Sexual differences in cricket calling song recognition

Summary Phonotactic behavior was studied in male crickets,Teleogryllus oceanicus. Tethered flying males were presented with electronically synthesized calling song models in a two-choice phonotaxis assay, and their song preferences were determined and compared with previous findings for females.Males are poorer at discriminating between songs than females; they do not display choice behavior as frequently as females, and the choices they do make are not as consistent as those of females (Figs. 3, 4). T. oceanicus calling song is composed of rhythmically different chirp and trill sections. The selectivity of males for these two components differs from that of females. Females prefer chirp to trill, but the opposite is true for males (Fig. 5B-F). Males are similar to females in that they prefer either a conspecific song model or its separate components to a heterospecific model (Fig. 5A, G, H).Behavioral and neural implications of these findings are discussed.     

Circadian timing of cricket calling song: a clock persisting from nymphs to adults

ABSTRACT. Male Australian field crickets (Teleogryllus commodus , Walker) reared in LD 12:12 h were transferred to LL at different developmental stages and the timing of their circadian calling song rhythm was analysed in regard to the previous zeitgeber. The phase settings for the onset and end of activity were similar in crickets experiencing the LD/LL transition: (i) 3–52 days after the final moult, (ii) within 24 h before the final moult, or (iii) 1–10 days before the final moult. For all groups the results reveal entrainment of the circadian mechanism at the last LD, thus excluding age-related differences. The rhythms of crickets, transferred from LD to LL as larval instars and also exposed to a reduced temperature (5–8^oC) during their last night, were delayed by about 11 h, an effect similar to that in adult crickets after a comparable cold exposure (Loher & Wiedenmann, 1981).
The results are interpreted showing that the circadian control of (the adult's) calling song already functions in the previous (non-singing) larval stages. Since the rhythmicity continued through moults and sexual maturation, it is concluded that the control centres regulating those physiological processes (e.g. pars intercerebralis, corpora allata) are not essential to the basic circadian mechanism.     

Gecko phonotaxis to cricket calling song: A case of satellite predation

Insectivorous Mediterranean house geckos, Hemidactylus tursicus, are found in the field close to the burrows of calling male decorated crickets, Gryllodes supplicans. In playback experiments where adult geckos were presented with calls of these crickets or calls of frogs as controls, geckos exhibited positive phonotaxis to broadcast cricket calling song. This indicates that geckos orient to and approach male cricket calls, even though the crickets call from burrows where they are protected from the geckos. However, this behaviour enables the geckos to intercept and consume female crickets that also respond phonotactically to the cricket calls. Thus geckos act as ‘satellite predators’, a situation which may impose sex-biased mortality on female crickets.     

Genotypic variation in calling song and female preferences of the field cricket Teleogryllus oceanicus

Geographically isolated populations often show phenotypic divergence in traits important in reproduction. A large proportion of the phenotypic variation in temporal parameters of the calling song of the field cricket Teleogryllus oceanicus is related to geographical location. Similarity between the songs recorded in different populations reflects geographical proximity. I used a common-garden breeding experiment to determine whether differences between the songs of two populations from the extremes of the geographical and phenotypic distribution (Oahu, Hawaii and Cairns, Australia) have a genetic basis. Differences in the total song duration and the proportion of the long-chirp element in the song remained after five generations of common-garden breeding, indicating that the populations had diverged genetically for these traits. Differences in a third song trait, the intervals between sound pulses and chirps, disappeared after common-garden breeding, suggesting that either the difference between populations in these traits represents phenotypic plasticity or the populations converged as a result of adaptation to the laboratory environment. A prospective analysis of the patterns of genetic variation within populations is presented. Full-sib analyses suggested high levels of genetic variability in song traits. Family mean covariance matrices suggested that populations differ in the genetic architecture of their songs. Females from both populations preferred songs with a high proportion of the long-chirp element, and preferences appeared to have high genetic and residual variability, although the sampling variances on these parameters were high. There was little evidence of a correlation between female preference for the long-chirp element and the amount of the long-chirp element produced by their brothers.     

