The movement patterns of lacertid lizards: speed, gait and pauses in Lacerta vivipara

Lacerta vivipara moving across an open space at their normal activity temperature alternate bursts of locomotion with short pauses which tend to occur at the extremes of the limb cycle, i.e. when individual limbs are maximally adducted or retracted and the spinal cord is maximally flexed in the lateral plane. The movement bursts and pauses in adult lizards have mean durations of 0–30 and 012 s, respectively, and within bursts the lizards move at a mean speed of 14–6 cm s^-1. Movement in juvenile lizards is 2–5 times faster (relative to body length) and the pauses are of longer duration (mean = 019 s), giving the locomotion of juveniles a more jerky appearance. Lizards which are chasing crickets increase the speed and the duration of locomo-tory bursts, although the pauses persist. Lizards which are searching for a previously perceived cricket increase pause duration (mean = 0–40 s). Lizards which are fleeing from a sudden disturbance move at almost twice (juveniles) or 3–7 times (adults) the speed of foraging animals: the pauses persist, although at much reduced frequency. Increases in speed result from increases in both stride length (Λ) and stride frequency (n); the ratio Λ/ n appears to remain constant at 006. The significance of these observations is discussed, although the functions of the pauses cannot yet be explained.     

Acoustic communication in a duetting grasshopper: receiver response variability, male strategies and signal design

In the duetting grasshopper Chorthippus biguttulus, a female's decision to reply to a conspecific male is based on the evaluation of a number of features of the male's song, which consists of uninterrupted syllables separated by pauses. Female responses are tuned to a restricted range of pause durations. However, males produce songs with noisy rather than silent pauses, which should make the measurement of pause durations more difficult for the female. We examined the adaptive value of these noisy pauses by testing female responses to (1) pairs of natural phrases, which differed only with respect to clear or noisy syllable pauses, and (2) synthetic phrases, in which the syllable onset accentuations and noise levels in the pauses were systematically varied. There was considerable variation between females, both in their preference for clear or noisy pauses in natural phrases, and in the optimal combinations of syllable onset accentuations and noise levels in pauses that they preferred in synthetic phrases. The response profiles of individual females were consistent. The experiments with synthetic phrases showed that, on average, females preferred more extreme values of syllable onset accentuations than were present in male songs. Noisy pauses increased the range of syllable pause durations accepted by females. The results suggest that noisy pauses could buffer signallers against the negative consequences of both signal degradation during transmission and extreme receiver choosiness.     

Long-term effects of suppressing the preratio pause

The preratio pause is a characteristic feature of performances under fixed-ratio schedules of reinforcement, even though the pause is not required by the schedule and it reduces the reinforcement rate. To investigate the reduction of pausing, five rats trained on fixed-ratio schedules were exposed to timeout punishment of pauses that exceeded a specified duration. After a series of 30 punishment sessions, most of the longest pauses were eliminated. For some subjects punishment was withdrawn abruptly, whereas for others a fading procedure was employed. Postpunishment observations then were continued for an additional 60 sessions. The reduced pausing was accompanied by reductions in the positive skew of the baseline distribution of pause durations, and by substantial increases in reinforcement rates. However, the results did not indicate differences as a function of the method of withdrawing the punishment contingency. Although postpunishment performances indicated some degree of recovery in the number of long pauses, performances had stabilized below prepunishment levels when the experiment ended. The results suggest the possibility that reduced pause durations can be self-maintained by the resulting increase in reinforcement rates.     

