Flower-feeding affects mating performance in male oriental fruit flies Bactrocera dorsalis

1. Males of the oriental fruit fly Bactrocera dorsalis are attracted to and feed on flowers of the golden shower blossom Cassia fistula. Flowers of this plant contain methyl eugenol, the metabolites of which apparently function in the synthesis of male sex pheromone. 2. The goal of the study reported here was to determine whether feeding on C. fistula flowers enhanced male mating success. Mating frequencies of unfed (control) and fed (treated) males were compared in trials conducted 0 (same day), 2, 7, or 21 days after treated males were exposed to the flowers. Trials were performed using flowers from three trees of C. fistula to investigate whether the effects of floral feeding were similar among different plants. 3. For all three trees, treated males accounted for a disproportionately large number of matings in trials performed 0, 2, and 7 days after floral feeding by the treated males. For two of the trees, treated males also had a mating advantage 21 days after flower‐feeding. 4. Additional tests were conducted to compare female attraction to perch sites of control and treated males. When at a lek, males exhibit rigorous wing‐fanning behaviour, presumably to increase dispersal of the sex pheromone. Floral feeding had no significant effect on the level of wing‐fanning. Significantly more female sightings were recorded for perches of treated than control males, however, suggesting that the treated males produced a pheromone more attractive to females than did control males.     

Effect of orange peel substances on mating competitiveness of male Ceratitis capitata

The response of wild Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) males to orange peel chemicals and their effect in mating competitiveness of males exposed to these chemicals was studied in the laboratory (25±2 °C, 65±5%, r.h.). Males were attracted, landed, and arrested on ripe oranges that were superficially wounded in the flavedo region of the peel, and fed on the wounds. Exposure to wounded oranges conferred to males a mating advantage over unexposed males. In flies of 1 to 10 days of age, this advantage was independent of the age of the flies during exposure and lasted at least 10 days following exposure. Twenty-four hours of exposure ensured this effect. Exposure to intact oranges, or to wounded oranges covered with a wire-screen, which allowed olfactory response and landing on the screen but not direct contact with the fruit, did not confer any mating advantage. Apparently, males required direct contact with wounded oranges in order to increase their mating competitiveness. It is suggested that the acquisition of certain substances of the flavedo, most probably through their ingestion, is responsible for the observed phenomenon. Our findings are discussed in relation to the sexual behaviour of this fly. Implications of these findings for the enhancement of the mating competitiveness of released sterile males and of the effectiveness of the Sterile Insect Technique programs are discussed as well.     

Exposure to Orange (Citrus sinensis L.) Trees, Fruit, and Oil Enhances Mating Success of Male Mediterranean Fruit Flies (Ceratitis capitata [Wiedemann])

Previous laboratory tests revealed that exposure to oranges (Citrus sinensis L.) increased the mating success of male Mediterranean fruit flies, Ceratitis capitata (Wiedemann) (medfly). This advantage may have resulted from male exposure to -copaene (a sesquiterpene hydrocarbon and known male attractant) in the peel, as pure -copaene has been shown to increase the mating success of male medflies. Working with orange trees as well, we investigated whether male exposure to nonfruiting trees, leaves (also known to contain -copaene albeit at a lower concentration than fruit), and fruit conferred a mating advantage to wild-like males in field-cage tests. Males exposed to entire nonfruiting trees or leaves had a mating advantage over control males (exposed to a nonhost plant) in trials conducted 1 day but not 3 days after exposure. Males exposed to orange fruits had higher mating success than control males (exposed to apples) in trials conducted 1 and 3 days after exposure. Enhanced mating success was observed only when males were permitted to contact the orange leaves and fruits; aroma alone did not affect male mating success. In addition, we examined whether exposure to commercially available orange oil, which also contains -copaene, enhanced the mating performance of wild-like and mass-reared sterile males. Heightened mating success was observed in trials conducted 1 and 3 days after exposure for both types of males, and in this case aroma alone had a positive effect on male mating success. Future research should attempt to identify the behavioral, physiological, or chemical mechanisms underlying the observed increases in male mating success.     

