Plasticity of signaling and mate choice in a trilling species of the Mecopoda complex (Orthoptera: Tettigoniidae).

ABSTRACT: Males of a trilling species in the Mecopoda complex produce conspicuous calling songs that consist of two motifs: an amplitude-modulated motif with alternating loud and soft segments (AM-motif) and a continuous, high-intensity trill. The function of these song motifs for female attraction and competition between males was investigated. We tested the hypothesis that males modify their signaling behavior depending on the social environment (presence/absence of females or rival males) when they compete for mates. Therefore, we analyzed acoustic signaling of males in three different situations: (1) solo singing, (2) acoustic interaction with another male, and (3) singing in the presence of a female. In addition, the preference of females for these song motifs and further song parameters was studied in two-choice experiments. As expected, females showed a preference for conspicuous and loud song elements, but nevertheless, males increased the proportion of the AM-motif in the presence of a female. In acoustic interactions, males reduced bout duration significantly compared to both other situations. However, song bouts in this situation still overlapped more than expected by chance, which indicates intentionally simultaneous singing. A multivariate statistical analysis revealed that the proportion of the AM-motif and the duration of loud segments within the AM-motif allow a reliable prediction of whether males sing in isolation, compete with another male, or sing in the presence of a female. These results indicate that the AM-motif plays a dominant role especially in close-range courtship and that males are challenged in finding a balance between attracting females and saving energy during repeated acoustic interactions. SIGNIFICANCE STATEMENT: Males of acoustic insects often produce conspicuous calling songs that have a dual function in male-male competition and mate attraction. High signal amplitudes and signal rates are associated with high energetic costs for signal production. We would therefore predict that males adjust their signaling behavior according to their perception of the social context. Here we studied signal production and mate choice in a katydid, where males switch between loud and soft song segments in a dynamic way. Additionally, we examined the attractiveness of different song elements in female choice tests. Our results show how males of this katydid deal with the conflict of remaining attractive for females and competing with a costly signal with rivals.

Spatial release from masking in insects: contribution of peripheral directionality and central inhibition.

The detection, identification and discrimination of sound signals in a large and noisy group of signalers are problems shared by many animals equipped with ears. While the signaling behavior of the sender may present several solutions, various properties of the sensory system in receivers may also reduce the amount of signal masking. We studied the effect of spatial release from masking, which refers to the fact that the spatial separation between the signaler and the masker can contribute to signal detection and discrimination. Except in a limited number of cases, the contribution of peripheral directionality or central nervous processing for spatial unmasking is not clear. We report the results of a study using a neurophysiological approach in two species of acoustic insects, whereby the activity of identified interneurons that either receive contralateral inhibitory input (crickets) or inhibit one another reciprocally in a bilateral pair (katydids) was examined. The analysis of the responses of a pair of omega neurons in katydids with reciprocal inhibition revealed that spatial separation of the masker from the signal facilitated signal detection by 19-20 dB with intact binaural hearing, but only by 2.5-7 dB in the monaural system, depending on the kind of analysis performed. The corresponding values for a behaviorally important interneuron of a field cricket (ascending neuron 1) were only 7.5 and 2.5 dB, respectively. We compare these values with those reported for hearing in vertebrates, and discuss the contribution of spatial release from masking to signal detection under real-world chorus conditions.

Male age and female mate choice in a synchronizing katydid.

In acoustically communicating species, females often evaluate the frequency content, signal duration and the temporal signal pattern to gain information about the age of the signaller. This is different in the synchronizing bush cricket Mecopoda elongata where females select males on the basis of relative signal timing in duets. In a longitudinal approach, we recorded songs of M. elongata males produced 2 weeks (young male) and 9 weeks (old male) after their ultimate moult. Signal timing of both age categories was studied in acoustic interactions, and female preference was investigated in choice situations. Young male chirps were significantly shorter and contained less energy compared to "old chirps". In mixed-age duets younger males timed their chirps as leader significantly more often. Females preferred the young male chirp when broadcast as leader over the old male chirp, but choice was random when the old male chirp was leader. This choice asymmetry was abolished after reducing the duration of the "old chirp". Results were mirrored in response of a bilateral pair of auditory neurons, where the asymmetry in spike count and first-spike latency correlated with behaviour. We suggest that older males may compensate their disadvantage in a more complex chorus situation.