An analysis of the pattern of feeding in the Costa Rican weevil, Exopthalmus jekelianus, on the tropical tree, Cedrela odorata

Feeding patterns were recorded and analysed for adult female weevils, Exopthalmus jekelianus (White) (Coleoptera: Curculionidae), feeding on Central American mahogany, Cedrela odorata L., in the field in Costa Rica. The study forms part of an investigation into the relationship between feeding patterns and the fine-scale variation in leaf chemistry occurring within the host plant. The weevils’ feeding patterns were the simplest in temporal structure of any reported to date for an insect herbivore. Weevils spent an average of only 3% of their time feeding during the 10-h observation periods. Meals lasted an average of 2.8 min and occurred at a mean intermeal interval of 84 min. The feeding patterns gave the appearance of a short-term rhythm underlying the onset of feeding (as has been found in locusts and caterpillars), although there were insufficient meals taken by individuals over the 10-h period to test this suggestion. Meals were notable in apparently lacking intrameal pauses and also commencing without preliminary sampling behaviours, such as palpating or biting. Whether the combination of short, infrequent meals, ingested without pauses and not preceded by sampling behaviour, represents an adaptation reducing apparency to natural enemies, or else simply reflects low nutritional needs, is discussed. Correlations between meal durations and following and preceding intermeal intervals suggested that variation in intermeal intervals stemmed largely from variation in meal duration, not vice versa, with variation in meal duration resulting from an external influence such as leaf nutritional and/or allelo-chemistry. The latter suggestion is currently being tested.     

Sequence Complexity Effects on Speech Production in Healthy Speakers and Speakers with Hypokinetic or Ataxic Dysarthria

The present study investigated the effects of sequence complexity, defined in terms of phonemic similarity and phonotoactic probability, on the timing and accuracy of serial ordering for speech production in healthy speakers and speakers with either hypokinetic or ataxic dysarthria. Sequences were comprised of strings of consonant-vowel (CV) syllables with each syllable containing the same vowel, /a/, paired with a different consonant. High complexity sequences contained phonemically similar consonants, and sounds and syllables that had low phonotactic probabilities; low complexity sequences contained phonemically dissimilar consonants and high probability sounds and syllables. Sequence complexity effects were evaluated by analyzing speech error rates and within-syllable vowel and pause durations. This analysis revealed that speech error rates were significantly higher and speech duration measures were significantly longer during production of high complexity sequences than during production of low complexity sequences. Although speakers with dysarthria produced longer overall speech durations than healthy speakers, the effects of sequence complexity on error rates and speech durations were comparable across all groups. These findings indicate that the duration and accuracy of processes for selecting items in a speech sequence is influenced by their phonemic similarity and/or phonotactic probability. Moreover, this robust complexity effect is present even in speakers with damage to subcortical circuits involved in serial control for speech.     

The perception of empty and filled time intervals by rats

In Experiment 1, rats were trained in a within-subjects design to discriminate durations of a filled interval, and durations of an empty interval (an unfilled interval marked at the beginning and end by a 500 ms tone). Training and psychophysical testing was conducted with three sets of anchor durations. Rats made more long responses for filled than for empty intervals at signal durations greater than the geometric mean. In Experiment 2, Group Same was trained similarly to the rats in Experiment 1 with the ambient conditions (houselight illumination) remaining the same during the intertrial interval and the empty intervals. Group Different was trained with the houselight turned off during empty and filled intervals. The similarity of ambient conditions during the intertrial interval and the empty intervals did not significantly affect timing. Filled intervals were timed more precisely and they were perceived as longer than empty intervals of the same duration. The psychophysical functions superimposed across anchor duration sets. These results are the first clear evidence of a filled interval illusion in rats, and they suggest that this difference may reflect a clock rate effect (greater for filled intervals) rather than a switch latency effect (slower for empty intervals).     

The perception of empty and filled time intervals by rats

In experiment 1, rats were trained in a within-subjects design to discriminate durations of a filled interval, and durations of an empty interval (an unfilled interval marked at the beginning and end by a 500 ms tone). Training and psychophysical testing was conducted with three sets of anchor durations. Rats made more long responses for filled than for empty intervals at signal durations greater than the geometric mean. In experiment 2, group same was trained similarly to the rats in experiment 1 with the ambient conditions (houselight illumination) remaining the same during the inter-trial interval and the empty intervals. Group different was trained with the houselight turned off during empty and filled intervals. The similarity of ambient conditions during the inter-trial interval and the empty intervals did not significantly affect timing. Filled intervals were timed more precisely and they were perceived as longer than empty intervals of the same duration. The psychophysical functions superimposed across anchor duration sets. These results are the first clear evidence of a filled interval illusion in rats, and they suggest that this difference may reflect a clock rate effect (greater for filled intervals) rather than a switch latency effect (slower for empty intervals).     

