Tettigoniid Species Research Articles

Causes of the differences in detection of low frequencies in the auditory receptor organs of two species of bushcrickets

AbstractThe causes of the differential sensitivity of auditory receptor cells of two tettigoniid species to low‐frequency airborne sound were investigated with neurophysiological, neuroanatomical, and bioacoustic methods. The experiments employed adult males of the Chinese species Gampsocleis gratiosa (Decticinae) and the Australian species Mygalopsis marki (Conocephalinae). G. gratiosa emits very broad‐band songs with a fundamental frequency component at 3.8 kHz, extremely low for a bushcricket; in contrast, the songs of M. marki have a narrow‐band frequency spectrum, from 9 to 25 kHz. Accordingly, the threshold of the auditory organ as a whole is low in the low‐frequency range in the case of G. gratiosa, whereas M. marki is similarly sensitive only at frequencies above 5 kHz.The experiments were designed to reveal the origin of this sensitivity difference. One possibility considered was that low‐frequency receptors of a particularly sensitive type are present in G. gratiosa and not in M. marki; alternatively, with a similar complement of receptor cells the whole‐organ threshold curve might be expanded or restricted as a result of differences in the lower cutoff frequency of the sound‐conducting system.The results confirm the latter interpretation. The proximal crista acustica and the distal intermediate organ comprise the same numbers and types of cells in the two species, and the difference in threshold of the low‐frequency receptors is produced by a shift of the frequency range in which the acoustic trachea has an amplifying effect. © 1995 Wiley‐Liss, Inc.

The effect of blocking inputs of the acoustic trachea on the frequency tuning of primary auditory receptors in two species of tettigoniids

AbstractThe effect of plugging the input structures of the acoustic trachea of the forelegs of two tettigoniid species on the frequency tuning of the auditory receptor cells of the intermediate organ and of the crista acoustica was investigated. This was performed by long‐lasting single cell recordings by which the threshold curves of the cells were studied before and after carrying out manipulations on the ipsilateral slits and/or the spiracles. In some cases the distal tibia was also cut off during the experiments. Plugging the ipsilateral slits and/or the spiracle with Vaseline has different effects on the frequency tuning of the auditory receptor cells. Closing the slits has a relatively small damping effect being uniform in the stimulus frequency range between 2 kHz and 40 kHz. The tuning curves are left basically unchanged apart from a low elevation of the threshold by a few dB. Occluding the ipsilateral spiracle leads to a frequency‐dependent damping on the activity of the receptors, becoming stronger with increase of the stimulus frequency. Generally, the threshold curves are a few dB less sensitive at their characteristic frequencies and the tuning curves are shifted to lower frequencies, whereby the low frequency threshold curve sides of the receptors are more sensitive by about +2dB to +10 dB and the high frequency sides of the neurons are less sensitive by −5 dB up to −30 dB, depending on the stimulus frequency. When calculating the threshold difference from the threshold curves before and after blocking the ipsilateral spiracle in Mygalopsis marki, three groups of receptor cells can be determined. All low frequency receptors and some of the middle range receptors have zero values (i.e., no difference before and after plugging the spiracle) of the threshold differences at 5 kHz. Many middle range receptors and some of the ultrasonic receptors possess zero values at 10 kHz, and some of the ultrasonic receptors even have them at 20 kHz. The conditions in Mygalopsis marki are similar to those in Gampsocleis gratiosa (the species investigated), although, in the latter, the whole effect is transformed to lower frequencies that may result from the different sensitivity of the organs at low frequency level. Gampsocleis gratiosa has a higher proportion of low frequency to high frequency receptor cells in the organs than Mygalopsis marki. The effect of plugging the inputs of the acoustic trachea on the tuning of the auditory receptor cells is explained by a simple (acousto‐mechanical) model of frequency‐induced movements at the receptor row inside the organ. © Wiley‐Liss, Inc.

Specific differences in sound production and pattern recognition in tettigoniids

A brief comparative description of the stridulatory songs of nine different tettigoniid species is given to introduce a set of four parameters (phase of sound production during opening and closing movement of the wings, syllable repetition mode, syllable similarity, and impulse pattern of the syllables) to characterize the temporal pattern of tettigoniid songs. The importance of different song parameters for female phonotaxis was investigated in two tettigoniid species ( Ephippiger ephippiger and Tettigonia viridissima). Two-choice experiments revealed that the impulse pattern of the closing syllable is an important parameter for the phonotactic behaviour of E. ephippiger, whereas the syllable pattern is a decisive parameter for species discrimination in T. viridissima.

