that the predatory behavior is established in mandrills as a feeding behavior pattern as in savanna-living baboons. New data are thus presented which are relevant to the discussion of the origins of hunting behavior in early hominids.     

Change in host rejection behavior mediated by the predatory behavior of its brood parasite

Passerine hosts of parasitic cuckoos usually vary in their abilityto discriminate and reject cuckoo eggs. Costs of discriminationand rejection errors have been invoked to explain the maintenanceof this within-population variability. Recently, enforcementof acceptance by parasites has been identified as a rejectioncost in the magpie (Pica pica) and its brood parasite, the greatspotted cuckoo (Clamator glandarius). Previous experimentalwork has shown that rejecter magpies suffer from increased nestpredation by the great spotted cuckoo. Cuckoo predatory behavioris supposed to confer a selective advantage to the parasitebecause magpies experiencing a reproductive failure may providea second opportunity for the cuckoo to parasitize a replacementclutch. This hypothesis implicitly assumes that magpies modulatetheir propensity to reject parasite eggs as a function of previousexperience. We tested this hypothesis in a magpie populationbreeding in study plots varying in parasitism rate. Magpie pairs thatwere experimentally parasitized and had their nests depredated,after their rejection behavior had been assessed, changed theirbehavior from rejection to acceptance. The change in host behaviorwas prominent in study plots with high levels of parasitism,but not in plots with rare or no cuckoo parasitism. We discussthree possible explanations for these differences, concludingthat in study plots with a high density of cuckoos, the probability fora rejecter magpie nest of being revisited and depredated bya cuckoo is high, particularly for replacement clutches, and,therefore, the cost for magpies of rejecting a cuckoo egg ina replacement clutch is increased. Moreover, in areas with highlevels of host defense (low parasitism rate), the probabilityof parasitism and predation of rejecter-magpie nests by thecuckoo is reduced in both first and replacement clutches. Therefore,rejecter magpies in such areas should not change their rejectionbehavior in replacement clutches.     

Fin-tail coordination during escape and predatory behavior in larval zebrafish

Larval zebrafish innately perform a suite of behaviors that are tightly linked to their evolutionary past, notably escape from threatening stimuli and pursuit and capture of prey. These behaviors have been carefully examined in the past, but mostly with regard to the movements of the trunk and tail of the larvae. Here, we employ kinematics analyses to describe the movements of the pectoral fins during escape and predatory behavior. In accord with previous studies, we find roles for the pectoral fins in slow swimming and immediately after striking prey. We find novel roles for the pectoral fins in long-latency, but not in short-latency C-bends. We also observe fin movements that occur during orienting J-turns and S-starts that drive high-velocity predatory strikes. Finally, we find that the use of pectoral fins following a predatory strike is scaled to the velocity of the strike, supporting a role for the fins in braking. The implications of these results for central control of coordinated movements are discussed, and we hope that these results will provide baselines for future analyses of cross-body coordination using mutants, morphants, and transgenic approaches.     

Submissive distance in the golden hamster Mesocricetus auratus

Observations on pairs of golden hamsters indicated that the average distance at which the animals show submissive behaviour patterns is significantly variable. This distance was significantly higher in hamsters which had been isolated than in those which had been housed in groups of four. Also, this distance was affected significantly for isolate animals by the previous amount of experience they had had in the observation box. Ranking animals by distance at which they showed submissive patterns was negatively correlated with a ranking by dominance.     

Relative importance of total versus external platelet-associated IgG

We present measurements of total platelet-associated immunoglobulin G following platelet lysis (PAIgG tot) and surface-restricted IgG (PAIgG ext) on intact, gel-filtered platelets from 36 normal human donors and 9 patients with human immunodeficiency virus (HIV) infection (CDC stages IIb-IV). For this purpose, an indirect micro ELI-SA technique was developed involving competition between PAIgG and solid-phase absorbed IgG for fixation of conjugated anti-human IgG antibody. In normal donors, the mean values of PAIgG tot was 8.3 +/- 7.4 (mean +/- 2 SD) and of PAIgG ext 4.2 +/- 4.4 fg/platelet. In HIV-infected subjects, PAIgG tot was 37.2 +/- 62.8 and PAIgG ext 17.1 +/- 23 fg/platelet. In healthy subjects the comparison of individual levels of PAIgG tot and PAIgG ext revealed a significant correlation (r:0.763; p: 0.003). These results are compared to those which have been reported in the literature. In addition, the major immunopathological mechanisms considered responsible for immune-mediated idiopathic thrombocytopenic purpura are discussed.     

