Female fecundity and offspring survival are not increased through sexual cannibalism in the spider Larinioides sclopetarius

Many hypotheses explaining the evolution and maintenance of sexual cannibalism incorporate the nutritional aspect of the consumption of males. Most studies have focused on a fecundity advantage through consumption of a male; however, recent studies have raised the intriguing possibility that consumption of a male may also affect offspring quality. In particular, recent studies suggest prolonged survival for offspring from sexually cannibalistic females. Here, we measured the protein and lipid content of males compared to insect prey (crickets), quantified female nutrient intake of both prey types and finally assessed how sexual cannibalism affects female fecundity and spiderling quality in the orb‐web spider Larinioides sclopetarius. We found no evidence that sexual cannibalism increased fecundity when compared to a female control group fed a cricket. Contrary to previous studies, spiderlings from females fed a male showed reduced survival under food deprivation compared to spiderlings from the control group. Offspring from females fed a male also tended to begin web construction sooner. The low lipid content of males compared to crickets may have reduced offspring survival duration. Whether additional proteins obtained through consumption of a male translate to enhanced silk production in offspring requires further investigation.     

Sexual cannibalism in the garden spider Araneus diadematus

In natural populations, courting males of Araneus diadematus are often consumed by females before they have successfully copulated. Despite the possible nutritional benefits of sexual cannibalism for females, the male can derive no benefit by being consumed before copulation. In this study, females that consumed a single male significantly increased their body mass, regardless of the quality of their diet. The implication is that, for A. diadematus, sexual cannibalism increases female fecundity. In experimentally controlled courtship sequences, larger males were less likely to be cannibalized than smaller males, but female size had no effect on male mating success. The mating success of males was not influenced by the age of the male, indicating that cannibalism is not the results of male senility.     

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.     

Sex,death, and genetic variation: natural and sexual selection on cricket song

Male field crickets, Gryllus integer, in Texas, USA, produce a trilled calling song that attracts female crickets, resulting in enhanced mating success. Gravid female parasitoid flies, Ormia ochracea, are also attracted to male cricket calling song, resulting in the death of the male within about seven days. Using playbacks of field-cricket calling song in the natural habitat, we show that both female crickets and female parasitoid flies prefer male calling song with average numbers of pulses per trill. Thus female crickets exert stabilizing sexual selection, whereas flies exert disruptive natural selection on male song. Disruptive natural selection will promote genetic variation and population divergence. Stabilizing sexual selection will reduce genetic variation and maintain population cohesiveness. These forces may balance and together maintain the observed high levels of genetic variation (ca. 40%) in male calling song.     

Female nursery web spiders (Pisaurina mira) benefit from consuming their mate

The often coincidental involvement of cooperation and conflict in animal reproduction is epitomized by sexual cannibalism, which can lead to obvious male costs while simultaneously providing direct benefits to developing offspring. Male nursery web spiders (Pisaurina mira) avoid postcopulatory sexual cannibalism by wrapping females with silk. Here, we test the hypothesis that this silk wrapping results in a loss of consumption cost for females. In specific, we hypothesize that females lose out on potential fitness benefits associated with cannibalizing their mating partners. To test this, we paired females with males that were experimentally manipulated to prevent the silk wrapping of females, thereby increasing the likelihood of sexual cannibalism. Females either did not kill their mate, and thus consumed nothing, or did kill their mate. If females killed their mating partner, we allowed them to consume the male, consume nothing, or consume a cricket. We found no effect of female or male body sizes on the likelihood of females killing their mate. While our treatments did not affect the number of offspring females produced, females that consumed either a male or a cricket produced egg sacs faster than females that consumed nothing, suggesting a benefit of increased postcopulatory food consumption. Further, only females that ate a male had heavier and longer lived offspring, suggesting a benefit of sexual cannibalism specifically. Our results support the hypothesis that females can receive fitness benefits associated with sexual cannibalism.     

Does a single meal affect female reproductive output in the sexually cannibalistic praying mantid Iris oratoria?

1. One explanation of the evolution of sexual cannibalism, the female’s consumption of a male during or following courtship or copulation, is that this behaviour increases the female’s fitness. This study tests the assumption that a single meal increases female reproductive output significantly in the sexually cannibalistic praying mantid Iris oratoria L. 2. In 38 mating trials, seven of the females cannibalised the males. In order to augment the number of females that fed, an additional nine females were each fed one cricket nymph at the end of the mating trial. 3. Three measures of female reproductive output – the occurrence of oviposition, the mass of the first ootheca, and the number of eggs in the first ootheca – increased significantly with female feeding condition, which was a reflection of food consumed before the mating trial. Females that copulated later in the season tended to lay lighter oothecae. 4. The females’ consumption of a meal during the mating trial, either a conspecific male or a cricket, did not influence any measure of reproductive output significantly, although possible effects upon subsequent oothecae cannot be ruled out. 5. If, as the present study suggests, a single meal provides a negligible or delayed benefit to female reproductive output, the evolution of sexual cannibalism might lie in alternative explanations, which include possible fitness benefits to cannibalistic females in the nymphal stage or possible paternity benefits to the cannibalised males.     

