Heart and ventilatory measures in crayfish during environmental disturbances and social interactions

Most animals assess the environment in which they live and alter their behavior according to various stimuli. When the animal does not make significant behavioral changes, as measured by bodily movements, the animal may be characterized as unresponsive to a given stimulus. This study demonstrates that when behavioral movements of crayfish cannot be observed, physiological measures of heart rate (HR) and ventilatory rate (VR) show dramatic changes in response to defined sensory stimuli. In the majority of cases, upon anticipation of a social interaction with another crayfish both HR and VR will increase. During an agonistic encounter between two crayfish, the level of HR and VR correlate with the intensity of the interaction. Such rapid responses in cardiac and respiratory systems to environmental disturbances and anticipation of a social interaction suggest an autonomic-like regulation associated with fear, flight or fight. Since behavioral observations do not allow an internal status to be readily assessed, we suggest that HR and VR may serve as a useful bioindex in crustaceans to their internal drive or possibly an awareness level to environmental cues.     

There must be something in the water: assessing the behavioral responses of rusty crayfish (<Emphasis Type="Italic">Orconectes rusticus</Emphasis>) to fish and amphibian predator kairomones

Animals use chemical cues to find food, locate mates, and detect potential predators. Detecting cues in a risky environment can induce behavioral changes to increase survival. Rusty crayfish (Orconectes rusticus) reduce activity, increase refuge use, and make defensive displays after detecting fish predator cues. However, no studies have introduced amphibian cues. We investigated crayfish responses to hellbender salamander (Cryptobranchus alleganiensis, a dominant predator of crayfish) cues and compared these to responses to largemouth bass (Micropterus salmoides) cues. Largemouth bass occur sympatrically with hellbenders and are known to induce distinct responses in rusty crayfish. We randomly assigned crayfish to predator cue and conspecific alarm cue combinations and recorded frozen behavior, appendage movement, locomotion, and refuge use. We found crayfish increased their proportion of time spent frozen and reduced their proportion of time spent active in the tank when exposed to either predator cue. Moreover, these responses were magnified when crayfish were exposed to predator cues in combination with conspecific alarm cues. Our experiment demonstrates evidence in support of the crayfish’s ability to detect and appropriately respond to predator cues alone and in combination with conspecific alarm cues. Future work should investigate the effects of these behavioral changes on trophic dynamics in a natural system.     

Alterations in habituation of the tail flip response in epigean and troglobitic crayfish

We demonstrate that the probability of the crayfish, P. clarkii, to tail flip in response to a touch on the dorsal tail fan is dependent on both the size and the behavioral state of the animal. Alterations in the animal's internal physical state, such as when the animal autotomizes its chelipeds, will cause larger-sized animals to tail flip; if they were not autotomized, then no tail flip response would occur. Altering the external environment by removal of water causes small crayfish, which normally habituate slowly, to rapidly habituate. Observation of large adult crayfish in a species, O. australis packardi, one that evolved to live in total cave darkness, revealed that they are more likely to tail flip than are the sighted, adult P. clarkii. Results indicate that the behavioral state of the crayfish can result in rapid and long-term alterations in the tail flip response and in habituation rates to repetitive stimuli. This ability to show plasticity in gain setting may be regulated by neuromodulators and can occur in large adults of the sighted crayfish. Differences between the two species indicate that size may not be the sole contributing factor to account for tail flip behaviors. J. Exp. Zool. 290:163-176, 2001.     

Viewing Pain and Happy Faces Elicited Similar Changes in Postural Body Sway

Affective facial expressions are potent social cues that can induce relevant physiological changes, as well as behavioral dispositions in the observer. Previous studies have revealed that angry faces induced significant reductions in body sway as compared with neutral and happy faces, reflecting an avoidance behavioral tendency as freezing. The expression of pain is usually considered an unpleasant stimulus, but also a relevant cue for delivering effective care and social support. Nevertheless, there are few data about behavioral dispositions elicited by the observation of pain expressions in others. The aim of the present research was to evaluate approach–avoidance tendencies by using video recordings of postural body sway when participants were standing and observing facial expressions of pain, happy and neutral. We hypothesized that although pain faces would be rated as more unpleasant than the other faces, they would provoke significant changes in postural body sway as compared to neutral facial expressions. Forty healthy female volunteers (mean age 25) participated in the study. Amplitude of forward movements and backward movements in the anterior-posterior and medial-lateral axes were obtained. Statistical analyses revealed that pain faces were the most unpleasant stimuli, and that both happy and pain faces were more arousing than neutral ones. Happy and pain faces also elicited greater amplitude of body sway in the anterior-posterior axes as compared with neutral faces. In addition, significant positive correlations were found between body sway elicited by pain faces and pleasantness and empathic ratings, suggesting that changes in postural body sway elicited by pain faces might be associated with approach and cooperative behavioral responses.     