The Effects of Stimulus Variability on the Perceptual Learning of Speech and Non-Speech Stimuli

Previous studies suggest fundamental differences between the perceptual learning of speech and non-speech stimuli. One major difference is in the way variability in the training set affects learning and its generalization to untrained stimuli: training-set variability appears to facilitate speech learning, while slowing or altogether extinguishing non-speech auditory learning. We asked whether the reason for this apparent difference is a consequence of the very different methodologies used in speech and non-speech studies. We hypothesized that speech and non-speech training would result in a similar pattern of learning if they were trained using the same training regimen. We used a 2 (random vs. blocked pre- and post-testing) × 2 (random vs. blocked training) × 2 (speech vs. non-speech discrimination task) study design, yielding 8 training groups. A further 2 groups acted as untrained controls, tested with either random or blocked stimuli. The speech task required syllable discrimination along 4 minimal-pair continua (e.g., bee-dee), and the non-speech stimuli required duration discrimination around 4 base durations (e.g., 50 ms). Training and testing required listeners to pick the odd-one-out of three stimuli, two of which were the base duration or phoneme continuum endpoint and the third varied adaptively. Training was administered in 9 sessions of 640 trials each, spread over 4–8 weeks. Significant learning was only observed following speech training, with similar learning rates and full generalization regardless of whether training used random or blocked schedules. No learning was observed for duration discrimination with either training regimen. We therefore conclude that the two stimulus classes respond differently to the same training regimen. A reasonable interpretation of the findings is that speech is perceived categorically, enabling learning in either paradigm, while the different base durations are not well-enough differentiated to allow for categorization, resulting in disruption to learning.     

我国东部北亚热带植物群落季相的时空变化

研究我国东部亚热带植物群落物候与气候变化的关系,对于揭示东部季风区生态系统对气候变化响应的整体特征和空间分异,具有重要的科学意义。作者利用物候累积频率拟合法对盐城、武汉、合肥、屯溪1982-1996年的植物群落季相阶段进行划分,并分析了季相阶段的时空变化及其与气温的统计关系。结果表明：（1）各站多年平均变绿期、旺盛光合期和休眠期初日均有随海拔升高而推迟的倾向,而多年平均季相阶段长度的空间分异特征不明显。休眠期初日随海拔升高而推迟的事实表明,树木秋季叶变色和落叶除受到气温的影响外,还可能与光照和霜等其它环境因素有关,从而使得海拔升高对秋季物候期提早的影响有所削弱,其生态机制有待进一步研究。（2）各站变绿期初日以提前为主,长度以延长为主;旺盛光合期和凋落期初日均以提前为主,长度延长与缩短参半;休眠期初日提前与推迟参半,长度以缩短为主。（3）各站变绿期和旺盛光合期初日与前期平均气温多呈显著负相关,而凋落期和休眠期初日与前期平均气温相关不显著。利用最佳时段气温-物候回归模型重建的1982-2006年季相阶段初日的时间序列显示,盐城、武汉和屯溪的变绿期初日呈显著提前的趋势,盐城、合肥和武汉旺盛光合期初日也呈显著提前的趋势。值得注意的是,在2002-2006年期间,各站变绿期和旺盛光合期初日均表现出明显推迟的倾向,与各地该时段前期平均气温呈下降的倾向一致。（4）从北亚热带各站到温带北部的哈尔滨,平均每向北1个纬度,多年平均变绿期和旺盛光合期初日分别显著推迟2.7-4.0 d和1.8-2.8 d,而长度则多呈不显著缩短的趋势;凋落期初日提前不显著,但长度显著缩短1.8-2.6 d;休眠期初日显著提前2.9-3.3 d,且长度显著延长5.8-7.0 d。总体上看,上述观测事实符合植物物候空间变化的一般规律,即在生长季节前半段,低纬地区的植物物候早于高纬地区;在生长季节后半段,高纬地区的植物物候早于低纬地区。     

