Worm Behavior Research Articles

Exploring minimal models of sensory integration in nematode C. elegans

To survive, animals must select and execute appropriate actions in response to cues in rich, variable environments. Key to effective sensory processing is the ability to integrate inputs from different sensory modalities in a behaviorally meaningful way. Remarkably, even the simplest animals exhibit non-trivial forms of sensory integration. The roundworm Caenorhabditis elegans is a particularly interesting system in this context, due to the compactness of its small nervous system: unlike the modular organization of vertebrate or even insect brains, in C. elegans, sensory neurons responding in all different modalities (smell, taste, touch, temperature, and much more) all project onto a single circuit, the so called head navigation circuit. How this circuit integrates these inputs to generate appropriate behaviors is a wide open question. In fact, past computational models of this system short circuit the problem, by connecting model sensory neurons directly to motor neurons. That said, this approach may be adequate for modeling sensory responses to a single set of sensory neurons, and a single stimulus type. Here we take the first steps to model sensory integration, with the aim of better understanding the computational role of the navigation circuit and its constituent neurons. We follow an iterative process of model design, validation and refinement against experimental data, and design and implementation of critical in silico experiments to test model predictions. We begin with a model, inspired by results from published sensory integration experiments [1], with a minimal set of neurons directly implicated in the computation. Importantly, this model includes sensory, interneuron and motor layers; it is embodied and fully situated, allowing us to test the model performance against experimentally obtained behavioral metrics. We explicitly demonstrate the necessity of including a full sensorimotor pathway to assess multi-sensory integration. The motor behavior of the worm is relatively well characterized. However, this classification relies mostly on experiments in the absence of external stimuli, or during navigation on gradients of attractive chemicals. Our integration experiments are based on responses to a combination of attractive and repulsive stimuli. Interestingly, we find that the existing repertoire of behaviors fails to account for the animal's responses to repellents. Therefore, a key prediction of our model is the existence of a novel motor behavior mediated by a distinct sensorimotor pathway. Surprisingly, we prove that a fully linear circuit, with rectified motor outputs is sufficient to qualitatively capture complex sensory integration as seen in behavioral data. This result is consistent with experimental findings implicating a single pair of interneurons in this form of sensory integration [1] but dispenses the postulated requirements for nonlinear input-output function of these neurons and feedback connections to the sensory layer. Furthermore, we show that changes in the ratios of afferent synaptic weights from different sensory neurons onto a linear integration interneuron allow precise control over the processing of single and combined stimuli. Implementation of novel sensory receptor properties and a sigmoidal activation function in the integration interneuron results in quantitatively correct model performance. Finally, we study the behavior of defective worms, (with virtually mutations or ablated neurons) and use this analysis to predict a role for additional interneurons in the navigation circuit.

The Tiniest Traps: Optical Manipulation Gets Smaller

Arthur Ashkin ushered in the field of optical manipulation more than 40 years ago. Today, smaller and smaller tools, such as optical “nanotweezers” and precisely focused lasers, are becoming practical for controlling single cells, individual proteins, DNA and even the behavior of worms.

Mathematical model on the transmission of worms in wireless sensor network

Wireless sensor networks (WSNs) have received extensive attention due to their great potential in civil and military applications. The sensor nodes have limited power and radio communication capabilities. As sensor nodes are resource constrained, they generally have weak defense capabilities and are attractive targets for software attacks. Cyber attack by worm presents one of the most dangerous threats to the security and integrity of the computer and WSN. In this paper, we study the attacking behavior of possible worms in WSN. Using compartmental epidemic model, we propose susceptible – exposed – infectious – recovered – susceptible with a vaccination compartment (SEIRS-V) to describe the dynamics of worm propagation with respect to time in WSN. The proposed model captures both the spatial and temporal dynamics of worms spread process. Reproduction number, equilibria, and their stability are also found. If reproduction number is less than one, the infected fraction of the sensor nodes disappears and if the reproduction number is greater than one, the infected fraction persists and the feasible region is asymptotically stable region for the endemic equilibrium state. Numerical methods are employed to solve and simulate the systems of equations developed and also to validate our model. A critical analysis of vaccination class with respect to susceptible class and infectious class has been made for a positive impact of increasing security measures on worm propagation in WSN.