Competition and cooperation in a synchronous bushcricket chorus.

Synchronous signalling within choruses of the same species either emerges from cooperation or competition. In our study on the katydid Mecopoda elongata, we aim to identify mechanisms driving evolution towards synchrony. The increase of signal amplitude owing to synchronous signalling and the preservation of a conspecific signal period may represent cooperative mechanisms, whereas chorus synchrony may also result from the preference of females for leading signals and the resulting competition for the leader role. We recorded the timing of signals and the resulting communal signal amplitudes in small choruses and performed female choice experiments to identify such mechanisms. Males frequently timed their signals either as leader or follower with an average time lag of about 70 ms. Females selected males in such choruses on the basis of signal order and signal duration. Two-choice experiments revealed a time lag of only 70 ms to bias mate choice in favour of the leader. Furthermore, a song model with a conspecific signal period of 2 s was more attractive than a song model with an irregular or longer and shorter than average signal period. Owing to a high degree of overlap and plasticity of signals produced in 'four male choruses', peak and root mean square amplitudes increased by about 7 dB relative to lone singers. Modelling active space of synchronous males and solo singing males revealed a strongly increased broadcast area of synchronous signallers, but a slightly reduced per capita mating possibility compared with lone singers. These results suggest a strong leader preference of females as the ultimate causation of inter-male competition for timing signals as leader. The emerging synchrony increases the amplitude of signals produced in a chorus and has the potential to compensate a reduction of mating advantage in a chorus. We discuss a possible fitness benefit of males gained through a beacon effect and the possibility that signalling as follower is stabilized via natural selection.

Maintaining acoustic communication at a cocktail party: heterospecific masking noise improves signal detection through frequency separation.

We examined acoustic masking in a chirping katydid species of the Mecopoda elongata complex due to interference with a sympatric Mecopoda species where males produce continuous trills at high amplitudes. Frequency spectra of both calling songs range from 1 to 80 kHz; the chirper species has more energy in a narrow frequency band at 2 kHz and above 40 kHz. Behaviourally, chirper males successfully phase-locked their chirps to playbacks of conspecific chirps under masking conditions at signal-to-noise ratios (SNRs) of -8 dB. After the 2 kHz band in the chirp had been equalised to the level in the masking trill, the breakdown of phase-locked synchrony occurred at a SNR of +7 dB. The remarkable receiver performance is partially mirrored in the selective response of a first-order auditory interneuron (TN1) to conspecific chirps under these masking conditions. However, the selective response is only maintained for a stimulus including the 2 kHz component, although this frequency band has no influence on the unmasked TN1 response. Remarkably, the addition of masking noise at 65 dB sound pressure level (SPL) to threshold response levels of TN1 for pure tones of 2 kHz enhanced the sensitivity of the response by 10 dB. Thus, the spectral dissimilarity between masker and signal at a rather low frequency appears to be of crucial importance for the ability of the chirping species to communicate under strong masking by the trilling species. We discuss the possible properties underlying the cellular/synaptic mechanisms of the 'novelty detector'.

Acoustic signal perception in a noisy habitat: lessons from synchronising insects.

Acoustically communicating animals often have to cope with ambient noise that has the potential to interfere with the perception of conspecific signals. Here we use the synchronous display of mating signals in males of the tropical katydid Mecopoda elongata in order to assess the influence of nocturnal rainforest noise on signal perception. Loud background noise may disturb chorus synchrony either by masking the signals of males or by interaction of noisy events with the song oscillator. Phase-locked synchrony of males was studied under various signal-to-noise ratios (SNRs) using either native noise or the audio component of noise (<9 kHz). Synchronous entrainment was lost at a SNR of -3 dB when native noise was used, whereas with the audio component still 50% of chirp periods matched the pacer period at a SNR of -7 dB. Since the chirp period of solo singing males remained almost unaffected by noise, our results suggest that masking interference limits chorus synchrony by rendering conspecific signals ambiguous. Further, entrainment with periodic artificial signals indicates that synchrony is achieved by ignoring heterospecific signals and attending to a conspecific signal period. Additionally, the encoding of conspecific chirps was studied in an auditory neuron under the same background noise regimes.