Auditory receptor organs in the forelegs of Gampsocleis gratiosa (Tettigoniidae): Morphology and function of the organs in comparison to the frequency parameters of the conspecific song

AbstractThe morphology and the physiology of the auditory receptor organs in the forelegs of the tettigoniid species Gampsocleis gratiosa were investigated in detail. According to the tonotopic organization of the receptor cells of the crista acoustica in bushcrickets the threshold curves of all receptors found in the organs were correlated with the morphology of the auditory receptor cells. This was done by arranging them in relation to their frequency tuning with the receptors along the chain of cells in both organs starting proximally with the extreme low frequency cell up to the highest ultrasonic cells at the distal end of the crista acoustica.This investigation reveals that the auditory receptor organs of Gampsocleis gratiosa possess a broard banded hearing threshold curve including very low frequency parts.Also the conspecific stridulatory song is very broard banded with extraordinarily low frequency components. Therefore the sender and the receiver of this species‐specific communication system seem to be well adapted to each other. © 1993 wiley‐Liss, Inc.

A peripheral mechanism for auditory directionality in the bushcricket Gampsocleis gratiosa: Acoustic tracheal system

The hypothesis that the acoustic tracheal system is a peripheral mechanism for auditory directionality was tested in the bushcricket Gampsocleis gratiosa. The acoustic tracheal system comprises the large spiracle, vesicle, and long tapering trachea. Based on its anatomy and cross-sectional areas against axial distance, an acoustic model was proposed; this model is analogous to an exponential horn with a flaring constant of about 0.075 mm−1. The effects of the acoustic tracheal system on auditory threshold and directionality were measured by using an electrophysiological recording from single auditory neurons. The intact tracheal system was found to be essential for directional hearing. Blockage of the spiracle markedly influenced the auditory threshold and directionality of the ipsilateral auditory neurons, but had very little effect on contralateral auditory neurons. The effects of blockage of the ipsilateral spiracle on auditory thresholds were frequency dependent with a gain of about 15–40 dB over a frequency range of 7–30 kHz. The directional threshold differences were measured for single auditory neurons. Blockage of the ipsilateral spiracle abolished directional sensitivity of these neurons. But blockage of the tympanal slits had less effect on directional sensitivity of this tettigoniid species, with a decrement of about 1 to 3 dB.

Acoustic transmission characteristics of the tympanal tracheae of bushcrickets (Tettigoniidae). II: Comparative studies of the tracheae of seven species

The transmission characteristics of the acoustic tracheae in the forelegs of seven tettigoniid species were investigated by sinusoidal analysis. The species were selected to represent a range of body sizes and leg lengths. Four subfamilies were included, with two species each from three of them; the tracheae in such closely related pairs could be expected to be similar in shape despite their different dimensions. The tracheae were dissected out for morphometric analysis and compared with one another with respect to their overall dimensions and those of typical subsections. The amplitude-versus-frequency response of acoustic transmission in the tracheae was measured at various positions with a probe microphone. The stimuli were continuous sinusoidal signals at an intensity of 100 or 110 dB SPL. The tracheae of all the species studied here (in males and females) are distinguished by a bandpass-limited transmission characteristic. In the frequency range above 5 kHz (at least to 40 kHz) the sound signals are amplified by 10–15 dB during passage through the tracheae. These results are compared with the threshold curves of the auditory organs and the spectra of the conspecific songs. Although in some cases there are considerable differences in the dimensions of the tracheae, the transmission characteristics are very similar; no specific adaptations to the frequency composition of the conspecific song were found.