The SOL-2/Neto Auxiliary Protein Modulates the Function of AMPA-Subtype Ionotropic Glutamate Receptors

The neurotransmitter glutamate mediates excitatory synaptic transmission by gating ionotropic glutamate receptors (iGluRs). AMPA receptors (AMPARs), a subtype of iGluR, are strongly implicated in synaptic plasticity, learning, and memory. We previously discovered two classes of AMPAR auxiliary proteins in C. elegans that modify receptor kinetics and thus change synaptic transmission. Here, we have identified another auxiliary protein, SOL-2, a CUB-domain protein that associates with both the related auxiliary subunit SOL-1 and with the GLR-1 AMPAR. In sol-2 mutants, behaviors dependent on glutamatergic transmission are disrupted, GLR-1-mediated currents are diminished, and GLR-1 desensitization and pharmacology are modified. Remarkably, a secreted variant of SOL-1 delivered in trans can rescue sol-1 mutants, and this rescue depends on in cis expression of SOL-2. Finally, we demonstrate that SOL-1 and SOL-2 have an ongoing role in the adult nervous system to control AMPAR-mediated currents.

Size matters: modeling the effects of body shape on locomotive behavior in the nematode C. elegans

The microscopic nematode worm, C. elegans, has a hard wired and comprehensively mapped neural circuit, with only 302 neurons in the adult. The organism's simplicity and the wealth of information available about it make C. elegans an inviting target for computer modeling. Locomotion is the clearest measure of the worm's behavior, and the undulatory waves used in the worm's movement are directly affected by the shape of the animal's body. As the worm develops from a larva to adulthood its body grows and changes in shape. More dramatically, mutant C. elegans exist with bodies that are considerably longer or shorter than in the wildtype, and these worms have severe locomotion phenotypes. Previous models for locomotion have often concentrated on either the worm's nervous system or body, modeling only one area in detail and greatly simplifying the other. This neglects important interactions between the physical and neural aspects of the worm's behavior, such as touch response, proprioception and the effects of its surroundings. We use an integrated neuromechanical model that incorporates the worm's neural circuit for locomotion, its body and its environment. We have previously used the model to predict that the L1 larva maintains robust forward locomotion using a similar gait to the adult worm, and now examine the behavior of the body shape mutants dpy-1, dpy-11 and lon-2, both in liquid and on gel. Testing model predictions against data from biological experiments, we can validate its robustness to such physical differences and its ability to capture the behavior of new phenotypes. Three candidates exist for the cause of behavioral abnormalities seen in such mutants; differences in the worm's neural circuit, muscle properties, or passive body properties. We make clear experimental predictions on the locus of change and the specific pathways through which it is effected.

Biology of the Swimming Acorn WormGlandiceps hacksifrom the Seto Inland Sea of Japan

The enteropneust hemichordate Glandiceps hacksi inhabits the muddy bottoms of the intertidal to subtidal zones of Koguno-shima Island, located in the central part of the Seto Inland Sea of Japan. Monthly collections from October 2005 to September 2007 revealed that their spawning occurs once a year, in the latter half of May. Parameters such as density and sex ratio, as well as the type of sediment, were also examined. Worm behavior and type of burrows revealed that G. hacksi are infaunal burrowers. Autotomy and regeneration of their posterior regions, and swimming behavior were also observed in an aquarium environment. This is the first comprehensive study on the biology of G. hacksi, the swimming acorn worm.

Chemosensory cue conditioning with stimulants in a Caenorhabditis elegans animal model of addiction.

