What determines the tuning of hearing organs and the frequency of calls? A comparative study in the katydid genus<i>Neoconocephalus</i>(Orthoptera, Tettigoniidae)

Journal of Experimental Biology

2004

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Male Neoconocephalus robustus and Neoconocephalus bivocatus produce remarkably fast calls, with pulse rates of approximately175-200·Hz. The temporal call patterns differ significantly between the two species. Male N. robustus produce calls with a single pulse rate of 200·Hz. In N. bivocatus, pulses are repeated with alternating periods, resulting in distinct pulse pairs: approximately 175·pulses·s -1 are grouped into 87 pulse pairs·s -1 . In order to identify the temporal parameters used to recognize calls with such fast pulse rates, female call recognition in both species was tested during phonotaxis on a walking compensator. Female N. robustus were attracted to calls without amplitude modulation. Amplitude-modulated signals were equally attractive, as long as the silent intervals were short enough. The maximally tolerated interval duration varied with pulse duration. Female N. bivocatus did not require the paired-pulse pattern but were attracted to call models in which each pulse pair was merged into one long pulse. Females used the pulse rate to recognize such signals: pulse rates close to 87·Hz were attractive, largely independent of the duty cycle. Thus, females of the sibling species N. robustus and N. bivocatus used qualitatively different call recognition mechanisms.

Section: Stimulationmentioning

confidence: 92%

“…40BF), positioned 1·cm above the top of the sphere, and a Bruel and Kjaer sound level meter (B&K 2231). This amplitude is representative for a distance of 2-3·m from a calling male (Büttner, 2002;Schul and Patterson, 2003).…”

Section: Stimulationmentioning

confidence: 99%

Recognition of calls with exceptionally fast pulse rates: female phonotaxis in the genus Neoconocephalus (Orthoptera:Tettigoniidae)

Deily

Journal of Experimental Biology

2004

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“…We recorded calls of males raised under both summer and winter conditions (for details of call recording and analysis see Schul & Patterson 2003). Calls of the summer generation were structured in verses, whereas winter males produced continuous calls; Whitesell & Walker (1978) reported the same pattern for summer and winter calls.…”

Section: Methodsmentioning

confidence: 99%

Developmental plasticity of mating calls enables acoustic communication in diverse environments

Beckers

2008

Proc. R. Soc. B.

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Male calls of the katydid Neoconocephalus triops exhibit substantial developmental plasticity in two parameters: (i) calls of winter males are continuous and lack the verse structure of summer calls and (ii) at equal temperatures, summer males produce calls with a substantially higher pulse rate than winter males. We raised female N. triops under conditions that reliably induced either summer or winter phenotype and tested their preferences for the call parameters that differ between summer and winter males.Neither generation was selective for the presence of verses, but females had strong preferences for pulse rates: only a narrow range of pulse rates was attractive. The attractive ranges did not differ between summer and winter females. Both male pulse rate and female preference for pulse rate changed with ambient temperature, but female preference changed more than the male calls.As a result, the summer call was attractive only at 258C, whereas the slower winter call was attractive only at 208C. Thus, developmental plasticity of male calls compensates for differences in temperature depen dency between calls and preferences and enables the communication system to function in heterogeneous environments. The potential role of call plasticity during the invasion of new habitats is discussed.

“…In the genus Neoconocephalus, most of the call energy is concentrated in a narrow low-frequency band, with ultrasonic frequency components at least 20·dB softer than the low-frequency band ( Fig.·1A) (Greenfield, 1990). The characteristic frequency (center frequency) of the lowfrequency band within the genus ranges from 7 to 16·kHz (Greenfield, 1990;Schul and Patterson, 2003). Based on measurements of hearing thresholds and the sound transmission properties of the habitats (tall grasslands and marshes), center frequencies close to 10·kHz are calculated to be most advantageous in this genus (Schul and Patterson, 2003).…”

Section: Introductionmentioning

confidence: 99%

“…Male calls of N. robustus have the lowest center frequency in the genus at 7·kHz (Schul and Patterson, 2003). This frequency is surprisingly low given the disadvantages of calling at 7·kHz: the hearing sensitivity in N. robustus is about 7·dB lower at 7·kHz than at 10·kHz, and there is no improvement in signal transmission between 10·kHz and 7·kHz to justify the use of a frequency that is mismatched with female sensitivity (Schul and Patterson, 2003).…”

Section: Introductionmentioning

confidence: 99%

Spectral selectivity during phonotaxis: a comparative study in Neoconocephalus (Orthoptera: Tettigoniidae)

Deily

Journal of Experimental Biology

2006

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SUMMARY The calls of male Neoconocephalus have most energy concentrated in a relatively narrow low-frequency band. In N. robustus this low-frequency band is centered around 7 kHz, whereas calls of N. nebrascensis and N. bivocatus have center frequencies close to 10 kHz. The importance of the position of the low-frequency band for female phonotaxis in these three species was determined using a walking compensator. Female N. robustus showed significant phonotaxis towards call frequencies from 5 to 10 kHz, and spectral selectivity towards higher frequencies did not change with stimulus amplitude. Significant responses in N. nebrascensis and N. bivocatus occurred at significantly higher frequency ranges than in N. robustus. In these species,spectral selectivity changed with stimulus amplitude; at 68 dB sound pressure level (SPL), upper cut-off frequency was significantly lower than at 80 dB SPL in both species. Adding a higher harmonic to the conspecific carrier frequency had a strong inhibitory effect on phonotaxis in N. robustus: at higher relative amplitudes of the harmonic, phonotaxis was completely suppressed. Adding a higher harmonic to the conspecific carrier frequency had a much weaker but significant inhibitory effect in N. nebrascensisand little, if any, effect in N. bivocatus. The processing of song spectrum in the sensory system is discussed with regard to the differences in spectral selectivity among the three species. The sharp spectral selectivity of N. robustus is interpreted as an adaptation for species isolation.