The Kinematics of Swimming and Relocation Jumps in Copepod Nauplii

Copepod nauplii move in a world dominated by viscosity. Their swimming-by-jumping propulsion mode, with alternating power and recovery strokes of three pairs of cephalic appendages, is fundamentally different from the way other microplankters move. Protozoans move using cilia or flagella, and copepodites are equipped with highly specialized swimming legs. In some species the nauplius may also propel itself more slowly through the water by beating and rotating the appendages in a different, more complex pattern. We use high-speed video to describe jumping and swimming in nauplii of three species of pelagic copepods: Temora longicornis, Oithona davisae and Acartia tonsa. The kinematics of jumping is similar between the three species. Jumps result in a very erratic translation with no phase of passive coasting and the nauplii move backwards during recovery strokes. This is due to poorly synchronized recovery strokes and a low beat frequency relative to the coasting time scale. For the same reason, the propulsion efficiency of the nauplii is low. Given the universality of the nauplius body plan, it is surprising that they seem to be inefficient when jumping, which is different from the very efficient larger copepodites. A slow-swimming mode is only displayed by T. longicornis. In this mode, beating of the appendages results in the creation of a strong feeding current that is about 10 times faster than the average translation speed of the nauplius. The nauplius is thus essentially hovering when feeding, which results in a higher feeding efficiency than that of a nauplius cruising through the water.     

Patterns of Detection and Capture Are Associated with Cohabiting Predators and Prey

Avoidance behaviour can play an important role in structuring ecosystems but can be difficult to uncover and quantify. Remote cameras have great but as yet unrealized potential to uncover patterns arising from predatory, competitive or other interactions that structure animal communities by detecting species that are active at the same sites and recording their behaviours and times of activity. Here, we use multi-season, two-species occupancy models to test for evidence of interactions between introduced (feral cat Felis catus) and native predator (Tasmanian devil Sarcophilus harrisii) and predator and small mammal (swamp rat Rattus lutreolus velutinus) combinations at baited camera sites in the cool temperate forests of southern Tasmania. In addition, we investigate the capture rates of swamp rats in traps scented with feral cat and devil faecal odours. We observed that one species could reduce the probability of detecting another at a camera site. In particular, feral cats were detected less frequently at camera sites occupied by devils, whereas patterns of swamp rat detection associated with devils or feral cats varied with study site. Captures of swamp rats were not associated with odours on traps, although fewer captures tended to occur in traps scented with the faecal odour of feral cats. The observation that a native carnivorous marsupial, the Tasmanian devil, can suppress the detectability of an introduced eutherian predator, the feral cat, is consistent with a dominant predator – mesopredator relationship. Such a relationship has important implications for the interaction between feral cats and the lower trophic guilds that form their prey, especially if cat activity increases in places where devil populations are declining. More generally, population estimates derived from devices such as remote cameras need to acknowledge the potential for one species to change the detectability of another, and incorporate this in assessments of numbers and survival.     

Prey Capture and Feeding in the Social Spider Anelosimus eximius

Wild colonies of the social spider Anelosimus eximius (Araneae, Theridiidae) appear often to be food-limited and not all females come to reproduction. Using a limited number of marked females in an artificial colony, set up in the laboratory, this study attempts a first analysis of the participation in prey capture and ingestion. Marked females of the same age and experience were observed during the attack of prey insects, the ensuing transportation of the prey to the retreat, and the feeding session. No correlation was found between the time females spent hunting and the time they spent feeding. Females that laid eggs had fed longer and imbibed more nutrients, but had not hunted more than those females that did not reproduce. These, it is speculated, were denied access to the prey by the reproducing females.     

Prey Capture Ecology of the Cubozoan Carukia barnesi

Adult Carukia barnesi medusae feed predominantly on larval fish; however, their mode of prey capture seems more complex than previously described. Our findings revealed that during light conditions, this species extends its tentacles and ‘twitches’ them frequently. This highlights the lure-like nematocyst clusters in the water column, which actively attract larval fish that are consequently stung and consumed. This fishing behavior was not observed during dark conditions, presumably to reduce energy expenditure when they are not luring visually oriented prey. We found that larger medusae have longer tentacles; however, the spacing between the nematocyst clusters is not dependent on size, suggesting that the spacing of the nematocyst clusters is important for prey capture. Additionally, larger specimens twitch their tentacles more frequently than small specimens, which correlate with their recent ontogenetic prey shift from plankton to larval fish. These results indicate that adult medusae of C. barnesi are not opportunistically grazing in the water column, but instead utilize sophisticated prey capture techniques to specifically target larval fish.     

