Field Cricket Gryllus Integer Research Articles

Behavioural syndromes shape evolutionary trajectories via conserved genetic architecture.

Behaviours are often correlated within broader syndromes, creating the potential for evolution in one behaviour to drive evolutionary changes in other behaviours. Despite demonstrations that behavioural syndromes are common, this potential for evolutionary effects has not been demonstrated. Here we show that populations of field crickets (Gryllus integer) exhibit a genetically conserved behavioural syndrome structure, despite differences in average behaviours. We found that the distribution of genetic variation and genetic covariance among behavioural traits was consistent with genes and cellular mechanisms underpinning behavioural syndromes rather than correlated selection. Moreover, divergence among populations' average behaviours was constrained by the genetically conserved behavioural syndrome. Our results demonstrate that a conserved genetic architecture linking behaviours has shaped the evolutionary trajectories of populations in disparate environments-illustrating an important way for behavioural syndromes to result in shared evolutionary fates.

Does acoustic environment modify boldness and related life-history traits in field cricket nymphs?

Between-individual differences in personality and life-history traits can arise from both genetic and environmental factors, with the latter possibly reflecting contrasting individual experiences during ontogeny. It is yet unclear how the acoustic environment may affect the development of boldness and related life-history traits such as growth rate, maturation age and longevity in species that normally rely on acoustic cues to adjust their behaviours. We studied if long-term exposure of field cricket Gryllus integer nymphs to traffic noise or acoustic conspecific signalling would affect the level or repeatability of boldness or life history traits. An integrative boldness score was statistically significantly repeatable in control and cricket sound groups, but not in the traffic noise group. However, our data did not show any effect of acoustic treatment on individual boldness. Acoustic treatments had no effects on life-history traits, either. Future studies are needed to confirm whether the acoustic environment could affect the development of personality and behavioural consistency.

Male Field Cricket Songs Are Altered After Aggressive Interactions

To address the hypothesis that male acoustic sexual advertisement signals might be indicators of aggressiveness, in addition to chemical signals, we examined the relationship between levels of aggression/dominance status and acoustic sexual advertisement signals in the field cricket Gryllus integer. Males were paired in aggression trials and recorded the night before and the night after the trial. This allowed us to test whether aggression is inherently linked to song phenotypes, or whether aggressive interactions cause males to alter their songs. We found that dominant (winning) males signaled with higher energy, amplitude and power the night after winning an aggressive encounter, but not before the encounter. Time spent calling and the number of calling bouts were unrelated to aggression, whereas whereas winning males increased their bout lengths after winning, and losing males decreased their bout lengths after losing.

Linking organismal growth, coping styles, stress reactivity, and metabolism via responses against a selective serotonin reuptake inhibitor in an insect

Evidence suggests that brain serotonin (5-HT) is one of the central mediators of different types of animal personality. We tested this assumption in field crickets Gryllus integer using a selective serotonin reuptake inhibitor (SSRI). Crickets were selected for slow and rapid development and tested for their coping styles under non-stressful conditions (time spent exploring a novel object). Resting metabolic rate, maximum metabolic rate and latency to resume activity were measured under stressful conditions (stress reactivity). Measurements were taken (i) before and (ii) during the SSRI treatment. Before the SSRI treatment, a strong negative correlation was observed between coping style and stress reactivity, which suggests the existence of a behavioral syndrome. After the SSRI treatment, the syndrome was no longer evident. The results of this study show that 5-HT may be involved in regulating behavior not only along a stress reactivity gradient but also along a coping styles axis. The relationship between personality and the strength and direction of 5-HT treatment on observed behaviors indicates trait-like individual differences in 5-HT signaling. Overall, these findings do not support recent ideas arising from the pace-of-life syndrome (POLS) hypothesis, which predict higher exploration and metabolic rates in rapidly developing bold animals.

