Male Bushcrickets Research Articles

The acoustic behaviour of male Isophya camptoxypha bush crickets (Orthoptera: Tettigonioidea) in the Uzh river valley: preliminary findings.

The research article presents a study of acoustic behaviour of the bush cricket Isophya camptoxypha from Ukrainian Carpathians. However, it has also been discovered in forest meadows located in the Uzh River valley, which is part of the Danube catchment basin. The article discusses the unique stridulations of this species in vivo and in natural settings, as well as the acoustic interactions between male bush-crickets during duet singing. This study provides valuable insights into the intricate acoustic behaviour of Isophya camptoxypha.

Adaptive plasticity of bushcricket acoustic signalling in socially heterogeneous choruses

In many species, males produce sounds to attract a female. In a chorus, males actively adjust their acoustic production depending on the presence and number of mating rivals. Plasticity in signal features might then be advantageous as males could tune their signalling activity to the contest intensity. However, the ability to exhibit plastic behaviour might be constrained and interindividual variation in plasticity can occur. In this field study, we examined the influence of body mass and social environment on the signal expression of male bushcrickets, Poecilimon veluchianus veluchianus. We tested whether differences in signal features of rivals of different body mass and number led to changes in the competition pressure perceived by focal males and, consequently, in their acoustic responses. We used the first principal component from a principal component analysis, reflecting verse duration, duty cycle and syllable number, as a measure of acoustic output. We found that the rivals' acoustic output depended only on their number, being higher for two rivals than one. However, the response of heavy focal males depended on the rivals' body mass. Contrary to what we expected, heavy males produced shorter verses with fewer syllables when competing against two heavy rivals than when competing against one or two light rivals or one heavy rival. Facing light competitors, heavy focal males responded more to two rivals than to one. In contrast, light focal males did not vary their signal features depending on competition conditions. These results indicate that body mass and social context drive interindividual variation in the capacity of P. v. veluchianus males to adjust their signal features to competition levels. We compare these findings with those previously obtained on congeneric species and discuss the outcomes' similarities and discrepancies. Lastly, we provide suggestions for future studies of socially induced plasticity in sexually selected acoustic signal features.

Male Bush-Crickets in Female-Biased Environment Allocate Fewer Sperm Per Ejaculation

The operational sex ratio (OSR) is one of the most important ecological factors affecting the structure of mating systems and individual mating investment. Bush cricket males produce a highly costly nuptial gift during mating, so it is expected that OSR would affect this investment. In this study, we confronted the bush cricket Isophya rizeensis with three different OSR environments, measuring effects on the males' spermatophore, spermatophylax, ampulla weight, and absolute sperm transfer. As expected, male I. rizeensis showed a decrease in the transferred sperm in a female-biased environment. When mating in different OSR environments, males did not modify their behavioral strategies with respect to spermatophore transfer and copulation duration, which was largely influenced by male body size, likely due to the high costs of nuptial gifts. Although we dismiss the “longer copulation durations function as a mate assessment period” hypothesis, longer copulations positively affect spermatophore size and sperm number.

Chamber music: an unusual Helmholtz resonator for song amplification in a Neotropical bush-cricket (Orthoptera, Tettigoniidae).

Animals use sound for communication, with high-amplitude signals being selected for attracting mates or deterring rivals. High amplitudes are attained by employing primary resonators in sound-producing structures to amplify the signal (e.g. avian syrinx). Some species actively exploit acoustic properties of natural structures to enhance signal transmission by using these as secondary resonators (e.g. tree-hole frogs). Male bush-crickets produce sound by tegminal stridulation and often use specialised wing areas as primary resonators. Interestingly, Acanthacara acuta, a Neotropical bush-cricket, exhibits an unusual pronotal inflation, forming a chamber covering the wings. It has been suggested that such pronotal chambers enhance amplitude and tuning of the signal by constituting a (secondary) Helmholtz resonator. If true, the intact system - when stimulated sympathetically with broadband sound - should show clear resonance around the song carrier frequency which should be largely independent of pronotum material, and change when the system is destroyed. Using laser Doppler vibrometry on living and preserved specimens, microcomputed tomography, 3D-printed models and finite element modelling, we show that the pronotal chamber not only functions as a Helmholtz resonator owing to its intact morphology but also resonates at frequencies of the calling song on itself, making song production a three-resonator system.