Prey Capture and Phagocytosis in the Choanoflagellate Salpingoeca rosetta

Choanoflagellates are unicellular and colonial aquatic microeukaryotes that capture bacteria using an apical flagellum surrounded by a feeding collar composed of actin-filled microvilli. Flow produced by the apical flagellum drives prey bacteria to the feeding collar for phagocytosis. We report here on the cell biology of prey capture in rosette-shaped colonies and unicellular “thecate” or substrate attached cells from the choanoflagellate S. rosetta. In thecate cells and rosette colonies, phagocytosis initially involves fusion of multiple microvilli, followed by remodeling of the collar membrane to engulf the prey, and transport of engulfed bacteria into the cell. Although both thecate cells and rosette colony cells produce ∼70 nm “collar links” that connect and potentially stabilize adjacent microvilli, only thecate cells were observed to produce a lamellipod-like “collar skirt” that encircles the base of the collar. This study offers insight into the process of prey ingestion by S. rosetta, and provides a context within which to consider potential ecological differences between solitary cells and colonies in choanoflagellates.     

Thermal Sensitivity as a Specialization for Prey Capture and Feeding in Snakes

Behavior can be regarded as a result of various processes ofdecision based on the information provided by the sensory organs.In this review the role of the so-called additional heat sense,next to vision, smell and mechanoreception is discussed withrespect to the feeding behavior of snakes. The hierarchy ofthe sensory information in various phases of the feeding behaviordiffers between snakes possessing heat receptors (e.g., speciesof the Crotalinae and Pythoninae) and those without (e.g., speciesof the Viperinae and Colubrinae). Probably depending on theinfluence of ecological demands, visual or chemical cues arethe main information in the behavioral phases before the strikeHowever, in situations with little visual input, e.g., in darkness,rodents' burrows, etc., hunting behavior is guided in the firstplace by radiation of warm objects in Crotalus, Python and Trimeresurusflavoviridis, and by substrate vibrations in Vipera aspis, Pituophismelanoleucus and Boa constrictor. I suggest that in the sensoryhierarchy, heat information functionally replaces the mechanicalinformation which is utilized by snakes without pit organs.Poststrike behavior on the other hand is mainly guided by chemicalcues in all snakes.     

Modelling the Effects of Prey Size and Distribution on Prey Capture Rates of Two Sympatric Marine Predators

Understanding how prey capture rates are influenced by feeding ecology and environmental conditions is fundamental to assessing anthropogenic impacts on marine higher predators. We compared how prey capture rates varied in relation to prey size, prey patch distribution and prey density for two species of alcid, common guillemot (Uria aalge) and razorbill (Alca torda) during the chick-rearing period. We developed a Monte Carlo approach parameterised with foraging behaviour from bird-borne data loggers, observations of prey fed to chicks, and adult diet from water-offloading, to construct a bio-energetics model. Our primary goal was to estimate prey capture rates, and a secondary aim was to test responses to a set of biologically plausible environmental scenarios. Estimated prey capture rates were 1.5±0.8 items per dive (0.8±0.4 and 1.1±0.6 items per minute foraging and underwater, respectively) for guillemots and 3.7±2.4 items per dive (4.9±3.1 and 7.3±4.0 items per minute foraging and underwater, respectively) for razorbills. Based on species'' ecology, diet and flight costs, we predicted that razorbills would be more sensitive to decreases in 0-group sandeel (Ammodytes marinus) length (prediction 1), but guillemots would be more sensitive to prey patches that were more widely spaced (prediction 2), and lower in prey density (prediction 3). Estimated prey capture rates increased non-linearly as 0-group sandeel length declined, with the slope being steeper in razorbills, supporting prediction 1. When prey patches were more dispersed, estimated daily energy expenditure increased by a factor of 3.0 for guillemots and 2.3 for razorbills, suggesting guillemots were more sensitive to patchier prey, supporting prediction 2. However, both species responded similarly to reduced prey density (guillemot expenditure increased by 1.7; razorbill by 1.6), thus not supporting prediction 3. This bio-energetics approach complements other foraging models in predicting likely impacts of environmental change on marine higher predators dependent on species-specific foraging ecologies.     

