Effects of self-generated wind on compensational recovery of escape direction in unilaterally cercus-ablated crickets, Gryllus bimaculatus

The effects of self-generated wind on the compensational recovery of escape direction were investigated in unilaterally cercus-ablated crickets, Gryllus bimaculatus. To separate walking and self-generated wind during walking, unilaterally cercus-ablated crickets were placed on a styrofoam ball that was easily rotated by leg motion during walking. The stationary walking on the ball did not produce self-generated wind, because no body motion occurred. Crickets that were trained on the ball but given no artificial air puff for 14 days after cercal ablation did not show any compensational recovery of escape direction. Therefore, spontaneous walking itself was not sufficient to compensate the wind-evoked escape direction in the crickets. Artificial air puffs from the anterior direction synchronized with the stationary walking were effective for the compensational recovery of escape direction, but those from the posterior direction were not. As most of the spontaneous walking was directed to the forward direction, only an artificial air puff from the anterior direction coincided well with actual self-generated wind occurring during the onset of normal walking. Therefore, self-generated wind during walking seems essential for the compensational recovery of escape direction in unilaterally cercus-ablated crickets. When artificial air puffs were unsynchronized with walking, no compensational recovery was observed. This result suggests that artificial air puffs should be given just after the onset of spontaneous walking. Otherwise, the artificial air puffs may not be recognized as self-generated wind.     

Compensation of escape direction in unilaterally cercus-ablated crickets, Gryllus bimaculatus, is associated with the distance walked during recovery period

In response to an air puff stimulus, intact crickets, Gryllus bimaculatus, make an escape almost 180 degrees opposite to the stimulus source. In order to verify our previous hypothesis that a self-stimulation of the wind-sensory system is necessary for a compensational recovery of the escape direction (behavioral compensation) in unilaterally cercus-ablated crickets, we investigated the relationship between the conditions of rearing after a unilateral cercal ablation and the degree of behavioral compensation. A unilaterally cercus-ablated cricket reared in a large cage to permit free locomotion showed a significantly higher degree of recovery of escape direction compared with those reared under restrained conditions in a small glass vial. However, the degree of behavioral compensation in a cricket reared alone in a large cage was smaller than that of crickets reared in a cage of the same size with 5-6 other cercus-ablated crickets. Mutual stimulation possibly increased the extent of locomotion of crickets reared in a group and improved the degree of compensational recovery of the escape direction. To ascertain this, the distance a cricket moved during the recovery period was associated with the degree of compensational change of the escape direction. The result suggests that the degree of compensation of the escape direction clearly depended on the distance walked by the crickets. The compensation seemed not to be caused by other factors such as chemical ones in the case of group rearing because forced locomotion induced by touch stimulation on the body surface was solely effective in improving the escape direction.     

Rearing under different conditions results in different functional recoveries of giant interneurons in unilaterally cercus-ablated crickets, Gryllus bimaculatus

The effects of rearing conditions on the functional recovery of wind-sensitive giant interneurons (GIs) after unilateral cercal ablation were investigated in the cricket, Gryllus bimaculatus. Crickets were reared in a glass vials to prohibit free walking for 14 days after unilateral cercal ablation ("14-day vial" crickets). Other crickets were reared in an apparatus called a "walking inducer" (WI) to increase the walking distance during the same 14-day period ("14-day WI" crickets). In these crickets, the response properties of GIs 8-1, 9-1, 9-2, and 9-3 to air currents from various directions were investigated. From the intensity-response curves obtained, directionality curves expressed in terms of threshold velocity and response magnitude were made independently. To understand changes in the functional recovery of GIs more thoroughly, the directional characteristics of GIs in crickets 1 day after unilateral cercal ablation ("1-day free" crickets) were also compared. Between the 1-day free and 14-day vial crickets, all the GIs showed differences in both threshold velocity and response magnitude for some stimulus directions. Between the 14-day vial and 14-day WI crickets, differences in the threshold velocities of GIs 9-1, 9-2, and 9-3, and in the response magnitudes of GIs 8-1, 9-1, and 9-3 were detected. Because the rearing condition after unilateral cercal ablation largely affects the compensatory recovery in some parameters of wind-evoked escape behavior, such as relative occurrence and escape direction, we discuss the functional differences in GIs revealed here in relation to the roles of GIs in the neural system that controls escape behavior.     