XVITH SYMPOSIUM OF THE INTERNATIONAL BIOACOUSTICS COUNCIL—ABSTRACTS

ABSTRACT

Three vocalisation types of the másafuera rayadito Aphrastura masafuerae are described using sonograms: common call, alarm call, and song. They are analysed according to their structure, kHz-frequency, duration and time of day. The common call can be uttered singly or in a series with regular pauses. This intensive call is heard even through fog and wind and seems to be used for contacting the partner as well as signalling the home range to neighbours. The alarm call is a continuous series of similar syllables without pauses. The song is given exclusively in the morning before sunrise by only one individual of the pair. It has one type of phrase only, which is repeated. Phrases are interrupted by regular pauses. These vocalisation types are clearly different from each other, but also have features in common: the monotonous structure, repetition of units and temporal frequency of elements.     

Effects of prey abundance on the foraging behaviour, diving efficiency and time allocation of breeding Guillemots Uria aalge

The foraging behaviour of Guillemots Uria aalge at sea was compared between 2 years of radically different food abundance. Radio telemetry was used to determine foraging locations and diving patterns. In the poor compared with the good food year, foraging trips were much longer, the birds foraged more than six times further from their breeding sites, they spent over five times as much time diving when at sea and their estimated energy expenditure was twice as great. Time spent foraging in the poor food year was at the expense of time spent sitting at the colony. The duration of a foraging trip was a poor indicator of distance travelled but a good indicator of the amount of time spent diving. Mean dive durations, surface pause durations and interbout periods did not differ between years, but individuals made more than four times as many dives per diving bout in the poor food year. Surface pause lengths did not vary with water depth in either year. In the poor food year, birds made shorter surface pauses for a dive of a gi^ven duration than in the good food year, possibly accepting a lactic acid debt in order to maximize searching time, The duration of the interbout period was positively related to the number of dives in the previous bout, and dives tended to get shorter in long diving sequences, suggesting possible exhaustion effects. These data demonstrate that breeding Guillemots have the capacity to adjust their foraging behaviour and time budgets in response to changes in food abundance, but this flexibility was not sufficient to compensate fully for the very low food abundance experienced by birds in this study.     

Hypothalamic autostimulation in rats at low frequencies of stimulation on the basis of locomotion]

A study was made of the hypothalamic autostimulation of rats with the impulse stimulation frequency of from 30 to 7 cycles/sec. The animals' brain was stimulated in Skinner's chamber and on the basis of locomotion. The duration of a series of impulses established by the animal on the basis of locomotion grew with reduction of the frequency of stimulation impulses. The pauses between the series of impulses and the duration of the series were also prolonged with a voltage reduction. With the help of stimulation frequency of 7 cycles it was possible to choose such a current that the sum of the total duration of pauses lay within 0 divided by 10% of the total experimental time. The duration of individual pauses was less than 0.5 sec.     

The relative importance of different direct benefits in the mate choices of a field cricket

Discussions about the evolution of female mating preferences have often suggested that females should express multiple strong preferences when different male traits are correlated with different mating benefits, yet few studies have directly tested this hypothesis by comparing the strength of female preferences for male traits known to be correlated with different benefits. In the variable field cricket, Gryllus lineaticeps, females receive fecundity and fertility benefits from mating with males with higher chirp rates and life-span benefits from mating with males with longer chirp durations. Although females prefer higher chirp rates and longer chirp durations when the other trait is held constant, it is possible that they give priority to one of these song traits when both vary. In this study, we examined the relative importance of chirp rate and chirp duration in female mate choice using single-stimulus presentations of songs that varied in both chirp rate and chirp duration. Females expressed both directional and stabilizing preferences based on chirp rate, responding most strongly to a chirp rate approximately one standard deviation above the population mean. Females did not express preferences based on chirp duration, and did not express correlational preferences. These results suggest that females may give priority to the reproductive benefits provided by males that produce higher chirp rates.     

