Schistosoma mansoni: Adult worm chemoattraction,with and without barriers

Heterosexual and homosexual chemoattraction studies were done with 8- to 12-week-old Schistosoma mansoni adults in linear chambers containing Earle's saline, in the absence and presence of both perforated and unperforated dialysis sac chimney barriers. In the absence of barriers attraction was seen in all heterosexual and homosexual combinations. After 90 min of observation at 37 C, organisms maintained at 4 or 37 C for at least 1 hr prior to the assay showed heterosexual attraction similar to those used immediately after perfusion. There was significantly more heterosexual attraction between worms from same than different pairs. In the presence of perforated barriers the greatest attraction was heterosexual, with males moving toward females; heterosexual attraction with females moving toward males was approximately equal to homosexual female attraction, and male homosexual attraction was not seen. In the presence of unperforated barriers the greatest attraction of females toward males occurred during the first 0.5 hr; within 3 to 4 hr females were no longer significantly attracted to males. However, after 0.5 hr males were more significantly attracted to females in unperforated than perforated chimneys. These studies demonstrate that adult schistosomes attract each other in vitro, and that there is a chemical basis for this attraction.     

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.     

Males of Hylamorpha elegans burmeister (Coleoptera: Scarabaeidae) are attracted to odors released from conspecific females

The behavioral responses of Hylamorpha elegans L. (Coleoptera: Scarabaeidae, Rutelinae) to the semiochemicals released from conspecific individual adults were studied, with particular attention paid to female attraction of males. Odors released from virgin females significantly attracted male conspecifics in both the field and laboratory olfactometer and wind tunnel bioassays. However, females did not attract other females, and males attracted no one. The response of male H. elegans to (1) compounds (1,4-hydroquinone and 1,4-benzoquinone) released only by unmated females; (2) the essential oil of the secondary host (Nothofagus obliqua); and (3) the blend of 1,4-hydroquinone and 1,4-benzoquinone with N. obliqua essential oil was studied. The blend of 1,4-benzoquinone mixed with essential oil at the trial concentration was attractive with males. The same response was found with 1,4-hydroquinone alone. The essential oil did not have the expected attractant effect on conspecific males. These results suggest that, when combined with essential oil, 1,4-benzoquinone may function in the sexual behavior of males and females. These findings are discussed in terms of the ecological role of this putative sexual pheromone and its potential use in a strategy of control of this pest.     

Evidence for a male-produced aggregation pheromone in Scyphophorus acupunctatus Gyllenhal (Coleoptera: Curculionidae)

Olfactory response of male and female Scyphophorus acupunctatus Gyllenhal (Coleoptera: Curculionidae) to volatiles released from the same or opposite conspecifics alone, or combined with host plant volatiles, was evaluated in the laboratory and field. We also evaluated the response to synthetic Rhynchophorinae pheromones in the laboratory. In laboratory tests, attraction of males and females in Y-tube olfactometer to conspecific males was greater than to females and clean air. Males and females preferred the combination males + agave over agave alone. Both sexes were significantly attracted to 2-methyl-4-heptanol and 2-methyl-4-octanol compared with hexane control. In field trials, weevils were successfully caught in the traps baited with conspecifics and plant material. These field results support those of the laboratory bioassays, showing that males attracted conspecific males and females and addition of plant material enhanced the attraction. These results further suggest that S. acupunctatus produces an aggregation pheromone.     

Attraction of the cabbage looper to host plants and host plant odor in the laboratory

In a laboratory flight tunnel, mated female, unmated female, and male adult cabbage loopers, Trichoplusia ni (Hübner), exhibited chemically mediated anemotaxis (attraction) in response to intact potted cabbage plants (Brassica oleracea L.), leading to contact with the plant. Similar attraction responses were also observed by mated females to potted soybean (Glycine max (L.)), tomato (Lycopersicon esculentum Miller), and celery (Apium graveolens L.) plants in noncompetitive comparisons. Mated females, unmated females, and males flew to cabbage plants throughout the scotophase. Response rates for mated females were higher than for unmated females and males. Mated female cabbage loopers were attracted by odors of cabbage, soybean, tomato, or celery piped into a flight tunnel from single plants held in glass jars and not to odors of the non-host plant Setcreasea purpurea, or to humidified air. They were also attracted to water washings of cabbage at dosages of 0.4 to 2.0 gram equivalents, when presented on cotton dental wicks in the flight tunnel.     