Signalling plasticity and energy saving in a tropical bushcricket.

Males of the tropical bushcricket Mecopoda elongata synchronize their acoustic advertisement signals (chirps) in interactions with other males. However, synchrony is not perfect and distinct leader and follower roles are often maintained. In entrainment experiments in which conspecific signals were presented at various rates, chirps displayed as follower showed notable signal plasticity. Follower chirps were shortened by reducing the number and duration of syllables, especially those of low and medium amplitude. The degree of shortening depended on the time delay between leader and follower signals and the sound level of the entraining stimulus. The same signal plasticity was evident in male duets, with the effect that the last syllables of highest amplitude overlapped more strongly. Respiratory measurements showed that solo singing males producing higher chirp rates suffered from higher metabolic costs compared to males singing at lower rates. In contrast, respiratory rate was rather constant during a synchronous entrainment to a conspecific signal repeated at various rates. This allowed males to maintain a steady duty cycle, associated with a constant metabolic rate. Results are discussed with respect to the preference for leader signals in females and the possible benefits males may gain by overlapping their follower signals in a chorus.

Neuronal correlates of a preference for leading signals in the synchronizing bushcricket Mecopoda elongata (Orthoptera, Tettigoniidae).

Acoustically interacting males of the tropical katydid Mecopoda elongata synchronize their chirps imperfectly, so that one male calls consistently earlier in time than the other. In choice situations, females prefer the leader signal, and it has been suggested that a neuronal mechanism based on directional hearing may be responsible for the asymmetric, stronger representation of the leader signal in receivers. Here, we investigated the potential mechanism in a pair of interneurons (TN1 neuron) of the afferent auditory pathway, known for its contralateral inhibitory input in directional hearing. In this interneuron, conspecific signals are reliably encoded under natural conditions, despite high background noise levels. Unilateral presentations of a conspecific chirp elicited a TN1 response where each suprathreshold syllable in the chirp was reliably copied in a phase-locked fashion. Two identical chirps broadcast with a 180 deg spatial separation resulted in a strong suppression of the response to the follower signal, when the time delay was 20 ms or more. Muting the ear on the leader side fully restored the response to the follower signal compared with unilateral controls. Time-intensity trading experiments, in which the disadvantage of the follower signal was traded against higher sound pressure levels, demonstrated the dominating influence of signal timing on the TN1 response, and this was especially pronounced at higher sound levels of the leader. These results support the hypothesis that the female preference for leader signals in M. elongata is the outcome of a sensory mechanism that originally evolved for directional hearing.

[Voluntary help in dementia - predictors for utilisation and expected quality from a family caregiver's point of view]. / Ehrenamtlicher Betreuungsdienst bei Demenz - Prädiktoren der Inanspruchnahme und Qualitätserwartungen aus Sicht pflegender Angehöriger.

Although support services are considered cost-effective in the relief of care-giving family members of dementia patients, there has been little research to date on the predictors of use and quality expectations. These two questions are examined for the first time based on cross-sectional data of 404 care-giving family members, users and non-users of voluntary help services. Quantitative data are evaluated using binary logistical regression analysis, qualitative data using content analysis. The rating of how helpful the use of a voluntary help service is in the personal situation was found to be the only significant predictor of use. With respect to quality, it is most important that the persons giving support be punctual and well-trained. To increase the rate of use, care-giving family members must be convinced of the relevant benefits of using a voluntary help service. In addition, attention must be paid to the professional organization and training of voluntary helpers.