Improved attractants for Mediterranean fruit fly, Ceratitis capitata (Wiedemann): responses of sterile and wild flies to (-) enantiomer of ceralure B1

Tests were conducted on wild Mediterranean fruit flies, Ceratitis capiata (Wiedemann), in Hawaii, Italy, and Kenya, and on sterile released flies in Florida and California with a new male attractant, (-)-ceralure B1. Compared on an equal dosage basis, Mediterranean fruit fly males were significantly more attracted to the (-)-ceralure B1 than to trimedlure in each of the sites tested except for California. Compared with the standard commercial 2 g trimedlure plug, 10 mg applied on cotton wicks (Kauai) was as attractive to wild males as trimedlure after the first 2 d of the test but not after 7 d. At a dose of 40 mg (50 times less than in the 2-g plug), the (-)-ceralure B1 was significantly more attractive to male flies than the 2-g trimedlure plug for the first week of service (Florida) but not after 2 wk. Studies using released sterile flies in Florida confirm our previous work on the improved attraction of (-)-ceralure B1 (40 mg) over trimedlure. However, this trend did not hold up in a single test conducted in a residential area in California that did not show a significant difference in attraction using 20 mg of compound. Future refinements in synthesis and costs of this compound and increased availability and testing will be needed before any final evaluation in the field can be carried out.     

Olfactory and Behavioral Mechanisms Underlying Enhanced Mating Competitiveness Following Exposure to Ginger Root Oil and Orange Oil in Males of the Mediterranean Fruit Fly, Ceratitis capitata (Diptera: Tephritidae)

Males of the Mediterranean fruit fly, Ceratitis capitata, are strongly attracted to various plant odors, and previous work has demonstrated that male exposure to certain odors, including the scent of orange oil (OO) and ginger root oil (GRO), increases their mating success relative to non-exposed males. However, the mechanism(s) underlying this mating increase is not known. Here, we describe several experiments that further investigate the association between GRO- and OO-exposure and male signaling activity, pheromone attractiveness, and mating success in male medflies. Exposure to GRO or OO increased time spent pheromone calling but did not accelerate the rate of male sexual maturation. Using a wind tunnel, we compared female attraction to the pheromone of control, non-exposed males versus males previously exposed to OO or GRO. There was no evidence that GRO exposure enhanced the attractiveness of the male pheromone. The data for OO were inconclusive: females tended to spend more time on spheres emanating pheromone from OO-exposed males than on spheres emanating pheromone from non-exposed males, but the number of female landings did not differ between the two types of pheromone sources. Female choice tests confirmed that GRO- and OO-exposure boost male mating success relative to non-exposed males. Application of GRO directly to the abdomen reduced male mating success, whereas similar application of OO boosted male mating success. The potential role and mode of action of plant chemicals in the mating behavior of male medflies are evaluated in light of these findings.     

Attraction of female Chiracanthium mildei(Araneae: Clubionidae) to olfactory cues from maleMediterranean fruit flies Ceratitis capitata(Diptera: Tephritidae)

Chiracanthium mildei, a common sac spider (Clubionidae) in Israel, is an important predator of pest insects in citrus and apple orchards. Field observations indicate that the females of this hunting spider are attracted to traps containing the parapheromone trimedlure and males of the Mediterranean fruit fly (Ceratitis capitata),which were caught in these traps. Laboratory testsshow that C. mildei females are attractedto olfactory cues from male C. capitata, but notto trimedlure. This suggests that C. mildeimay be an important nocturnal predator of C.capitata.     