An attractive male trait and aggressiveness are negatively correlated in wild field crickets, but uncorrelated in lab-reared crickets

It is generally thought that attractive male traits are positively correlated with dominance (aggressiveness). However, growing evidence suggests that this is not necessarily the case. We investigated whether calling song, a male mating display used by females to evaluate potential mates in a field cricket (Gryllus integer), is correlated with aggressiveness. In this species, females prefer males with longer durations of singing time. We measured singing time by measuring song over three continuous days using a custom-designed audio-monitor and assessed aggressiveness by pairing males in agonistic interactions. Our results showed that for males caught in the field, the percentage of time spent singing was negatively correlated with aggressiveness. However, in males that were raised in the laboratory, the percentage of time spent singing was not correlated with aggressiveness. Since calling duration is an attractive male trait in these crickets, our data show that the attractiveness of males can be either negatively related to aggressiveness (field) or unrelated to aggressiveness (lab). Neither of these results fit the traditional view that preferred male mating cues should be positively correlated with dominance (aggressiveness). These results also suggest that measurements of aggressiveness made in the lab do not necessarily correspond with aggressiveness in the field.

Juvenile exposure to acoustic sexual signals from conspecifics alters growth trajectory and an adult personality trait

Animal personalities have become an established concept in animal behaviour. Despite this, the potential influence of early life experiences on adult personality is often overlooked. Juvenile exposure to environmental cues such as conspecific signalling or predator cues may provide relevant information regarding the make-up of the forthcoming environment. Individuals might be able to use these cues to adjust developmental trajectory and adult personality to prevent a personality–environment mismatch. Using the field cricket Gryllus integer, we show that individuals reared in the presence of conspecific acoustic sexual signals alter both growth rate and an adult personality trait. Males reared in the presence of acoustic sexual signals were less aggressive and less likely to become dominant relative to those reared in the absence of acoustic signals. Additionally, acoustic treatment interacted with juvenile body mass: large juveniles reared in the presence of acoustic signals were larger than small juveniles reared in the presence of acoustic signals and larger than all juveniles reared in silence. We discuss the potential adaptive significance of the observed developmental and personality differences.

Predator-induced changes in the boldness of naïve field crickets, Gryllus integer, depends on behavioural type

In recent years, using a personality approach for studies of animal behaviour has increased our ability to predict an individual's or population's behavioural responses to external stimuli. At a population level, different behavioural types (e.g. bold and shy) often exist, and the behaviour of different types may not be free to vary across different situations. In the present study, we examined whether a predator introduction induced shifts in boldness and if predator-induced changes in behaviour depended on the individual's original behavioural type in the field cricket Gryllus integer. We also studied whether exposure to a natural predator affected the formation of a behavioural syndrome between aggression and boldness or the consistency of boldness. We define a behavioural syndrome as an association between functionally different behaviours or consistency in a behaviour over time or contexts. We found that exposure to a predator affected behavioural antipredator responses, measured as the time to recover from freezing (immobility). Moreover, we found that the different behavioural types expressed different behavioural responses to predator introduction (i.e. shy individuals became bolder and bold individuals more shy). However, an aggressiveness–boldness behavioural syndrome was not detected in either the treatment or control groups, and early antipredator responses were rank order repeatable only in the control group. We suggest that individuals' behavioural antipredator responses under increased predation risk depend on the individual's original behavioural type and that increased risk may break apart the consistency of behaviour.

Long-distance signals influence assessment of close range mating displays in the field cricket, Gryllus integer

Male sexual displays often include components detected across long distances, and those perceived only at close range. Understanding what information females gain from each component of a complex display and how they use these signals to make decisions are questions of major interest in sexual selection research. We evaluated content-based hypotheses (‘redundant signals’ and ‘multiple messages’) for the courtship displays of field crickets (Gryllus integer) by measuring female responses to males’ long-distance calling song (calls) and close-range chemical cues. Females’ responses to a male’s calls and chemical cues were uncorrelated, supporting the ‘multiple messages’ hypothesis. We also tested the ‘inter-signal interaction’ hypothesis by investigating how long-distance calls influence evaluation of close-range courtship. The relationship between long- and close-range signals was complex and conditional: females accepted close-range courtship more quickly after exposure to attractive calling song than they did after exposure to either unattractive calling song or silence, and unattractive calls were no more or less effective than silence. This inter-signal interaction could affect our understanding of mate choice in species with multiple mating signals because it implies that females may save time and energy by not assessing the close-range signals of attractive long-distance signalers. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 856–865.

