Dynamics of local maxima chains in spectra of human electroencephalogram

The continuous wavelet transform was applied to the human EEG signals recorded in different states of brain activity. The dynamics of local maxima chains in the matrices of the continuous wavelet transform coefficients was studied. The typologization method was developed for local maxima chains to separate by their drift in the frequency space as well as by dynamics of their signal “energy.” The method proved to be highly informative. It was shown that it was highly sensitive to a selection of one of two responses to the test question. It is determined that local maxima chains in most cases are gradually increasing and decreasing in the frequency space and by changes in the values of their continuous wavelet transform coefficients. The functional asymmetry in local maxima chains types’ distribution is determined. The results obtained allow us to consider the types of the local maxima chains dynamics as a new phenomenon of EEG activity.     

The influence of carotid arterial sounds on hearing sensitivity in mammals

Pulsations of the internal carotid and stapedial arteries produce unwanted sounds (noise) in the middle ear cavity which influence hearing in some mammals. 'Noise' pressure levels calculated from pulse rates, volume pulsations of the arteries, and Fourier analysis of arterial waveforms, correlate well with low frequency thresholds of hearing in the Long-eared hedgehog, Tree shrew and Kangaroo rat. In mammals adapted to hear low frequency sounds, such as the Kangaroo rat and fossorial insectivores, the arteries are enclosed in noise attenuating bony tubes. However, most small mammals possess extended high frequency hearing with little sensitivity at the low frequencies of the arterial sounds. In lower tetrapods such as anurans and most lizards, the broad connection between the middle ear cavity and the pharynx creates a leakage pathway which greatly reduces the noise from the stapedial artery. It is probably for these reasons that the large intratympanic arteries did not disturb hearing in early mammals or submammalian forms.     

Amplitude modulation in sound signals by mammals

Periodic variations in amplitude of a signal, or amplitude modulation (AM), affect the structure of communicative messages spectrum. Within the spectrum of AM-signals, side frequencies are formed both above and below the carrier frequency that is subjected to modulation. In case of harmonic signal structure they are presented near fundamental frequency as well as near harmonics. Thus, AM may by viewed as a relatively simple mechanism for controlling the spectrum of messages transmitted by mammals. Examples of AM affecting the spectrum structure of functionally different sound signals are discussed as applied to representatives of four orders of mammals: rodents (Reodentia), duplicidentates (Lagomorpha), pinnipeds (Pinnipedia), and paridigitates (Artiodactia). For the first time, the classification of AM in animals' sound signals is given. Five forms of AM are picked out in sound signals by mammals: absence of AM, continuous AM, fragmented, heterogeneous, and multilevel one. AM presence/absence is related neither with belonging to any specific order nor with some particular function of a signal. Similar forms of AM can occur in different orders of mammals in parallel. On the contrary, different forms of AM can be detected in signals meant for similar functions. The assumption is made about AM-signals facilitating information encoding and jamprotection of messages transmitted by mammals. Preliminry analysis indicates that hard-driving amplitude modulation is incompatible with hard-driving frequency modulation.     

Exploring the Potential Use of Seismic Waves as a Communication Channel by Elephants and Other Large Mammals

Bioseismic studies have previously documented the use of seismicstimuli as a method of communication in arthropods and smallmammals. Seismic signals are used to communicate intraspecificallyin many capacities such as mate finding, spacing, warning, resourceassessing, and in group cohesion. Seismic signals are also usedin interspecific mutualism and as a deterrent to predators.Although bioseismics is a significant mode of communicationthat is well documented for relatively small vertebrates, thepotential for seismic communication has been all but ignoredin large mammals. In this paper, we describe two modes of producingseismic waves with the potential for long distance transmission:1) locomotion by animals causing percussion on the ground and2) acoustic, seismic-evoking sounds that couple with the ground.We present recordings of several mammals, including lions, rhinoceroses,and elephants, showing that they generate similar acoustic andseismic vibrations. These large animals that produce high amplitudevocalizations are the most likely to produce seismic vibrationsthat propagate long distances. The elephant seems to be themost likely candidate to engage in long distance seismic communicationdue to its size and its high amplitude, low frequency, relativelymonotonic vocalizations that propagate in the ground and havethe potential to travel long distances. We review particularanatomical features of the elephant that would facilitate thedetection of seismic waves. We also assess low frequency soundsin the environment such as thunder and the likelihood of seismictransmission. In addition, we present the potential role ofseismic stimuli in human communication as well as the impactof modern anthropogenic effects on the seismic environment.     