Sex attraction in Bactericera cockerelli (Hemiptera: Triozidae)

The potato psyllid, Bactericera (=Paratrioza) cockerelli (?ulc) (Hemiptera: Triozidae), is a major pest of potato. We examined the role of chemical signals in sex attraction, assessing male and female response to male- and female-produced volatile chemicals. In laboratory olfactometer assays, potato psyllid males were attracted to odorants emitted from live females and from solvent extract of females. These results indicate that the female-produced chemicals responsible for attracting males may be isolated by means of insect extractions. Males were also attracted to volatile chemicals from males and extracts of males, providing the first example of male-male attraction in the Psylloidea. Males exposed simultaneously to odorants from conspecific females and males were preferentially attracted to female odorants, suggesting the presence of a female-specific sex attractant for males. Potato psyllid females avoided volatile chemicals emitted by females and extracts of females and by volatile chemicals emitted by males and extracts of males. Possible explanations for avoidance of conspecifics by females are discussed. This study is the first report of male attraction to volatile chemicals emitted by females and female extracts in the Triozidae and more specifically in the potato psyllid.     

Evidence for acoustic communication in the parasitoid wasp Glyptapanteles flavicoxis

Females of the parasitoid wasp Glyptapanteles flavicoxis (Marsh) (Hymenoptera: Braconidae) deposit sex pheromone on substrate that elicits attraction and wing fanning in conspecific males. We tested the hypothesis that wing fanning sound induces a behavioral response from females which, in turn, affects the males’ orientation toward them. Females exposed to playback of the males’ wing fanning sound engaged in short flights, with sound characteristics different from those of the males’ wing fanning sound. In two‐choice bioassays, playback of the females’ flight sound attracted significantly more males than a silent control stimulus, and in combination with pheromone‐containing body extract of females it attracted more males than female body extract alone. Our data support the conclusion that the males’ wing fanning induces sound and visual reply signals from females that help males orient toward them.     

Behavioural effects of minor sex pheromone components in Brazilian apple leafroller Bonagota cranaodes (Lep., Tortricidae)

Abstract:  The behavioural response of Brazilian apple leafroller males, Bonagota cranaodes (Meyrick), to natural and synthetic sex pheromone was studied in a wind tunnel. Calling females elicited upwind flights followed by landing and wingfanning at the source in 72% of the males tested. Female gland extracts, with the main compound ( E , Z )3,5dodecadienyl acetate released at 100 pg/min, attracted 57% of the males to the source. Few males (1%) were attracted to the main compound alone, released at the same rate. Even a synthetic blend of all five gland compounds eliciting an antennal response, formulated according to their proportion in female gland extracts, was barely attractive (7%). Comparison of this synthetic blend and female gland extracts indicates a behavioural role of other gland compounds. Male attraction was significantly increased (34%) in response to a 100 : 5 : 5 : 5-blend of the main compound and three minor gland compounds, ( Z )-5-dodecenyl acetate, ( E , Z )-3,5-tetradecadienyl acetate, and ( Z )-9-hexadecenyl acetate.     

Electroantennographic and behavioral responses of adults of raspberry weevil Aegorhinus superciliosus (Coleoptera: Curculionidae) to odors released from conspecific females

The raspberry weevil, Aegorhinus superciliosus (Guérin) (Coleoptera: Curculionidae), is the most important pest in blueberry and raspberry fields in the south of Chile. In this study, we investigated the electroantennographic and behavioral responses of A. superciliosus to semiochemicals released from conspecific individual adults, with particular attention to male attraction to females. Odors released from females significantly attracted males in a Y-tube olfactometer. Gas chromatographic and mass spectral analysis of female volatile extracts revealed the presence of limonene and α-pinene. Electroantennogram recordings from both sexes indicated that males of A. superciliosus possess olfactory sensitivity for the R isomer of limonene and α-pinene, whereas females only perceived R-limonene. Behavioral assays using synthetic compounds showed that only R-limonene elicited an attraction response from male weevils. Field experiments confirmed the laboratory results, showing that R-limonene was attractive to weevils. This is the first report of intraspecific chemical communication in this weevil. We discuss the origin of these compounds, their possible role in the sexual behavior of this species, and their potential use in a pest control strategy.     