Multiscale trend analysis of microtubule transport in melanophores

Microtubule-based transport is critical for trafficking of organelles, organization of endomembranes, and mitosis. The driving force for microtubule-based transport is provided by microtubule motors, which move organelles specifically to the plus or minus ends of the microtubules. Motor proteins of opposite polarities are bound to the surface of the same cargo organelle. Transport of organelles along microtubules is discontinuous and involves transitions between movements to plus or minus ends or pauses. Parameters of the movement, such as velocity and length of runs, provide important information about the activity of microtubule motors, but measurement of these parameters is difficult and requires a sophisticated decomposition of the organelle movement trajectories into directional runs and pauses. The existing algorithms are based on establishing threshold values for the length and duration of runs and thus do not allow to distinguish between slow runs and pauses, making the analysis of the organelle transport incomplete. Here we describe a novel algorithm based on multiscale trend analysis for the decomposition of organelle trajectories into plus- or minus-end runs, and pauses. This algorithm is self-adapted to the characteristic durations and velocities of runs, and allows reliable separation of pauses from runs. We apply the proposed algorithm to compare regulation of microtubule transport in fish and Xenopus melanophores and show that the general mechanisms of regulation are similar in the two pigment cell types.     

Quantification of rhythm problems in disordered speech: a re-evaluation

Disordered speech can present with rhythmic problems, impacting on an individual''s ability to communicate. Effective treatment relies on the availability of sensitive methods to characterize the problem. Rhythm metrics based on segmental durations originally designed for cross-linguistic research have the potential to provide such information. However, these measures may be associated with problems that impact on their clinical usefulness. This paper aims to address the perceptual validity of cross-linguistic metrics as indicators of rhythmic disorder. Speakers with dysarthria and matched healthy participants performed a range of tasks, including syllable and sentence repetition and a spontaneous monologue. A range of rhythm metrics as well as clinical measures were applied. Results showed that none of the metrics could differentiate disordered from healthy speakers, despite clear perceptual differences, suggesting that factors beyond segment duration impacted on rhythm perception. The investigation also highlighted a number of areas where caution needs to be exercised in the application of rhythm metrics to disordered speech. The paper concludes that the underlying speech impairment leading to the perceptual and acoustic characterization of rhythmic problems needs to be established through detailed analysis of speech characteristics in order to construct effective treatment plans for individuals with speech disorders.     

Effect of conspecific alarm calls in the parental behaviour of nesting southern house wrens

Alarm calls are usually used to signal the presence of a threat to members of the same species and have been studied broadly in social foraging species. We analysed the effects of conspecific alarm calls on the parental behaviour of a territorial species, the southern house wrens (Troglodytes aedon musculus), during nestling stage. We compared the parental response of adults feeding 9–11-day-old nestlings when faced with conspecific alarm calls and with a control non-sympatric species’ song broadcast from a neighbouring territory. We measured the time required by parents to return to the nest (latency) when exposed to the stimuli and estimated parent’s nest visitation rate and mean visit duration. Parents took longer to resume parental activities when we broadcast a conspecific alarm call, but they did not modify their nest visitation rate or the mean visit duration. Heterospecific songs did not seem to affect parental behaviour. Our results suggest that nesting southern house wrens can use alarm calls uttered from neighbouring territories to assess the presence of a threat and adjust their parental behaviour accordingly.     