Reproduction of the least weasel in captivity: basic observations and the influence of food availability

The least weaselMustela nivalis nivalis Linnaeus, 1766 is unique among carnivores because of its small body size and capacity for fast reproduction. It has been suggested to be the main agent for maintaining cyclic fluctuations in northern vole populations, largely based on its high reproductive potential and dependence on small rodents. This study describes basic reproductive data on the least weasel obtained during a captive breeding program. In the experiments, food availability was manipulated at the onset of breeding. Altogether, 65 litters were born during the 5-year study. The mean litter size was 5.1 (in 53 litters of known litter size), the most common litter size being six. The sex ratio of weaned young was not biased from 1∶1. The median date of birth was June 4. Food manipulations did not affect mating frequency suggesting that the observation of failure in breeding in years of low abundance of small mammals is due to mortality of embryos or young before weaning, but not due to avoidance of breeding at low food availability. In this respect, weasels differ from other main vole predators, owls and raptors, which often skip breeding if small mammals are scarce.     

Evolutionary advantage of small populations on complex fitness landscapes

Recent experimental and theoretical studies have shown that small asexual populations evolving on complex fitness landscapes may achieve a higher fitness than large ones due to the increased heterogeneity of adaptive trajectories. Here, we introduce a class of haploid three-locus fitness landscapes that allow the investigation of this scenario in a precise and quantitative way. Our main result derived analytically shows how the probability of choosing the path of the largest initial fitness increase grows with the population size. This makes large populations more likely to get trapped at local fitness peaks and implies an advantage of small populations at intermediate time scales. The range of population sizes where this effect is operative coincides with the onset of clonal interference. Additional studies using ensembles of random fitness landscapes show that the results achieved for a particular choice of three-locus landscape parameters are robust and also persist as the number of loci increases. Our study indicates that an advantage for small populations is likely whenever the fitness landscape contains local maxima. The advantage appears at intermediate time scales, which are long enough for trapping at local fitness maxima to have occurred but too short for peak escape by the creation of multiple mutants.     

“氯敌鼠”防治对农田小哺乳动物群落结构的影响及群落演替分析

对不同防治对策下施用氯敌鼠作为杀鼠剂对农田小哺乳动物群落结构的影响进行了研究．结果表明,杀鼠剂对群落组成有很大影响,灭鼠时机、灭鼠次数不同,群落的反应也不同．秋季灭鼠,小哺乳动物数量逐年下降,３ 年后可达到较低密度．群落多样性也逐年下跌,且回升极弱．春季灭鼠,数量可持续在低水平,群落多样性较其它处理高,对化学灭鼠破坏的生物多样性有较强的恢复力．灭鼠频次的增加对小哺乳动物总体数量降低有强化作用．可以认为,化学灭鼠明显地降低了群落中小哺乳动物的密度,也降低了群落的多样性．促使小哺乳动物群落向着优势种突出、种类单调、群落稳定性差的方向演替．     

Comparison of Species-Specific Bird Signals and Human Speech

We carried out a comparative study of spectral-prosodic characteristics of bird vocalization and human speech. Comparison was made between the relative characteristics of the fundamental frequency and spectral maxima. Criteria were formulated for the comparison of bird's signals and human speech. A certain correspondence was found between the vocal structures of birds and humans. It was proposed that in the course of evolution, man adopted the main structural principles of his acoustic signalling from birds.     

miR390, Arabidopsis TAS3 tasiRNAs,and Their AUXIN RESPONSE FACTOR Targets Define an Autoregulatory Network Quantitatively Regulating Lateral Root Growth

Plants adapt to different environmental conditions by constantly forming new organs in response to morphogenetic signals. Lateral roots branch from the main root in response to local auxin maxima. How a local auxin maximum translates into a robust pattern of gene activation ensuring the proper growth of the newly formed lateral root is largely unknown. Here, we demonstrate that miR390, TAS3-derived trans-acting short-interfering RNAs (tasiRNAs), and AUXIN RESPONSE FACTORS (ARFs) form an auxin-responsive regulatory network controlling lateral root growth. Spatial expression analysis using reporter gene fusions, tasi/miRNA sensors, and mutant analysis showed that miR390 is specifically expressed at the sites of lateral root initiation where it triggers the biogenesis of tasiRNAs. These tasiRNAs inhibit ARF2, ARF3, and ARF4, thus releasing repression of lateral root growth. In addition, ARF2, ARF3, and ARF4 affect auxin-induced miR390 accumulation. Positive and negative feedback regulation of miR390 by ARF2, ARF3, and ARF4 thus ensures the proper definition of the miR390 expression pattern. This regulatory network maintains ARF expression in a concentration range optimal for specifying the timing of lateral root growth, a function similar to its activity during leaf development. These results also show how small regulatory RNAs integrate with auxin signaling to quantitatively regulate organ growth during development.     