Wing mechanics, vibrational and acoustic communication in a new bush-cricket species of the genus Copiphora (Orthoptera: Tettigoniidae) from Colombia

Male bush-crickets produce acoustic signals by wing stridulation to call females. Several species also alternate vibratory signals with acoustic calls for intraspecific communication, a way to reduce risk of detection by eavesdropping predators. Both modes of communication have been documented mostly in neotropical species, for example in the genus Copiphora. In this article, we studied vibratory and acoustic signals and the biophysics of wing resonance in Copiphora vigorosa, a new species from the rainforest of Colombia. Different from other Copiphora species in which the acoustic signals have been properly documented as pure tones, C. vigorosa males produce a complex modulated broadband call peaking at ca. 30kHz. Since males of this species do rarely sing, we also report that substratum vibrations have been adopted in this species as a persistent communication channel. Wing resonances and substratum vibrations were measured using a μ-scanning Laser Doppler Vibrometry. We found that the stridulatory areas of both wings exhibit a relatively broad-frequency response and the combined vibration outputs fits with the calling song spectrum breadth. The broadband calling song spectrum results from several wing resonances activated simultaneously during stridulation. Under laboratory conditions the calling song duty cycle is very low and males spend more time tremulating than singing.

Mating Behavior and Spermatophore Characteristics in Two Closely Related Bushcricket Species of the Genus Phonochorion (Orthoptera: Phaneropterinae)

Bushcrickets comprise an important group of model organisms, which are intensively studied to understand the evolution of mating behavior. During the mating process, the male bushcricket transfers a costly and edible spermatophore consisting of two parts to the female. This unique behavior makes bushcricket species appropriate study organisms for investigating spermatophore size variations across entire bushcricket family (Tettigoniidae). The functions of the spermatophylax and the ampulla, which constitute the spermatophore, have been addressed in many studies. Although the costs and benefits of mating for male and female bushcrickets may vary depending on species, there are some common evolutionary traits. In the present study, mating behaviors and spermatophore characteristics of two endemic bushcricket species, Phonochorion uvarovi and P. artvinensis, distributed at the high altitudes of the Kackar Mountains, northeastern Turkey, were examined. The data on two closely related species belonging to the genus of Phonochorion show that they have different reproductive investments in terms of spermatophore and sperm numbers in spite of similar habitat and nutritional preferences. P. artvinensis had a larger spermatophore, spermatophylax and ampulla, but transferred fewer sperm. Male age and weight had a significant effect on spermatophore, spermatophylax and ampulla investments in P. uvarovi while only male weight was a significant factor in P. artvinensis. A positive relationship between the spermatophylax and the ampulla weights in both species supports the ejaculate protection hypothesis in the Phonochorion species. Even though further studies on Phonochorion should be conducted to provide a more clear comparison with other groups in the barbitistine, this study demonstrates that both P. uvarovi and P. artvinensis make little spermatophore investment relative to their body size in comparison to other barbitistines.

Spermatophore allocation strategy over successive matings in the bushcricket Isophya sikorai (Orthoptera Phaneropterinae)

