Martin Jatho

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.

Stimulus transmission in the auditory receptor organs of the foreleg of bushcrickets (Tettigoniidae) I. The role of the tympana.

The auditory organs of the tettigoniid are located just below the femoral tibial joint in the forelegs. Structurally each auditory organ consists of a tonotopically organized crista acustica and intermediate organ and associated sound conducting structures; an acoustic trachea and two lateral tympanic membranes located at the level of the receptor complex. The receptor cells and associated satellite structures are located in a channel filled with hemolymph fluid. The vibratory response characteristics of the tympanic membranes generated by sound stimulation over the frequency range 2-40 kHz have been studied using laser vibrometry. The acoustic trachea was found to be the principal structure through which sound energy reached the tympana. The velocity of propagation down the trachea was observed to be independent of the frequency and appreciably lower than the velocity of sound in free space. Structurally the tympana are found to be partially in contact with the air in the trachea and with the hemolymph in the channel containing the receptor cells. The two tympana were found to oscillate in phase, with a broad band frequency response, have linear coherent response characteristics and small time constant. Higher modes of vibration were not observed. Measurements of the pattern of vibration of the tympana showed that these structures vibrate as hinged flaps rather than vibrating stretched membranes. These findings, together with the morphology of the organ and physiological data from the receptor cells, suggest the possibility of an impedance matching function for the tympana in the transmission of acoustic energy to the receptor cells in the tettigoniid ear.

The acoustic trachea of Tettigoniids as an exponential horn: Theoretical calculations and bioacoustical measurements

The morphology and acoustic characteristics of the acoustic tracheal system were examined in certain tettigoniid species. Morphological measurements and statistical analysis reveal that in all species of bushcrickets investigated the shape of the acoustic trachea can be approximated by the equation of an exponential horn. Based on this approximation the transmission functions of the different tracheae were calculated theoretically. Because of its small size, the acoustic trachea must not be treated as an infinite exponential horn but its transmission function must be calculated by means of the equations for a finite‐length horn. The finite horn amplifies sound from a certain frequency on (cutoff frequency) in a broad range of frequencies as the infinite horn does. But the broadbanded transmission is superposed by a few resonances which are caused by reflections inside the horn. Bioacoustical measurements were made with a probe microphone. As expected from the theoretical considerations the course of the measured transmission function corresponds much better with the one calculated for the finite exponential horn than with the one calculated for the infinite horn. The present results are discussed referring to the consequences of the transmission properties of the acoustic trachea for the hearing ability of Tettigoniids. Additionally, they are compared with other investigations concerning the function of the acoustic trachea in tettigoniid hearing.

The auditory-vibratory sensory system of the bushcricket Polysarcus denticauda (Phaneropterinae, Tettigoniidae) II. physiology of receptor cells

The complex tibial organs of the bushcricket Polysarcus denticauda (Phaneropterinae) have some exceptional morphological features. In the forelegs, these organs have an extremely thick uncovered tympanum and about 50 receptor cells in the crista acustica. In the mid- and hindlegs, the cristae are extraordinarily reduced, with only seven or eight receptor cells. Physiological investigation of the receptor organs reveals that, in spite of the thick tympana, the auditory receptor cells of the forelegs have surprisingly low threshold values; they are as sensitive as the receptor cells of other bushcrickets, with very thin tympana. The high sensitivity is valid for the frequency range from at least 3–4 kHz up to 20 kHz. However, receptor cells tuned to frequencies above 20 kHz are less sensitive, suggesting a lack of discriminatory ability. This may be caused by the crowded arrangement of receptors at the distal part of the crista acustica. The frequency range of the conspecific proclamation song is therefore picked up only in the lower part of its power spectrum (10–20 kHz). The sensitive, low-frequency detection may originate from the broad-band sound transmission of the elaborate acoustic trachea of the forelegs, with a cut-off frequency at 4.5 kHz. The bimodal vibratory-auditory receptor cells of the tibial organs in the mid- and hindlegs are very sensitive to vibration, especially in the midlegs. They have significantly lower thresholds than receptors in the forelegs which are tuned to the same frequencies. This response property seems to have its origin within the specific structure of the organs in the mid- and hindlegs.

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.

Species-specific sound production in three ephippigerine bushcrickets

Songs of three Ephippigerine species (Ephippiger ephippiger, E. discoidalis and E.perforatus) have been recorded and analysed. Manipulation experiments have been carried out by removing single teeth from the pars stridens. The songs of manipulated animals show characteristic gaps within the impulse structure of the opening and closing syllables. Morphological measurements were carried out by means of SEM-photographs of the pars stridens. Combining both the bioacoustic and morphological results reveals that only the lateral part of the pars stridens is used during stridulation. Furthermore it could be shown that the individual impulse interval pattern within one syllable is also highly constant between syllables. The impulse interval pattern correlates with the pattern of tooth spacing on the pars stridens.

