Duetting Behaviour in the Leafhopper Aphrodes makarovi (Hemiptera: Cicadellidae)

Mate recognition and location in Cicadellidae is mediated exclusively via substrate-borne vibrational signals. In the present study we investigated vibrational signals and mate searching behaviour of the leafhopper Aphrodes makarovi. We studied mating behaviour and exchange of vibrational signals between live insects and in playback experiments. Males emitted long and complex calling signals composed of several sections. Female reply was long and always overlapped the end of the male call. The exchange of male and female vibrational signals was a complex and dynamic interaction during which both partners modified their signals according to partner’s reply. The duration of female reply was influenced by the duration of the male call to which she was responding, while the duration of male call was influenced by the duration of the previous female reply. Such relationship suggests the role of sexual selection in the evolution of male vibrational signals.     

The Influence of Age on Male Mate‐Searching Behaviour in Thornbug Treehoppers

One prediction from life‐history theory is that males should increase investment in reproductive effort as they age because the opportunity for future reproductive events declines. However, older males may not be able to increase their reproductive effort if condition declines with age. The effect of age‐related changes in condition may be especially important for energetically costly activities such as moving within and between habitat patches while searching for mates. Although such searching is a component of many mating systems, the relationship between age and active mate searching has not been investigated. We investigated whether mate‐searching effort increased with age in the thornbug treehopper, Umbonia crassicornis (Hemiptera: Membracidae). In this species, males search for females using a ‘fly‐call‐walk’ strategy consisting of three phases: (1) flying from one plant to another; (2) walking and signalling while on a plant; and (3) close‐range courtship of encountered females. We measured several aspects of mate‐searching behaviour over the month‐long period of a male’s reproductive lifetime. Over the relevant period of male sexual activity (19–33 d), male condition remained stable. However, older males (25–33 d) did not search more actively than younger males as predicted; instead, younger males (19 d) had greater plant‐to‐plant flight activity and found females faster. Within‐plant walking rates and courtship duration did not differ among age classes. These results suggest that thornbug males may be investing so heavily in mate searching at younger ages that they are unable to increase investment in searching effort when they get older. As a result, older males are likely to be at a competitive disadvantage when active searching is required to locate sparsely distributed females.     

The Effect of Variation in Male Sexually Dimorphic Traits on Female Behaviour in Pronghorn (Antilocapra americana)

Several sexually dimorphic morphological, behavioural, and territory characteristics of male pronghorn, Antilocapra americana, are highly variable. To test the hypothesis that females respond to variation among males for mate choice, I examined the relationship between these male characteristics and female congregation size and variability. Increased movement up to and during rut and differential female congregation on the territories of males with favoured characteristics were detected as predicted. Individual females increased their home ranges nearly fourfold from summer to rut and visited 88% of the territories in the study area. Female congregation size was related to male phenotype but not to territory characteristics. A canonical correlation analysis revealed that not only were several male traits simultaneously related to female congregation size and variability, but the importance of these traits varied across years. However, male courtship, cheek-patch size, and scent marking behaviours were consistently correlated to female congregation patterns across years. Female congregation was significantly related to male courtship, but there was no correlation between former territory owner's and newcomer's attraction of females. This finding is consistent with the hypothesis that females were primarily assessing males instead of territories.     

Effect of Post-Weaning Individual Housing on Autonomic Responses in Male Rats to Sexually Receptive Female Rats

Post-weaning individual housing induces significant alterations in the reward system of adult male rats presented with sexually receptive female rats. In this study, we examined the effects of post-weaning individual housing on autonomic nervous activity in adult male rats during encounters with sexually receptive female rats to assess whether different affective states depending on post-weaning housing conditions are produced. Changes in heart rate and spectral parameters of heart rate variability indicated that in post-weaning individually housed male rats, both sympathetic and parasympathetic activity increased with no change in the sympathovagal balance, while in post-weaning socially housed male rats, both sympathetic and parasympathetic activity decreased with a predominance of parasympathetic activity. These two patterns of shifts in sympathovagal balances closely resembled changes in autonomic nervous activity with regard to classical appetitive conditioning in male rats. The autonomic changes in male rats housed individually after weaning corresponded to changes associated with the reward-expecting state evoked by the conditioned stimulus, and the autonomic changes observed in male rats housed socially after weaning corresponded to changes associated with the reward-receiving state evoked by the unconditioned stimulus. These results suggest that different affective states were induced in adult male rats during sexual encounters depending on male–male social interactions after weaning. The remarkable change caused by post-weaning individual housing may be ascribed to alteration of the reward system during sexual encounters induced by deficiency of intermale social communication after weaning.     