Effect of Algal Food on Animal Prey Consumption Rates in the Omnivorous Copepod,Mesocyclops thermocyclopoides

We measured the food consumption rates in the omnivorous copepod Mesocyclops thermocyclopoides on different animal prey types in the presence of, and in the absence of one of the algal food types, the small, nonmotile Chlorella, or the large, motile Chlorogonium. Animal prey tested included different zooplankton species covering a size range of 88 to 1446 μm. The number of animal prey consumed was inversely proportional, but the total weight consumed was directly proportional, to the body size and dry weight of the prey item. There was a significant reduction in animal prey consumption in the presence of algae, being higher with cladoceran prey than with ciliates and rotifers, and in the presence of Chlorogonium than in the presence of Chlorella. Cannibalism in M. thermocyclopoides was low when algal food was available.     

Development of Prey Capture in the Indian False Vampire Bat Megaderma Lyra

We studied development of prey capture, under captive conditions, on five newly weaned Indian false vampire bats Megaderma lyra. We tested the hypothesis that the young bats are able to improve the ability of hunting by trial and error. An additional hypothesis was that their rate of prey consumption and method of handling prey improve with age. We separated the juveniles from their mothers and observed them individually at different ages. At 58 d of age, M. lyra roosted 2 m above floor level, flew down only towards moving frogs, landed >1 m away from them and returned to roosts without showing attempt to capture. At day 60, bats roosted at 50‐cm heights, landed approx. 1 m away from frogs and moved towards them. Although bats intercepted frogs, their attempts to capture were still unsuccessful. At day 62, bats landed <1 m from frogs, made similar attempts and most of them were successful. Bats carried frogs, roosted at heights of 100 cm and started consuming. Numbers of jumps made by frogs and attempts made by bats during successful captures decreased with increase in age of bats. Furthermore, the distance between landing sites of bats and places where frogs stayed during landings decreased with advancement of age. Until 75 d of age, M. lyra devoured frogs with legs‐first on significantly more occasions. After 75 d, most of the consumptions started with heads of frogs, similar to adults. Duration of feeding on single frogs was significantly longer compared with that of mothers until young were 75‐d old. The study revealed that juveniles were inefficient on localization, rate of consumption, and handling prey at earlier ages (e.g. 60 d). They became efficient on these behavioural components at later age, i.e. after 75 d. Thus, the results were in accordance with both the hypotheses. Bats did not respond to stationary frogs.     

Prey Capture Behaviour in the Social Spider Anelosimus eximius (Araneae: Theridiidae): Responses to Prey Size and Type

Some species of web building spiders use different capture tactics for different prey types. The main factors influencing the attack behaviour are the ability of the insect to escape, the risks of injury to the spiders and prey size. This study evaluated the effects of size and prey type on prey capture behaviour of the social spider Anelosimus eximius as influenced by the number of spiders attracted by prey movements that did not bite until the immobilization (bystanders) and the number of spiders that contributed to prey immobilization (catchers). We carried out a two‐factor (prey size and type) experiment offering prey belonging to four orders: Diptera, Lepidoptera, Hymenoptera and Orthoptera, in a size gradient within each prey type. Both factors influenced the number of spiders recruited as bystanders, but only prey body size influenced the number of catchers in the subduing process. The possible advantages of the presence of bystanders around the interception site are discussed.     

虚拟视觉刺激引起幼年斑马鱼捕食行为放弃的研究

目的 当动物重复某种行为以逃避危险或获取奖励而无法成功时，会产生放弃。放弃是一种常见且基本的行为，在小鼠等模式动物中已经被广泛研究，但是其部分神经机制仍未被阐明。幼年斑马鱼适合进行全脑光学成像，是神经科学领域的重要模式生物。已经有研究者通过持续电击等消极刺激诱发斑马鱼放弃行为，然而奖励刺激能否引起斑马鱼放弃尚无报道。本文对奖励刺激引起的斑马鱼放弃行为进行了探究。方法 通过给予斑马鱼虚拟的食物视觉刺激，检验斑马鱼对虚拟食物的捕食情况，比较斑马鱼捕食频率和单次捕食时长随时间的变化。结果 虚拟的食物视觉刺激可以引起斑马鱼的捕食行为，接受25 min虚拟刺激后，8日龄以上斑马鱼的捕食频率和单次捕食时长均出现显著下降。结论 此研究丰富了斑马鱼放弃行为的研究范式，实验结果表明，缺失真实奖励的虚拟食物刺激可以诱导斑马鱼放弃捕食行为，这将进一步加深对动物放弃行为的理解，推动对其神经机制的研究。     

Diurnal Tiger Beetles (Coleoptera: Cicindelidae) Capture Prey Without Sight

Although much research has examined the process of prey capture by tiger beetles, an underlying assumption in this work is that tiger beetles are principally, or even exclusively, visual predators. Because this assumption is untested, we performed a series of experiments on four diurnally active tiger beetles in the Genus Cicindela. Individual beetles were placed in chambers in complete darkness and allowed to forage on apterous Drosophila for 6 h. Contrary to expectations, adults of all tested species captured more than 90% of prey items. These results show that other modalities can be used by tiger beetles during prey capture. Beyond potentially providing an explanation for observed night activity in tiger beetle species, the significance of these findings lies in the need to test underlying assumptions of even well-studied organisms.     

