Pressure-induced silk spinning mechanism in webspinners (Insecta: Embioptera)

The articulated appendages of arthropods are highly adaptable and potentially multifunctional, used for walking, swimming, feeding, prey capture, or other functions. Webspinners (Order Embioptera) are a paragon in this context. In contrast to other arthropods producing silk, they utilize their front feet for silk production. However, employing the same leg for alternative functions rather than for pure locomotion potentially imposes constraints and compromises. We here present morphological and experimental evidence for a "passive" pressure-induced silk spinning mechanism induced by external mechanical stimuli. Furthermore, we demonstrate that, as a consequence of the conflicting functions for their front feet, webspinners have evolved a unique style of walking that reduces the potentially problematic contact between silk ejectors and the substrate. Here we answer for the first time a long-term question within this enigmatic group of insects-how webspinners can use their front feet to spin their nanoscale silk. This knowledge may open the door for experimental studies on an artificial spinning process and for future utilization in applied fields of robotics or chemistry.

Lead exposure-induced cognitive impairment through RyR-modulating intracellular calcium signaling in aged rats

Lead is widely distributed in the environment and has become a global public health issue. It is well known that lead exposure induces not only neurodevelopmental toxicity but also neurodegenerative diseases, with learning and memory impairment in the later stage. However, the molecular mechanisms remain elusive. The present study investigated the effects of early life and lifetime lead exposure on cognition and identified the molecular mechanisms involved in aged rats. The results herein demonstrated that the lead concentration in peripheral blood and brain tissues in aged rats was significantly increased in a lead dose-dependent manner. High-dose lead exposure caused cognitive functional impairment in aged rats, concomitant with a longer escape latency and a lower frequency of crossing the platform via Morris water maze testing compared to those in the control and low-dose lead exposure groups. Importantly, neuron functional defects were still observed even in early life lead exposure during the prenatal and weaning periods in aged rats. The neurotoxicity induced by lead exposure was morphologically evidenced by a recessed nuclear membrane, a swollen endoplasmic reticulum, and mitochondria in the neurons. Mechanistically, the exposure of aged rats to lead resulted in increasing free calcium concentration, reactive oxygen species, and apoptosis in the hippocampal neurons. Lead exposure increased RyR3 expression and decreased the levels of p-CaMKIIα/CaMKIIα and p-CREB/CREB in the hippocampus of aged rats. These findings indicated that early life lead exposure-induced cognition disorder was irreversible in aged rats. Lead-induced neurotoxicity might be related to the upregulation of RyR3 expression and high levels of intracellular free calcium with increasing lead concentration in injured neurons.

A procedure for human safety assessment during hydropeaking events

A method for human safety assessment on a hydropeaked river reach is proposed and applied to an Alpine river. The human safety analysis during hydropeaking events is of particular interest because most of the Alpine watercourses are affected by hydropower plant energy production that cause rapid and frequent flow alterations (hydropeaking), but at the same time these watercourses are used by the population for recreational purposes. In literature, many studies have focused on the effect of hydropeaking on the biota but a study of the interaction between a hydropeaking wave and human safety does not yet exist. The proposed procedure is characterized by the combination of hydraulic numerical simulations to study the characteristics of the flow field with a human safety analysis and is applied to a case study in north Italy. Human safety can be assessed in two different ways: one is by studying human stability during hydropeaking events and the other is exploring the possibility of a "target person" leaving the reach during hydropeaking waves, adapting proper escape strategies. For the escape strategy Dijkstra's algorithm is used, where the distance between adjacent nodes is defined as the difficulty (penalty) of moving from one node to the other. For this reason, an original set of penalty functions is proposed that takes into account the steepness (slope between two adjacent computational cells), the roughness, and the product between the water depth and flow velocity. The results show that the difficulty in escaping increases with the flow rate. Moreover, the areas where the human safety is very low are mainly located in the central part of the watercourse. The present work proposes a possible investigational tool to evaluate and parameterize the risk for the population during hydropeaking events through quantitative indices.