Glandular Trichomes on Alfalfa Impede Searching Behavior of the Potato Leafhopper Parasitoid

New cultivars of alfalfa, Medicago sativa L., have been released with glandular trichomes for resistance to potato leafhopper, Empoasca fabae (Harris). Yet, the impact of the glandular trichomes on the primary natural enemy of the leafhopper, Anagrus nigriventris Girault, is unknown. We compared the host searching behavior of the egg parasitoid on four alfalfa clones varying in trichome characters. Female wasps were videotaped on Ranger, a susceptible clone with relatively sparse trichomes, B14, a resistant clone with dense but nonglandular trichomes, and FG12 and FG18, two resistant clones with glandular trichomes. Although the number of leafhopper eggs per stem exposed to wasps did not significantly differ among the four clones, the frequency of foraging and total foraging time were less on the two clones with glandular trichomes than on the two clones with nonglandular trichomes. In addition, an analysis of covariance demonstrated that, although the number of ovipositional probes increased with egg density on a stem, the number of probes on stems with glandular trichomes was significantly less than that on stems without glandular trichomes. The allocation of time by wasps among drumming, probing, and grooming behaviors was similar among the clones. Wasps tended to fly off of clones with glandular trichomes more often than off of clones with nonglandular trichomes. This study suggests that cultivars with glandular trichomes may interfere with host searching by A. nigriventris.     

Involvement of Ethylene Biosynthesis and Signalling in the Transition from Male to Female Flowering in the Monoecious Cucurbita pepo

It is well established that ethylene is the main hormonal regulator of sexual expression in the Cucurbitaceae family, controlling not only the sexual fate of individual floral buds, but also the female flower transition, that is, the time at which the first female flower appears and therefore the number of female flowers per plant. Although sex determination of individual flower buds is known to be controlled by specific ethylene biosynthesis ACS genes in melon and cucumber, the role of ethylene genes in the control of the transition to female flowering is still unknown. We have identified two contrasting monoecious inbred lines of Cucurbita pepo, Bolognese (Bog) and Vegetable spaghetti (Veg), which differ in female flower transition but not in flower development. In Bog, which is very sensitive to ethylene, the transition to female flowering is very early, whereas in Veg, which is much less sensitive to ethylene, the transition occurs much later. In this article we compare the production of ethylene and the expression profiles of seven genes involved in the biosynthesis, perception, and signalling of ethylene in the two contrasting lines. Bog, with earlier female flower transition, showed higher ethylene production and CpACO1 expression in the apex at an earlier stage of plant development, when Bog is already producing female flowers, but Veg has not transitioned to female flowering yet. Moreover, the expression of the ethylene receptor and CTR-like genes in the apex of Veg and Bog plants indicates that these genes negatively regulate female flower transition during the earlier stages of plant development. The earlier transition to female flowering in Bog is not only associated with a higher production of ethylene in the apex but also with a premature decline of ethylene negative regulators (receptors and CTR-like) in the apex of the plant. These results provide the basis for a model that explains the regulation of female flowering transition in monoecious cucurbits.     