Attraction of Mexican Fruit Flies (Diptera: Tephritidae) to Grapefruit: Enhancement by Mechanical Wounding of and Experience with Grapefruit

Wild strain, mated, female Mexican fruit flies, Anastrepha ludens (Loew), with no prior experience with fruit (naive), were not attracted to grapefruit, a preferred cultivated host, in wind tunnel experiments. Naive, mated laboratory strain females were attracted. Prior experience with grapefruit increased attraction of both laboratory and wild strains. More females were attracted to fruit with peel damage than to undamaged fruit, indicating that fruit odor mediated attraction. More naive than experienced females attempted to oviposit on the sides of the wind tunnel. Experienced laboratory males, but not wild males or naive males, were attracted to grapefruit. Attraction and oviposition behavior of laboratory flies was greater than that of wild flies.     

Macronutrient intake affects reproduction of a predatory insect

Prey quality has previously been shown to affect the growth and reproduction of predatory arthropods, however relatively little is known about the specific nutrients responsible for these effects. We tested if the macronutrient content (i.e. lipid and protein) of live prey affected mate attraction, reproductive behavior, egg production and nutrient reserves of adult female praying mantids, Pseudomantis albofimbriata. Females on a high‐protein diet produced more than twice as many eggs as females on a high‐lipid diet despite being fed the same overall biomass of prey. Furthermore, the lipid and protein composition of eggs and the female body was directly related to the diet that females were fed (i.e. high lipid content on the high‐lipid diet). Even more striking was the effect of diet treatment on the number of males attracted to females – only one male was attracted to females on the high‐lipid treatment and 56 males were attracted to females on the high‐protein treatment. Although it is not unexpected that females with more eggs would attract more males, the extreme nature of this difference is certainly surprising because previous studies have shown that females with only a couple of eggs can attract multiple males. Hence, our results suggest that female pheromone production may be affected by the quality/nutritional composition of eggs rather than simply the number of eggs. We found no significant difference in any of the other behaviours measured during mating trials, including the frequency of sexual cannibalism. The positive effects of prey protein content on mate attraction and egg production suggest that praying mantids might be expected to choose more protein‐biased prey in nature or, if prey choice is limited, to have higher reproductive output or population growth in communities dominated by protein‐rich prey.     

SEXUAL SELECTION AND FEMALE CHOICE IN MOLE CRICKETS (SCAPTERISCUS: GRYLLOTALPIDAE): MODELLING THE EFFECTS OF INTENSITY AND MALE SPACING

ABSTRACT

Attraction of flying mole crickets to individual males calling in an outdoor arena was influenced significantly by the relative intensity of the males calling in the arena. Louder males attracted more individuals than males whose calling songs were less intense. Making simple assumptions about the acoustic output from calling males and about the flight pattern and response of flying females, the differential attraction can be explained by a mathematical model. Computer simulation of the model was used to examine the importance of a male's intensity relative to others and the effect of distance between males on the attraction of females. The model and its relation to active female choice and passive attraction are discussed. The model makes predictions about differences in spacing behaviour of males that maximize attraction relative to other males.     

Disruption of sexual communication in the mirid bug Lygocoris pabulinus by hexyl butanoate

1 The metathoracic scent gland in Lygocoris pabulinus contains mostly hexyl butanoate. As secretions of this gland in Heteroptera may serve as an alarm pheromone, we determined whether hexyl butanoate is released by disturbed bugs, and whether this compound disrupts sexual attraction of L. pabulinus males towards females. 2 Undisturbed males and females, and disturbed males released less than 100 ng/h hexyl butanoate, whereas disturbed females released a highly variable amount, ranging from 25 ng/h to more than 1 μg/h. 3 In the field, traps with virgin females and rubber septa containing 20 mg hexyl butanoate, caught a total of one male in a month. In control traps without hexyl butanoate, 36 males were caught in the same period. 4 In Y‐track olfactometer tests, males were not attracted to virgin females when a dispenser with 20 mg hexyl butanoate was placed in the bottle with females. Males were attracted to females when the dispenser was placed downwind from the females, but upwind from the point of male release. 5 These results suggest that males are not repelled by hexyl butanoate, but that this compound inhibits sex pheromone release in females. Application possibilities for pest management are discussed.     