Cardiac activity of freshwater crayfish at wakefulness, rest, and “animal hypnosis”

In laboratory experiments, simultaneous continuous recording of the circadian cycle of behavioral reactions and cardiac activity of freshwater crayfish Astacus astacus and Procambarus clarkii was carried out. A non-invasive fiber-optic method of recording of the heart rate (HR) was used. The obtained data were analyzed by the method of variational pulsometry (VP). It was revealed that certain values of HR and characteristics of VP corresponded to the physiological states of active wakefulness and rest. It was found that during long immobilization of crayfish it is possible to identify the states of operative rest and sleep by the animal behavioral reactions and parameters of cardiac activity. Crayfish were studied in the state of artificially evoked immobilization (“animal hypnosis”). During this state, a high HR level, an increase of indexes of tension and autonomic equilibrium, and changes of other VP characteristics were observed. It is suggested that the different level of cardiac activity in different physiological states of crayfish (active wakefulness, operative rest, sleep, and “animal hypnosis”) is regulated by nervous influences analogous to sympathetic and parasympathetic influences in vertebrates. It was concluded that freshwater crayfish as a representative of the highly organized invertebrates can serve an effective model for studying mechanisms of sleep-like states and “animal hypnosis” in animals.     

Opercular beat rate for rainbow darters Etheostoma caeruleum exposed to chemical stimuli from conspecific and heterospecific fishes

Opercular beat rates of rainbow darters Etheostoma caeruleum were used as a measure of a physiological response to chemical stimulation. Rainbow darters responded significantly to some chemical cues (active and ambush predators, competitors, novel stimuli and to conspecific and heterospecific alarm cues) with increases in opercular movements; neutral cues and novel alarm cues did not elicit significant changes. Changes in opercular movements may be a good bioassay for determining detection of chemical stimuli by rainbow darters.     

Multimodal individual recognition in the crayfish cherax destructor

There is some evidence that macrurans recognize each other as individuals. In freshwater crayfish there are conflicting reports and there is limited information about the sensory mechanisms involved. To determine the extent to which the crayfish Cherax destructor is capable of individual recognition, we performed experiments that familiarized animals with each other and then manipulated their recent success in dominance contests. Crayfish were more likely to win an encounter when paired against a familiar opponent than an unfamiliar one after the manipulation stage. In other experiments, animals were attracted to familiar conspecifics when only visual or chemical cues were present. This demonstrates that C. destructor is able to discriminate between a familiar and an unfamiliar opponent. The results highlight the complex nature of intraspecific communication in crayfish and suggest elements likely to be of importance in the social interactions of groups in the wild state.     

Perception of alarm cues influences the outcome of shelter competition in crayfish20

The effects of predators on prey populations may significantly alter many aspects of prey biology, including spatial distribution, foraging activities, and social interactions. In aquatic habitats, chemosensation is an important mode of communication and has been shown for many taxa, including crayfish, to be used in detection of predator and/or conspecific alarm cues. Here, we report on an experiment to test the hypothesis that detection of alarm cues results in greater individual investment in contests over shelters. We tested this hypothesis through dyadic contests between sex- and size-matched, non-reproductive individuals of Faxonius virilis. We found that crayfish responded to exposure to alarm cues by spending more time inside a shelter. We also report that in contests between pairs in which one crayfish had been exposed to alarm cues and the other had not, exposed individuals were significantly more likely to win ownership of a single shelter. However, we did not detect any differences in the contest parameters we recorded between exposed and unexposed crayfish. These impacts on both individual and social behavior indicate that the presence of predators is likely to have large effects on the distribution and structure of crayfish populations.     