Repeated matings offset costs of reproduction in female crickets

Summary Courtship food gifts can be a significant source of nutrition to females and costly for males to produce; hence, costs of reproduction should be reduced for multiple-mating females and increased for multiplemating males in a gift-giving species. We tested this hypothesis by experimentally manipulating mating opportunities of males and females of two cricket species,Gryllodes sigillatus, a gift-giving species andGryllus veletis, a non-gift-giving species. Females of both species consume the externally attached spermatophore after mating, but inG. sigillatus, the sperm-containing ampulla is accompanied by a large gelatinous spermatophylax. In both species, survival of mated females given limited access to males was reduced relative to virgin females, thus suggesting a cost of reproduction to females. However, females given unlimited mating opportunities lived as long as virgins and also produced significantly more offspring than limited-access females. These results suggest that benefits of repeated matings, particularly those arising through spermatophore consumption, offset costs of reproduction in females. Lack of a treatment by species interaction suggests that females of both species derive nutritional benefits through spermatophore consumption, and that any additional advantage to the consumption of the spermatophylax inG. sigillatus is offset by more frequent mating byG. veletis females. In contrast to females, varying mating opportunities had no effect on male survival, suggesting that mating effort is not very costly to males. Male survival increased linearly with body mass but only when males were food-deprived, suggesting that larger males possess greater initial energy reserves to sustain their longevity when food-stressed.     

Field evaluation of the relative attractiveness of enriched ginger root oil (EGO)lure and trimedlure for African Ceratitis species (Diptera: Tephritidae)

The males of some fruit flies (Diptera: Tephritidae) are known to be attracted to specific parapheromones. The trapping results between trimedlure (TML) and enriched ginger root oil (EGOlure) were compared at two experimental sites in Morogoro (Central Tanzania) for a period of 12 weeks co‐inciding with the main citrus season. Both attractants captured a comparable diversity of fruit flies, except that EGOlure also attracted fruit flies, such as Ceratitis cosyra, not normally found in TML‐baited traps. Both EGOlure and TML attracted mainly or exclusively male fruit flies, but the catches with EGOlure were equal or superior to those with TML. It is concluded that EGOlure should be considered as a suitable alternative for TML in detection, monitoring and control programs for African fruit flies of the genus Ceratitis. It has the added advantage that it combines the attractiveness with regard to species spectrum of both TML and terpinyl acetate.     

Aromatherapy in the Mediterranean fruit fly (Diptera: Tephritidae): sterile males exposed to ginger root oil in prerelease storage boxes display increased mating competitiveness in field-cage trials

Previous research showed that exposure to ginger root, Zingiber officinale Roscoe, oil increased the mating success of mass-reared, sterile males of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann). This work, however, involved the exposure of small groups of males (n = 25) in small containers (volume 400 ml). Several sterile male release programs use plastic adult rearing containers (so-called PARC boxes; hereafter termed storage boxes; 0.48 by 0.60 by 0.33 m) to hold mature pupae and newly emerged adults before release (approximately = 36,000 flies per box). The objective of the current study was to determine whether the application of ginger root oil to individual storage boxes increases the mating competitiveness of sterile C. capitata males. Irradiated pupae were placed in storage boxes 2 d before adult emergence, and in the initial experiment (adult exposure) ginger root oil was applied 5 d later (i.e., 3 d after peak adult emergence) for 24 h at doses of 0.0625, 0.25, 0.5, 1.0, and 2.0 ml. In a second experiment (pupal-adult exposure), ginger root oil was applied to storage boxes immediately after pupal placement and left for 6 d (i.e., 4 d after peak adult emergence) at doses of 0.25 and 1.0 ml. Using field cages, we conducted mating trials in which ginger root oil-exposed (treated) or nonexposed (control) sterile males competed against wild-like males for copulations with wild-like females. After adult exposure, treated males had significantly higher mating success than control males for all doses of ginger root oil, except 2.0 ml. After pupal-adult exposure, treated males had a significantly higher mating success than control males for the 1.0-ml but not the 0.25-ml dose of ginger root oil. The results suggest that ginger root oil can be used in conjunction with prerelease, storage boxes to increase the effectiveness of sterile insect release programs.     

Females prefer the scent of outbred males: good-genes-as-heterozygosity?