Convergent song preferences between female field crickets and acoustically orienting parasitoid flies

Traits that increase the attractiveness of males to femalesoften make them more conspicuous to predators. In the fieldcricket (Gryllus lineaticeps), males are attacked by parasitoidtachinid flies (Ormia ochracea) that locate males through theircalls. Female flies larviposit on crickets and the larvae burrowinto and feed on the cricket, killing the cricket upon emergence.To determine whether traits preferred by females increase amale's risk of attracting a predator, I examined the effectof variation in male singing behavior on mate and predator attraction.Both female crickets and female flies preferred male callingsongs with higher chirp rates, longer chirp durations, and higherchirp amplitudes. In addition, both female crickets and femaleflies preferred male calling songs with higher chirp rates andlonger chirp durations, even when these songs were of loweramplitude. These results suggest that sexual selection by femalechoice will favor the evolution of higher chirp rates and longerchirp durations. However, call types that increase a male'sattractiveness to females also appear to increase a male's riskof attracting parasitoids. Sexual and natural selection appearto have opposing effects on the evolution of male singing behaviorin this species.[Behav Ecol 7: 279-285 (1996)]     

Abdominal Tubercles of Adult Male Camel Crickets, Pristoceuthophilus marmoratus Rehn (Orthoptera: Rhaphidophoridae), Produce Cues Attractive to Females

In contrast to many crickets and katydids, adult male camel crickets (Orthoptera: Raphidophoridae) do not stridulate and do not produce audible air-borne calling songs to attract females for mating. The mating behavior of most camel cricket species is undescribed; how pair-formation occurs is unknown, but chemical cues seem one likely possibility. In the camel cricket Pristoceuthophilus marmoratus Rehn, we test (1) the role of chemical cues in conspecific attraction, and (2) the role of the abdominal tubercles of adult males in producing those cues. We show (1) that virgin adult females are attracted to paper towels previously exposed to adult males, and (2) that paper towels previously exposed to adult males with exposed tubercles are more attractive than paper towels previously exposed to adult males with experimentally closed tubercles. In addition, we present Scanning Electron Microscope photos of adult male tubercle structure that are consistent with their putative role in producing chemical cues.     

Female crickets assess relatedness during mate guarding and bias storage of sperm towards unrelated males

Recent evidence shows that females exert a post‐copulatory fertilization bias in favour of unrelated males to avoid the genetic incompatibilities derived from inbreeding. One of the mechanisms suggested for fertilization biases in insects is female control over transport of sperm to the sperm‐storage organs. We investigated post‐copulatory inbreeding‐avoidance mechanisms in females of the cricket Teleogryllus oceanicus. We assessed the relative contribution of related and unrelated males to the sperm stores of double‐mated females. To demonstrate unequivocally that biased sperm storage results from female control rather than cryptic male choice, we manipulated the relatedness of mated males and of males performing post‐copulatory mate guarding. Our results show that when guarded by a related male, females store less sperm from their actual mate, irrespective of the relatedness of the mating male. Our data support the notion that inhibition of sperm storage by female crickets can act as a form of cryptic female choice to avoid the severe negative effects of inbreeding.     

Cuticular lipids and odors induce sex-specific behaviors in the male cricket Gryllus bimaculatus

Male crickets display sex-specific (e.g., mating and agonistic) behaviors towards conspecific individuals. One of the key signals for these behaviors is the chemical substance on the cricket body surface. In the present study, we analyzed female and male cuticular substances in behavioral assays. Antennal contact stimulation using female forewings elicited a mating behavior in males, while that using male forewings elicited an agonistic behavior in males. Thin-layer-chromatographic and other techniques analysis showed that saturated cuticular lipids were present in both female and male cuticles and that unsaturated lipids were present only in the male cuticle. Filter papers soaked with saturated or unsaturated cuticular lipids were applied to antennae of male crickets. Males showed mating behavior in response to stimulation with saturated lipids from both females and males but showed avoidance behavior in response to stimulation with male unsaturated lipids. Because cuticular lipids did not induce agonistic behavior in males, we collected odors from male crickets and found that these odors induced agonistic behavior in males. Therefore, we concluded that the key signals for mating, avoidance and agonistic behaviors of male crickets are comprised of at least three different components, saturated and unsaturated cuticular lipids and male odors, respectively.     