Novelty stress and reproductive state alters responsiveness to sensory stimuli and 5-HT neuromodulation in crayfish

Sensory stimuli can produce varied responses depending on the physiological state of an animal. Stressors and reproductive stage can result in altered biochemical status that changes the responsiveness of an animal to hormones and neuromodulators, which affects whole animal behavior in relation to sensory stimuli. Crayfish serve as a model for examining the effects of neuromodulators at the neuromuscular junctions (NMJs) and for alterations in stereotypic behaviors for particular stimuli. Thus, we used crayfish to examine the effect of novelty stressors in males and the effect of being gravid in female crayfish to exogenous application of serotonin (5-HT). The responsiveness of neuromuscular junctions to 5-HT revealed that stressed as well as gravid crayfish have a reduced response to 5-HT at NMJs. The stressed crayfish were not fatigued since the basal synaptic responses are large and still showed a pronounced response to 5-HT. Using intact animals to examine a tail flip behavior, we showed that the rate of habituation in tail flipping to a strong repetitive stimulus on the telson is reduced in stressed males. Gravid females show no tail flipping behavior upon telson stimulation.     

Heart rate within male crayfish: social interactions and effects of 5-HT

Behaviors, such as those that establish dominant and subordinate social status, are thought to be driven by various neuromodulators and hormones. In crustaceans, the level of serotonin (5-HT) in the hemolymph is correlated with degree of aggressiveness. The crustacean heart is neurogenic and is modulated by neural secretion of 5-HT in the hemolymph, which bathes the cardiac tissue. We discuss and present the results of measuring heart rate (HR) of crayfish during interactions, as an indication of their state of excitability. HR is the result of multiple influences: a cocktail of hormones and modulators. HR was monitored during the periods in which crayfish established aggressive and submissive social status, during sham injections, and following injections of various doses of 5-HT. Crayfish, during an interaction to establish social status, can increase HR. Both the aggressive and submissive crayfish can dampen their HR within seconds during a pause in the interaction, while still posturing in an aggressive or submissive state. Injections of 5-HT to obtain systemic levels of approximately 100 nM-10 microM increase HR substantially for hours. This suggests that aggressive interactions and the establishment of a dominant posture may not be related to large increases in the free concentrations of 5-HT within the circulating hemolymph, since a sustained HR is not observed in aggressive animals. Instead, the results may demonstrate that inhibitory cardiac regulation is present in the aggressors during interactions and that a regulator is possibly 5-HT.     

Exploring the Effects of Antisocial Personality Traits on Brain Potentials during Face Processing

Antisocial individuals are characterized to display self-determined and inconsiderate behavior during social interaction. Furthermore, recognition deficits regarding fearful facial expressions have been observed in antisocial populations. These observations give rise to the question whether or not antisocial behavioral tendencies are associated with deficits in basic processing of social cues. The present study investigated early visual stimulus processing of social stimuli in a group of healthy female individuals with antisocial behavioral tendencies compared to individuals without these tendencies while measuring event-related potentials (P1, N170). To this end, happy and angry faces served as feedback stimuli which were embedded in a gambling task. Results showed processing differences as early as 88–120 ms after feedback onset. Participants low on antisocial traits displayed larger P1 amplitudes than participants high on antisocial traits. No group differences emerged for N170 amplitudes. Attention allocation processes, individual arousal levels as well as face processing are discussed as possible causes of the observed group differences in P1 amplitudes. In summary, the current data suggest that sensory processing of facial stimuli is functionally intact but less ready to respond in healthy individuals with antisocial tendencies.     

Social learning of predators in the dark: understanding the role of visual,chemical and mechanical information

The ability of prey to observe and learn to recognize potential predators from the behaviour of nearby individuals can dramatically increase survival and, not surprisingly, is widespread across animal taxa. A range of sensory modalities are available for this learning, with visual and chemical cues being well-established modes of transmission in aquatic systems. The use of other sensory cues in mediating social learning in fishes, including mechano-sensory cues, remains unexplored. Here, we examine the role of different sensory cues in social learning of predator recognition, using juvenile damselfish (Amphiprion percula). Specifically, we show that a predator-naive observer can socially learn to recognize a novel predator when paired with a predator-experienced conspecific in total darkness. Furthermore, this study demonstrates that when threatened, individuals release chemical cues (known as disturbance cues) into the water. These cues induce an anti-predator response in nearby individuals; however, they do not facilitate learnt recognition of the predator. As such, another sensory modality, probably mechano-sensory in origin, is responsible for information transfer in the dark. This study highlights the diversity of sensory cues used by coral reef fishes in a social learning context.     