Male and female crickets use different decision rules in response to mating signals

Males that produce conspicuous mating signals may attract competitors in addition to sexually receptive females. In manyspecies, for example, females use male calls to locate and choose mates and males respond to competitors’ signals by modulatingsignal production or changing location, thereby escalating or decreasing competition. Do these different receivers make deci-sions using male signals in the same way? We compared how male and female field crickets (Gryllus integer) made decisions toapproach male calls differing in calling bout length, a heritable trait known to play an important role in female mate choice.When offered a simultaneous choice between playbacks, both males and females preferred calls with long bouts to those withshort bouts. When presented with calls in isolation, however, only females preferred long-bout calls. Females thus appear to usean internal standard to evaluate calls, whereas males apparently compare the relative attractiveness of alternatives. We also foundthat males assess calls in relation to their own competitive potential by testing 2 hypotheses that make different predictionsregarding variation in male responses to competitor signals. We found no support for the satellite male hypothesis, as unattractivemales did not preferentially approach female-preferred calls; in support of the aggressive displacement hypothesis, males likely towin contests preferentially approached the female-preferred call. Our work demonstrates that even though the sexes process thesame information, different mechanisms of reproductive success (mate location vs. mate attraction) can result in sex differencesin the perception and use of conspecifics’ signals. Key words: contests, decision rules, Gryllus integer, male phonotaxis, matechoice, satellite males, sexual dimorphism, thresholds. [Behav Ecol]

A behavioural syndrome in the field cricket Gryllus integer: intrasexual aggression is correlated with activity in a novel environment

Behavioural syndromes, or suites of correlated behaviours across different contexts and situations, have recently drawn attention from evolutionary biologists. In the field cricket Gryllus integer, males are aggressive with one another and fight vigorously over females and territories. We examined whether aggressiveness with other males was correlated with activity in a potentially dangerous context (a novel environment) in laboratory-raised virgin males. Aggressiveness was measured as fighting ability against a weight-matched opponent. First, we measured each cricket’s latency to become active in a novel environment and latency to emerge from a refuge within a novel environment. Next, we determined which of two weight-matched males was more aggressive, by pitting the males together in an agonistic contest and counting the number of fights won by each male. More aggressive males, who won more fights, had shorter latencies to become active when placed in a novel environment and shorter latencies to emerge from a safe refuge. These results suggest that a behavioural syndrome exists in G. integer, in which more aggressive males are also more active in general, and possibly less cautious towards predation risk. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 91, 475–482.

The scent of dominance: female field crickets use odour to predict the outcome of male competition

Pheromones may convey information about mate quality and social status. In the field cricket Gryllus integer, females mount the males for copulation, such that males cannot coerce females to mate. We examined whether virgin G. integer females preferred the scent of potentially dominant males to that of subordinate males. First, we collected pheromones by confining males on filter paper. Next, we offered filter paper from each of two size-matched males and control paper to females that had never been exposed to males, and measured the time spent by the female on each kind of paper. Finally, dominance status of the males in each size-matched pair was determined by pitting the two males against one another in agonistic contests. When offered filter paper from subsequently dominant versus subsequently subordinate males, females spent more time on the paper from the dominant male than the subordinate male, and much less time on control paper. Thus, pheromones may inform female G. integer about a male's potential to achieve dominant social status. Male pheromones were also associated with the female's tendency to mount a male. In contrast to cockroaches, where females prefer the scent of subordinate males (presumably to avoid risk of injury), female crickets prefer the scent of potentially dominant males and are more likely than males to wound their mating partners.

Detection of the Spider Predator, Hololena Nedra By Naïve Juvenile Field Crickets (Gryllus Integer) Using Indirect Cues

Summary In many species, prey detect predators using chemical cues, which may be based on the predator’s previous diet. Furthermore, the predator’s previous hunting strategy and diet may affect the prey’s behavioural strategies to avoid predation. Juvenile Gryllid field crickets face predation by spiders, but the responses of juvenile crickets to spiders are unknown. We studied whether naive juvenile field crickets can detect a predatory spider, Hololena nedra, using chemotactile cues (silk, secretions and excreta). We also studied the effect of the predator’s diet on the juvenile field cricket’s anti-predator behaviour. Cricket nymphs avoided the chemotactile spider cues when the spiders were previously fed with crickets, but not when spiders were not fed crickets. Our study suggests that the ability to detect the indirect cues of a potential predator may be an important factor determining the anti-predator responses of insects towards spiders.