Calls of Recently Introduced Coquí Frogs Do Not Interfere with Cricket Phonotaxis in Hawaii

Acoustically-signaling animals such as crickets may experience interference from environmental noise, a particular concern given the rise in anthropogenic or other novel sources of sound. We examined the potential for acoustic interference of female phonotaxis to calling song in the Pacific field cricket (Teleogryllus oceanicus) by invasive coqui frogs (Eleutherodactylus coqui) in Hawaii. The frogs were introduced to Hawaii from Puerto Rico in the 1980s. When female crickets were exposed to male calling songs with and without simultaneous broadcast of a coqui chorus, they were equally likely to move toward the cricket song, regardless of the location of the frog sound (ground level or above ground). Unlike some species of frogs and birds, T. oceanicus do not appear to experience acoustic interference from an introduced signaler, even though the introduced species’ calls subjectively seem to be masking the crickets’ songs.     

Jamaican Field Cricket Mate Attraction Signals Provide Age Cues

Older males often have a mating advantage, either resulting from the fact that they live longer or resulting from the fact that they both live longer and signal this to females. Male field crickets signal acoustically to attract potential mates. Some field cricket mating signals provide cues about male age while others do not. We explored whether male Jamaican field crickets, Gryllus assimilis, mating signals change with age. Our results show that older males produce chirps with longer pulses, more pulses, at higher pulse and chirp rates, and their chirps are both longer and louder than those produced by younger males. Our findings suggest that Jamaican field cricket mating signals provide cues about male age, explaining between 10% and 54% of the variation in signaling traits. Females might be able to use these mating signal differences to distinguish between older and younger mates.     

Seasonal Variation in Female Response to Male Calling Song in the Field Cricket, Gryllus rubens

Conspicuous traits that make males attractive to females may make them vulnerable to predators. Females that approach conspicuous males may increase their risk of predation. This means that selection for reduced male conspicuousness in the presence of predators may be due to sexual selection resulting from altered female behavior in the face of increased predator risk. We examine this hypothesis in the field cricket, Gryllus rubens, in which male calling song attracts both conspecific females for mating and parasitoid flies (Ormia ochracea) which kill their hosts within a week. Female crickets are also parasitized by these flies as a result of associating with calling males. In northern Florida crickets that emerge in the spring are not subject to fly parasitism whereas autumn crickets encounter large numbers of flies. We predicted that autumn females should be less attracted to male song than spring females. We tested female response to male calls in a rectangular arena in which male calling song was broadcast from a speaker. Spring females readily approached the speaker but autumn females were less likely to approach and remain in the vicinity of the speaker. These results emphasize the importance of considering how risk affects the evolution of conspicuous male behavior both directly through its effect on the male and indirectly through its effect on female responses to males.     

Haemolymph juvenile hormone III esterase activity during adult life of female and male crickets,Gryllus bimaculatus de Geer (Ensifera,Gryllidae)

Using an in vitro method, juvenile hormone III degradation was studied in the plasma of adult female and male crickets, Gryllus bimaculatus. The primary route of juvenile hormone III metabolism in cricket haemolymph is ester hydrolysis to juvenile hormone III acid by juvenile hormone III esterase. Juvenile hormone III esterase activity in females' haemolymph is low just after imaginal moulting. A sharp peak of enzyme activity is observed on day 3 after emergence, and two subsequent peak values occur in older animals. Plasma juvenile hormone III esterase activity in freshly ecdysed males is also low, but increases rapidly thereafter. Another increase in enzyme activity is observed in older males. The fluctuations in juvenile hormone III esterase activity are discussed in correlation with changes in haemolymph volume, haemolymph protein content, haemolymph juvenile hormone III titer, and the rates of juvenile hormone III biosynthesis in vitro of the corpora allata.     

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。     

Male hosts are responsible for the transmission of a trophically transmitted parasite, Pterygodermatites peromysci, to the intermediate host in the absence of sex-biased infection

Field studies have identified that male-biased infection can lead to increased rates of transmission, so we examined the relative importance of host sex on the transmission of a trophically transmitted parasite (Pterygodermatites peromysci) where there is no sex-biased infection. We experimentally reduced infection levels in either male or female white-footed mice (Peromyscus leucopus) on independent trapping grids with an anthelmintic and recorded subsequent infection levels in the intermediate host, the camel cricket (Ceuthophilus pallidipes). We found that anthelmintic treatment significantly reduced the prevalence of infection among crickets in both treatment groups compared with the control, and at a rate proportional to the number of mice de-wormed, indicating prevalence was not affected by the sex of the shedding definitive host. In contrast, parasite abundance in crickets was higher on the grids where females were treated compared with the grids where males were treated. These findings indicate that male hosts contribute disproportionately more infective stages to the environment and may therefore be responsible for the majority of parasite transmission even when there is no discernable sex-biased infection. We also investigated whether variation in nematode length between male and female hosts could account for this male-biased infectivity, but found no evidence to support that hypothesis.     