Regulation of Chorusing in the Vibrational Communication System of the Leafhopper Graminella nigrifrons

Male Graminella nigrifrons participate in alternating choruses.Vibrational calls emitted by males consist of three sections(S1, S2, and S3) that differ in pattern of amplitude modulation.In this study we examined the response of single males to syntheticchoruses and to isolated call components to gain insight intothe regulation of chorus structure. Males initiated calls primarilyduring the silent periods within synthetic choruses. In all15 trials the number of overlapping calls and the duration ofoverlap was significantly less than expected if males call atrandom. Playback of S2, S3, or random noise while males emittedS1 caused males to interrupt calling, whereas males continuedto call when S1 or no signal was played. In a related experiment,we played S2 or no signal while males were beginning to emitthe S1, S2, or S3 phase of their calls. In response to thisplayback the duration of S1 and S3 was reduced, but the durationof S2 was not affected. These results suggest that an inhibitory-resettingmechanism may result in alternation of calls in this leafhopper.     

Male Courtship Pheromones Affect Female Behaviour in the Swordtail Characin (Corynopoma riisei)

Pheromones constitute an important cue used by both males and females during courtship. Here, we investigate the effect of male pheromones on female behaviour in the swordtail characin (Corynopoma riisei), a species of fish where males have a caudal pheromone gland which has been suggested to affect female behaviour during courtship. We subjected female C. riisei to male courtship pheromones and investigated the effect on both female behaviour and brain serotonergic activity levels compared to a control group. While no difference in serotonergic activity was found, the pheromone‐treated females showed lower stress levels compared to the control group. Furthermore, pheromone‐treated females increased locomotor activity over time, while a decrease in locomotor activity was observed in the control group. These results suggest that the male courtship pheromones may serve to reduce female stress and increase female activity, possibly to aid males in gaining access to females and facilitating sperm transfer.     

The Effect of Social Stress on Chronic Pain Perception in Female and Male Mice

The current investigations on social stress primarily point to the negative health consequences of being in a stressful social hierarchy. The repetitive nature of such stressors seems to affect behavioral response to pain both in rodents and humans. Moreover, a large discrepancy in the possibility of social stresses affecting pain perception in the two genders exists. The present study examined the effect of chronic social stress on nociceptive responses of both sexes by implementing of food deprivation, food intake inequality and unstable social status (cage-mate change every 3 days) for a period of 14 days in 96 Balb/c mice. In this regard we injected 20 µl formalin 2% into the plantar surface of hind paw at the end of stress period and scored pain behaviors of all subjects, then serum concentrations of proinflammatory cytokines were measured. Our results showed that there was significant difference in chronic phase of formalin test following implementation of food deprivation and inequality (P<0.05) as compared to control group, so that pain perception was decreased considerably and this decline in inequality exposed subjects was well above isolated ones (P<0.05); whereas unstable social situation did not affect pain perception. Moreover, IL-1 and IL-6 concentrations in serum of stressed mice of both genders were well above control group (p<0.05). Finally, despite chronic pain perception in control and unstable male subjects was larger than females; the decrease of chronic pain perception in male stressed animals (poverty and inequality experienced subjects) was much more than stressed females. These results revealed that although food deprivation and social inequality can induce hypoalgesia, some socioeconomic situations like social instability don''t affect pain sensation, whereas there were similar increases of proinflammatory cytokines level in all socially stressed subjects. In addition, males display larger hypoalgesic responses to inequality as compared with females.     

Effect of the Min System on Timing of Cell Division in Escherichia coli

In Escherichia coli the Min protein system plays an important role in positioning the division site. We show that this system also has an effect on timing of cell division. We do this in a quantitative way by measuring the cell division waiting time (defined as time difference between appearance of a division site and the division event) and the Z-ring existence time. Both quantities are found to be different in WT and cells without functional Min system. We develop a series of theoretical models whose predictions are compared with the experimental findings. Continuous improvement leads to a final model that is able to explain all relevant experimental observations. In particular, it shows that the chromosome segregation defect caused by the absence of Min proteins has an important influence on timing of cell division. Our results indicate that the Min system affects the septum formation rate. In the absence of the Min proteins this rate is reduced, leading to the observed strongly randomized cell division events and the longer division waiting times.     