Responses to features of the calling song by ascending auditory interneurones in the cricket Gryllus campestris

ABSTRACT. In female Gryllus campestris L., three functional types of ascending auditory intemeurones have been studied by recording from them extracellularly in the split cervical connectives using suction electrodes. Type 1 neurones are characterized by an optimal sensitivity to the carrier frequency of the species calling song (4–5 kHz). They copy the syllable and pause structure of the call at all intensities. The patterned spike discharge is observable at least 8 dB above absolute threshold. With suprathreshold stimulation, the neurones exhibit maximal responses (number of spikes/chirp) around the carrier frequency. The intensity response curves are approximately linear in the range of 40–90 dB SPL. The envelope of each syllable is reflected by a corresponding change in the firing rate, and syllable periods of 24ms and longer are resolved. This type can be considered as a neural correlate for phonotactic behaviour of the female where the syllable period has been found to be the most important temporal parameter. Type 2 neurones are most sensitive in the range of 4–6 and 11–13 kHz. They copy the syllable and pause structure of the species calling song at low and moderate intensities. However, the spikes invade the intersyllable pauses, when stimulated with the calling song at higher intensities (above 85 dB). This is particularly apparent at the onset of a chirp series. The slope of the intensity—response curve mimics that of type 1 units. The neurones cannot follow syllable periods shorter than 32 ms. Type 3 neurones differ from types 1 and 2 by a rather broad-band sensitivity in the range of 3–16 kHz, and in copying the chirp as a whole. Even at low stimulus intensities, the intersyllable pauses are filled with spikes, and information about the syllable—pause structure is lost. Stimulation with suprathreshold intensities gives rise to a rather uniform, broad-band response without distinctive peaks. The intensity—response curve is characterized by a higher absolute threshold, and by the reduction in the response magnitude starting above 70–80 dB. These units are not suitable for copying the calling song temporal structure in detail, but would indicate the chirping rhythm. Their strong response in the range of the species courtship song carrier frequency make them suitable to copy the courtship song.     

Fluctuating asymmetry and immune function in a field cricket

Recently, fluctuating asymmetry (FA) of morphological traits has attracted great attention as a short-cut measure of individual quality. Whereas there is some evidence that FA of sexual ornaments is negatively associated with immune function, studies concerning FA and immune function in non-ornamental traits are absent. Here, we tested whether FA of three non-ornamental traits in hind limbs is related to male immune function in a population of the Mediterranean field cricket, Gryllus bimaculatus. As different measures of male immune function, we used encapsulation rate and lytic activity. We found that a composite measure of FA (cFA) was negatively related to encapsulation rate. However, lytic activity was not related to cFA, but there was a tendency that males with higher body mass had higher lytic activity than males with lower body mass. Our results suggest that FA in non-ornamental traits indicates male immunocompetence in G. bimaculatus .     

Three different diel rhythms of the calling song in the cricket,Gryllus campestris,and their control mechanisms*

ABSTRACT. Males of the cricket, Gryllus campestris L. (Orthoptera: Gryllidae), displayed three different diel patterns in the timing of their calling song: 55% of all males investigated were dark-active, 25% light-active and 20% light-and-dark-active. Dark-active males continued to stridulate in both constant darkness (DD) and constant light (LL) during the subjective night, with a circadian period usually shorter (in DD) or longer (in LL) than 24h. Light-active males were mainly silent in DD but showed a circadian rhythm in LL, though with a 180° phase shift, i.e. activity during subjective night. This suggests that daytime activity has developed from nocturnal activity by a mechanism which prevents stridulation during darkness, and that both patterns are driven by the same endogenous clock. In the light-and-dark-active males some stridulation takes place during darkness, so dark inhibition is not complete. Such incomplete inhibition seemed to occur only in highly active animals. The three diel distribution patterns of the calling song are discussed in relation to sharing the chances of attracting females.     