The underlying molecular mechanisms of drug abuse and addiction behaviors are poorly understood. Caenorhabditis elegans (C. elegans) provide a simple, whole animal model with conserved molecular pathways well suited for studying the foundations of complex diseases. Historically, chemotaxis has been a measure used to examine sensory approach and avoidance behavior in worms. Chemotaxis can be modulated by previous experience, and cue-dependent conditioned learning has been demonstrated in C. elegans, but such conditioning with drugs of abuse has not been reported. Here we show that pairing a distinctive salt cue with a drug (cocaine or methamphetamine) results in a concentration-dependent change in preference for the cue that was paired with the drug during conditioning. Further, we demonstrate that pairing of either drug with a distinctive food type can also increase preference for the drug-paired food in the absence of the drug. Dopamine-deficient mutants did not develop drug-paired, cue-conditioned responses. The findings suggest that, like vertebrates, C. elegans display a conditioned preference for environments containing cues previously associated with drugs of abuse, and this response is dependent on dopamine neurotransmission. This model provides a new and powerful method to study the genetic and molecular mechanisms that mediate drug preference.

A Behaviour based Framework for Worm Detection

Increasing threats from worms in the internet continue to be a challenge for current content-based Network Intrusion Detection Systems (NIDS). Worms use different obfuscation techniques (You & Yim 2010) to evade detection and if the worm's signature is not previously known, such systems fail. This paper proposes the use of behavioral signatures for network intrusion detection. The different infection phases exhibited by a worm can be used to characterize its network behaviour. Such behaviour of worms can be captured in the proposed scheme by using behavioural signatures.

Resistive switching non-volatile and volatile memory behavior of aromatic polyimides with various electron-withdrawing moieties

In this study, N,N′-bis(4-aminophenyl)-N,N′-di(4-methoxyl-phenyl)1,4-phenylenediamine [(OMe)2TPPA-diamine] and various dianhydrides such as oxydiphthalic dianhydride (ODPA), 3,3′,4,4′-diphenylsulfonetetracarboxylic dianhydride (DSDA), pyromellitic dianhydride (PMDA), and 1,4,5,8-naphthalenetetracarboxylic dianhydride (NPDA) were used to synthesize new functional polyimides (OMe)2TPPA-ODPI (ODPI), (OMe)2TPPA-DSPI (DSPI), (OMe)2TPPA-PMPI (PMPI), and (OMe)2TPPA-NPPI (NPPI), respectively for memory device applications. For comparison, the corresponding (OMe)2TPPA-6FPI (6FPI) was also added into the discussion. The differences of HOMO energy levels, LUMOs energy levels, and dipole moment among these five polyimides with different electron-withdrawing linkage were investigated and demonstrated the effect on the memory behavior. With the electron-withdrawing moiety intensity of polyimides increasing, the retention time of corresponding memory device increases. ODPI didn't have memory properties, 6FPI exhibited DRAM characteristic, and PMPI with stronger electron-withdrawing linkage revealed SRAM behavior. NPPI with the strongest electron-withdrawing linkage showed WORM type non-volatile memory behavior. Interestingly, DSPI have the LUMO energy levels between 6FPI and PMPI but revealed non-volatile WORM behavior resulting from the highest dipole moment 5.45 D.

Tracking Movement Behavior of Multiple Worms on Food

Neurobiological research in genetically tractable organisms relies heavily on robust assays for behavioral phenotypes. The simple body plan of the nematode Caenorhabditis elegans makes it particularly amenable to the use of automated microscopy and image analysis to describe behavioral patterns quantitatively. Forward genetic screens and screens of drug libraries require high-throughput phenotyping, a task traditionally incompatible with manual scoring of quantitatively varying behaviors. High-throughput automated analysis of C. elegans movement behavior is now possible with several different tracking software packages. The Multiworm Tracker (MWT) described here is designed for high-throughput analysis: it can record dozens of worms simultaneously at 30 frames per second for hours or days at a time. This is accomplished by performing all image analysis in real time, saving only the worm centroid, bearing, and outline data to the disk. To simplify image processing, the system focuses only on worms that have moved, and detects and discards worms that are touching rather than trying to isolate them computationally. Because the software is entirely automated, protocols can run unattended once the worms have been placed and the software has been started. The MWT does not save images for later analysis, but behavior can be validated manually with a companion analysis tool that replays recorded body postures. This protocol describes a basic basal movement assay on food using the MWT; similar protocols apply to related assays and to similar multiple animal trackers. The protocol can be extended to a variety of assays ranging from tap response to chemotaxis.