The tettigoniid (Orthoptera : Tettigoniidae) ear: Multiple functions and structural diversity

The ears of bushcrickets (Orthoptera : Tettigoniidae) consist of a pair of membranes situated beneath the knee of the foretibia. These membranes, or tympana, are backed by a tracheal system dedicated to sound reception. In most species, a trachea opens through a hole, the auditory spiracle, in the pleuron of the prothorax adjacent to the ventilatory spiracle. Experimental evidence clearly shows that in those species possessing such an opening, sound entering through this route is amplified by the shape of the trachea, or at least is modified through resonances created by its tracheal cavities or tubes. In some species the external surface of the tympanic membrane is surrounded by cuticular folds, which may be formed into small resonating cavities or sound guiding pinnae. In other species the tympana are naked. Sound interacts with the external surface of the tympana, either through these cuticular cavities or directly at the surface of the membrane. As with auditory tracheae, the shape of these cavities may modify sound through resonances. This review examines the role of both external and internal sound-guides in sound reception. It discusses how different species may utilize different sound receiving systems and suggests how, in some cases, both external and internal routes may respond to different frequency bands. The maximum sensitivity of the ear invariably coincides with the male's call carrier frequency. Two Australian species of tettigoniid where the ear is clearly not tuned to the male's call are described. The biology of one undescribed species belonging to the subfamily, Zaprochilinae, where not only is the ear untuned, but there is marked sexual dimorphism in ear structure, is elaborated on. The review concludes with an examination of the routes selection may have taken to arrive at the extreme morphologies present in the Tettigoniidae.

Sexual differences in auditory sensitivity: mismatch of hearing threshold and call frequency in a tettigoniid (orthoptera, tettigoniidae: Zaprochilinae)

Sexual dimorphism of the ear of an undescribed species of zaprochiline tettigoniid is described. The internal trachea, dedicated to hearing in other tettigoniids, is unmodified in the male but fully developed in the female. The external auditory spiracle is also lost in the male. In contrast, there is no difference between the sexes in the number of sensilla within the hearing organ. The male is 10 dB less sensitive than the female. The characteristic frequency of the hearing organ at 35 kHz does not match the carrier frequency of the male's call at 51 kHz. As a result of this mismatch the female is remarkably insensitive to the male's call (threshold at 75 dB SPL), and the male is even less sensitive (thresholds⩾80 dB SPL). In nature this provides a maximum hearing range of the male of less than 50 cm.

SOUND PRODUCTION AND SOUND EMISSION IN SEVEN SPECIES OF EUROPEAN TETTIGONIIDS. PART I. THE DIFFERENT PARAMETERS OF THE SONG; THEIR RELATION TO THE MORPHOLOGY OF THE BUSHCRICKET

Abstract Comparative studies of sound production and sound emission in seven species of European tettigoniids have been carried out. The species chosen were two Tettigoniines (Tettigonia cantans, Tettigonia viridissima), two Ephippigerines (Ephippiger discoidalis, Ephippiger ephippiger), and three Decticines (Decticus albifrons, Decticus verrucivorus, Psorodonotus illyricus). The factors which determined the choice of species were the different morphology (for example body shape and weight, and wing size) of the three subfamilies. The parameters of the different songs (e.g. dominant frequency, intensity) are normally not correlated to any of the investigated morphological characteristics of the animals. In the brachypterous species intraspecific correlations exist between wing size and the dominant low frequency band of the call. This frequency band is also observable at related higher frequencies in the ultrasonic range (20–60 kHz), the observed band width increasing with frequency. Sound emission in all...

Ultrasound production by genital stridulation in Syntonarcha iriastis (Lepidoptera: Pyralidae): long-distance signalling by male moths?

Males of the pyralid moth, Syntonarcha iriastis Meyrick, perch on vegetation at the tops of trees and bushes and produce ultrasound while their wings are spread and while sclerites at the end of the abdomen are spread to expose the genitalia. Exposing the genitalia appears to engage the sound-producing mechanism; the male genitalia and eighth abdominal sternite of this species are greatly modified and include a file and scraper and possible resonating areas. Sounds produced are consistent between individuals and comprise pulses which are narrow in frequency range, the first pulse being at about 42 kHz and two following pulses at about 57 kHz. The signal is detectable with an ultrasound ‘bat’ detector from 20 m. Two tettigoniid species (Orthoptera) at the same site produced ultrasonic calls of similar frequencies at the same times as the moth; differences in time-amplitude patterns could be used by orienting moths to recognize conspecifics. Signalling by male S. iriastis is compared with that of other pyralid species in which females are attracted to signalling males. The behaviour of S. iriastis males differs from that of other pyralids in that they do not signal in groups or from a resource attractive to females, and do not possess glands known to produce a ‘calling’ pheromone. It is suggested, because of these differences, that sound production in this species does not function at close range, as argued for the wax moth Achroia grisella (Fabricius), but instead as a long-distance calling signal.