Association of depressive symptoms with habitual sleep duration and sleep timing in junior high school students

ABSTRACT

This study aims to investigate independent associations of habitual sleep durations and sleep timings on weekdays and weekends with depressive symptoms in adolescents who have classes in the morning. We studied grade 7–9 students (942 males and 940 females, aged 12–15 years), who had classes in the morning, at public junior high schools in Japan in a cross-sectional design. The students answered a self-report questionnaire, which covers habitual sleep durations, bedtimes and wake-up times on weekdays and weekends, and depressive symptoms. The Short Mood and Feelings Questionnaire (SMFQ) was used to determine the level of depressive symptoms. The relationship between the variables on sleep habits and the SMFQ score were studied using multivariate linear regression and generalized additive models (GAM), controlling for sex, age and school. Multivariate linear regression analysis revealed that sleep duration on weekdays and relative mid-sleep time on weekdays (i.e. mid-sleep time on weekdays – mid-sleep time on weekends) were independently significantly (p < .001) associated with the SMFQ score. GAM analysis also revealed that sleep duration on weekdays (a reverse J-shaped relationship) and the relative mid-sleep time on weekdays (a negative monotonic/linear relationship) were independently significantly (p < .001) associated with the SMFQ score. These associations were confirmed in both males and females when they were analyzed separately. These results suggest that sleep duration on weekdays and the relative mid-sleep time on weekdays may be independently associated with the level of depressive symptoms in junior high school students who have classes in the morning. These findings may have important implications for the development of novel strategies for preventing mental health problems in adolescents.     

Neuronal adaptation improves the recognition of temporal patterns in a grasshopper

The recognition of the temporal structure of sound patterns by grasshopper males was investigated in behavioural experiments. Males were tested with short (165–335 ms) song models in which the characteristic subunit pattern of syllables and pauses was modified either at the beginning or at the end of the stimuli. The highly specific responses of the animals indicate that neuronal adaptation has a substantial influence on the detection of the pauses which are essential cues for the subunit structure: pauses were less likely detected shortly after the beginning of a song model than at later positions. Even adaptation in auditory neurons that was induced by unspecific stimulation (with unmodulated noise) facilitated the processing of sound envelopes. The effects of stimulus prolongation and introduction of pauses appeared to combine linearly, similar to the effects of introducing two pauses instead of a single one. In the responses to some song models large interindividual differences were observed. Comparison across stimuli and repeated testing of a smaller number of individuals indicated a considerable consistency of behavioural preferences. However, the data yielded no clear evidence for the existence of individually distinct processing types among males, that conceivably would focus on different features of the stimuli.     

Host preferences in a phonotactic parasitoid of field crickets: the relative importance of host song characters

Abstract.  1. Predators, including insect parasitoids, often eavesdrop on prey signals, and as a result, predation can have important effects on the evolution of prey signalling behaviour.
2. The phonotactic parasitoid fly, Ormia ochracea , uses the calling songs of male field crickets to locate their field crickets hosts. In the western USA, this fly parasitises the variable field cricket, Gryllus lineaticeps . Previous work with one fly population suggested that female flies, like female field crickets, preferentially orient to male songs with higher chirp rates and longer chirp durations, although a limited range of male song types was used in this previous study. The current study, with a different fly population, used field-based, two-speaker choice tests to examine: (1) the effect of male chirp rate and chirp duration on fly attraction, using a natural range of song types; and (2) the relative importance of these song types in host selection by the flies.
3. Three lines of evidence suggested that chirp rate is more important than chirp duration in host selection. (a) The flies consistently preferred higher chirp rates but only sometimes preferred longer chirp durations. (b) The flies consistently preferred higher chirp rate/shorter chirp duration songs to lower chirp rate/longer chirp duration songs. (c) Preferences for longer chirp durations could be eliminated by increasing the amplitude of the less attractive song type, while preferences for higher chirp rates could only sometimes be eliminated by increasing the amplitude of the less attractive song type.
4. Fly predation may favour lower chirp rates and shorter chirp durations in G. lineaticeps , and may have resulted in stronger selection on chirp rate than on chirp duration.