Male mating behaviour reduces the risk of sexual cannibalism in an Australian praying mantid

In cases where sexual cannibalism represents a sexual conflict, we should expect to find male traits that reduce the risk of cannibalism. In fact, a wide variety of such traits have been proposed, including elaborate courtship displays, cautious approach behaviours, and opportunistic mating whilst a female is feeding. However, there is very little direct evidence that these behaviours actually reduce the risk of sexual cannibalism for males, and the evidence that does exist comes mainly from spider studies. In this study of Pseudomantis albofimbriata praying mantids we found evidence of various male behaviours that reduced the risk of sexual cannibalism. Most males attempted to avoid detection entirely and others moved in a slow and stealthy manner. We also observed five cases of opportunistic mating, but saw no evidence of any male courtship routine. It seems that mounting from the rear of a female or slowly approaching her from the front, allows many males to go unnoticed and, therefore, substantially reduces the risk of sexual cannibalism in this mating system. Interestingly, we could not identify any female traits that males use to assess the risk of sexual cannibalism. It may be that P. albofimbriata males use alternative means to assess these risks. The presence of these behavioural strategies by males suggests a net cost of being consumed, and that sexual cannibalism is likely to be a female strategy in this system.     

Agonistic behavior and electrical stimulation of the antennae induces Fos‐like protein expression in the male cricket brain

Immediate early genes (IEG) such as c‐Fos and Fos‐related antigens (FRA) have been used as markers of neuronal activation. In this study, we determined whether the expression of c‐Fos/FRAs is increased in the brains of adult male Acheta domesticus crickets following agonistic interactions. We looked for c‐Fos/FRA proteins in the brain of un‐fought, control male crickets and of dominant and subordinate male crickets sacrificed at different time periods following an agonistic interaction. Using immunoblot analysis, we found four different c‐Fos/FRA‐like proteins in the adult cricket brain. Continuous agonistic interaction increased c‐Fos/FRA protein expression in the brains of subordinate males compared to control and dominant males. In addition, direct electrical stimulation of the male cricket antennae increased c‐Fos/FRA‐like protein in the brain. We identified the specific brain regions that exhibit c‐Fos/FRA‐like immunoreactivity in crickets. We detected c‐Fos/FRA‐like cellular immunoreactivity in different functional regions of the adult brain including the pars intercerebralis, protocerebrum, deutocerebrum, and the cortex of the mushroom bodies. © 2010 Wiley Periodicals, Inc.     

Ecdysone metabolism in adult crickets,Gryllus bimaculatus

The fate of injected [³H]ecdysone has been investigated in female and male adults of the Mediterranean field cricket, Gryllus binaculatus (de Geer). The metabolism is similar in both sexes and at various stages of adult life. Several classes of apolar metabolites (A1–A5) represent the major compounds. The amount of polar conjugates is low in all tissues, as are the concentrations of 20-hydroxyecdysone. Ovaries are the only organs capable of storing considerable amounts of ecdysteroids. The amount of radiolabelled ecdysteroid activity (mostly [³H]ecdysone) excreted during the first 24 hr after injection is high.The chemical identity of the apolar metabolites is not yet known. A2, which is the major apolar compound, has recently been identified as a complex of ecdysone conjugates with abundant long-chain fatty acids (Hoffman et al., 1985 Life Sci.37, 185–192). Incubations with tissue homogenates in vitro have shown that several organs are capable of converting ecdysone into apolar compounds. Apolar ecdysteroid acyl esters represent a newly identified class of ecdysone conjugates from insects. Their role in regulation of free ecdysteroid titres during the reproductive period in female crickets is discussed.     

Divergent Preferences for Song Structure between a Field Cricket and its Phonotactic Parasitoid

In many animals, males produce signals to attract females for mating. However, eavesdropping parasites may exploit these conspicuous signals to find their hosts. In these instances, the strength and direction of natural and sexual selection substantially influence song evolution. Male variable field crickets, Gryllus lineaticeps, produce chirped songs to attract mates. The eavesdropping parasitoid fly Ormia ochracea uses cricket songs to find its hosts. We tested female preferences for song structure (i.e., chirped song vs. trilled song) in crickets and flies using choice experiments. Female crickets from a parasitized and a non-parasitized population significantly preferred the species-typical chirped song, whereas flies significantly preferred a trilled song, which is expressed by other hosts in different regions. Sexual selection due to female choice and natural selection due to fly predation both appear to favor the chirped song structure of G. lineaticeps in the parasitized population, whereas sexual selection favors the chirped structure in the non-parasitized population.