Effect of hibernation length on termination of diapause in European Tettigoniidae (Insecta: Orthoptera).

The effect of the length of cold treatment on development time of embryos of eight Central European tettigoniid species was investigated in laboratory experiments, using chilling periods of 3, 4, 5, 6, 9, and 12 months. Two different types of response were observed: (1) The hatching date was not influenced by hibernation length (Conocephalus) or only after the 3-month cold treatment (Phaneroptera, Platycleis), or (2) The time required for post-diapause development was significantly reduced by each 1-month increase in the length of cold treatment up to 6 months (Meconema, Metrioptera, Tettigonia).Thus, the correct timing of hatching is achieved by one of two different strategies. In lat-hatching species, the influence of hibernation length is small. Premature appearance is prevented by a high thermal threshold. In early-hatching species, the embryos are obviously able to measure the length of the chilling period. Thus, they gradually change their physiological state so that the potential speed of postdiapause development increases as the 'winter' is prolonged. This strategy can be understood as an adaptation to the necessity of hatching at low or moderate temperatures. Field experiments with two Tettigonia species confirm the laboratory data.

Neurophysiology of the vibration sense in locusts and bushcrickets: The responses of ventral-cord neurones

In the locustid Locusta migratoria and the tettigoniids Decticus verrucivorus and Tettigonia cantans, comparative aspects of physiological properties of vibratory/auditory ventral-cord neurones were studied by single cell recordings. These neurones all receive inputs from both vibratory and auditory receptors. Nevertheless, they can be classified into “V neurones” responding preferentially to vibration stimuli, “VS neurones” responding to vibration and airborne sound, and “S neurones” responding preferentially to airborne sound. In every group, there are several types with different physiological properties, normally represented by one neurone on each body side. In Locusta and in the tettigoniid species, the same physiological types of vibratory/auditory neurones were found, although there are differences in the synaptic connectivity of the vibration receptors of the different legs. In Locusta, the middle leg receptors have the strongest influence on the generation of suprathreshold responses of the central neurones, whereas in the tettigoniids the receptors of the ipsilateral fore leg are the most influential. Two of the V neurones receive inputs mainly from campaniform sensilla and other low-frequency vibration receptors, the other V and VS neurones are mainly influenced by the subgenual receptors. Central information processing results in preferential responses to different frequency/intensity ranges in different neurones. Most VS neurone types show the same response characteristics (e.g. time pattern of response, habituation) either to vibration or to airborne-sound stimuli. Simultaneous presentation of both stimuli leads to qualitative changes in the response characteristics. Therefore, the co-processing of auditory and vibratory signals seems to be very important in the acoustic behaviour of grasshoppers.

Auditory function in tettigoniidae (Orthoptera:Ensifera)