Acoustic Monitoring Reveals Congruent Patterns of Territorial Singing Behaviour in Male and Female Tropical Wrens

Many animals defend territories against conspecific individuals using acoustic signals. In birds, male vocalizations are known to play a critical role in territory defence. Territorial acoustic signals in females have been poorly studied, perhaps because female song is uncommon in north‐temperate ecosystems. In this study, we compare male vs. female territorial singing behaviour in Neotropical rufous‐and‐white wrens Thryothorus rufalbus, a species where both sexes produce solo songs and often coordinate their songs in vocal duets. We recorded free‐living birds in Costa Rica using an eight‐microphone Acoustic Location System capable of passively triangulating the position of animals based on their vocalizations. We recorded 17 pairs of birds for 2–4 consecutive mornings and calculated the territory of each individual as a 95% fixed kernel estimate around their song posts. We compared territories calculated around male vs. female song posts, including separate analyses of solo vs. duet song posts. These spatial analyses of singing behaviour reveal that males and females use similarly sized territories with more than 60% overlap between breeding partners. Territories calculated based on solo vs. duet song posts were of similar size and similar degrees of overlap. Solos and duets were performed at similar distances from the nest for both sexes. Overall, male and female rufous‐and‐white wrens exhibit very similar spatial territorial singing behaviour, demonstrating congruent patterns of male and female territoriality.     

Genotype-by-Environment Interactions for Female Mate Choice of Male Cuticular Hydrocarbons in Drosophila simulans

Recent research has highlighted the potential importance of environmental and genotype-by-environment (G×E) variation in sexual selection, but most studies have focussed on the expression of male sexual traits. Consequently, our understanding of genetic variation for plasticity in female mate choice is extremely poor. In this study we examine the genetics of female mate choice in Drosophila simulans using isolines reared across two post-eclosion temperatures. There was evidence for G×Es in female choosiness and preference, which suggests that the evolution of female mate choice behaviour could differ across environments. However, the ranked order of preferred males was consistent across females and environments, so the same males are favoured by mate choice in spite of G×Es. Our study highlights the importance of taking cross-environment perspectives in order to gain a more comprehensive understanding of the operation of sexual selection.     

A Test of the Effect of Male Song on Female Nesting Behaviour in the Serin (Serinus serinus): a Field Playback Experiment

It is well established, through laboratory experiments, that male song in birds can stimulate female reproductive activity, affecting their behaviour and physiology, such as follicular growth, nest building and egg‐laying. However no clear demonstration has yet been provided that this effect works under natural conditions. Previous work in natural populations of serins showed that female nest‐building behaviour correlated with male singing time. Furthermore male serin song peaked exactly in the day that rapid follicular growth was estimated to start in females, suggesting that in this species song may also serve to stimulate the female's reproductive development. Direct causal evidence, however, was lacking. We conducted field playback experiments to investigate how song can influence female nesting activity during nest building. Our results show that females who listened daily to playbacks of serin songs, during the nest‐building stage, spent more time nest building than females that were not exposed to additional songs. Moreover, the singing behaviour of the mated males was not affected by the playbacks, suggesting that the song playback treatment had a direct positive effect on female nesting behaviour.     

Natural Variation in the Strength and Direction of Male Mating Preferences for Female Pheromones in Drosophila melanogaster

Many animal species communicate using chemical signals. In Drosophila, cuticular hydrocarbons (CHCs) are involved in species and sexual identification, and have long been thought to act as stimulatory pheromones as well. However, a previous study reported that D. melanogaster males were more attracted to females that were lacking CHCs. This surprising result is consistent with several evolutionary hypotheses but is at odds with other work demonstrating that female CHCs are attractive to males. Here, we investigated natural variation in male preferences for female pheromones using transgenic flies that cannot produce CHCs. By perfuming females with CHCs and performing mate choice tests, we found that some male genotypes prefer females with pheromones, some have no apparent preference, and at least one male genotype prefers females without pheromones. This variation provides an excellent opportunity to further investigate the mechanistic causes and evolutionary implications of divergent pheromone preferences in D. melanogaster males.     