双尾新小绥螨的形态特征及捕食性功能

【目的】通过对新疆本地捕食螨双尾新小绥螨Neoseiulus bicaudus Wainstein的形态学特征观察及其对新疆农作物上两种重要害螨的捕食量测定,为该捕食螨的保护、研究、扩繁和释放提供理论基础。【方法】在实验室(26±1)℃,RH60%,16L︰8D条件下,借助显微成像系统观察其各个螨态形态特征及生物学习性;定量小室饲养技术对不同密度下对新疆两种重要害螨各螨态的捕食量进行研究。【结果】双尾新小绥螨有卵、幼螨、第一若螨、第二若螨和成螨5个螨态,嗜好阴暗条件,活动范围小,通过有性生殖进行繁殖,有多次交配行为,产卵方式为单产;单头双尾新小绥螨雌成螨每日对截形叶螨Tetranychus truncatus卵和幼螨的捕食量(106.8粒/日·雌和45.4头/日·雌)要显著大于土耳其斯坦叶螨Tetranychus turkestani(64.4粒/日·雌和39.4头/日·雌),而对两种叶螨的若螨和成螨捕食量无明显差异。【结论】本研究表明双尾新小绥螨对土耳其斯坦叶螨和截形叶螨的卵和幼螨的捕食较对若螨和成螨的效果好,对新疆害螨有一定控制能力。     

Optimal diet theory: behavior of a starved predatory snail

Summary The tenets of optimal foraging theory are used to contrast the behavior of the predatory snail Acantina spirata when feeding on the barnacles Balanus glandula and Chthamalus fissus under conditions of satiation and starvation. As predicted in optimal diet models, A. spirata is less selective (ratio of attack frequency on a prey species to number of individuals available) when the higher ranking prey has low abundance. When given a choice, starved snails attack both barnacle species equally, whereas satiated individuals preferentially attack B. glandula, the more profitable prey (ash-free dry weight of barnacles ingested per unit handling time). Under starvation conditions, equal attack frequency does not result in equal prey species consumption because Acanthina spirata is more successful at attacking C. fissus than B. glandula.The assumption of constant prey encounter rates in optimal diet models is not met when A. spirata goes from a state of satiation to starvation. The encounter rate on B. glandula is lowered due to a decrease in attack success. A loss of feeding skills in starved A. spirata is responsible for the greater difficulty snails have in gaining access through the opercular plates of B. glandula.Behavioral changes in A. spirata as snails pass from satiation to hunger translate into an energetic disadvantage during feeding for hungry snails for two reasons. First, higher prey handling times result in a decreased rate of biomass intake. Second, alteration in the relative attack frequency between barnacle species, combined with a decrease in attack success on the more profitable prey leads to more frequent ingestion of the less profitable prey.     

Predator interference alters foraging behavior of a generalist predatory arthropod

Interactions between predators foraging in the same patch may strongly influence patch use and functional response. In particular, there is continued interest in how the magnitude of mutual interference shapes predator–prey interactions. Studies commonly focus on either patch use or the functional response without attempting to link these important components of the foraging puzzle. Predictions from both theoretical frameworks suggest that predators should modify foraging efforts in response to changes in feeding rate, but this prediction has received little empirical attention. We study the linkage between patch departure rates and food consumption by the hunting spider, Pardosa milvina, using field enclosures in which prey and predator densities were manipulated. Additionally, the most appropriate functional response model was identified by fitting alternative functional response models to laboratory foraging data. Our results show that although prey availability was the most important determinant of patch departure rates, a greater proportion of predators left enclosures containing elevated predator abundance. Functional response parameter estimation revealed significant levels of interference among predators leading to lower feeding rates even when the area allocated for each predator was kept constant. These results suggest that feeding rates determine patch movement dynamics, where interference induces predators to search for foraging sites that balance the frequency of agonistic interactions with prey encounter rates.     

TRPs in our senses

In the last decade, studies of transient receptor potential (TRP) channels, a superfamily of cation-conducting membrane proteins, have significantly extended our knowledge about the molecular basis of sensory perception in animals. Due to their distinct activation mechanisms and biophysical properties, TRP channels are highly suited to function in receptor cells, either as receptors for environmental or endogenous stimuli or as molecular players in signal transduction cascades downstream of metabotropic receptors. As such, TRP channels play a crucial role in many mammalian senses, including touch, taste and smell. Starting with a brief survey of sensory TRP channels in invertebrate model systems, this review covers the current state of research on TRP channel function in the classical mammalian senses and summarizes how modulation of TRP channels can tune our sensations.     

Relative binding affinity of novel steroids to androgen receptors in hamster prostate

The in vivo and in vitro antiandrogenic activity of four aromatic esters 10a-10d, one aliphatic ester 10e based on the pregna-4,16-diene-6, 20-dione structure and two aromatic 17c, 17d and two aliphatic valeroyloxy esters 17a, 17b based on the more saturated 4-pregnene-6,20-dione skeleton was examined. The biological activity of steroids 9, 10a-10e and 17a-17d, was determined using prostate glands from gonadectomized adult male golden hamsters. In the in vitro studies, the relative binding affinity of these steroids to cytoplasmic androgen receptor (AR) of hamster prostate was determined from, the corresponding IC50 values obtained from the competitive binding plots. The standards dihydrotestosterone (DHT) and cyproterone (CA) acetate used have displaced [3H]DHT from the AR with an IC50 value of 3.2 and 4.4 nM respectively. All steroidal compounds synthesized in this study showed a binding affinity for the androgen receptor, present in the cytosol from prostate hamster; compounds 10a-10c showed the highest affinities for this receptor. The in vivo experiments showed that all steroidal derivatives were subcutaneously active, since they decreased the weight of the prostate gland in gonadectomized hamsters treated with DHT, and are antagonists for the androgen receptor since they block the DHT-induced prostate weight gain. The derivatives having the more conjugated 4,16-pregnadiene-6, 20-dione system (10a-10c) exhibited a higher antiandrogenic activity than the corresponding steroids (17a-17d) based on the more saturated 4-pregnene-6,20-dione system.