1. An ascending, auditory unit has been extracellularly recorded from the cervical connective in specimens of two tettigoniid species. Spike potentials arising from unilateral afferent input were monitored in response to airborne sounds in the frequency range 6.3–40 kHz and incident from different directions. Recordings were also obtained of the massed auditory response in the tympanal nerve in a third species. 2. Frequency sensitivities of auditory organs were measured at threshold and suprathreshold levels. Optimum frequencies generally corresponded with energy peaks in relevant song spectra (Figs. 3, 4). Intensity characteristics of the ascending unit were obtained near the corresponding frequency optimum (Fig. 5). Directional sensitivities of the auditory organs near the frequency optima were measured at 15 ° intervals around the preparation at threshold and suprathreshold levels of stimulation (Fig. 6). Threshold sensitivities to ipsilateral and contralateral stimulation were compared over the range 6.3–40 kHz. 3. Directional sensitivity of the ascending unit generally increased with increasing sound frequency. Maximum differences of from 8–25 dB were observed between sensitivities to ipsilateral and contralateral sound presentation in the frequency range 6.3–40 kHz (Fig. 8). Similar results were obtained for the massed primary response. 4. The frequency sensitivity and the directional sensitivity of the auditory organs, for sound frequencies higher than 8–10 kHz (depending on species) and at threshold and suprathreshold levels, were found to be independent of pressure-gradient effects at the auditory tympana (Figs. 7, 8). 5. The gross morphology of the prothoracic spiracle and associated trachea to the level of the tympanic membranes has been examined in each species. In the thorax, the trachea abruptly reduces in cross sectional area by about a factor of five. From the coxa to the distal femur the trachea undergoes a further three to four-fold reduction in cross section (Fig. 2). 6. Physiological experiments and direct measurements using miniature probe microphones indicate that, in the frequency range 8–40 kHz (depending on species) the acoustic gain of the trachea leading from the prothoracic spiracle to the auditory tympana is 10–30 dB (Figs. 9, 10). The shape of the hearing threshold curve, however, only partially matches the gain curve of the trachea. 7. Near the frequency optimum of the auditory organ, the sound pressure measured by a probe microphone in the thoracic tracheal vesicle adjacent to the prothoracic spiracle changes by 10–16 dB as a function of the direction of the incident sound (Fig. 12 A). 8. Simultaneous measurements using two probe microphones show that relative sound pressure in the thoracic tracheal vesicle changes by 10–16 dB, whereas that in the trachea distal in the femur may change by 8–24 dB for different directions of sound (Fig. 12C). Directional sensitivities measured neurophysiologically are, therefore, fully explained by the relative sound pressure level in the fore-leg trachea leading to the auditory tympana. 9. Dissimilarities sometimes observed between the directivity patterns of the sound pressures measured in the thoracic vesicle and in the femoral trachea possibly are due to the effects of sound entering the trachea along the length of the leg. 10. These results are discussed in relation to the properties of acoustic horns and to other recent studies of auditory function in tettigoniids.

Habitats and habits ofPlatycleisspp. (Orthoptera, Tettigoniidae) in southern France

Summary Five species of tettigoniid of the Decticine genus, Platycleis (sensu stricto), are found in the environs of Montpellier, Herault, S. France. P. intermedia, P. sabulosa and P. albopunctata are essentially early-evening singers. There is a nycthemeral cycle of vertical migration in these three species—they sing from a greater height than that at which they rest during the daytime. P. affinis and P. falx sing both during the day and during the evening. As the syllables of the songs of the five species are similar, and since these insects sing at the same time of year and at least during the evening, interspecific acoustic interference would seem likely. However, such interference appears to be avoided by spatial separation of singing individuals (the males only). The difference in habitat preferences may be so distinct that two species do not occur in the same locality (e.g. P. falx and P. albopunctata). Where two species do occur in one local area, one of them is generally confined to one type of v...

The stridulatory apparatus of two species of Tettigoniid

A scanning electron microscopical examination has been made of the stridulatory apparatus of Homorocoryphus nitidulus vicinus (Wlk.) and Jamaiciana flava (Wlk.). Its structure is discussed in relation to function, and the probable affinities of the two species within the Tettigoniidae.

Chromosome Survey of Some Australian Tettigoniids (Orthoptera-Tettigonioidea): Two Species with Neo-XY Sex-Determining Mechanism

The chromosome number of 11 species of Australian tettigoniids, (Orthoptera-Tettigonioidea) are reported in this paper. The main characteristics of the karyotype of these species are given in the following table.In Polichne parvicauda (specimen no. 6) and Caedicia marginata a centric fusions between the former X and a small autosome was found. These fusions gave rise to a neo-XY sex-determining mechanism in both species. Besides, two centric fusions between autosomes occurred in the former species, forming two pairs of metacentric chromosomes and reducing the chromosome number to 2n=16.In Torbia viridissima a reduction to 2n=19 due to an integration of chromatin between apparently two small autosomes took place.The desynchronized movement of the chromosomes during first anaphase due to their bimodality in length as well as the difference in chiasma frequency was discussed.

The structure of the eggs of the British Tettigoniidae (Orthoptera)

SYNOPSISDescriptions of the chorion structure of the eggs of 10 of the 11 species of British Tettigoniids are given. The eggs of the eleventh species, Phaneroptera falcatu, were unobtainable but those of the closely related P. nana are described instead. The chorion structure shows fundamental differences between the subfamilies, but only minor differences within them. A key for the identification of the eggs is included.