Functional changes of cricket giant interneurons caused by chronic unilateral cercal ablation during postembryonic development

One of a pair of cerci was ablated in the first-, fourth- and last-instar nymphs of the cricket, Gryllus bimaculatus. The insects were then reared until the final molt, after which the intensity-response (I-R) relationships for four giant interneurons (GIs) 8-1, 9-1, 9-2 and 9-3 with regard to a controlled air current stimulus were measured. In order to examine the functional changes during postembryonic development and the differences in the physiological plasticity of GIs between nymphs and adults, the obtained I-R curves for each GI were compared with those measured in intact and unilaterally cercus-ablated adult crickets. Each GI showed a distinctive change in response magnitudes after the long-term unilateral cercal ablation. In most cases, the I-R curves for each GI in the crickets ablated from nymphal periods were different from those in the adult crickets mentioned above. Moreover, the pattern of change in response magnitude was different from GI to GI. In contrast to these observations, it was reported that some important characteristics of the wind-evoked escape behavior such as relative occurrence and escape direction in unilaterally cercus-ablated crickets investigated after a long-term rearing were almost identical with those in intact crickets. Therefore, the results obtained in the present study suggest that functional changes occur not only in GIs but also in many other neural elements in the escape-eliciting system in order to maintain the features of wind-evoked escape behavior.     

Rearing conditions required for behavioral compensation after unilateral cercal ablation in the cricket Gryllus bimaculatus

The rearing condition necessary for behavioral compensation after sensory deprivation was investigated in the cricket Gryllus bimaculatus. The right-cercus-ablated cricket was reared in a glass vial with a slightly larger diameter than the body length of the cricket. After two weeks of rearing in the vial, the air-puff-evoked escape behavior of the cricket was investigated. The response rate (relative occurrence of the escape behavior after a standard air puff) obtained was identical with that of crickets reared in a large cage. On the other hand, unlike crickets reared in a large cage, the distorted escape directional property of the cricket reared in the vial was not compensated at all. Control experiments proved that the restraint in the vial did not affect the motor system, and the air motion from environments was not essential for the compensational recovery of the escape direction. Therefore, the ablated crickets required spontaneous walking in order to compensate the directionality of their escape. A self-generated wind caused by spontaneous walking appears necessary for the crickets to realize the defect of their sensory system and to compensate the related escape behavior. A hypothesis for the compensation mechanism based on the efference copy signal is proposed.     

Behavioral analyses of wind-evoked escape of the cricket, Gryllodes sigillatus

The wind-evoked escape behavior of the cricket Gryllodes sigillatus was investigated using an air puff stimulus. A high velocity air puff elicited the escape behavior in many crickets. The crickets tended to escape away from the stimulus source, but the direction was not accurately oriented 180 degrees from the stimulus. After bilateral cercal ablation, only a few crickets showed wind-evoked escape behavior, and their response rates did not increase even 19 days after ablation. Therefore, information on air motion detected by cercal filiform hairs is essential for triggering wind-evoked behavior. After unilateral cercal ablation, the 81.3% response rate of intact crickets decreased to 16.5%, that is, it decreased to almost 20% that of intact crickets. One week after unilateral cercal ablation, the response rate recovered to more than 60% that of intact crickets. However, the accuracy rate of the escape direction of G. sigillatus showed no change even immediately after the unilateral cercal ablation. Therefore, both cerci are not necessarily required to determine the escape direction. The behavioral characteristics of wind-evoked escape of G. sigillatus are compared with those of another species of cricket, Gryllus bimaculatus. The two species of cricket employ different strategies for wind-evoked escape.     