Background  

There is increasing interest to determine the relative importance of non-additive genetic benefits as opposed to additive ones for the evolution of mating preferences and maintenance of genetic variation in sexual ornaments. The 'good-genes-as-heterozygosity' hypothesis predicts that females should prefer to mate with more heterozygous males to gain more heterozygous (and less inbred) offspring. Heterozygosity increases males' sexual ornamentation, mating success and reproduction success, yet few experiments have tested whether females are preferentially attracted to heterozygous males, and none have tested whether females' own heterozygosity influences their preferences. Outbred females might have the luxury of being more choosey, but on the other hand, inbred females might have more to gain by mating with heterozygous males. We manipulated heterozygosity in wild-derived house mice (Mus musculus musculus) through inbreeding and tested whether the females are more attracted to the scent of outbred versus inbred males, and whether females' own inbreeding status affects their preferences. We also tested whether infecting both inbred and outbred males with Salmonella would magnify females' preferences for outbred males.     

Reduction in the attraction of males to females after mating in the rice leaf bug Trigonotylus caelestialium

The influence of mating on the extent to which males are attracted to females in Trigonotylus caelestialium (Heteroptera: Miridae) was examined. No differences in attraction of males to mated and virgin females were observed within 3–5 h of mating, but males became less attracted to females 1 to 2 days after the first mating. The difference in male attraction to mated vs virgin females disappeared at 4 days after mating. These results indicate that reduced attraction of males to mated females occurs after a certain time interval, and persists for a few days. Furthermore, males were less attracted to females that had mated with virgin vs recently mated males, i.e. males that had just mated with another female at 1 and 2 days after mating. The ejaculate expenditure of recently mated males was less than that of virgin males. Hence, the amount of male ejaculate transferred to females during mating, rather than the act of mating, might influence the attraction of males to females. The results demonstrate that mating reduces the attraction of males to females in T. caelestialium on the basis of direct observation of male behavior.     

The Behavioral Significance of Male Body Size in the Tarantula Hawk Wasp Hemipepsis ustulata (Hymenoptera: Pompilidae)

Large males of the tarantula hawk wasp Hemipepsis ustulata appear to have an advantage in the competition for mates. Large males are more likely to acquire perch territories used to scan for incoming receptive females and territorial males appear more likely to mate than non‐territorial males. In addition, among the males that do secure a mate, those that intercept a female on a territory are larger than those that do so elsewhere. Despite the mating advantages apparently enjoyed by larger males of this species, average male size has remained essentially constant over the last 25 yr. Moreover, larger males are not seen to employ certain competitive tactics that might otherwise enhance their reproductive success. Thus, larger males did not preferentially visit the most popular landmark territory compared to a site that attracted fewer visitors overall. Nor were larger males more likely to return to potential territories after marking, capture, and release, either immediately or on a subsequent day. Finally, although large males made up a significantly greater proportion of the males captured at two territories as the 2005 flight season progressed, over all the years of the study, receptive females have not been concentrated in the latter part of the flight seasons.     

Rhythmicity of mating and oviposition inCallosobruchus subinnotatus (Pic) (Coleoptera: Bruchidae)

Mating and oviposition behaviors were studied inCallosobruchus subinnotatus. Copulation was most frequent during the late scotophase, 2–3 h before onset of photophase. The females were less willing to mate during photophase, which increased the time to initiate mating while decreasing the duration of mating. Females exhibited increased movement prior to mating, resting immediately after mating, and remained stationary for 6 h when oviposition commenced. Multiple mating by both males and females affected the number of eggs laid, duration of mating, and uncoupling time at the end of mating. Females that mated two or three times laid more eggs than females that mated once or more than three times. Females that remainedin copula for less than 18 min showed greater readiness to remate than those that remainedin copula longer. There was a gradual decrease in the number of eggs females could lay with an increase in the number of previous matings by males.     