Upregulation of hippocampal extracellular signal-regulated kinase (ERK)-2 induces antidepressant-like behavior in the rat forced swim test

The hippocampus mediates responses to affect-related behavior in preclinical models of pharmacological antidepressant efficacy, such as the forced swim test. However, the molecular mechanisms that regulate escape-directed behavior in this preclinical model of despair are not well understood. Here, using viral-mediated gene transfer, we assessed how overexpression of extracellular signal-regulated protein kinase (ERK)-2 within the dorsal hippocampus influenced behavioral reactivity to inescapable swimming stress in adult male Sprague-Dawley rats. When compared to controls, rats overexpressing hippocampal ERK-2 displayed increases in the time to initially adopt a posture of immobility, along with decreases in total time spent immobile, without influencing general locomotor activity. Collectively, the results indicate that hippocampal upregulation of ERK-2 increases escape-directed behavior in the rat forced swim test, thus providing insight into the neurobiological mechanisms that mediate antidepressant efficacy. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

The evolution of variance in sequential defences

The defences used by organisms against predators display a great degree of variability. Defence phenotypes can differ substantially among individuals of the same species, and a single individual can itself deploy a variety of defences. Here, we use a mathematical model that includes mutation and selection to understand the evolutionary origin of this variability in a population of a species that deploys defences sequentially ("first" and "second" defences). Typically, the first defence evolves to have lower variance, i.e. appears more closely accumulated around the ideal phenotype, than the second defence (even when the breaching the first defence incurs more fitness loss than breaching the second defence with the other parameters the same for both defences). However, if the first defence is much less effective in repelling predators, or is much less tolerant of deviation from the ideal phenotype, then the first defence can evolve to have higher variance than the second. Other factors like mutation strength and the losses in the fitness when each defence fails also influence the defence variance. Larger mutation rate incurs larger equilibrium variances, and when the comparative importance in fitness of one defence increases, then the ratio between the variances of this defence and the other defence decreases. Sequentially acting defences are found in many organisms, so we encourage empirical research to test our theoretical predictions.

What color are emergency exit signs? Egress behavior differs from verbal report

Illuminated emergency exit signs inform building occupants about safe egress routes in emergencies. These exit signs are often found in the presence of other colored signs, which may distract occupants when searching for safe exits. Such distractions can lead to confusing and even harmful outcomes, especially if occupants misinterpret the sign colors, mistaking non-exit signs for exit signs. We studied which colored signs people were most likely to infer were exit signs in a simulated emergency evacuation using virtual reality (VR). Participants were immersed in a virtual room with two doors (left and right), and an illuminated sign with different colored vertical bars above each door. They saw all pairwise combinations of six sign colors across trials. On each trial, a fire alarm sounded, and participants walked to the door that they thought was the exit. We tested two hypotheses: a local exposure hypothesis that color inferences are determined by exit sign colors in the local environment (i.e., red) and a semantic association hypothesis that color inferences are determined by color-concept associations (i.e. green associated with "go" and "safety"). The results challenged the local exposure hypothesis and supported the semantic association hypothesis. Participants predominantly walked toward green signs, even though the exit signs in the local environment-including the building where the experiment took place-were red. However, in a post-experiment survey, most participants reported that exit signs should be red. The results demonstrated a dissociation between the way observers thought they would behave in emergency situations (red = exit) and the way they did behave in simulated emergencies (green = exit). These findings have implications for the design of evacuation systems. Observers, and perhaps designers, do not always anticipate how occupants will behave in emergency situations, which emphasizes the importance of behavioral evaluations for egress safety.

The Basolateral Amygdala Is Essential for Rapid Escape: A Human and Rodent Study

Rodent research delineates how the basolateral amygdala (BLA) and central amygdala (CeA) control defensive behaviors, but translation of these findings to humans is needed. Here, we compare humans with natural-selective bilateral BLA lesions to rats with a chemogenetically silenced BLA. We find, across species, an essential role for the BLA in the selection of active escape over passive freezing during exposure to imminent yet escapable threat (Timm). In response to Timm, BLA-damaged humans showed increased startle potentiation and BLA-silenced rats demonstrated increased startle potentiation, freezing, and reduced escape behavior as compared to controls. Neuroimaging in humans suggested that the BLA reduces passive defensive responses by inhibiting the brainstem via the CeA. Indeed, Timm conditioning potentiated BLA projections onto an inhibitory CeA pathway, and pharmacological activation of this pathway rescued deficient Timm responses in BLA-silenced rats. Our data reveal how the BLA, via the CeA, adaptively regulates escape behavior from imminent threat and that this mechanism is evolutionary conserved across rodents and humans.