The spatial frequency discrimination function at low contrasts

Spatial frequency difference thresholds for sinewave gratings near contrast threshold were measured using a two-alternative forced-choice technique, and the threshold frequency differences were plotted as a proportion of standard frequency for standards from 2 to 7 cycles/degree. This function shows reliable local maxima and minima, and these features are more pronounced than they are when stimuli of 30% contrast are used. This result is consistent with the notion that at low contrasts, fewer spatial frequency channels are above threshold in the area of the visual field covered by the stimulus than when the stimulus is at high contrast.     

长江江豚声信号及其声行为的初步研究

长江江豚的声信号可分为两大类,即高频脉冲信号和低频连续信号。高频脉冲信号可能与回声定位有关,而低频连续信号可能与通信和情感表达有关。不管是高频脉冲信号还是低频连续信号,在豚处于自由状态时,夜间的发声次数要多于白天。       

The nuclei of the lateral lemniscus in the rufous horseshoe bat,Rhinolophus rouxi

In the rufous horseshoe bat, Rhinolophus rouxi, responses to pure tones and sinusoidally frequency modulated (SFM) signals were recorded from 289 single units and 241 multiunit clusters located in the nuclei of the lateral lemniscus (NLL). The distribution of best frequencies (BFs) of units in all three nuclei of the lateral lemniscus showed an overrepresentation in the range corresponding to the constant-frequency (CF) part of the echolocation signal ('filter frequency' range): in the ventral nucleus of the lateral lemniscus (VNLL) 'filter neurons' represented 43% of all units encountered, in the intermediate nucleus (INLL) 33%, and in dorsal nucleus (DNLL) 29% (Fig. 2a). Neurons with best frequencies in the filter frequency range had highest Q10dB-values (maxima up to 400, Fig. 2c) and only in low-frequency units were values comparable to those found in other mammals. On the average, filter neurons in ventral nucleus had higher Q10dB-values (about 220) than did those in intermediate and dorsal nucleus (both about 160, Fig 2d). Response patterns and tuning properties showed higher complexity in the dorsal and intermediate nucleus than in the ventral nucleus of the lateral lemniscus (Figs. 4 and 6). Multiple best frequencies were found in 12 neurons, nine of them with harmonically related excitation maxima (Fig. 5c, d). Best frequencies of six of these harmonically tuned units could not be correlated with any harmonic components of the echolocation signal. Half of all multiple tuned neurons were located in the caudal dorsal nucleus the other half in the caudal intermediate nucleus. Synchronization of responses to sinusoidally frequency modulated (SFM) signals occurred in VNLL-units in the average up to modulation frequencies of 515 Hz (maximum about 800 Hz) whereas in the intermediate and dorsal nucleus of the lateral lemniscus responses were synchronized in the average only up to modulation frequencies of about 300 Hz (maximum about 600 Hz) (Figs. 7 and 8). A tonotopic arrangement of units was found in the intermediate nucleus of the lateral lemniscus with units having high best frequencies located medially and those with low best frequencies laterally. In the dorsal nucleus the tonotopic distribution was found to be fairly similar to that in the intermediate nucleus but much less pronounced. In more rostral parts of the dorsal nucleus additionally higher best frequencies predominated whereas in caudal areas of that nucleus and also of the intermediate nucleus low BFs were found more regularly.(ABSTRACT TRUNCATED AT 400 WORDS)     

Factors influencing diet variation in a generalist predator across its range distribution