Sexual Selection of Zorion guttigerum Westwood (Coleoptera: Cerambycidae: Cerambycinae) in Relation to Body Size and Color

Zorion guttigerum is a flower-visiting longhorned beetle endemic to New Zealand. Sexual selection of this species in relation to the body size and color form of different sexes was investigated in the field. The population sex ratio, based on censuses of feeding and mating sites (flowers), is male-biased. Females are significantly larger than males. Both sexes have antennae of similar length but the antennal length relative to the elytral length is greater in males than in females, and the antennal length of males increases more with an increase in body size than that of females. Both sexes have dark blue (DB) and yellowish-brown (YB) individuals. Both pair-bonded and solitary males are similar in elytral and antennal length. In pair-bonded males, DB individuals are significantly more numerous than YB ones, but in solitary males, the number of both color forms is similar. Males tend to have territory protection behavior, fighting with and chasing away rival males from feeding and mating sites. Larger males usually win the fight but the size-dependent fighting advantage does not translate into mating success. Male color plays an important role in mating success, with DB males having a significantly better chance to mate than YB males. Furthermore, male body size and color also have interactions in mating success: males of DB color morph obtain a greater mating advantage according to body size. Pair-bonded females are significantly larger and have longer antennae than solitary females, suggesting that males prefer larger females for mating. In addition, females of DB color morph with longer antennae are also preferred by males for mating. The significance of these findings is discussed.     

Attraction of the sexes inFormica lugubris Zett (Hymenoptera: Formicidae)

Summary Sexuals ofFormica lugubris fly to mating places, where females attract males by using a sex pheromone. Females collected on the nest surface before departing on a mating flight are much less attractive than those collected on the mating place after the mating flight, suggesting that the mating flight triggers the release of the sex pheromone. Olfactory cues are essential for males to locate females while they patrol. Males probably use visual cues to locate females once they have alighted nearby them. Males are also attracted by aggregations of other males on the ground, probably because one or several females are likely to be close to male aggregations.     

Removal of Surface Glycoproteins and Transfer among <Emphasis Type="Italic">Brachionus</Emphasis> species

Glycoproteins on the body surface of females of the rotifer Brachionus plicatilis are a key signal in their mate recognition system. When B. plicatilis Russian strain females were exposed to 50 mM EDTA or EGTA, several surface glycoproteins were removed. Females exposed to EDTA died, but remained intact and were used in mating bioassays with conspecifics males. Live control females elicited a male mating response in 21% of encounters, freeze-killed control females elicited responses in 23%, but EDTA extracted females elicited a mating response in only 5% of encounters. At least some of the EDTA-extractable proteins on the surface of females appear to be critical to male mate recognition. EDTA treated females could be exposed to proteins extracted from other females and some proteins re-attached to their body surface, restoring their attractiveness to males. SDS-PAGE of these proteins revealed 15–17 prominent bands, most ranging in molecular mass from 66 to 12 kD. The EDTA-extractable proteins were separated using ion exchange chromatography and each fraction was tested for its ability to restore female attractiveness. When proteins in fraction 22 were bound to females, they restored 80% of the females’ ability to elicit male mating responses. Exposing EDTA treated females to bovine serum albumin or casein had no effect on their attractiveness to males. EDTA treated females from different Brachionus clades and species were exposed to proteins from fraction 22. Female attractiveness could be restored in most clades of B. plicatilis, but no transfer of mating attractiveness was observed to B. rotundiformis or B. ibericus females. Conspecific males treated with EDTA and exposed to proteins in fraction 22 could not be feminized and made attractive to other males. A sexual dimorphism in surface proteins therefore exists between B. plicatilis females and males. Successful transfer of glycoproteins critical in mate recognition is dependent on signal glycoprotein structure and the structure of the other proteins present on the surface of females.     

Behaviour of cyclic bank voles under risk of mustelid predation: do females avoid copulations?

Mustelid odours have been shown to suppress breeding in captive bank voles (Clethrionomys glareolus) from cyclic populations (Ylönen 1989; Ylönen and Ronkainen 1994). The mechanism behind the suppression is unknown. Based on a series of behavioural trials and breeding experiments with pairs of bank voles in breeding condition, we suggest that the primary cause for breeding suppression is a change in female mating behaviour. Experimental female-male pairs (n=34) exposed to mustelid odour decreased their general activity compared to control pairs (n=34). When encountering males in behavioural trials, females exposed to stoat odour were more aggressive and actively avoided precopulatory behaviours of males. No copulations were observed in experimental pairs compared to five in control pairs during the behavioural trials. Males actively approached females in general but male behaviour did not change under exposure to mustelid odours. We suggest that females are more vulnerable to mustelid predators than males and therefore actively avoid copulations in the (indirect) presence of mustelids. As well as this behavioural response, internal abortive mechanisms (cf. Bruce 1959) could play a role in the observed breeding suppression.     