Social Status-Related Differences in Motor Activity Between Wild-Type and Mutant Zebrafish

Use of zebrafish as a model organism in biomedical research has led to the generation of many genetically modified mutant lines to investigate various aspects of developmental and cellular processes. However, the broader effects of the underlying mutations on social and motor behavior remain poorly examined. Here, we compared the dynamics of social interactions in the Tüpfel long-fin nacre mutant line, which lacks skin pigmentation, to wild-type zebrafish; and we determined whether status-dependent differences in escape and swimming behavior existed within each strain. We show that despite similarities in aggressive activity, Tüpfel long-fin nacre pairs exhibit unstable social relationships characterized by frequent reversals in social dominance compared to wild-type pairs. The lack of strong dominance relationships in Tüpfel long-fin nacre pairs correlates with weak territoriality and overlapping spatial distribution of dominants and subordinates. Conversely, wild-type dominants displayed strong territoriality that severely limited the movement of subordinates. Additionally, the sensitivity of the startle escape response was significantly higher in wild-type subordinates compared to dominants. However, status-related differences in sensitivity of escape response in Tüpfel long-fin nacre pairs were absent. Finally, we present evidence suggesting that these differences could be a consequence of a disruption of proper visual social signals. We show that in wild-type pairs dominants are more conspicuous, and that in wild-type and Tüpfel long-fin nacre pairings wild-type fish are more likely to dominate Tüpfel long-fin nacres. Our results serve as a cautionary note in research design when morphologically engineered zebrafish for color differences are utilized in the study of social behavior and central nervous system function.

The effect of rearing structures on behaviour and movement of juvenile steelhead Oncorhynchus mykiss

The relative movement of juvenile steelhead Oncorhynchus mykiss reared on two treatments was investigated to provide insight on the effect of structure in the rearing environment on the behaviour of the fish before potential release into a natural river system. The progeny of wild broodstock were reared either in the presence or absence of structure in the tank environment for 7 months at the Oregon Hatchery Research Center located in Oregon, U.S.A. Behavioural assessments, including movement response to a simulated predator, showed that fish reared on structure moved a similar amount (based on line crosses) as fish reared in bare hatchery tanks. No significant difference was observed in the proportion of time spent near a small structure within the behavioural test tank between the two treatments, but all fish showed decreased movement over time with each subsequent predation event. Fish from both treatments spent 30% of their time in the section of the tank containing the structure, which was one section out of a total of eight sections. In both treatments, fish foraged 20% of the time in the 2 min following the introduction of live tubifex prey (two separate events). Overall, similar movement and foraging responses occurred following mock predation events for juveniles reared either with or without structure. Developing assessment tools such as these, that measures behaviours related to survival based on rearing environment should allow managers to better predict the survival and effect of rearing conditions on the release of hatchery-origin fish into the wild.

Born to Run? Quantifying the Balance of Prior Bias and New Information in Prey Escape Decisions

Animal behaviors can often be challenging to model and predict, though optimality theory has improved our ability to do so. While many qualitative predictions of behavior exist, accurate quantitative models, tested by empirical data, are often lacking. This is likely due to variation in biases across individuals and variation in the way new information is gathered and used. We propose a modeling framework based on a novel interpretation of Bayes's theorem to integrate optimization of energetic constraints with both prior biases and specific sources of new information gathered by individuals. We present methods for inferring distributions of prior biases within populations rather than assuming known priors, as is common in Bayesian approaches to modeling behavior, and for evaluating the goodness of fit of overall model descriptions. We apply this framework to predict optimal escape during predator-prey encounters, based on prior biases and variation in what information prey use. Using this approach, we collected and analyzed data characterizing white-tailed deer (Odocoileus virginianus) escape behavior in response to human approaches. We found that distance to predator alone was not sufficient to predict deer flight response and show that the inclusion of additional information is necessary. We also compared differences in the inferred distributions of prior biases across different populations and discuss the possible role of human activity in influencing these distributions.