Integrated Capture and Spectroscopic Detection of Viruses

The goal of this work is to develop an online monitoring scheme for detection of viruses in flowing drinking water. The approach applies an electrodeposition process that is similar to the use of charged membrane filters previously employed for collection of viruses from aqueous samples. In the present approach, charged materials are driven onto a robust optical sensing element which has high transparency to infrared light. A spectroscopic measurement is performed using the evanescent wave that penetrates no more than 1 μm from the surface of an infrared optical element in an attenuated total reflectance measurement scheme. The infrared measurement provides quantitative information on the amount and identity of material deposited from the water. Initial studies of this sensing scheme used proteins reversibly electrodeposited onto germanium chips. The results of those studies were applied to design a method for collection of viruses onto an attenuated total reflectance crystal. Spectral signatures can be discriminated between three types of protein and two viruses. There is the potential to remove deposited material by reversing the voltage polarity. This work demonstrates a novel and practical scheme for detection of viruses in water systems with potential application to near-continual, automated monitoring of municipal drinking water.Despite the application of multibarrier, conventional treatment approaches for municipal water, disease outbreaks associated with tap water continue to occur in the United States (37). An etiological agent is not determined in approximately half of all identified drinking water outbreaks; however, the characteristic symptomatology of the causative agent frequently indicates a viral pathogen. The need for rapid and effective methods of virus collection and detection is apparent for the assurance of water security and water quality and certainly also for medical diagnostics.Commercial systems exist for continual monitoring of municipal drinking water for parameters such as pH, total organic carbon, turbidity, and salt (electrical conductivity). Biological monitoring schemes are available to quantify bacteria, spores, and parasites based on their size or their light scattering or absorbing properties (2, 3, 9). No such approach is available for viruses, which have a smaller size and present a sizeable health concern. Conventional virus detection methods are performed in an off-line manner. These methods have high specificity but are costly, time-consuming, require significant laboratory preparation, and have difficulties adapting to new emerging viruses.Development of the best available technology for effective monitoring of viral pathogens is critical for evaluating and maintaining potable water sources, treatment reliability, and posttreatment distribution water quality. Current methods of virus detection in environmental samples are compromised by the presence of inhibitory compounds, such as humic and fulvic acids, and detection of nonviable microbes (PCR) or by toxicity and lengthy assay times (conventional cell culture), conditions often leading to false-positive or false-negative results (23). Although the use of an integrated cell culture/PCR method has been shown to overcome major flaws of each individual method (1, 22, 24), this approach is neither automated nor rapid.Sampling from water systems (source waters and treated water) for detection of viral pathogens is usually performed with either positively charged membranes, which allow fluid to pass through the filter and collect viruses based on charge, or hollow fiber concentrators, which allow fluid to move across the membrane surface rather than being forced through and concentrate viruses by removal of liquid and larger molecules. In neutral solutions and most environmental drinking water sources, viruses are negatively charged. Adsorption to hollow fiber or filter surfaces is largely due to electrostatic and hydrophobic interactions and is controlled by environmental factors, such as pH and electrolytes (16). Once adsorbed to electrocharged filters, viruses are typically eluted via high-pH buffers or bioflocculants, such as beef extract. Collected materials are then analyzed using culture or primer-specific molecular detection methods. We aim to replace one of these fibers within a hollow fiber concentrator with an optically addressable fiber for spectroscopic detection of viruses deposited using electrophoretic collection, similar in process to commercial electronic air filters.The long-term goal of the present work is to develop an automatable means to detect viruses in aqueous samples using electrodeposition to capture viruses on the surfaces of optical fibers for infrared spectroscopic characterization and identification. Infrared spectroscopy is noninvasive and can provide information in minutes on the composition of a material. The components of a virus (nucleic acids, proteins, phospholipids, and other small molecules) present distinct vibrational fingerprints in the infrared (10-12) which can be used to identify and quantify the type of virus. Other materials present in typical drinking water systems produce minimal signals.Since infrared light is low energy (compared to UV or visible light), the sample may be repeatedly probed without causing damage, permitting continual measurement over the deposition process (10, 13). The vibrational spectrum collected provides an infrared signature very specific to each chemical or biological species. Spectra are typically collected over the range of 4,000 to 620 cm⁻¹ (2.50 to 16.13 μm), which contains the fundamental vibrations and overtones of many biochemicals, including proteins, nucleic acids, phosphates, ammonia, and lipids. For ease of interpretation, the spectral regions are divided into three zones (29). The first, 3,000 to 2,800 cm⁻¹, contains two primary bands at 2,852 cm⁻¹ and 2,922 cm⁻¹, which are attributed to CH₂ asymmetric and symmetric vibrations, respectively. CH₂-containing compounds are present predominantly in long-chain hydrocarbons, such as lipids. The two lower-intensity bands at 2,874 cm⁻¹ and 2,960 cm⁻¹ correspond to the symmetric and asymmetric CH₃ vibrations, respectively, found in lipids and proteins (25). The second (1,700 to 1,400 cm⁻¹) region contains the amide I (1,690 to 1,630 cm⁻¹) and amide II (1,548 cm⁻¹) features typical of proteins. The third spectral region, between 1,100 and 900 cm⁻¹, contains primarily C—O—C and C—O ring vibrations due to carbohydrates and P=O and P—O—P, representative of nucleic acids and phospholipids (18).The reason for the use of Fourier transform infrared (FTIR) spectroscopy in remote optical sensing is the recent availability of infrared transmitting fibers with low losses and sufficient chemical durability (13, 14). Chalcogenide glasses are one of very few materials that combine large optical windows in the infrared, low optical losses, chemical durability, and the ability to be drawn into fibers (15, 35). These glasses also have semiconducting properties similar to those of silicon and therefore have the appropriate electrical properties for use as an electrode during electrophoretic collection of negatively charged viruses. In the present work, we demonstrate the proof of concept for an electrophoretic optical sensor using a germanium (Ge) attenuated total reflectance (ATR) crystal with transparency from 2 to 13 μm in wavelength that spans the region of interest for identification of viral species. Ge is also a good semiconductor and can therefore act as both an optical element and an electrode. Charge-based collection and deposition of viruses have been demonstrated for a number of applications, including collection of viruses on sand and FeO particles and in column chromatography (19, 21, 31, 33). To our knowledge, this approach has not been previously applied by combining electrodeposition with infrared analysis.     