Effect of pulse direct current signals on electrotactic movement of nematodes Caenorhabditis elegans and Caenorhabditis briggsae.

The nematodes (worms) Caenorhabditiselegans and Caenorhabditisbriggsae are well-known model organisms to study the basis of animal development and behaviour. Their sinusoidal pattern of movement is highly stereotypic and serves as a tool to monitor defects in neurons and muscles that control movement. Until recently, a simple yet robust method to initiate movement response on-demand did not exist. We have found that the electrical stimulation in a microfluidic channel, using constant DC electric field, induces movement (termed electrotaxis) that is instantaneous, precise, sensitive, and fully penetrant. We have further characterized this behaviour and, in this paper, demonstrate that electrotaxis can also be induced using a pulse DC electric signal. Worms responded to pulse DC signals with as low as 30% duty cycle by moving towards the negative electrode at the same speed as constant DC fields (average speed of C. elegans = 296 ± 43 μm/s and C. briggsae = 356 ± 20 μm/s, for both constant and pulse DC electric fields with various frequencies). C. briggsae was found to be more sensitive to electric signals compared to C. elegans. We also investigated the turning response of worms to a change in the direction of constant and pulse DC signals. The response for constant DC signal was found to be instantaneous and similar for most worms. However, in the case of pulse DC signal, alterations in duty cycle affected the turning response time as well as the number of responding worms. Our findings show that pulse DC method allows quantitative measurement of response behaviour of worms and suggest that it could be used as a tool to study the neuronal basis of such a behaviour that is not observed under constant DC conditions.

Microfluidic Devices for Analysis of Spatial Orientation Behaviors in Semi-Restrained Caenorhabditis elegans

This article describes the fabrication and use of microfluidic devices for investigating spatial orientation behaviors in nematode worms (Caenorhabditis elegans). Until now, spatial orientation has been studied in freely moving nematodes in which the frequency and nature of encounters with the gradient are uncontrolled experimental variables. In the new devices, the nematode is held in place by a restraint that aligns the longitudinal axis of the body with the border between two laminar fluid streams, leaving the animal's head and tail free to move. The content of the fluid streams can be manipulated to deliver step gradients in space or time. We demonstrate the utility of the device by identifying previously uncharacterized aspects of the behavioral mechanisms underlying chemotaxis, osmotic avoidance, and thermotaxis in this organism. The new devices are readily adaptable to behavioral and imaging studies involving fluid borne stimuli in a wide range of sensory modalities.

Copper ions influence the toxicity of β-amyloid(1–42) in a concentration-dependent manner in a Caenorhabditis elegans model of Alzheimer’s disease

β-amyloid (Aβ) and copper play important roles in the pathogenesis of Alzheimer's disease (AD). However, the behavioral correlativity and molecular mechanisms of Aβ and copper toxicity have been investigated less often. In the present study, we investigated the interaction and toxicity of Aβ1-42 and copper in the Aβ1-42 transgenic Caenorhabditis elegans worm model CL2006. Our data show that the paralysis behavior of CL2006 worms significantly deteriorated after exposure to 10(-3) mol L(-1) copper ions. However, the paralysis behavior was dramatically attenuated with exposure to 10(-4) mol L(-1) copper ions. The exogenous copper treatment also partially changed the homeostatic balance of zinc, manganese, and iron. Our data suggest that the accumulation of reactive oxygen species (ROS) was responsible for the paralysis induced by Aβ and copper in CL2006. The ROS generation induced by Aβ and copper appear to be through sod-1, prdx-2, skn-1, hsp-60 and hsp-16.2 genes.

Some like it hot: decoding neurotransmission in the worm's thermotaxis circuit

Some like it hot: decoding neurotransmission in the worm's thermotaxis circuit

Stability Analysis of P2P Worm Propagation Model with Dynamic Quarantine Defense

The propagation of P2P worm covers large area and causes great damage. A dynamic quarantine protocol is designed to quarantine the suspicious host in the P2P system. Then a mathematical model of PWPQ is proposed which considering the dynamic process of peer joining and leaving. The effect of dynamic quarantine on active P2P worm is analyzed. Through stability analysis for PWPQ model, a key argument of infection-free stable point which affect the P2P worm propagation, the basic reproduction number, is deduced. Simulation results show that the propagation model of P2P worms can reflect the P2P worm behaviors and the performance of our model is significantly better than other models, in terms of decreasing the number of infected hosts and reducing the worm propagation speed. When the basic reproduction number is less than 1, infection-free stable point is global stability and the P2P worm are eliminated. The PWPQ model gives some way to control P2P worm break out and gives guidelines to P2P worm detection and defense.