Passion or addiction? Correlates of healthy versus problematic use of videogames in a sample of French-speaking regular players

A criticism of current diagnostic approaches to gaming disorder is that they fail to take into account that high and repeated engagement is not problematic per se, nor is it necessarily associated with adverse consequences. To tackle this controversy, we used Confirmatory Factor Analysis (CFA) to test, in regular gamers (N = 268), whether high (but healthy) engagement can be distinguished from problematic engagement by using the Addiction-Engagement Questionnaire (Charlton & Danforth, 2007). We then tested whether differential relationships exist between the engagement and addiction constructs, DSM-5 criteria for Internet gaming disorder (IGD), and psychological factors linked to gaming use and misuse (self-reported impulsivity, motives to play, and depression). Results indicated that a model holding engagement and addiction as two distinct, but related, constructs fits the data well. Second, we showed that although both constructs are linked to the number of IGD criteria endorsed, the relationship is more pronounced for the addiction construct. Third, a differential pattern of correlations was observed with the other study variables, further supporting the need to distinguish the two constructs. Our study emphasizes that research is needed to refine the diagnostic approach to gaming disorder to avoid conflating healthy passion with pathological behavior.

Differential effects of voluntary wheel running and toy rotation on the mRNA expression of neurotrophic factors and FKBP5 in a post-traumatic stress disorder rat model with the shuttle-box task

Life-threatening experiences can result in the development of post-traumatic stress disorder. We have developed an animal model for post-traumatic stress disorder (PTSD) using a shuttle box in rats. In this paradigm, the rats were exposed to inescapable foot-shock stress (IS) in a shuttle box, and then an avoidance/escape task was performed in the same box 2 weeks after IS. A previous study using this paradigm revealed that environmental enrichment (EE) ameliorated avoidance/numbing-like behaviors, but not hyperarousal-like behaviors, and EE also elevated hippocampal brain-derived neurotrophic factor (BDNF) expression. However, the differential effects of EE components, i.e., running wheel (RW) or toy rotation, on PTSD-like behaviors has remained unclear. In this experiment, we demonstrated that RW, toy rotation, and EE (containing RW and toy rotation) ameliorated avoidance/numbing-like behaviors, induced learning of avoidance responses, and improved depressive-like behaviors in traumatized rats. The RW increased the hippocampal mRNA expression of neurotrophic factors, especially BDNF and glial-cell derived neurotrophic factor. Toy rotation influenced FK506 binding protein 5 mRNA expression, which is believed to be a regulator of the hypothalamic-pituitary-adrenal (HPA)-axis system, in the hippocampus and amygdala. This is the first report to elucidate the differential mechanistic effects of RW and toy rotation. The former appears to exert its effects via neurotrophic factors, while the latter exerts its effects via the HPA axis. Further studies will lead to a better understanding of the influence of environmental factors on PTSD.

Photoreceptor specialization and the visuomotor repertoire of the primitive chordate Ciona

The swimming tadpole larva of Ciona has one of the simplest central nervous systems (CNSs) known, with only 177 neurons. Despite its simplicity, the Ciona CNS has a common structure with the CNS of its close chordate relatives, the vertebrates. The recent completion of a larval Ciona CNS connectome creates enormous potential for detailed understanding of chordate CNS function, yet our understanding of Ciona larval behavior is incomplete. We show here that Ciona larvae have a surprisingly rich and dynamic set of visual responses, including a looming-object escape behavior characterized by erratic circular swims, as well as negative phototaxis characterized by sustained directional swims. Making use of mutant lines, we show that these two behaviors are mediated by distinct groups of photoreceptors. The Ciona connectome predicts that these two behavioral responses should act through distinct, but overlapping, visuomotor pathways, and that the escape behavior is likely to be integrated into a broader startle behavior.

Testing an Integrative Model of Affect Regulation and Avoidance in Non-Suicidal Self-Injury and Disordered Eating

This research tested a model that integrates risk factors among non-suicidal self-injury (NSSI) and eating disorder (ED) behaviors with the aim of elucidating possible shared and unique mechanisms underlying both behaviors. Emotional distress, limited access to emotion regulation (ER) strategies, experiential avoidance, and NSSI/ED frequency were examined in a sample of 230 female undergraduates. Structural equation modeling indicated that limited access to ER strategies and avoidance mediated relationship between emotional distress and avoidance, which in turn was associated with NSSI and ED behaviors. Results suggest NSSI and ED behaviors may serve similar emotion regulation functions, and specifically highlight the role of experiential avoidance in these behaviors.