Neural Basis of Stimulus-Angle-Dependent Motor Control of Wind-Elicited Walking Behavior in the Cricket Gryllus bimaculatus

Crickets exhibit oriented walking behavior in response to air-current stimuli. Because crickets move in the opposite direction from the stimulus source, this behavior is considered to represent ‘escape behavior’ from an approaching predator. However, details of the stimulus-angle-dependent control of locomotion during the immediate phase, and the neural basis underlying the directional motor control of this behavior remain unclear. In this study, we used a spherical-treadmill system to measure locomotory parameters including trajectory, turn angle and velocity during the immediate phase of responses to air-puff stimuli applied from various angles. Both walking direction and turn angle were correlated with stimulus angle, but their relationships followed different rules. A shorter stimulus also induced directionally-controlled walking, but reduced the yaw rotation in stimulus-angle-dependent turning. These results suggest that neural control of the turn angle requires different sensory information than that required for oriented walking. Hemi-severance of the ventral nerve cords containing descending axons from the cephalic to the prothoracic ganglion abolished stimulus-angle-dependent control, indicating that this control required descending signals from the brain. Furthermore, we selectively ablated identified ascending giant interneurons (GIs) in vivo to examine their functional roles in wind-elicited walking. Ablation of GI8-1 diminished control of the turn angle and decreased walking distance in the initial response. Meanwhile, GI9-1b ablation had no discernible effect on stimulus-angle-dependent control or walking distance, but delayed the reaction time. These results suggest that the ascending signals conveyed by GI8-1 are required for turn-angle control and maintenance of walking behavior, and that GI9-1b is responsible for rapid initiation of walking. It is possible that individual types of GIs separately supply the sensory signals required to control wind-elicited walking.     

The precision of auditory lateralization in the cricket, Gryllus bimaculatus

ABSTRACT. The precision of auditory lateralization was determined behaviourally for the cricket, Gryllus bimaculatus L. A forced-choice Y-maze test was devised in which the cricket, on entering the test arena, could not — in contrast to free phonotactic approaches — change its walking direction until after it had passed through a narrow wire-mesh tunnel. For a sound frequency of 4.7 kHz, matching the species' calling frequency, the minimum audible angle for correct side discrimination was 15°. For stimulus angles smaller than 15° from the longitudinal body axis, the crickets walked randomly to either side; stimulus angles greater than 25° resulted in all crickets turning correctly. These data reveal a sharply tuned lateral sensitivity for the auditory pathway of crickets, with an optimum at the species' calling frequency of 4.7 kHz (when compared with 3.5 and 6.0 kHz). The results for the forced-choice test are compared with the walking pattern during free phonotactic approaches, in order to determine the possible strategy underlying the acoustic orientation behaviour of the cricket.     

Ecology and behavior of Gecarcoidea natalis, the Christmas Island red crab, during the annual breeding migration.

The terrestrial crab Gecarcoidea natalis is endemic to the forests of Christmas Island but must migrate each year to the coast to breed. During 1993 and 1995, radio-tracking, mark and recapture, and counting methods were used to establish the routes, walking speeds, direction of travel, and destinations of migrating crabs, as well as crab numbers and distribution. The density of crabs ranged from 0.09 to 0.57 crabs per square meter, which gave a population estimate of 43.7 million adult crabs on the island. During the dry season the crabs were relatively inactive but on arrival of the wet season immediately began their migration. The crabs generally walked in straight lines, and most crabs from around the Island traveled toward the northwest shore instead of simply walking toward the nearest shore. The maximum recorded distance walked by a red crab in one day was 1460 m, but the mean was 680 m per day in 1993 and 330 m in 1995. Comparing the 1993 and 1995 study seasons, there was a 3-week difference in the timing of the start of the migration, but the spawning date was fixed by the lunar phase and took place 17 to 18 days after mating. In 1993, late rain prompted a "rushed" migration and crabs walked directly to their shore destinations; in contrast, in 1995 most crabs made stops of 1 to 7 days during the downward migration. By giving the crabs a chance to feed along the way and minimizing the time that the population was concentrated near the shore, these stops may be important in ensuring that the animals have enough food after the long dry season. Furthermore, this behavior implies that the crabs are able to judge how far away they are from the shore during the migration.     