Male dominance and immunocompetence in a field cricket

Female preference for dominant males has been found in manyspecies, and it is generally thought that winners of male-malecompetition are of superior quality. Success in contests probablydepends on male condition and overall health. Thus, femalescould avoid infection and gain genetic benefits in terms ofmore viable offspring by mating with dominant males. In thepresent study, we tested whether dominant males of the Mediterraneanfield cricket, Gryllus bimaculatus, had higher immunocompetencethan did their subordinates in experimental trials. We foundthat dominant males had better immune defense, as indicatedby significantly higher encapsulation rate and lytic activity,than did subordinate males of the same size. Dominant maleswere also more successful in obtaining matings, but this wasmeasured nonindependently of dominance status. Our results suggestthat a male's dominance status and success in fights may indicatehis immunocompetence to females.     

Inbreeding and courtship calling in the cricket Teleogryllus commodus

Male field crickets produce two acoustic signals for mating: advertisement calls and courtship calls. While the importance of advertisement calling in mate attraction is well understood, the function of courtship calling is less clear. Here, we tested if the courtship call of male crickets Teleogryllus commodus signals aspects of male quality by comparing the calls of inbred and outbred males. We examined the effect of one generation of full sibling mating on fine‐scale call structure, along with several life history traits. Inbreeding reduced nymph survival but had no significant effect on weight or development time. Inbreeding resulted in a small but significant change in two of the six call parameters measured. We then tested if inbreeding affects call trait combinations that are important to females by using the results of a previous selection analysis to compare the multivariate attractiveness of the calls of inbred and outbred males. There was no difference. We conclude that the courtship call of T. commodus is not a reliable signal of aspects of male quality that are affected by inbreeding (which generally reduces fitness‐enhancing traits). It might, however, signal components of male fitness that are not affected by changes in heterozygosity.     

蟋蟀对召唤声识别的趋声性定位行为

为了探究蟋蟀种内个体间的声音通讯原理,本研究通过回放利用Cool-edit2000声音采集软件采集的双斑蟋Gryllus bimachlatus召唤声,分别对雌、雄蟋蟀识别召唤声的趋声性定位行为进行了观测研究。实验结果表明:雌、雄双斑蟋对回放的召唤声均有较强的识别反应,但雌蟋蟀的趋声定位性较强,能在较短的时间内积极寻找到声源,路径成s型;雄蟋蟀反应相对较弱,路径较长,找到声源时间比雌蟋蟀长。本研究结果揭示召唤声在蟋蟀种内通讯中不仅对个体间的联系有作用,对异性求偶也有重要作用。     

Intracellular activity in cricket neurons during generation of song patterns

Summary During production of song patterns by the semi-isolated CNS of Gryllus campestris, intracellullar recordings were made in fibers of the mesothoracic ganglion, including synaptic areas of identified wing opener and closer motor neurons. The normal calling song pattern and some transitional songs toward courtship and toward aggression were generated by the CNS in the absence of any phasic sensory timing (Figs. 1, 4). Intracellular activity of the opener motor neurons was characterized by an absence of events in the interchirp interval, an EPSP underlying each burst, and an IPSP following the burst if the closer motor neurons were to be activated (Fig. 1). Intracellular activity of the closer motor neurons was characterized by an absence of events in the interchirp interval, an IPSP immediately following the onset of the opener motor neuron burst, and an EPSP after the IPSP (Figs. 2, 3). Units were found which fired in a burst during the period when both the opener and closer motor neurons were inhibited (Fig. 5). Complementary sets of units were found which displayed an oscillation of activity at the chirp rhythm but not at the pulse rhythm (Fig. 6). Gaps in the calling song were observed whose characteristics indicated that motor neuron activity was neither required for, nor effective in, resetting the chirp timing oscillator (Fig. 8). A possible model for the song generating mechanism is outlined.