Effect of elevated CO2 and small boat noise on the kinematics of predator-prey interactions

Oceans of the future are predicted to be more acidic and noisier, particularly along the productive coastal fringe. This study examined the independent and combined effects of short-term exposure to elevated CO2 and boat noise on the predator-prey interactions of a pair of common coral reef fishes (Pomacentrus wardi and its predator, Pseudochromis fuscus). Successful capture of prey by predators was the same regardless of whether the pairs had been exposed to ambient control conditions, the addition of either playback of boat noise, elevated CO2 (925 µatm) or both stressors simultaneously. The kinematics of the interaction were the same for all stressor combinations and differed from the controls. The effects of CO2 or boat noise were the same, suggesting that their effects were substitutive in this situation. Prey reduced their perception of threat under both stressors individually and when combined, and this coincided with reduced predator attack distances and attack speeds. The lack of an additive or multiplicative effect when both stressors co-occurred was notable given the different mechanisms involved in sensory disruptions and highlights the importance of determining the combined effects of key drivers to aid in predicting community dynamics under future environmental scenarios.

Delay-Induced Super-Latent Inhibition as a Function of Order of Exposure to Two Flavours Prior to Compound Conditioning

A number of recent conditioned taste aversion (CTA) experiments have demonstrated a super-latent inhibition (LI) effect—namely, a time-induced increase in the effects of stimulus preexposure when the interval between acquisition and test is spent in a context that is different from the other experimental contexts. Two CTA experiments with rats were conducted to examine the role of primacy in producing super-LI. In Experiment 1, one of two flavours was pre-exposed, following which a second flavour was preexposed. After the second preexposure, animals were conditioned by pairing a compound of the two preexposed flavours with LiCl. The test stage was conducted 1 or 21 days after conditioning, with the interval being spent in either the same or different contexts. In the test, animals were confronted with two bottles, each with one of the two preexposed flavours. Super-LI was obtained only for the first preexposed flavour in the 21-day delay group that spent the interval in a different context. Experiment 2 was designed to ensure that the effects in Experiment 1 represented LI, and to control for order of presentation of the flavours and time between preexposure and acquisition. The results replicated those of Experiment 1. The two experiments support the importance of primacy in the general super-LI experiment where CS-alone preexposure precedes CS–US.

Metabolic, behavioral, and locomotive effects of feeding in five cyprinids with different habitat preferences

Fish generally perform routine swimming behaviors during food digestion; thus, changes in swimming performance and adjustments to spontaneous behavior resulting from digestion can have important ecological significance for wild fishes. The effects of feeding on metabolism, spontaneous activity, fast-start escape movement, and critical swimming speed (U _crit) were investigated in five cyprinids with different habitat preferences, specifically the Chinese crucian carp (Carassius auratus), common carp (Cyprinus carpio), black carp (Mylopharyngodon piceus), Chinese bream (Parabramis pekinensis), and qingbo (Spinibarbus sinensis). Generally, species in still water exhibited increased feeding metabolism, whereas species in flowing water showed higher spontaneous activity and locomotion performance. Digestion had no significant effects on either spontaneous activity or fast-start escape movement in the five cyprinids. These results could be due to the small meal sizes (approximately 2% body mass) and active foraging modes of cyprinids. The changes in aerobic swimming performance due to feeding were more complex. No effect of digestion on U _crit was observed in crucian carp (still water, high feeding metabolism, and low U _crit), common carp (widely distributed, high feeding metabolism, and high U _crit), and qingbo (flowing water, low feeding metabolism, and high U _crit), but digestion resulted in a significant decrease in the U _crit of Chinese bream (moderate feeding metabolism but high U _crit) and black carp (moderate feeding metabolism and low U _crit), suggesting no connection between postprandial U _crit changes and feeding metabolism (or between U _crit and preferred habitat). The maximum metabolic rate (MMR) of common carp and crucian carp increased after feeding, whereas the corresponding values for the other three cyprinids remained the same. The oxygen uptake capacity appears to meet the oxygen demand of both aerobic swimming and digestion in common carp and crucian carp, whereas qingbo sacrifices digestion for locomotion, and black carp and Chinese bream sacrifice locomotion for digestion under postprandial swimming conditions. The locomotion-priority mode of qingbo is adaptive to its active foraging mode in the demanding swimming habitat of rapidly flowing water, whereas the high respiratory capacities of postprandial crucian carp and common carp and hence the maintenance of their aerobic swimming performances might be a by-product of natural selection for hypoxia tolerance rather than for swimming speed.