Fine-scale temperature effects on cricket calling song

The effects of temperature on the structure of cricket calling song were examined in the trilling field cricket Gryllus integer. A repeated-measures design was used to assess the effects of temperature and individual differences among males simultaneously. Temperature affected most aspects of calling song, specifically pulse length, interpulse length, peak frequency, trill length, intertrill length, and pulse duty cycle. Unaffected by temperature were the number of pulses per trill, the proportion of pulses missed within a trill, and the trill duty cycle. After controlling for temperature, significant individual differences among crickets were found in peak frequency, number of pulses per trill, trill length, and intertrill interval. Both the environmental and individual, that is, possibly genetic, influences on calling song may influence sexual communication in this species.

Crickets with extravagant mating songs compensate for predation risk with extra caution.

Modern models for the evolution of conspicuous male mating displays assume that males with conspicuous displays must bear the cost of enhanced predation risk. However, if males can compensate behaviourally for their increased conspicuousness by acting more cautiously towards predators, they may be able to lower this cost. In the field cricket Gryllus integer, males call to attract females, and differ in their durations of uninterrupted trilling (calling-bout lengths). Differences among males in calling-bout lengths are heritable, and females prefer males with longer calling bouts. In this study, males with longer, more conspicuous songs behaved more cautiously than males with shorter songs on two different tests of predator avoidance. They took longer to emerge from a safe shelter within a novel, potentially dangerous environment, and they ceased calling for a longer time when their calls were interrupted by a predator cue. Thus, these males appear to compensate behaviourally for their more conspicuous mating displays. Additionally, latencies to emerge from a shelter in the novel environment were consistent over time for both individual males from the field and males that had been reared in the laboratory, indicating that the differences in latency among males may be heritable.

Variance in female responses to the fine structure of male song in the field cricket, Gryllus integer

Although female mating preferences are a focus of current controversy, little detailed information exists on female preferences within natural populations. In the field cricket Gryllus integer, male calls attract sexually receptive females, and females preferentially move toward male calls with longer calling bouts (periods of calling containing no pause greater than 0.10 s in real time). This study investigated female preferences for other variables of the male song, including syllable period, chirp pause, and number of syllables per chirp. Male song was measured in the field to determine mean values for each variable in nature. Female preferences were determined using a locomotor-comp ensator device, on which females ran in response to sequential playbacks of synthesized male song. Mean female preferences corresponded roughly to mean male song variables. Nonetheless, females varied greatly in their responses to synthesized calls differing in syllable period, syllable number, and chirp pause. Moreover, individual females who were more selective for any one variable also tended to be more selective for others. These results show that females may differ from one another in their mating preferences and degrees of selectivity, even within a single population. Key words: crickets, female mating preferences, Gryllus integer, mate recognition, phonotaxis, song. [Behav Ecol 9:582-591 (1998)]

AN ELECTRONIC TECHNIQUE FOR MONITORING THE TEMPORAL ASPECTS OF ACOUSTIC SIGNALS OF CAPTIVE ORGANISMS

ABSTRACT We introduce an inexpensive electronic technique for monitoring the temporal aspects of any captive animal's acoustic signals. The electronic apparatus, attached to a data acquisition unit and personal computer, compares microphone output to a pre-set level and stores calling/non-calling data to disk. Total time calling and temporal signaling patterns of up to 256 individuals can be monitored for indefinite lengths of time. Sampling rate is adjustable, with a maximum rate of 6 samples/microphone/second. The capabilities of the system are illustrated with the field cricket Gryllus integer. Temporal aspects of acoustic signaling are discussed in terms of monitoring time scale and recognition of individual variation, energetics research, and hypothesis testing of the costs and benefits associated with mating success and predation.