Fish oil induced increase in walking distance, but not ankle brachial pressure index, in peripheral arterial disease is dependent on both body mass index and inflammatory genotype

Peripheral arterial disease (PAD) is an atherosclerotic disease. Evidence suggests that atherosclerosis is an inflammatory condition and long chain n-3 fatty acids, found in oily fish and fish oils, have been shown to reduce inflammation. Genetic and lifestyle factors such as body mass index (BMI) also influence inflammation. In this study we have examined the effect of fish oil in patients with claudication secondary to PAD. Fish oil supplementation, providing 1g EPA and 0.7 g DHA per day for 12 weeks, increased walking distance on a treadmill set at 3.2 km/h with a 7% incline. Walking distance to first pain increased from 76.2+/-8.5 m before fish oil to 140.6+/-25.5 m after fish oil (mean+/-SEM, p=0.004) and total distance walked increased from 160.0+/-21.5 m before fish oil to 242.1+/-34.5 m after fish oil (p=0.002). Fish oil supplementation also improved ankle brachial pressure index (ABPI) from 0.599+/-0.017 before fish oil to 0.776+/-0.030 after fish oil (p<0.001). The increase in walking distance was dependent on both BMI and genotype for single nucleotide polymorphisms in the genes encoding the pro-inflammatory cytokines tumour necrosis factor-alpha and interleukin (IL)-1beta and the anti-inflammatory cytokine IL-10 (detected using amplification refractory mutation system polymerase chain reaction). Neither BMI nor any of the genotypes examined affected the ability of fish oil to increase ABPI. The mechanisms by which fish oil affects walking distance and ABPI do not appear to be the same.     

Effects of age and physical activity status on the speed-aerobic demand relationship of walking.

Older adults tend to show lower preferred walking speeds and higher aerobic demands per distance walked than young adults. It has been suggested that a more sedentary life-style contributes to diminished musculoskeletal functioning, which in turn contributes to poorer economy of motion in the aged and sedentary adults. The purpose of this study was to quantify the speed-aerobic demand relationship during walking for old (greater than 65 yr of age) and young adults and to determine whether physical activity status affects this relationship. Aerobic demands for 30 young and 30 old individuals representing sedentary and physically active groups were measured as the subjects performed treadmill walking at seven speeds ranging from 0.67 to 2.01 m/s. All four age/physical activity groups displayed U-shaped speed-aerobic demand curves with minimum gross oxygen consumption per unit distance walked (ml.kg-1.km-1) at 1.34 m/s. A statistically significant age effect on walking aerobic demand was observed, with old subjects showing an 8% higher mean aerobic demand than the young subjects. This age-related effect was not associated with shifts in the speed at which aerobic demand was minimized or with the preferred walking speed of older individuals falling on a less economical portion of the speed-aerobic demand curve. Rather, it was speculated that declines in force-generating capacity of muscle in the aged may require recruitment of additional motor units and perhaps an additional proportion of less economical fast twitch muscle fibers to generate necessary forces. Physical activity status had no significant effect on walking aerobic demand.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of food deprivation on the ambulatory movement of the Colorado potato beetle,Leptinotarsa decemlineata

Modification of dispersal behaviour is a common response of insects to food and water deprivation. The literature suggests that different insects respond with different strategies: changing walking parameters, switching dispersal mode (walking to flight or vice versa), or changing the host searching path. The goal of this study was to add to the limited literature on the subject by investigating, whether the walking parameters of adult male Colorado potato beetles, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), change in response to food and water deprivation. Observations on the distance walked, the travel speed, and the frequency of walking bouts were carried out in laboratory arenas using motion monitoring equipment. Summer and overwintered beetles were exposed to short starvation periods (2, 4, 8, 24 h) and two ranges of long starvation periods (1, 2, 4, 8 days and 1, 2, 4, 8, 16, and 32 days). Only the longest food deprivation periods of 16 and 32 days significantly reduced the walking distance, speed, and frequency of walking bouts of summer beetles. No changes were observed with overwintered beetles. The tolerance of the beetles without access to water to the different periods of food deprivation was similar to that for beetles with water except after a starvation period of 32 days, when the travel speed of summer beetles was significantly reduced by 33%. The absence of increased walking parameters found in this study and earlier observations of increased flight frequency suggest that the strategy of summer beetles will be to change the dispersal mode from walking to flight and/or to change the walking host searching path. The same results of this study and earlier observations of a decrease in the mean frequency of daily flights suggest that the strategy of overwintered L. decemlineata, exposed to food deprivation, will be to change the host search walking path rather than the walking parameters themselves.     