Neural Circuitry that Evokes Escape Behavior upon Activation of Nociceptive Sensory Neurons in Drosophila Larvae

Noxious stimuli trigger a stereotyped escape response in animals. In Drosophila larvae, class IV dendrite arborization (C4 da) sensory neurons in the peripheral nervous system are responsible for perception of multiple nociceptive modalities, including noxious heat and harsh mechanical stimulation, through distinct receptors [1-9]. Silencing or ablation of C4 da neurons largely eliminates larval responses to noxious stimuli [10-12], whereas optogenetic activation of C4 da neurons is sufficient to provoke corkscrew-like rolling behavior similar to what is observed when larvae receive noxious stimuli, such as high temperature or harsh mechanical stimulation [10-12]. The receptors and the regulatory mechanisms for C4 da activation in response to a variety of noxious stimuli have been well studied [13-23], yet how C4 da activation triggers the escape behavior in the circuit level is still incompletely understood. Here we identify segmentally arrayed local interneurons (medial clusters of C4 da second-order interneurons [mCSIs]) in the ventral nerve cord that are necessary and sufficient to trigger rolling behavior. GFP reconstitution across synaptic partners (GRASP) analysis indicates that C4 da axons form synapses with mCSI dendrites. Optogenetic activation of mCSIs induces the rolling behavior, whereas silencing mCSIs reduces the probability of rolling behavior upon C4 da activation. Further anatomical and functional studies suggest that the C4 da-mCSI nociceptive circuit evokes rolling behavior at least in part through segmental nerve a (SNa) motor neurons. Our findings thus uncover a local circuit that promotes escape behavior upon noxious stimuli in Drosophila larvae and provide mechanistic insights into how noxious stimuli are transduced into the stereotyped escape behavior in the circuit level.

Potential Nematode Alarm Pheromone Induces Acute Avoidance in Caenorhabditis elegans

It is crucial for animal survival to detect dangers such as predators. A good indicator of dangers is injury of conspecifics. Here we show that fluids released from injured conspecifics invoke acute avoidance in both free-living and parasitic nematodes. Caenorhabditis elegans avoids extracts from closely related nematode species but not fruit fly larvae. The worm extracts have no impact on animal lifespan, suggesting that the worm extract may function as an alarm instead of inflicting physical harm. Avoidance of the worm extract requires the function of a cGMP signaling pathway that includes the cGMP-gated channel TAX-2/TAX-4 in the amphid sensory neurons ASI and ASK. Genetic evidence indicates that the avoidance behavior is modulated by the neurotransmitters GABA and serotonin, two common targets of anxiolytic drugs. Together, these data support a model that nematodes use a nematode-specific alarm pheromone to detect conspecific injury.

The angular position of a refuge affects escape responses in staghorn sculpin Leptocottus armatus

The effect of the presence and angular position of a refuge on the direction and kinematics of mechanically-induced escape responses was observed in staghorn sculpins Leptocottus armatus using high-speed video. The results showed that the angular position of the refuge did not affect locomotor performance (speed and acceleration), although it did affect the escape trajectories. Therefore, the angular position of a refuge can modulate the direction taken by the L. armatus during the early stages of their escape response and this response can be affected by both repulsive (i.e. threats) and attractive (i.e. refuges) points of reference.

Rapid Spatial Learning Controls Instinctive Defensive Behavior in Mice

Instinctive defensive behaviors are essential for animal survival. Across the animal kingdom, there are sensory stimuli that innately represent threat and trigger stereotyped behaviors such as escape or freezing [1-4]. While innate behaviors are considered to be hard-wired stimulus-responses [5], they act within dynamic environments, and factors such as the properties of the threat [6-9] and its perceived intensity [1, 10, 11], access to food sources [12-14], and expectations from past experience [15, 16] have been shown to influence defensive behaviors, suggesting that their expression can be modulated. However, despite recent work [2, 4, 17-21], little is known about how flexible mouse innate defensive behaviors are and how quickly they can be modified by experience. To address this, we have investigated the dependence of escape behavior on learned knowledge about the spatial environment and how the behavior is updated when the environment changes acutely. Using behavioral assays with innately threatening visual and auditory stimuli, we show that the primary goal of escape in mice is to reach a previously memorized shelter location. Memory of the escape target can be formed in a single shelter visit lasting less than 20 s, and changes in the spatial environment lead to a rapid update of the defensive action, including changing the defensive strategy from escape to freezing. Our results show that although there are innate links between specific sensory features and defensive behavior, instinctive defensive actions are surprisingly flexible and can be rapidly updated by experience to adapt to changing spatial environments.