Effect of pairing in vitro on the glutathione level of male Schistosoma mansoni

The effect of in vitro incubation on the level of the intracellular nucleophile, glutathione (GSH), in adult Schistosoma mansoni was investigated. The GSH levels of freshly collected adult male and female parasites were 8.5 +/- 2.5 and 2.7 +/- 0.7 nmol/10 worms, respectively, as determined by an enzymatic assay. Twenty-four-hour incubation of unpaired males in RPMI-1640 medium at 37 C resulted in a 1.7-fold increase (P less than 0.001) in GSH level that remained elevated for at least 7 days. The increase was dependent on exogenous L-cystine, suggesting that it was due to biosynthesis of GSH. Biosynthesis in male S. mansoni was confirmed by isolating [3H] GSH from parasites incubated in medium containing L-[3H] cystine or [3H] glycine. In contrast to unpaired males, the GSH level of paired males as well as that of unpaired or paired females did not increase after 24 hr in vitro. When males that had been incubated unpaired for 24 hr were allowed to couple in vitro with freshly collected females, their GSH level fell to that of continuously paired males. These observations provide evidence that in vitro female schistosomes can influence the physiology of the male.     

Attraction of Lutzomyia longipalpis to human skin odours

Abstract. Male and female Lutzomyia longipalpis sandflies showed attraction to human skin emanations placed on warmed glass Petri dishes. Unfed virgin females were more strongly attracted than males, which also showed attraction. Four human subjects were tested and significant variation was found between the numbers of sandflies attracted to their skin emanations. This suggests that some individuals were more attractive than others. There was a significant difference between the response shown by sandflies from the Jacobina and Lapinha regions of Brazil, suggesting that sandflies from the Jacobina region were more anthropophilic. In addition, sandflies from Jacobina had a significantly higher level of activity than those from Lapinha. The role of sandfly attraction to humans as a risk factor in Leishmania transmission is considered.     

Age at reproductive maturity and effect of age and time of day on sex attraction in the potato psyllid Bactericera cockerelli

Abstract The potato psyllid, Bactericera (= Paratrioza) cockerelli (?ulc) (Hemiptera: Triozidae), is a major pest of potato. Studies were conducted to determine the age at which both males and females reach reproductive maturity and the effect of age and time of day on sex attraction. Adult B. cockerelli reach reproductive maturity within 48 h post‐eclosion, with females being mature on the day of eclosion and males at 1 day post‐eclosion. Oviposition generally began 2 days after mating but was delayed when females mated within 2 days post‐eclosion. In laboratory olfactometer assays, the age of females used as odor sources and the age of males assayed to these odors did not affect sex attraction, with both younger (1–4‐day‐old) and older (8–10‐day‐old) males being attracted to females, regardless of female age (1–4‐day‐old or 8–10‐day‐old). Males assayed to live females at different times during the photophase (between 8:00 and 20:00 hours) were attracted to females between 11:00 and 17:00 hours, showing a temporal periodicity in sex attraction with B. cockerelli at least during the photophase.     

The attraction of virgin female hide beetles (Dermestes maculatus) to cadavers by a combination of decomposition odour and male sex pheromones

ABSTRACT: INTRODUCTION: The hide beetle Dermestes maculatus (Coleoptera: Dermestidae) feeds as an adult and larva on decomposing animal remains and can also be found on human corpses. Therefore, forensic entomological questions with regard to when and how the first receptive females appear on carcasses are important, as the developmental stages of their larvae can be used to calculate the post-mortem interval. To date, we know that freshly emerged males respond to the cadaver odour of post-bloated carcasses (approximately 9 days after death at Tmean = 27degrees), being attracted by benzyl butyrate. This component occurs at its highest concentration at this stage of decay. The aim of our study was to determine the principle of attraction of virgin females to the feeding and breeding substrate. For this purpose, we tested the response of these females to headspace samples of piglet cadavers and male sex pheromones [(Z9)-unsaturated fatty acid isopropyl esters] in a Y-olfactometer. Because we expected that such an odour combination is of importance for virgin female attraction, we tested the following two questions: 1) Are virgin female hide beetles attracted by a combination of cadaver odour and male sex pheromones? 2) During which decomposition stage do the first virgin females respond to cadaver odour when combined with male sex pheromones? RESULTS: We found that young virgin females were attracted to the cadaver by a combination of cadaver odour and male sex pheromones. Neither cadaver odour alone nor male sex pheromones alone was significantly more attractive than a solvent control. Our results also gave a weak indication that the first young virgin females respond as early as the post-bloating stage to its associated decomposition odour when combined with male sex pheromones. CONCLUSIONS: Our results indicate that freshly emerged males possibly respond to cadaver odour and visit carcasses before virgin females. Being attracted to cadavers when male sex pheromone is perceived as well, virgin females can optimise their reproductive possibilities.     