During mating, male bushcrickets transfer edible spermatophores that consist of a large sperm-free spermatophylax and a sperm-containing ampulla. The effect of consecutive matings on nuptial gift and sperm numbers in the bushcricket Isophya sikorai was examined. Males and females differed in body weight and mating history influenced their weight. Males differed in spermatophore weight, as well as the weights of spermatophylax and ampulla. Spermatophore (spermatophylax + ampulla) and spermatophylax weight of I. sikorai increased with male body weight, but not with ampulla weight. Male age had a significant effect on sperm number, with older males producing more sperm. Female weight but not mating number of female had a significant effect on spermatophore weight. Males increased the size of the spermatophylax and sperm number when presented with larger females, but they did not adjust their ampulla weight. Male age affected spermatophylax weight when mating with heavier females. Males reached their maximal absolute sperm number point at about middle age of their mating period due to an age-dependent shift in covariation between the ampulla and spermatophylax weight and ampulla size increases over a longer period. We conclude that production of a spermatophore and its components is costly, therefore males should strategically adjust their spermatophore components among mating opportunities. Female quality is an important predictor in searching males, and those males transfer significantly larger spermatophore and ejaculates to higher quality (heavier) females. Briefly, this study suggest that male I. sikorai strategically allocate spermatophore size and sperm number with respect to various factors such as his age, sperm competition and female size in a multiple mating system.

Comparison of Sperm Number, Spermatophore Size, and Body Size in Four Cricket Species

This paper examines the relationships between male body size, spermatophore size, and number of sperm per spermatophore, in four cricket species: Teleogryllus commodus, Acheta domesticus, Gryllus bimaculatus, and Gryllus assimilis. Within each species, individuals varied considerably in all three characters measured, and generally, spermatophore size, number of sperm, and body size were all correlated; i.e., ampulla diameter and sperm number per spermatophore significantly increased with body mass (p < 0.001) according to a linear regression function. Interspecific investigations found considerable differences between species: G. assimilis had the largest mean male body mass and length, largest ampullas, and highest numbers of spermatozoa per spermatophore, whilst A. domesticus had a small body mass and length, the smallest ampullas, and lowest sperm numbers. Regression analyses of all four cricket species revealed similar results as intraspecific regression computations. Hence, both intra- and interspecifically, larger males produce larger spermatophores containing more sperm, than do smaller males. These results differ from bush crickets (Tettigoniidae), where larger male body size does not necessarily correlate with larger ampullas and more sperm. Possibly male bush crickets have evolved to invest a higher proportion of their resources in the size of the nuptial gift, as opposed to number of spermatozoa.

Lifetime spermatophore investment in natural populations of two closely related bush-cricket species (Orthoptera: Tettigoniidae: Poecilimon)

Summary Male bush-crickets transfer a substantial spermatophore to females during copulation. The spermatophore comprises a large spermatophylax and a sperm-containing ampulla which is consumed by the female while the ejaculate transfers into her. Spermatophores are costly to produce and investment trade-offs are expected to occur between the ejaculate, sperm and spermatophylax. While models of ejaculate allocation predict strategic allocation between current and potential reproductive rates, no comparative studies to date have analysed interspecific spermatophore component variation between bush-cricket species over the entire mating season. Here we compare field data from two bush-cricket species (Poecilimon )t hat differ in spermatophore investment. While Poecilimon thessalicus invests heavily in spermatophore production and was variable in body mass and spermatophylax size over the season, they consistently produced similar-sized ampullae and transferred constant numbers of sperm. In contrast, the ampulla size of the less investing species, P. veluchianus minor, varied considerably over the season, yet the body, spermatophylax mass and sperm number remained constant. Differences between the two species reflect within-species adjustments that male bush-crickets make to specific spermatophore components as conditional strategies in order to maximize reproductive output.

The Relationship Between Morphological Symmetry and Immune Response in Wild-Caught Adult Bush-Crickets

Despite interest in the relationship between fluctuating asymmetry (FA), immune response and ecological factors in insects, little data are available from wild populations. In this study we measured FA and immune response in 370 wild-caught male bush-crickets, Metrioptera roeseli, from 20 experimentally introduced populations in southern-central Sweden. Individuals with more-symmetric wings had a higher immune response as measured by the cellular encapsulation of a surgically-implanted nylon monofilament. However, we found no relationship between measures of FA in other organs (i.e. tibia and maxillary palp) and immune response, suggesting that this pattern may reflect differing selection pressures.