Factors linked with intraspecific variation in trophic diversity are still poorly understood in generalist species like the Montagu’s harrier (Circus pygargus) but may have important implications for conservation management at a wide scale. We described geographic patterns of Montagu’s harrier diet across Eurasia, gathering diet data from 30 studies in 41 areas from 11 countries. We grouped prey as invertebrates, reptiles, small mammals, large mammals, eggs, small birds and large birds, and calculated the contribution of each prey type to the diet (as % biomass) and Shannon’s Diversity Index for each study site. We analysed qualitative estimates of prey abundance in relation to latitude and longitude, then diet composition in relation to habitat of the study area and prey abundance estimates. Diet diversity of Montagu’s harriers increased from north to south, while abundance of all prey groups other than small mammals showed the opposite trends. Agricultural areas in northern latitudes seemed to hold high densities of small mammals, but low densities of alternative prey. Overall, birds were the main prey in most of Montagu’s harrier’s distribution range, although the relative importance of each prey type in the diet was significantly explained by its local abundance and habitat, confirming the opportunistic foraging strategy of this raptor species. Consumption of mammals was an exception to this trend, being negatively associated with the abundance of alternative prey, suggesting that this prey is not preferred. Trophic diversity in this species could be influenced by land-use changes through variations in the abundance and availability of prey, which could impact its population dynamics. This may be particularly important for northern populations of Montagu’s harriers breeding in agricultural habitats, where trophic diversity is already low.     

The dolphin cochlear nucleus: Topography,histology and functional implications

Despite the outstanding auditory capabilities of dolphins, there is only limited information available on the cytology of the auditory brain stem nuclei in these animals. Here, we investigated the cochlear nuclei (CN) of five brains of common dolphins (Delphinus delphis) and La Plata dolphins (Pontoporia blainvillei) using cell and fiber stain microslide series representing the three main anatomical planes. In general, the CN in dolphins comprise the same set of subnuclei as in other mammals. However, the volume ratio of the dorsal cochlear nucleus (DCN) in relation to the ventral cochlear nucleus (VCN) of dolphins represents a minimum among the mammals examined so far. Because, for example, in cats the DCN is necessary for reflexive orientation of the head and pinnae towards a sound source, the massive restrictions in head movability in dolphins and the absence of outer ears may be correlated with the reduction of the DCN. Moreover, the same set of main neuron types were found in the dolphin CN as in other mammals, including octopus and multipolar cells. Because the latter two types of neurons are thought to be involved in the recognition of complex sounds, including speech, we suggest that, in dolphins, they may be involved in the processing of their communication signals. Comparison of the toothed whale species studied here revealed that large spherical cells were present in the La Plata dolphin but absent in the common dolphin. These neurons are known to be engaged in the processing of low‐frequency sounds in terrestrial mammals. Accordingly, in the common dolphin, the absence of large spherical cells seems to be correlated with a shift of its auditory spectrum into the high‐frequency range above 20 kHz. The existence of large spherical cells in the VCN of the La Plata dolphin, however, is enigmatic asthis species uses frequencies around 130 kHz. J. Morphol. 2011. © 2011 Wiley Periodicals, Inc.     

中国云南部分小兽体表吸虱昆虫群落相似性及群落分类研究(英文)

应用系统聚类分析方法对云南省境内24种主要小型哺乳动物(小兽)体表吸虱昆虫群落相似性及群落分类进行了研究。研究中将每一种小兽体表的所有吸虱昆虫定义为一个相应的吸虱群落单位。结果表明,小兽体表吸虱群落结构简单,物种多样性很低。多数小兽有固定的吸虱种类寄生,其吸虱的宿主特异性高。在动物分类上隶属同一个属的小兽,其体表吸虱群落相似程度高,在系统聚类分析中大多被归为一类。在动物分类上近缘的小兽,其体表吸虱群落相似,优势虱种相同或相似,此情形尤其表现在鼠属、白腹鼠属、姬鼠属和绒鼠属。吸虱群落相似性大小与相应小兽宿主在动物分类地位上的近缘性高低呈现高度一致。从生态学角度来看,吸虱昆虫与其所寄生的小兽宿主动物之间存在密切的协同进化关系。     

Non-image-forming ocular photoreception in vertebrates

It has been accepted for a hundred years or more that rods and cones are the only photoreceptive cells in the retina. The light signals generated in rods and cones, after processing by downstream retinal neurons (bipolar, horizontal, amacrine and ganglion cells), are transmitted to the brain via the axons of the ganglion cells for further analysis. In the past few years, however, convincing evidence has rapidly emerged indicating that a small subset of retinal ganglion cells in mammals is also intrinsically photosensitive. Melanopsin is the signaling photopigment in these cells. The main function of the inner-retina photoreceptors is to generate and transmit non-image-forming visual information, although some role in conventional vision (image detection) is also possible.     