Low Incidence of Miscarriage Induced by the Scent of Male Littermates of Original Mates: Male Kinship Reduces the Bruce Effect in Female Mice,Mus musculus

The scent of a novel male can elicit pregnancy block in recently mated female mice (Mus musculus), a phenomenon known as the Bruce effect. Despite abundant literature on the Bruce effect in rodents, it remains unclear whether males related to a female’s original mate can induce the Bruce effect in out-bred, communally living mice. We investigated this question using Kunming (KM) male mice of varying genetic relatedness. Recently mated females were subjected to three treatments: exposure to the urine of the mate, urine of the mate’s male littermate, and urine of a male unrelated to the mate. It was found that the urine of male littermates of the females’ mates did not elicit more pregnancy block than that of the females’ mates. However, the urine of novel males caused a higher rate of female miscarriage than that of the females’ mates. By using a habituation-dishabituation paradigm, we found that unmated females could discriminate the urine scents of two male littermates from those of a novel male unrelated to the littermates. To understand how females use urinary cues to discriminate between males with different genetic relationships, we used gas chromatography coupled with mass spectrometry (GC-MS) to examine the volatile composition of urine from males with varying relatedness. It was found that KM male littermates shared similar volatile compositions in their urine. Our results suggest that male kinship reduces the Bruce effect in female KM mice, and provide additional evidence for mate choice being partly mediated by the Bruce effect in KM mice.     

Preference for Male Traits Differ in Two Female Morphs of the Tree Lizard,Urosaurus ornatus

Non-random female mating preferences may contribute to the maintenance of phenotypic variation in color polymorphic species. However, the effect of female preference depends on the types of male traits used as signals by receptive females. If preference signals derive from discrete male traits (i.e., morph-specific), female preferences may rapidly fix to a morph. However, female preference signals may also include condition-dependent male traits. In this scenario, female preference may differ depending on the social context (i.e., male morph availability). Male tree lizards (Urosaurus ornatus) exhibit a dewlap color polymorphism that covaries with mating behavior. Blue morph males are aggressive and defend territories, yellow males are less aggressive and defend smaller territories, and orange males are typically nomadic. Female U. ornatus are also polymorphic in dewlap color, but the covariation between dewlap color and female behavior is unknown. We performed an experiment to determine how female mate choice depends on the visual and chemical signals produced by males. We also tested whether female morphs differ in their preferences for these signals. Female preferences involved both male dewlap color and size of the ventral color patch. However, the female morphs responded to these signals differently and depended on the choice between the types of male morphs. Our experiment revealed that females may be capable of distinguishing among the male morphs using chemical signals alone. Yellow females exhibit preferences based on both chemical and visual signals, which may be a strategy to avoid ultra-dominant males. In contrast, orange females may prefer dominant males. We conclude that female U. ornatus morphs differ in mating behavior. Our findings also provide evidence for a chemical polymorphism among male lizards in femoral pore secretions.     

Effects of Eavesdropping on Subsequent Signalling Behaviours in Male Canaries

Signalling interactions could provide information for an observing third party. This behaviour has been labelled as eavesdropping. Studies on eavesdropping in birds have concerned only few species and have mainly been conducted in the wild. Our experiment was designed to evaluate the effects of eavesdropping on subsequent interactions in male canaries in a controlled laboratory context. The experiment had two stages: a presentation stage and a test stage. During the presentation stage, subjects heard three different interaction types: an alternating interaction, an overlapping interaction or two song sequences presented separately one after the other, i.e. without interaction. Then during the test stage, subjects were allowed to listen to the songs previously heard separately. We noted calls emitted by subjects during the two stages. During the presentation stage, responses of male canaries did not differ according to the type of interaction they could hear. During the test stage, we found a clear effect of the song status on the calls emitted by subjects. They emitted less calls during the songs of the winner than during all other songs. Surprisingly, subjects also produced intermediate responses by emitting fewer calls during the second song previously heard during the presentation phase, and during the song of the looser when compared to the three other songs. Our results show that male canaries obtain information on the relative threat from an overlapping interaction whereas an alternating interaction does not seem to provide any kind of relative information on singers' status. In following encounters, the higher the potential threat of a singer was, the less the subjects emitted calls, probably to avoid the more serious rival. This inhibiting effect is discussed.