Calling heights chosen by male speckled bush crickets (Leptophyes punctatissima)

Calling heights chosen by male speckled bush crickets (Leptophyes punctatissima)

Condition-dependent spermatophore size is correlated with male's age in a bushcricket (Orthoptera: Phaneropteridae)

During mating, male bushcrickets transfer a spermatophore that consists of a sperm-containing ampulla and a product of the accessory glands, the spermatophylax, which females directly ingest. In the present study, we demonstrate male spermatophore allocation in the bushcricket Poecilimon zimmeri. Males of this species show condition-dependent spermatophore investment. This investment depended upon the age at first mating of males, with older individuals transferring larger spermatophores than younger ones of the same body mass. Independently of age, heavier males transfer larger spermatophores, but the size of males (as measured by femur length) was not a good predictor. Heavier males allocate a lower proportion of their mass to spermatophores and reach their maximal investment point earlier than less heavy males. Spermatophylax production levelled off to a species specific maximum earlier than that of sperm investment (measured as ampulla mass), suggesting that males face high levels of sperm competition. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 96, 354–360.

Bushcricket song as a clue for spermatophore size?

Bushcricket males of Poecilimon zimmeri transfer large and protein-rich spermatophores during mating, which females directly ingest. There is correlational evidence that heavier males transfer larger nuptial gifts. In no-choice mating trials, females mated randomly with respect to male’s body weight. In contrast, in two-choice mating trials, female bushcrickets exhibit clear choice for the heavier male. This heavier male advantage was also found in pre-mating choice during phonotaxis. With manipulated mute males, females mated at random with regard to body weight of the competitors. The number of physical encounters between a female and males was low in all tests with a single male (no choice) and greater in choice-tests with two competing males. The latencies to mate also differed significantly between treatments. The time mating pairs spent in precopula was short in experiments where the males could hear rivals and significantly longer in all other tests using either a single male or mute males. Thus, acoustic signalling in male bushcrickets seems to signal male body weight. A preference for heavier males may reflect a female’s preference for a larger spermatophore and therefore a greater direct benefit.

Sex Differences in “Time Out” from Reproductive Activity and Sexual Selection in Male Bushcrickets (Orthoptera: Zaprochilinae: Kawanaphila mirla)

Animals of many species prefer some partners over others. Discriminating among potential mates causes strong sexual selection that shapes characters and behaviors. In bushcrickets the sexes shows different latencies to remate due to differences in investment in production of the nuptial gift by males and the induced refractory period in females. We conducted experiments with the Australian bushcricket Kawanaphila mirla to test the variation in male mating success by female choice. Male remating intervals under unlimited access to food and mates were around two days, whereas most females did not remate within 12 days. Males had therefore a much shorter “time-out” from mating than females. The adult sex ratio from field samples was near to 1:1. Consequently, the OSR was male-biased with more males than females ready to mate. This male-biased OSR led to mating competition in males and choosiness in females. In a field enclosure with unlimited supply of receptive females the number of matings varied widely between males, with twenty percent of males neglected by the females. The number of matings within this enclosure was neither related to male size nor to song characters, recorded previously in the lab. However, the number of matings by individual males was positively correlated to the size of their spermatophore producing accessory gland. Females appear to

Effects of mating status on copulation investment by male bushcricket Gampsocleis gratiosa (Tettigoniidae, Orthoptera)

Male's copulation investment, including spermatophore and sperm investment were very high in the Chinese bushcricket Gampsocleis gratiosa. The effects of mating status of both males and females on male's copulation investment were examined in this study. The fresh weight of spermatophylax increased positively with the weight of males' body. This indicated that the nutritional investment during copulation depended on male's quality. Spermatophore investment showed insignificant differences in every copulation protocols. This finding supported the paternal investment hypothesis, that is, males contributed to their offspring with little attention to their partners. Sperm releasing per ejaculation varied significantly among the trials. Males decreased 54.19% sperm in second mating than in its first mating, demonsrated that males regarded the first mating highly, and were more prudent in subsequent mating. These males' strategies may contribute to the viability of the offspring.