Mammals of Borneo – small size on a large island

Aim Island mammals have featured prominently in models of the evolution of body size. Most of these models examine size evolution across a wide range of islands in order to test which island characteristics influence evolutionary pathways. Here, we examine the mammalian fauna of a single island, Borneo, where previous work has detected that some mammal species have evolved a relatively small size. We test whether Borneo is characterized by smaller mammals than adjacent areas, and examine possible causes for the different trajectories of size evolution between different Bornean species. Location Sundaland: Borneo, Sumatra, Java and the Malay/Thai Peninsula. Methods We compared the mammalian body size frequency distributions in the four areas to examine whether the large mammal fauna of Borneo is more depauperate than elsewhere. We measured specimens belonging to 54 mammal species that are shared between Borneo and any of the other areas in order to determine whether there is an intraspecific tendency for Bornean mammals to evolve small body size. Using data on diet, body size and geographical ranges we examine factors that are thought to influence body size. Results Borneo has fewer large mammals than the other areas, but this is not statistically significant. Large Bornean mammals are significantly smaller than their conspecifics in the other regions, while there are no differences between the body sizes of mammals on Sumatra, Java and the Malay/Thai Peninsula. The finding that large mammals show the greatest size difference between Borneo and elsewhere contrasts with some models of size evolution on islands of different areas. Diet does not correlate with the degree of size reduction. Sunda region endemics show a weaker tendency to be small on Borneo than do widespread species. Main conclusions We suggest that soil quality may drive size evolution by affecting primary productivity. On Borneo, where soils are generally poor in nutrients, this may both limit biomass and cause mammals to be reduced in body size. We hypothesize that widespread species respond to low resource abundance by reducing in size, while endemic elements of the fauna have had longer to adjust to local conditions by altering their behaviour, physiology and/or ecology, and are thus similar in size across the region.     

SIMILARITY COMPARISON AND CLASSIFICATION OF SUCKING LOUSE COMMUNITIES ON SOME SMALL MAMMALS IN YUNNAN, CHINA

Abstract  The similarity and classification of sucking louse communities on 24 species of small mammals were studied in Yunnan Province, China, through a hierarchical cluster analysis. All the louse species on the body surface of a certain species of small mammals are regarded as a louse community unit. The results reveal that the community structure of sucking lice on small mammals is simple with low species diversity. Most small mammals usually have certain louse species on their body surface; there exists a high degree of host specificity. Most louse communities on the same genus of small mammals show a high similarity and are classified into the same group based on hierarchical cluster analysis. When the hosts have a close affinity in taxonomy, the louse communities on their body surface would tend to be similar with the same or similar dominant louse species (as observed in genus Rattus, Niviventer, Apodemus and Eothenomys ). The similarity of sucking louse communities is highly consistent with the affinity of small mammal hosts in taxonomy. The results suggest a close relationship of co-evolution between sucking lice and their hosts.     

Vibratory signals of the harlequin bug and their transmission through plants

Abstract. Males of the harlequin bug, Murgantia histrionica (Hahn), produce five different vibrational songs, whereas females produce one song. Songs differ from those of other stink bugs primarily in their species‐specific temporal characteristics. The broad band male courtship songs of M. histrionica are achieved by a combination of different frequency modulated and/or narrow band subunits, with several higher harmonic frequencies. Males rather than females initiate substrate‐borne vibrational communication, and the longer‐range calling songs found typically in other pentatomid species are lacking. Interindividual differences in song temporal and spectral characteristics are discussed. Transmission of vibrational songs through a cabbage head is more efficient along veins than along lamina. Attenuation of signals transmitted through veins is low and similar to that reported previously for plant stalks. On the leaf vein, distances between peak amplitude minima and maxima are different for the dominant and subdominant frequencies. At any distance from the vibration source, a different relationship between spectral peak amplitudes can be recorded. Resolution of these differences, together with velocity differences between signals recorded on the vein and lamina, may help small stink bugs to estimate distance and to locate each other on a plant.     

巴基斯坦旁遮普中部仓鸮食性的季节性变化

在巴基斯坦对仓鸮食性的季节变化进行了研究。通过分析连续3年在6个地区搜集的2 360个仓鸮回吐食物团,发现其食物主要是小型哺乳动物(95.6 %)。其中,家(Suncus murinus)有最高的比例,达65.6%(冬季最多78%,夏季最少27%)。就生物量而言,小型哺乳动物占仓鸮食物总生物量的99% 。