The auditory‐vibratory sensory system of Polysarcus denticauda (Phaneropterinae, Tettigoniidae): III. Physiology of the ventral cord neurons ascending to the head ganglia

In Polysarcus denticauda, a phaneropterine bushcricket with extremely thick uncovered tympana and an aberrant morphology of the cristae acusticae of the complex tibial organs, the electrophysiology of the auditory-vibratory ventral cord neurons ascending to the brain was investigated. Although the receptor organs in this species have some extraordinary response properties, the central auditory-vibratory neurons could be basically classified into the same functional types of S-, V-, and VS- neurons previously described for other bushcricket species. However, in some details the responses of most of the S- and VS- neurons are different. The S-neurons are generally more tonic and the VS-neurons give smaller responses to airborne sound stimulation than do the neurons belonging to the same functional types in most other bushcricket species. Adult males of P. denticauda use an extremely complicated and variable proclamation song for intraspecific acoustic communication. The song, which is often broadcast for a long time, can be divided into three phases on the basis of its time-amplitude structure. The syllable sequence exhibits some constant and other highly variable parameters. The basic, repeated element of the proclamation song is a pair of syllables; both syllables in the pair differ in duration and amplitude as well as in repetition rate between the three phases. When P. denticauda was stimulated with the conspecific male song, the responses of most S-neurons were found to copy the time patterns relatively well. Some of the V- and VS-neurons also responded relatively well to the syllables when vibrational signals were presented simultaneously. However, under these conditions the time structure was not copied, as it was by the S-neurons. In comparative investigations, the responses of central neurons of Decticus albifrons and Tettigonia viridissima, two species with more simply constructed songs having either low or high repetition rates, reflect the parameters of the song of P. denticauda less well than do the central neurons of P. denticauda. Therefore, some physiological adaptations to this complex male proclamation song seem to be inherent in the reactions of these central neurons in P. denticauda. J. Exp. Zool. 279:9–28, 1997.© 1997 Wiley-Liss, Inc.

The Auditory-Vibratory Sensory System in Bushcrickets (Tettigoniidae, Ensifera, Orthoptera) II. Signal Production and Acoustic Behavior

In insects, sound and/or vibration is usually produced by the friction of two body parts moving across one another [14]. This event is termed stridulation. Stridulation using the forewings is widespread in Orthoptera of the suborder Ensifera. The bushcrickets produce sound (and vibration) signals by elytro-elytral stridulation. During evolution they have developed two specialized (asymmetrical) regions on their forewings, used for sound production. The right elytron bears on its median edge a plectrum and a structure called mirror, a raised area of thin cuticle bounded partly or completely by thickened veins. The latter is possibly responsible for some resonance phenomena. On the ventral side of the left elytron there is a row of teeth (pars stridens) [9, 10]. The stridulatory movement of the forewings results in the teeth of the pars stridens serially scraping over the plectrum. Each tooth impact produces a damped oscillation of both wings, thereby generating a very brief sound impulse. The opening and closing movements of the elytra produce a succession of sound impulses causing the opening (small) and closing (main) syllables [19, 14, 22]. A species-specific number of opening and closing syllables forms a verse. The pressing of both forewings against each other and the velocity of the wing movement results in the typical time-amplitude pattern of the song in tettigoniids. The time-amplitude pattern and the fundamental frequencies of each sound impulse and of the whole song are determined by the structure and vibration properties of the wings [29].

“The most beautiful profession in the world…” In memoriam Klaus Kalmring (1931–2015)

Klaus Kalmring taught both subjects in the central school in Unterpörlitz near Ilmenau, Thuringia, then in East Germany. In 1955 he relocated to Gelnhausen, then West Germany, to join his parents and worked as an assistant educator for youth in the children’s sanatorium in Weilmünster/ Taunus from July to December. He also enrolled again in a high school, the Goethe-Gymnasium in Frankfurt am Main, where he attended evening classes and graduated in 1959. Immediately thereafter he started his studies in geography, biology and chemistry at the Johann-WolfgangGoethe-University in Frankfurt am Main. It was during an excursion in 1963 that he first met his wife-to-be, Elke Bremm. Two years later they were married. To finance his studies, Klaus Kalmring took up a position as a teacher for biology and geography at a private high school in Königshofen/Taunus until 1966, when he cancelled his contract to focus on his studies (Fig. 1). The school’s letter of reference explicitly acknowledges his extraordinary enthusiasm for his subject and for motivating and supporting the students—qualities, which he maintained throughout his life. In 1969 Klaus Kalmring received his doctoral degree (Dr. phil. nat.) with a dissertation on the neurophysiology of muscles in cats, supervised by Prof. Rolf Hassler Life and career

The Auditory-Vibratory Sensory System in Bushcrickets (Tettigoniidae, Ensifera, Orthoptera) I Comparison of Morphology, Development and Physiology

In bushcrickets, complex tibial organs exist in the pro-, meso- and metathoracic legs. In each leg, the complex tibial organs consist of three scolopale organs: the subgenual organ, the intermediate organ, and the crista acustica. Only in the forelegs are the tibial organs specialized as tympanal organs where the crista acustica and the distal parts of the intermediate organ serve as auditory receptors [51]. In tettigoniids the prothoracic spiracles are the main input for airborne sound. The acoustic trachea transmits sound to the tympanal organs in the proximal tibiae of the forelegs; the vibrations of the tympana are caused by sound acting on the inner surface of the tympanum [25, 31, 9].