Crayfish recognize the faces of fight opponents

The capacity to associate stimuli underlies many cognitive abilities, including recognition, in humans and other animals. Vertebrates process different categories of information separately and then reassemble the distilled information for unique identification, storage and recall. Invertebrates have fewer neural networks and fewer neural processing options so study of their behavior may reveal underlying mechanisms still not fully understood for any animal. Some invertebrates form complex social colonies and are capable of visual memory-bees and wasps, for example. This ability would not be predicted in species that interact in random pairs without strong social cohesion; for example, crayfish. They have chemical memory but the extent to which they remember visual features is unknown. Here we demonstrate that the crayfish Cherax destructor is capable of visual recognition of individuals. The simplicity of their interactions allowed us to examine the behavior and some characteristics of the visual features involved. We showed that facial features are learned during face-to-face fights, that highly variable cues are used, that the type of variability is important, and that the learning is context-dependent. We also tested whether it is possible to engineer false identifications and for animals to distinguish between twin opponents.     

A Test of Temporal Variation in Risk and Food Stimuli on Behavioral Tradeoffs in the Rusty Crayfish, Orconectes rusticus: Risk Allocation and Stimulus Degradation

The effects of temporal variation in exposure to predation risk on behavioral tradeoffs were tested in the rusty crayfish, Orconectes rusticus. Based on the risk allocation hypothesis, we predicted that increasing the frequency of encounter with predation risk would yield increasing responses to a food stimulus in the presence of both a risk stimulus and a food stimulus. Crayfish were exposed to risk every 12 h, every 6 h, or left undisturbed for 24 h prior to testing. The risk stimuli used were a plain water control, snapping turtle (Chelydra serpentina) cue, and conspecific alarm cue. After 24 h of conditioning, the crayfish were exposed to a combination of risk cue and food cue. The behavioral responses of the crayfish were recorded for 5 min immediately following the introduction of the cues and again for 5 min, 1 h after stimulus exposure. The crayfish were observed at the two times to determine how their responses to the combination of risk and food cues changed over time. The responses of the crayfish were significantly influenced by stimulus treatment, time, and the interaction of time and stimulus treatment. Further analysis indicated that responses to the stimulus treatments changed differently over time. Immediately after exposure, the crayfish were more active in the control and snapping turtle treatments than in the conspecific alarm treatment. The high levels of activity initially observed in the control and snapping turtle treatments waned over time, such that the behaviors recorded 1 h after exposure were not significantly affected by stimulus treatment. Neither frequency nor the interactions of frequency with stimulus and/or time significantly affected crayfish behavior. The results of this study did not support the risk allocation model and contrast with results from similar work on the virile crayfish, Orconectes virilis.     

Recording Behavioral Responses to Reflection in Crayfish

Social behavior depends on sensory input from the visual, mechanical and olfactory systems. One important issue concerns the relative roles of each sensory modality in guiding behavior. The role of visual inputs has been examined by isolating visual stimuli from mechanical and chemosensory stimuli. In some studies (Bruski & Dunham, 1987: Delgado-Morales et al., 2004) visual inputs have been removed with blindfolds or low light intensity, and effects of remaining sensory modalities have been elucidated. An alternative approach is to study the effects of visual inputs in the absence of any appropriate mechanical and chemosensory cues. This approach aims to identify the exclusive role of visual inputs. We have used two methods to provide visual stimuli to crayfish without providing chemical and mechanical cues. In one method, crayfish are videotaped in an aquarium where half of the walls are covered in mirrors to provide a reflective environment, and the other half are covered in a non-reflective (matte finish) plastic. This gives the crayfish a choice between reflective and non-reflective environments. The reflective environment provides visual cues in the form of reflected images of the crayfish as it moves throughout half of the tank; these visual cues are missing from the non-reflective half of the tank. An alternative method is to videotape the behavior of crayfish in an aquarium separated by a smaller chamber at each end, with a crayfish in one small chamber providing visual cues and an inert object in the opposite small chamber providing visual input from a non-moving, non-crayfish source. Our published results indicate that responses of crayfish to the reflective environment depend on socialization and dominance rank. Socialized crayfish spent more time in the reflective environment and exhibited certain behaviors more frequently there than in the non-reflective environment; isolated crayfish showed no such differences. Crayfish that were housed in same-sex pairs developed a social rank of either dominant or subordinate. Responses to reflection differed between dominant and subordinate crayfish (May & Mercier, 2006; May & Mercier, 2007). Dominant crayfish spent more time on the reflective side, entered reflective corners more frequently and spent more time in reflective corners compared to the non-reflective side. Subordinate crayfish walked in reverse more often on the reflective side than on the non-reflective side. Preliminary data suggest similar effects from visual cues provided by a crayfish in a small adjoining chamber (May et al., 2008).Download video file.^{(129M, mp4)}     