Distribution, abundance and trail characteristics of acorn worms at Australian continental margins

Acorn worms (Enteropneusta), which were previously thought to be a missing link in understanding the evolution of chordates, are an unusual and potentially important component of many deep-sea benthic environments, particularly for nutrient cycling. Very little is known about their distribution, abundance, or behaviour in deep-sea environments around the world, and almost nothing is known about their distribution within Australian waters. In this study, we take advantage of two large-scale deep-sea mapping surveys along the eastern (northern Lord Howe Rise) and western continental margins of Australia to quantify the distribution, abundance and trail-forming behaviour of this highly unusual taxon. This is the first study to quantify the abundance and trail behaviour of acorn worms within Australian waters and provides the first evidence of strong depth-related distributions. Acorn worm densities and trail activity were concentrated between transect-averaged depths of 1600 and 3000 m in both eastern and western continental margins. The shallow limit of their depth distribution was 1600 m. The deeper limit was less well-defined, as individuals were found in small numbers below 3000 down to 4225 m. This distributional pattern may reflect a preference for these depths, possibly due to higher availability of nutrients, rather than a physiological constraint to greater depths. Sediment characteristics alone were poor predictors of acorn worm densities and trail activity. High densities of acorn worms and trails were associated with sandy-mud sediments, but similar sediment characteristics in either shallower or deeper areas did not support similar densities of acorn worms or trails. Trail shapes varied between eastern and western margins, with proportionally more meandering trails recorded in the east, while spiral and meandering trails were both common in the west. Trail shape varied by depth, with spiral-shaped trails dominant in areas of high acorn worm densities (2000–3000 m water depth) while meandering trails were common over a much broader depth range and were the only trails recorded in deep environments >3000 m. While species-specific patterns may in part explain these differences, evidence suggests that nutrient availability is also likely to be an important driving factor, supporting the hypothesis put forward by Smith et al. (2005) that acorn worms meander when searching for food and form a spiral when feeding in a nutrient-rich area.

Computer aided analysis on the meshing behavior of a height-modified dual-torus double-enveloping toroidal worm drive

A flank modification methodology is proposed for the double-enveloping toroidal worm drive and a novel type of the dual-torus double-enveloping toroidal worm drive (the DTT worm drive) is developed. Because the height variation of the tool relative to the position during generating an unmodified worm is the unique modification parameter, this novel type of worm drive can be named as the height-modified DTT worm drive. Based on a strict meshing analysis, the selection principle of the modification style is recommended. A systematic and thorough study is conducted on the meshing behavior of the height-modified DTT worm pair by means of a computer simulation. The investigation results show that the height-modified DTT worm drive has favorable meshing performance.

Invertebrate insights into autism

Autism is a neurodevelopmental disorder characterized by deficits in social communication and interaction, impaired language development, and stereotyped repetitive behaviors. The broader category of autism spectrum disorders (ASDs) includes individuals with subsets of these symptoms ([Geschwind and

A computational model of associative learning and chemotaxis in the nematode worm C. elegans