ACOUSTIC COMMUNICATION AND MATING BEHAVIOUR IN WATER BUGS OF THE GENUS MICRONECTA

ABSTRACT

The role of male sounds in attracting females and in mating was investigated in the three most common species of Micronecta found in ponds 60 km NE of Melbourne, Australia: M. concordia, M. tasmanica and M. robusta. In playback experiments using recorded male signals, females were attracted to signals of conspecific males, in preference to signals of heterospecific sympatric males. Studies of mating behaviour, using video recording, showed that signals were obligatory for mating. These findings strongly suggest that acoustic signalling is important in reproductive isolation in Micronecta. Comparisons between matings and rejected matings showed that, within each species, copulation only occurred following a certain minimum number of acoustic signals with more pulse-trains than the mean for the species. Low amplitude sounds (after signals) were also important in courtship, immediately preceding mating. No sounds occurred during copulation.     

Female preference for large males in sailfin mollies,<Emphasis Type="Italic"> Poecilia latipinna</Emphasis>: the importance of predation pressure and reproductive status

We examined the effect of predation risk on female association patterns in the live-bearing sailfin molly (Poecilia latipinna). We tested two classes of females, with and without the risk of predation by a green sunfish (Lepomis cyanellus): (1) postpartum females (maintained with males until visibly gravid, then isolated and tested within 24–48 h of dropping a brood); and (2) non-postpartum females (different females, isolated from males for >50 days). When there was no apparent risk of predation, postpartum females showed a significant preference for large over small males, whereas non-postpartum females showed no size preference at all. When there was an apparent risk of predation, postpartum females maintained their preference for larger males and non-postpartum females continued to show no preference for large or small males. These results suggest that reproductive status (receptivity) plays a greater role in mate preference than predation risk. For postpartum females, the cost of not choosing a preferred mate may outweigh the potential cost of predation. Non-postpartum females either do not benefit from mating or are being indecisive about mating and thus are less likely to be choosy whether or not a predator is present.Communicated by I. Schlupp     

Sand goby (Pomatoschistus minutus) males exposed to an endocrine disrupting chemical fail in nest and mate competition

Endocrine disrupting chemicals (EDCs) are a widely studied group of chemicals that interfere with the endocrinology of organisms. So far, few studies have demonstrated the effect of EDCs on the reproductive behavior of aquatic wildlife. Here we show that sand goby males' (Pomatoschistus minutus) success in mating competition greatly decreases after an exposure for 7 to 24 days to 17α-ethinyl estradiol (EE2, measured concentration 4 ng L^− 1). The sand goby exhibits a polygynous mating system with male parental care, in which males compete for nest sites and females. The aim of this study was to test how EE2 exposure affects the ability of males to compete for breeding resources, i.e. nest sites and mates. First, EE2 exposed males competed over a nest site against a non-exposed, control male of the same size. Secondly, we examined male courtship behavior and female mate preferences for EE2 exposed males and similar-sized non-exposed, control males. In addition to the behavioral experiments we determined the zona radiata protein (Zrp) mRNA gene expression and measured morphometric indicators of sexual maturation. Our study revealed that EE2 treated males were not able to acquire or defend a nest site. Additionally, EE2 treated males spent significantly less time in active courtship and nest leading behavior than control males. As a result, females clearly preferred to mate with control males. However, we found no significant differences in Zrp mRNA expression or the morphometric indicators between treatments. Our study illustrates that exposure to this EDC can greatly reduce the chances of an individual reproducing successfully. Moreover, it demonstrates that severe behavioral effects can be seen before any effects are detectable at the molecular or morphometric level.