Potential lifetime reproductive success of male bushcrickets parasitized by a phonotactic fly

Males of the bushcricket Poecilimon mariannae are parasitized by the acoustically orienting fly Therobia leonidei . Developing fly larvae reduce male bushcricket survival and reproductive effort. We estimated potential lifetime reproductive success (PLRS) of male bushcrickets to investigate the likely costs of this parasitism. Our analysis explored the relative reduction in PLRS caused by parasitoid infection by examining effects on survival, calling attractiveness and spermatophylax size. We also incorporated nonparasitoid-related mortality. Parasitized males lost 42% of their PLRS compared to nonparasitized males. The shortened life span after parasitism accounted for half of the PLRS reduction. Decreased spermatophylax production also had a major effect on PLRS, while decreased calling attractiveness had a smaller effect. This fitness loss was context dependent and changed with extrinsic nonparasitoid-related mortality. If nonparasitoid-related mortality was high, the selection on host males to avoid parasitism was weak; if it was low, parasitized males lost a considerable amount of reproductive opportunities compared with unparasitized males.

WHEREFORE ART THOU, ROMEO?

![Figure][1] To us, the calls of male bushcrickets are a comforting sound on warm summer evenings. But to a female insect, they are a cacophony of potential mates, each competing for her attention; she has to decide which call is produced by a suitor from her own species. Species differ in

Male Bushcrickets Favoured by Parasitoid Flies when Acoustically more Attractive for Conspecific Females (Orthoptera: Phanopteridae / Diptera: Tachinidae)

In many animals, males [MM] have traits that increase their attractiveness to females [FF]. Their signals, however, can also increase conspicuousness to predators. In the bushcricket Poecilimon thessalicus Brunner von Wattenwyl 1891, MM are attacked by the parasitoid ormiine fly Therobia leonidei (Mesnil 1965) that locate them through their calls. MM, parasitized by the fly in a field experiment, attracted more conspecific FF in a previous phonotactic experiment than unparasitized MM. This result suggests that calling behaviour, which increases a M's probability of attracting a F, also increases his risk of attracting parasitoids. This supports the idea that sexual selection favours male adaptations that lead to high reproductive success even at the cost of increased predation.

Carotenoids in the spermatophores of bushcrickets (Orthoptera: Ephippigerinae).

During mating male bushcrickets transfer large spermatophores, which have been demonstrated to play an important role in female nutrition and egg production. Until now only relatively unspecific substances such as water and proteins were known to be present within these spermatophores. We found that in the bushcricket Ephippiger zelleri the spermatophores contain substantial amounts of carotenoids (mainly lutein and zeaxanthin) that are also found in the eggs of this species. Carotenoids are well known for their positive effects on survival and reproduction in animals. This is the first example, to our knowledge, where such specific vitamin-like substances were found to be transferred from male to female during mating.

Spermatophore characteristics in bushcrickets vary with parasitism and remating interval

Male bushcrickets provide females with a nuptial gift, a spermatophore, which is transferred to females at mating. The spermatophore consists of a gelatinous mass, the spermatophylax, and the sperm-containing ampulla. Male spermatophore size is positively correlated with insemination rate and female refractory period and therefore with male reproductive success. In this study, we examined spermatophylax weight, ampulla weight and sperm number in males of Poecilimon mariannae parasitized by the acoustically orienting fly Therobia leonidei. We show that in parasitized males, spermatophylax weight decreases with the level of parasitism. In line with the hypothesis that parasitism is a cost to reproduction, we found that spermatophylax weight was reduced at remating. In contrast, the replenishment of the spermatophylax in unparasitized males was complete after 2 days and was increased no further after 3 days. Both sperm number and ampulla weight showed an increase over time since last mating and sperm production was estimated at a constant rate of 500,000 per day in all individuals, regardless of parasitism. The allocation of investment in components of the spermatophore varies greatly with parasitism and remating. Both factors had rather independent effects on spermatophore constitution, revealing functional constraints acting on spermatophore characteristics in bushcrickets, which are important for understanding the selection pressures working on its components.