The nematode worm C. elegans is an exciting model system for experimentalists and modelers alike. It has a relatively small nervous system, made up of just 302 neurons in the adult hermaphrodite, that has been mapped in detail using serial section electron microscopy. Despite the simplicity of its nervous system C. elegans displays a range of interesting behaviors. This includes thermo- and chemotaxis and the modulation of locomotion strategies in response to the presence of food. In chemotaxis C. elegans will move up or down a chemical gradient dependent on whether the chemical acts as an attractant or repellent. It does this in two distinct ways, first by gradually steering left or right until the worm points up or down the gradient and second by modulating the probability of initiating a sharp series of turns (known as a piroeutte) along with the final orientation of the worm after the pirouette has finished. Experimental work has shown that the chemotaxis response is dynamic and that the degree of influence a particular chemical has on navigation can be changed, or even reversed depending on experience. Changes are reversible, specific to the chemical in question, and can be generated by classical conditioning experiments. All of these are hallmarks of associative learning, a sophisticated process that requires integration of multiple signals to produce a coordinated change in a behavioral response. Despite the wealth of experimental data on learning in chemotaxis in C. elegans, comparatively little is known about how the known circuitry of C. elegans carries out the computations that underlie it. Even less is known about how that circuitry changes during associative learning. Here, we focus on the worm's chemotaxis and the ability of C. elegans to learn associations between salt (NaCl) concentrations and food. We draw upon existing experimental data from a variety of sources including electrophysiological and anatomical data to construct a simplified NaCl chemotaxis circuit in C. elegans. This circuit consists of the left and right ASE amphid sensory neurons, which comprise the dominant NaCl sensation pathway in C. elegans, eight pairs of interneurons, and ten head motor neurons. Where possible the properties of individual neurons are constrained by electrophysiological and calcium imaging data. We next define a set of experimentally observed behaviors we wish to reproduce, including gentle turning, modulation of pirouette frequency, control of final orientation following a pirouette, and associative learning. In particular, we are interested in the alteration in behavioral response to NaCl that arises due to the pairing of high concentrations of NaCl with food or starvation. We use this to derive a family of model networks with specific synaptic polarities, time scales of neuronal responses, and intrinsic neuronal properties that have the capacity to generate the specified set of behaviors. We implement one of these models and record the behaviour of model worms that are placed in a variety of simulated environments. We observe qualitatively realistic chemotaxis behavior and adaptation and demonstrate that our model is robust and tolerant to noise. Our proposed chemotaxis circuit leads to a number of distinct predictions that could be used to test the model experimentally. This includes postulating the computational role of each neuron in the network and the locus and nature of the plasticity underpinning the experimentally observed associative learning. Our model also suggests that this plasticity be expressed not by changes in synaptic strength but by changes in the sensory neurons themselves. Thus, contrary to the prevailing view in the C. elegans community, plasticity in our model of chemotaxis is expressed at a neuronal rather than synaptic level. C. elegans offers a unique opportunity to push the boundaries of systems neuroscience. The ability to model a neuronal circuit in such detail is a remarkable opportunity to study associative learning in an animal displaying a sophisticated set of behaviors and nontrivial learning. A biologically grounded model of behavior and learning in C. elegans has great potential to offer detailed and integrated understanding of sensory processing, synaptic plasticity and associative learning. Lessons learned from such models can be applied to other sensory and sensorimotor modalities in the worm with the eventual goal of producing an integrated model of the worm's sensorimotor system. We believe that theoretical insights gained from this endeavour will be invaluable in our study of larger, more complex nervous systems.

WORM DETECTION USING HONEYPOTS FOR WINDOWS ENVIRONMENT

Recent cybersecurity incidents suggest that internet worms can spread so fast that in-time human-mediated reaction is not possible, and therefore initial response to cyberattacks has to be automated. In this paper we present a system for detecting known and unknown worms using honeypots. The proposed system detects worms by monitoring connection activity and watching for patterns of traffic that are expressions of some of the essential characteristics of worm behavior. The implementation is a signature-based detection as a first tier and an anomaly-based as a second tier in the detection process. At a network's gateway, the proposed system runs a vantage point from which all traffic into and out of the network is visible. The system employs a honeypot to capture traffic, after discarding whitelisted patterns; as it automatically generates worm signatures which are matched with the signatures of the known worms stored in original database. When a signature is matched, the system reports it by issuing an alert that also includes the IP addresses involved in the transaction. Otherwise, the system monitors the changes in the performance of CPU, RAM and changes in files in the gateway which are considered as indicators to the presence of worms. The proposed system was evaluated using a dataset collected from internet for several days, and potentially showed good results for detecting and collecting information about worms from local network. It was noticed that the performance was increased up to 23% more than other systems that uses honeypots.