Temporal patterns of parasitoid fly (Ormia ochracea) attraction to field cricket song (Gryllus integer)

Female flies, Ormia ochracea (Diptera, Tachinidae), orient to the calling song of the field cricket Gryllus integer (Orthoptera, Gryllidae) and deposit larvae that burrow into and consume the cricket host. Selection pressure from O. ochracea has probably been important in the evolution of male cricket songs and mating behaviour in G. integer and other cricket species. Tape-recorded G. integer calling song was broadcast to study the temporal rate of attraction of O. ochracea. Flies became phonotactic to cricket song approximately at sunset, and the highest level of attraction was observed in the following hours of the evening. Fly phonotaxis decreased in the hours immediately preceding sunrise and no flies were attracted during daylight hours. More male G. integer call at sunrise and in the preceding hours than earlier in the evening, perhaps in response to the lower probability of attracting O. ochracea.

Effects of a tachinid parasitoid, Ormia ochracea, on the behaviour and reproduction of its male and female field cricket hosts ( Gryllus spp)

The larvae of the tachinid parasitoid fly, Ormia ochracea, develop within the body of their host, the field crickets Gryllus integer and Gryllus rubens. The fly will also develop within the cricket Gryllus bimaculatus, which is not the natural host. For the first 3 days after entering a cricket, the first instar larvae grew inside the large thoracic muscles, but did little damage to the muscles during this time. They then migrated into the abdomen where they moulted, attached themselves to the body wall and fed primarily on the host's muscle and fat body, sparing the digestive system and CNS. Usually the host's reproductive system was only partially damaged. After the larvae entered the abdominal cavity, the host's mating, egg-laying and fighting ability (males) declined. This decline probably occurred due to the tissue damage wrought by the parasitoid. Less energy-demanding behaviours, such as grooming and feeding, were not affected during the entire period of infestation. During the first instar (when the parasitoid is embedded in the host's muscle), male crickets showed an increased tendency to attack other males. This increased incidence of agonistic behaviour occurred before the parasitoid caused significant tissue damage to the host and must therefore have been due to some other effect of the parasitoid.

The response of an insect parasitoid, Ormia ochracea (Tachinidae), to the uncertainty of larval success during infestation

Ormia ochracea is a parasitoid fly which lays its larvae on its hosts, the field crickets Gryllus integer and Gryllus rubens, in two distinct modes: (1) directly on the host and (2) around the host. In the field, 12.7% of male crickets were parasitized and 3.2% were super-parasitized. Despite the disadvantages of parasitizing infested hosts, there was no evidence that O. ochracea avoided superparasitism. This and other experiments suggest that the host assessment ability of O. ochracea is less than that reported for many hymenopteran parasitoids. by manipulating the number of larvae in each cricket, we determined that four to five larvae per host resulted in the largest number of adult flies. However, as larval number per host increased from one to six, pupal size, and hence adult size, declined. In the field, hosts were found with a mean of 1.7 ± 1.0 (SD) larvae per cricket, suggesting that there may be some selection pressure against larger clutch sizes. Nevertheless clutch sizes larger than the host can support were sometimes found in the field. During the first mode of larviposition, gravid flies deposited no more than three larvae directly onto the host. Larvae deposited directly on the host had a high probability of infesting it. During the second mode of larviposition, gravid flies laid a larger number of larvae around the host (6.1 ± 5.2). Larvae that were laid around the host were less likely to infest a cricket than were larvae that were deposited directly onto it. O. ochracea is unique in that its two different modes of larviposition have different probabilities of larval success. Even though the success rate for larvae laid during the second mode of larviposition was low, the possibility of parasitizing more hosts appears to have selected for flies laying more larvae (e.g. increasing clutch size) than is optimal if all the larvae successfully entered a single host.

Female Choice and the Heritability of Attractive Male Traits: An Empirical Study

Many authors have hypothesized that in mating systems in which males do not offer resources or parental care to their mates and/or offspring, female choice is based on heritable male traits. Although the validity of this hypothesis has been questioned on theoretical grounds, recent empirical evidence suggests that male traits preferred by females might be heritable. Moreover, models for the evolution of female choice incorporate the heritability of preferred male traits as a necessary assumption. Here, I test the hypothesis that preferred male traits are heritable, using quantitative genetics to measure the heritability of calling-bout length in male field crickets (Gryllus integer). Previous experiments showed that females of this species use the length of the males' calling bouts to discriminate among potential mates. In the present study, father-son regressions and full-sib correlations gave a mean estimated heritability of 74% for calling-bout length. These results demonstrate that male traits on whic...