Fast and reliable decisions for a dynamic song parameter in field crickets

We investigated the choice of female crickets for a dynamic song parameter (chirp rate) on a walking compensator, and the underlying neuronal basis for the choice in the form of discharge differences in the pair of AN1-neurons driving the phonotactic steering behaviour. Our analysis reveals that decisions about chirp rate in a choice situation are made fast and reliably by female crickets. They steered towards the higher chirp rate after a delay of only 2.2–6 s, depending on the rate difference between the song alternatives. In this time period, the female experienced only one to two additional chirps in the song model with the higher rate. There was a strong correlation between the accumulated AN1 discharge difference and the amount of steering towards the side with the stronger response.     

The influence of auditory and visual experience on the phonotactic behavior of the cricket,Gryllus bimaculatus

Female crickets lacking experience with phonotaxis to conspecific calling song respond to trains of continuously repeated sound pulses (trill), whereas experienced females do not. In the present study such inexperienced crickets were tested for their responsiveness to trills of pulse repetition periods from 30 to 70 ms on a Y- shaped maze. Stimulation with a repetition period of 30 ms led to unexpectedly low phonotactic and exploratory activity. Initial stimulation with trills of 30- ms repetition period drastically reduced the responsiveness of inexperienced animals to conspecific calling song and other attractive stimuli. Effects of visual stimulation on the phonotactic behavior of female crickets are demonstrated. Threatening visual stimuli changed the behavior of experienced animals to a state that resembles that of inexperienced animals. The relevance of these observations is discussed with respect to the development of the auditory pattern recognition mechanism in crickets.     

Carbon monoxide and exercise tolerance in chronic bronchitis and emphysema.

The effects of carbon monoxide on exercise tolerance as assessed by the distance walked in 12 minutes were studied in 15 patients with severe chronic bronchitis and emphysema (mean forced expiratory volume in one second 0.56 1, mean forced vital capacity 1.54 1). Each subject walked breathing air and oxygen before and after exposure to sufficient carbon monoxide to raise their venous carboxyhaemoglobin concentration by 9%. There was a significant reduction in the walking distance when the patients breathed air after exposure to carbon monoxide (p less than 0.01), and the significant increase in walking distance seen after exercise when breathing oxygen at 2 1/minute via nasal cannulae was abolished if carbon monoxide has previously been administered. Thus concentrations of carboxyhaemoglobin frequently found in bronchitic patients who smoke may reduce their tolerance of everyday exercise, possibly by interfering with the transport of oxygen to exercising muscles.     

Costs of compensation: effect of early life conditions and reproduction on flight performance in zebra finches

Conditions experienced in early life have been shown to affect the development or programming of physiological processes. While animals may recover from earlier periods of adversity, this process can carry long-term costs. Such long-term effects are likely to be most evident when individuals are placed in demanding situations that require high performance. Escape flight speed in passerine birds is crucial to predator evasion and requires very rapid take-off. Here, we examine whether the ability to maintain escape flight performance during the immediate post-breeding period is influenced by conditions in early life. We manipulated the early life conditions experienced by zebra finches (Taeniopygia guttata) by rearing them on either low or high quality food through the growth period, or by changing conditions halfway through the nestling period, moving from high to low or vice versa. While there was no difference amongst the treatment groups in body size attained by adulthood, amongst the birds that experienced low quality food, the body size of those that were switched to a high quality diet halfway through the nestling growth period recovered faster than those that had low quality food until fledging. We found no differences amongst the dietary groups in flight performance at adulthood prior to breeding, and all groups showed a decline in average escape flight performance over the breeding period. However, the magnitude of the post-breeding decline in flight performance for a given level of reproductive output was significantly greater for those females that had experienced a switch from a low to a high quality diet during the nestling phase. These results suggest that this diet-induced rapid recovery of body size, which may have immediate competitive advantages, nonetheless carries locomotory costs in later life manifest in the capacity to sustain the high performance escape response during the post-reproductive recovery phase.     

Nonexercise movement in elderly compared with young people

The association between free-living daily activity and aging is unclear because nonexercise movement and its energetic equivalent, nonexercise activity thermogenesis, have not been exhaustively studied in the elderly. We wanted to address the hypothesis that free-living nonexercise movement is lower in older individuals compared with younger controls matched for lean body mass. Ten lean, healthy, sedentary elderly and 10 young subjects matched for lean body mass underwent measurements of nonexercise movement and body posture over 10 days using sensitive, validated technology. In addition, energy expenditure was assessed using doubly labeled water and indirect calorimetry. Total nonexercise movement (acceleration arbitrary units), standing time, and standing acceleration were significantly lower in the elderly subjects; this was specifically because the elderly walked less distance per day despite having a similar number of walking bouts per day compared with the young individuals. The energetic cost of basal metabolic rate, thermic effect of food, total daily energy expenditure, and nonexercise activity thermogenesis were not different between the elderly and young groups. Thus, the energetic cost of walking in the elderly may be greater than in the young. Lean, healthy elderly individuals may have a biological drive to be less active than the young.     