Chemosensory Cues to Conspecific Emotional Stress Activate Amygdala in Humans

Alarm substances are airborne chemical signals, released by an individual into the environment, which communicate emotional stress between conspecifics. Here we tested whether humans, like other mammals, are able to detect emotional stress in others by chemosensory cues. Sweat samples collected from individuals undergoing an acute emotional stressor, with exercise as a control, were pooled and presented to a separate group of participants (blind to condition) during four experiments. In an fMRI experiment and its replication, we showed that scanned participants showed amygdala activation in response to samples obtained from donors undergoing an emotional, but not physical, stressor. An odor-discrimination experiment suggested the effect was primarily due to emotional, and not odor, differences between the two stimuli. A fourth experiment investigated behavioral effects, demonstrating that stress samples sharpened emotion-perception of ambiguous facial stimuli. Together, our findings suggest human chemosensory signaling of emotional stress, with neurobiological and behavioral effects.     

The influence of shape and colour cue classes on facial health perception

Facial appearance signals information about an individual, and one trait in particular is vitally important for social interaction and mate choice decisions: physical health. Facial cues to health can be divided into two broad classes - facial shape, which is linked to previous health and is relatively fixed; and facial colouration, which changes over the short-term, reflecting current health. These cue classes in themselves give insight into the kinds of health condition valued by human observers when making social inferences. Here, using novel and generalizable methods, the influence of these cue classes on health perception and their link to a measure of general health are examined. Study One employs a Brunswik lens model approach, finding that observers utilise exclusively shape cues to judge health, and that of these shape cues, only averageness is related to a measure of self-reported general health. Study Two shows that when averageness and carotenoid colouration are varied together, both make separable contributions to perceived health, but that averageness explains a larger proportion of variance. Taken together, these results indicate that humans may have evolved to favour cues to previous condition when judging health, because they are more valid. However, the findings also suggest that the role of facial appearance in perceiving health is more complex than previously thought, with different cues potentially reflecting specific aspects of physiological health.     

OMR-Arena: Automated Measurement and Stimulation System to Determine Mouse Visual Thresholds Based on Optomotor Responses

Measurement of the optomotor response is a common way to determine thresholds of the visual system in animals. Particularly in mice, it is frequently used to characterize the visual performance of different genetically modified strains or to test the effect of various drugs on visual performance. Several methods have been developed to facilitate the presentation of stimuli using computer screens or projectors. Common methods are either based on the measurement of eye movement during optokinetic reflex behavior or rely on the measurement of head and/or body-movements during optomotor responses. Eye-movements can easily and objectively be quantified, but their measurement requires invasive fixation of the animals. Head movements can be observed in freely moving animals, but until now depended on the judgment of a human observer who reported the counted tracking movements of the animal during an experiment. In this study we present a novel measurement and stimulation system based on open source building plans and software. This system presents appropriate 360 stimuli while simultaneously video-tracking the animal''s head-movements without fixation. The on-line determined head gaze is used to adjust the stimulus to the head position, as well as to automatically calculate visual acuity. Exemplary, we show that automatically measured visual response curves of mice match the results obtained by a human observer very well. The spatial acuity thresholds yielded by the automatic analysis are also consistent with the human observer approach and with published results. Hence, OMR-arena provides an affordable, convenient and objective way to measure mouse visual performance.     

The effects of serotonin and octopamine on behavioral arousal in the crayfish

1. In the crayfish, behavioral arousal is known to elicit walking and to enhance compensatory eye movements.2. To see if serotonin and octopamine modulate arousal, we measured their effects on walking and eye movements in tethered crayfish, Procambarus clarkii. Serotonin strongly suppresses both walking and eye movements.3. In contrast, octopamine elicits an arousal-like state of continuous jittery leg movements and increased eye movements.4. Serotonin's effect on arousal is uncertain, but octopamine remains a plausible modulator of behavioral arousal.