[Care groups. Predictors for utilisation and expected quality from the dementia caregiver's point of view]. / Betreuungsgruppen. Prädiktoren der Inanspruchnahme und Qualitätserwartungen aus Sicht pflegender Angehöriger eines Demenzkranken.

BACKGROUND: To relieve family caregivers of dementia patients the utilisation of care groups should be fostered. In order to do this the influencing factors must be investigated. INVESTIGATION: Which variables of the care situation, the family caregivers and their attitudes act as predictors for the utilisation of care groups? What are the views of family caregivers about the quality of care groups? METHOD: A cross-sectional study was carried out as an anonymous, written survey of family caregivers of dementia patients in four regions of Germany. There was a 20 % response rate and the quantitative and qualitative data from 404 family caregivers were analysed. Predictors for utilisation were evaluated using binary logistic regression analysis. The answers about quality were evaluated using qualitative content analysis. Additionally ten telephone interviews with people from managerial positions in care groups, regarding their concept of quality, were carried out. RESULTS: Besides estimating how helpful the support of a care group is for their own care situation, only the level of education of the caregiver is a significant predictor for utilisation--lower education level, higher utilisation. Family caregivers, who had already had experience with a care group, expressed a wish for an adequate form of occupation for the dementia patient such as physical exercise or play followed by "well-trained" staff and a loving atmosphere in the care group. CONCLUSIONS: In order to increase the rate of utilisation, family caregivers must be convinced of the relevant advantages of using care groups.

Chirp rate is independent of male condition in a synchronising bushcricket.

Males of the bushcricket Mecopoda elongata synchronise their chirps with neighbouring males, but because synchrony is imperfect, one male's chirp preceeds the other by some 50-200 ms. Since a male's intrinsic chirp rate is critical for the establishment of the leader role in a duet, and females prefer the leader in a choice situation, we investigated a possible condition dependence of this male trait. In a duet leader males are usually those calling at a higher intrinsic rate; therefore, we investigated whether calling at a higher rate indicates male condition. The calling metabolism was quantified in a respirometer; the factorial slope of males calling at a high rate was three times higher compared to males calling at lower rates. Males produce on average 3.4 singing bouts/per night, and there is a significant increase in chirp periods (CPs) with successive singing bouts. Call properties were investigated throughout a male's life; chirp period increases significantly with age. Two groups of males were reared on either a low- or a high-nutrition diet, and the influence of male condition on different song parameters was investigated. CPs in two feeding regimes did not differ significantly, although males of the low-nutrition diet group were significantly affected by nutrition with respect to mortality, a delayed last moult and reduced weight as adults. We therefore conclude that solo chirp rates do not reflect phenotypic male condition properly.

Medical management of facial pain.

This article describes some of the means used to manage facial pain once serious pathology or any treatable cause has been excluded. It includes pharmacological, physical and psychological therapies.

Glutathione transferase isozyme genotypes in patients with prostate and bladder carcinoma.

Genotype distributions for GSTP1, GSTM1, and GSTT1 were determined in 91 patients with prostatic carcinoma and 135 patients with bladder carcinoma and compared with those in 127 abdominal surgery patients without malignancies. None of the genotypes differed significantly with respect to age or sex among controls or cancer patients. In the group of prostatic carcinoma patients, GSTT1 null allele homozygotes were more prevalent (25% in carcinoma patients vs. 13% in controls, Fisher P =0.02, chi2 P=0.02, OR=2.31, CI = 1.17-4.59) and the combined M1-/T1 -null genotype was also more frequent (9% vs. 3%, chi2 P=0.02, Fisher P = 0.03). Homozygosity for the GSTM1 null allele was more frequent among bladder carcinoma patients (59% in bladder carcinoma patients vs 45% in controls, Fisher P=0.03, chi2 P=0.02, OR=1.76, CI=1.08-2.88). In contrast to a previous report, no significant increase in the frequency of the GSTP1b allele was found in the tumor patients. Except for the combined GSTM1-/ T1-null genotype in prostatic carcinoma, none of the combined genotypes showed a significant association with either of the cancers. These findings suggest that specific single polymorphic GST genes, that is GSTM1 in the case of bladder cancer and GSTT1 in the case of prostatic carcinoma, are most relevant for the development of these urological malignancies among the general population in Central Europe.