Migratory-stage sea lamprey Petromyzon marinus stop responding to conspecific damage-released alarm cues after 4 h of continuous exposure in laboratory conditions

This study investigated the length of avoidance response of migratory-stage sea lamprey Petromyzon marinus exposed continuously to conspecific damage-released alarm cues for varying lengths of time in laboratory stream channels. Ten replicate groups of P. marinus, separated by sex, were exposed to either deionized water control or to P. marinus extract for 0, 2 or 4 h continuously. Petromyzon marinus maintained their avoidance response to the conspecific damage-released alarm cue after continuous exposure to the alarm cue for 0 and 2 h but not 4 h. Beyond being one of the first studies in regards to sensory-olfactory adaptation-acclimation of fishes to alarm cues of any kind, these results have important implications for use of conspecific alarm cues in P. marinus control. For example, continuous application of conspecific alarm cue during the day, when P. marinus are inactive and hiding, may result in sensory adaptation to the odour by nightfall when they migrate upstream.

Learning in mosquito larvae (Aedes aegypti): Habituation to a visual danger signal

In spite of the mosquito Aedes aegypti being a vector of several infectious diseases, a limited number of studies has been undertaken on learning in this species. Moreover, larval stages have been neglected as model organisms, although they are active, aquatic and perform stereotyped behavioural responses, e.g. the escape response when disturbed. To study the learning abilities of mosquito larvae, we focused on habituation, a form of non-associative learning widely studied in vertebrates and invertebrates. Habituation was defined as the progressive and reversible decrease in response to a reiterative stimulus. We first aimed at confirming habituation of the escape response in mosquito larvae (4th instar). Then, we determined whether a mnesic trace was established. Larvae were individually stimulated with a visual danger stimulus inducing the escape response. We set up a protocol for testing larvae individually, allowing the control of different parameters that are crucial for the study of cognitive abilities. After 15 trials, the escape response of mosquitoes was significantly lower. A disturbance stimulus presented after the 15th trial, induced the escape response and reversed habituation. Retention was confirmed up to 1h after the last habituation trial. This original bioassay can be adapted for studying the physiology of learning and memory in mosquito larvae, for analysing the effects of chemicals in the water, the characterisation of the cognitive abilities related to the life history of different mosquito species across preimaginal stages.

Interspecific differences in how habitat degradation affects escape response

Degradation of habitats is widespread and a leading cause of extinctions. Our study determined whether the change in the chemical landscape associated with coral degradation affected the way three fish species use olfactory information to optimize their fast-start escape response. Water from degraded coral habitats affected the fast-start response of the three closely-related damselfishes, but its effect differed markedly among species. The Ward's damselfish (Pomacentrus wardi) was most affected by water from degraded coral, and displayed shorter distances covered in the fast-start and slower escape speeds compared to fish in water from healthy coral. In the presence of alarm odours, which indicate an imminent threat, the Ambon damsel (P. amboinensis) displayed enhanced fast-start performance in water from healthy coral, but not when in water from degraded coral. In contrast, while the white-tailed damsel (P. chrysurus) was similarly primed by its alarm odour, the elevation of fast start performance was not altered by water from degraded coral. These species-specific responses to the chemistry of degraded water and alarm odours suggest differences in the way alarm odours interact with the chemical landscape, and differences in the way species balance information about threats, with likely impacts on the survival of affected species in degraded habitats.

Age-related differences in decision-making for digital escape route signage under strenuous emergency conditions of tilted passenger ships

This age-differentiated study investigated preferences for new digital, situation-adaptive escape route signage with informative and flashing elements under simulated emergency conditions of tilted passenger ships. The decision-making behaviour of 26 young (20-30 years) and 26 elderly (60-77 years) participants was observed in four conditions varying in applied stressors and in level versus uphill walking at 7° and 14°. In line with previous studies, decisions of young participants were significantly influenced by flashing elements on signs. In contrast, elderly participants based their decisions significantly stronger on integrated information about the sign's updatedness and reported irritation by flashing elements. These preferences were also persistent under increased mental, emotional and physical strain, evaluated by ratings and (psycho-)physiological measures. The findings demonstrate the importance to carefully design digital, situation-adaptive signage for passenger ships in a way that it not only attracts attention but also inspires trust especially for the elderly population.