Activating and Relaxing Music Entrains the Speed of Beat Synchronized Walking

Inspired by a theory of embodied music cognition, we investigate whether music can entrain the speed of beat synchronized walking. If human walking is in synchrony with the beat and all musical stimuli have the same duration and the same tempo, then differences in walking speed can only be the result of music-induced differences in stride length, thus reflecting the vigor or physical strength of the movement. Participants walked in an open field in synchrony with the beat of 52 different musical stimuli all having a tempo of 130 beats per minute and a meter of 4 beats. The walking speed was measured as the walked distance during a time interval of 30 seconds. The results reveal that some music is ‘activating’ in the sense that it increases the speed, and some music is ‘relaxing’ in the sense that it decreases the speed, compared to the spontaneous walked speed in response to metronome stimuli. Participants are consistent in their observation of qualitative differences between the relaxing and activating musical stimuli. Using regression analysis, it was possible to set up a predictive model using only four sonic features that explain 60% of the variance. The sonic features capture variation in loudness and pitch patterns at periods of three, four and six beats, suggesting that expressive patterns in music are responsible for the effect. The mechanism may be attributed to an attentional shift, a subliminal audio-motor entrainment mechanism, or an arousal effect, but further study is needed to figure this out. Overall, the study supports the hypothesis that recurrent patterns of fluctuation affecting the binary meter strength of the music may entrain the vigor of the movement. The study opens up new perspectives for understanding the relationship between entrainment and expressiveness, with the possibility to develop applications that can be used in domains such as sports and physical rehabilitation.     

Limited flexibility in female Pacific field cricket (Teleogryllus oceanicus) exploratory behaviors in response to perceived social environment

How populations adapt, or not, to rapid evolution of sexual signals has important implications for population viability, but is difficult to assess due to the paucity of examples of sexual signals evolving in real time. In Hawaiian populations of the Pacific field cricket (Teleogryllus oceanicus), selection from a deadly parasitoid fly has driven the rapid loss of a male acoustic signal, calling song, that females use to locate and evaluate potential mates. In this newly quiet environment where many males are obligately silent, how do phonotactic females find mates? Previous work has shown that the acoustic rearing environment (presence or absence of male calling song) during late juvenile stages and early adulthood exposes adaptive flexibility in locomotor behaviors of males, as well as mating behaviors in both sexes that helps facilitate the spread of silent (flatwing) males. Here, we tested whether females also show acoustically induced plasticity in walking behaviors using laboratory‐reared populations of T. oceanicus from Kauai (HI; >90% flatwings), Oahu (HI; ~50% flatwings), and Mangaia (Cook Islands; no flatwings or parasitoid fly). Though we predicted that females reared without song exposure would increase walking behaviors to facilitate mate localization when song is rare, we discovered that, unlike males, female T. oceanicus showed relatively little plasticity in exploratory behaviors in response to an acoustic rearing environment. Across all three populations, exposure to male calling song during development did not affect latency to begin walking, distance walked, or general activity of female crickets. However, females reared in the absence of song walked slower and showed a marginally non‐significant tendency to walk for longer durations of time in a novel environment than those reared in the presence of song. Overall, plasticity in female walking behaviors appears unlikely to have facilitated sexual signal loss in this species.     

Behavioural evidence for polarization vision in crickets

ABSTRACT. Tethered field crickets, Gryllus campestris L., walking on an air-suspended bail exhibit a spontaneous response to the e-vector of polarized light presented from above: E-vector orientation controls strength and direction of turning tendency. Experiments in which different eye regions are covered with paint suggest that this response is mediated by the anatomically and physiologically specialized dorsal rim area of the compound eye. We conclude that crickets have polarization vision and that the dorsal rim area of the eye plays a key role in this sensory capacity.