Defined Cell Types in Superior Colliculus Make Distinct Contributions to Prey Capture Behavior in the Mouse

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Cooperation and Prey Capture Efficiency in a Social Spider,Anelosimus eximius (Araneae,Theridiidae)

We studied the efficiency of the hunt and the characteristics of cooperation during the prey capture in a social spider Anelosimus eximius. Two natural types of prey of roughly the same length (20 mm) were used: grasshoppers (Orthoptera) and moths (Lepidoptera); 128 tests were made on 14 colonies, the smallest with 20 and the largest with 1,700 individuals. Test times were 12.00 h, defined as an inactive period for the spiders and 18.00 h, defined as an active period. Overall capture rate of intercepted prey was 66%: it was higher in large colonies or at 18.00 h, when more spider alerts were triggered by the struggling prey. Characteristics of cooperation during capture did not vary with colony size. Capture rate was higher for grasshoppers than moths (73%-58%) in spite of similar number of alerts (76%-87%); so moths must have been more difficult to capture. For both prey types, large colonies capture more rapidly and so had advantages in terms of time gain. We showed that cooperation depended on prey type: more spiders mobilised to attack moths and attack was faster than on grasshoppers. This may be interpreted as an adaptive response of the group to the prey type.     

Chemical Detection of Microbial Prey by Bacterial Predators

A motile, predacious bacterium which degraded Pythium debaryanum was strongly attracted to substances released into the medium by the fungus. A nonpredacious bacterium was not attracted to these substances. The predator bacterium was specifically attracted to cellulose and its oligomers which are known to be components of the cell wall of Pythium. Ethanol inhibited chemotaxis of the bacterium without affecting either its motility or its ability to degrade cellulose. A second predacious bacterium was isolated for the alga, Skeletonema costatum. The role of chemoreception in the detection of microbial prey by bacterial predators in natural habitats is discussed.     

Vertebrate Predation and Tool-Aided Capture of Prey by Savannah Wild Capuchin Monkeys (Sapajus libidinosus)

International Journal of Primatology - Vertebrate predation was a vital behavior during human evolution. Some Afro-Eurasian primates, such as baboons (Papio spp.) and chimpanzees (Pan troglodytes),...