A gain-control mechanism for processing of chorus sounds in the afferent auditory pathway of the bushcricket Tettigonia viridissima (Orthoptera; Tettigoniidae).

The representation of alternative conspecific acoustic signals in the responses of a pair of local interneurons of the bushcricket Tettigonia viridissima was studied with variation in intensity and the direction of sound signals. The results suggest that the auditory world of the bushcricket is rather sharply divided into two azimuthal hemispheres, with signals arriving from any direction within one hemisphere being predominantly represented in the discharge of neurons of this side of the auditory pathway. In addition, each pathway also selects for the most intense of several alternative sounds. A low-intensity signal at 45 dB sound pressure level is quite effective when presented alone, but completely suppressed when given simultaneously with another signal at 60 dB sound pressure level. In a series of intracellular experiments the synaptic nature of the intensity-dependent suppression of competitive signals was investigated in a number of interneurons. The underlying synaptic mechanism is based on a membrane hyperpolarization with a time-constant in the order of 5-10 s. The significance of this mechanism for hearing in choruses, and for the evolution of acoustic signals and signalling behaviour is discussed.

Cytotoxicity of ochratoxin A and citrinin in different cell typesin vitro.

Cytotoxic effects resulting from the two mycotoxins ochratoxin A (OTA) and citrinin were evaluatedin vitro using cell cultures of different origin. Cytotoxicity was estimated by the neutral red (NR) uptake assay which allows to determine the viability of cells by detecting dye uptake into the cells and its storage in the lysosomes. The assay was performed with primary cell cultures derived from isolated porcine urinary bladder epithelial cells (PUBEC), which are competent in metabolism of xenobiotics, and with V79 hamster fibroblasts, a well established and frequently used cell line. In both systems, OTA was more cytotoxic compared to citrinin. When both mycotoxins were applied simultaneously no additive or synergistic effects were detected. Obviously, the primary cell culture system which represents a target tissue of the mycotoxins was more susceptible to the toxins, expressed in lower IC50-values. These results indicate that origin of a cell system and its competence in metabolism of xenobiotics have to be considered inin vitro investigations particularly when different systems were used.

[Nutrient utilization in children with acute diarrhea fed with formulas containing chicken and soybean]. / Utilización de nutrientes en niños con diarrea aguda alimentados con formula a base de pollo y de soya.

The objective of this study was to measure in children with acute diarrhea the apparent absorption and retention of the macronutrients and some micronutrient present in a formula prepared with chicken and a formula prepared with soybean protein. Fourteen male children (9 months old) with acute diarrhea were assigned to each of these formulas and the consumption and excretion of the studied nutrients were monitored during 48 h. The results showed that the children assigned to the chicken formula consumed more protein and less fat than those in the soybean protein formula. These differences however were associated with differences in the composition of the formulas offered rather than to differences in protein or fat utilization. Fecal mass (800 g/48 h) was similar in both groups and the macronutrient content of the feces, reflected well the amount consumed. The apparent absorption of fat (63%), nitrogen (75%) and carbohydrates (78%) resulted similar in both groups and there were no differences in the retention of nitrogen which approximated 55%. The digestible energy and the metabolizable energy of both formulas, also resulted equal. In general the children excreted more urinary ammonia and less creatinine than healthy children but there were no differences in the excretion of these metabolites between the children assigned to the chicken or to the soybean protein formulas. The retention of Zn (47%) and Ca (72%) were also similar in both groups and they excreted a high (0.17 mg/48 hr) but similar amount of Vitamin A. In summary, these results showed that from a nutritional point of view, the chicken and the soybean protein formulas were equally utilized during the acute phase of diarrhea.

Strategies for hearing in noise: peripheral control over auditory sensitivity in the bushcricket sciarasaga quadrata (Austrosaginae: tettigoniidae)

The carrier frequency of the call of the Australian bushcricket Sciarasaga quadrata is unusually low for tettigoniids at 5 kHz. The sound transmission measured in the habitat of the insect reflects the advantages of producing low- rather than high-frequency signals; attenuation is explained almost entirely by the spherical spreading of sound. The natural vibration frequency of the wings is controlled by size and stiffness. The small tegmina are unusually fleshy, with an order-of-magnitude higher water content than in comparable sagine species. Reduced stiffness allows the insect to call at low carrier frequencies, albeit at lower intensity levels (60 dB SPL at 1 m), than bushcrickets of comparable size (80-90 dB SPL). The responses of the tympanic nerve and a first-order interneurone (omega neurone) in the afferent auditory pathway showed that the hearing system is most sensitive to frequencies of 15-20 kHz, an effective mismatch to the conspecific call resulting in a reduced sensitivity of approximately 20 dB at the carrier frequency of the call. S. quadrata can occlude its spiracular opening, which increases the sensitivity of the ear to lower frequencies. Under such conditions, the best frequency of the ear matched that of the carrier frequency of the call. We measured the activity of auditory neurones in the field, noting the ability of the open and partially closed ear to filter out potentially masking calls of congenerics. At the same time, the directionality of the system was only slightly reduced in the closed relative to the open spiracle status. We discuss the evolutionary advantages of an insect both calling with a low carrier frequency and having the ability to close down the tracheal system to avoid the effects of masking. In addition, we consider the advantages of such a signalling system in avoiding the most significant predator of the male, the ormine fly Homotrixa alleni.

A survey of the practice of thoracic epidural analgesia in the United Kingdom.

A postal survey of the practice of thoracic epidural analgesia was sent to 275 hospitals in the United Kingdom. Responses were received from 70% of hospitals. Informed consent is rarely adequately obtained, with only 28% of respondents mentioning even the most common complications. Epidural cannulation is most often (60%) performed following induction of general anaesthesia, rather than in the awake patient. A test dose of local anaesthetic without adrenaline is usual. Neither aspirin nor low-dose heparin are considered a contraindication. The majority of respondents used a combination of bupivacaine with fentanyl (51%) or diamorphine (40%), usually administered by continuous infusion. Drugs were frequently prepared and adjusted by anaesthetic staff. The majority of epidurals (63%) are nursed in intensive care units postoperatively. Properly funded pain management teams, at present unusual, would facilitate ward-based epidural management and release intensive care resource. A central register of epidural complications is required to provide valuable evidence for the optimum practice of thoracic epidural analgesia.

Sexual signalling in bladder grasshoppers: tactical design for maximizing calling range.

Pair formation in the bladder grasshopper (Bullacris membracioides) is by duetting and male phonotaxis. Low-frequency stridulatory signals are emitted by an abdominal resonator in the male and are answered by females using a species-specific time delay. Acoustic transmission in the natural environment was studied using playback of sexual signals over distances of 450m under two atmospheric conditions (day and night). Upward-refracting sound conditions and a sound shadow zone beyond approximately 50m prevailed during the day. Acoustic enhancement was demonstrated at night when downward-refracting temperature inversions created a tunnel effect with sound caught between the ground and zones of different temperatures. Transmission conditions are almost ideal at night when the species actually calls; calling distances of 150m for the male signal in the afternoon increased to 1.5-1.9km at night, arguably the largest calling distance yet reported for insects. In contrast, female calls transmit over a maximum of 50m, signifying a marked discrepancy in the active space of sex-specific signals. Transmission distance may, however, be profoundly affected by levels of masking noise. Adaptations to increase the signal range may variously be found in the signal itself, in behaviour patterns or in the sensory system. Here we demonstrate aspects of the first two types of adaptation in the sexual signalling system of a grasshopper in which maximizing the calling range appears to be the major selection pressure, with lesser effects imposed by inter- and intraspecific pressures and by the transmission channel.