Schistosoma mansoni: male-biased sex ratios in snails and mice

Adult sex ratios of Schistosoma mansoni, in mice, were shown to be biased toward males (3:1) despite the finding that sex ratios of miracidia were 50:50. The adult male bias was caused by greater male infectivity of miracidia for snails and cercariae for mice. A significantly higher percentage of male miracidia developed to cercarial production in unimiracidial infections (57 male, 34 female), and a significantly higher percentage of male cercariae developed to adulthood in mice (143 male, 79 female worms resulted from 900 male and 900 female cercariae). No significant differences were found between male and female parasites for longevity of miracidia (both sexes, 10 hr) and cercariae (males 21.3 +/- 5.75 hr, females 25.0 +/- 7.02 hr), prepatent periods in snail hosts (male 34 +/- 2.92 days, females 33 +/- 2.36 days), longevity of snail infections (males 96.6 +/- 25.15 days, females 115.2 +/- 82.43 days), and the numbers of cercariae produced per snail lifetime (males 30,751.44 +/- 18,064.33, females 34,083.00 +/- 33,732.82). Present results provide a better understanding of the life cycle of S. mansoni, are of theoretical significance for theories of biased sex ratios (which at present cannot account for the male-biased ratio of S. mansoni), and also suggest that schistosomiasis transmission models assuming a 50:50 sex ratio at all stages of the life cycle should be reassessed.     

Effects of female feeding regime in a sexually cannibalistic mantid: fecundity,cannibalism, and male response in Stagmomantis limbata (Mantodea)

1. Female feeding regime exhibited a cascade of effects on reproductive biology and behaviour in the mantid Stagmomantis limbata (Hahn). 2. Well‐fed females (High diet) consistently attained greater body mass, thicker abdomens, and higher fecundity than food‐limited females (Low diet) in four annual generations. Dorso‐ventral abdominal thickness strongly correlated with fecundity. 3. In an experiment in captivity, Low diet females were more likely to cannibalize males than High diet females. 4. High diet females attracted more males than Low diet females in several contexts. In terms of long‐range attraction, caged High diet females attracted more males in the field. In terms of short‐range attraction, males preferentially mounted and copulated with High diet females in captive paired choice trials. In naturally‐occurring pairs in the field, a preference for females with thick abdomens was evident. These results point to two possible explanations: male choice for well‐fed females and state‐dependent female pheromone emission. 5. Two years of field data indicate considerable variation in female feeding success, as measured by abdominal thickness. Average feeding success in nature appears to be relatively high, when comparing the rate of abdominal expansion in the field to captive females maintained on High diets. 6. In the field, nearly all mounts and copulations occurred in September in both years, when female feeding success is expected to be high. If mating activity occurs during a window of high female feeding success, so as to reduce the risk of cannibalism for males, then the female feeding regime may be implicated in the phenology of mating activity in cannibalistic species.     

Sex recognition in zebrafish (<Emphasis Type="Italic">Danio rerio</Emphasis>)

We investigated sex recognition in female zebrafish (Danio rerio) to better understand the underlying sensory mechanisms and identify male secondary sexual traits. Females were simultaneously presented with two fish, a male and a female, in a flow-chamber apparatus, and females’ relative attraction towards males was observed under different conditions. With domesticated fish, females were more attracted to males when presented with both visual and chemosensory cues from stimulus fish. They still discriminated the sexes when only visual cues were provided, but not when white ambient light was changed to yellow, indicating that colour plays a role. Sex discrimination under yellow light was improved when chemosensory cues were also provided. Surprisingly, females’ attraction to males was not more pronounced in the morning when mating occurs. Domesticated females discriminated the sexes when presented with wild-derived, as well as domesticated fish, whereas wild-derived females did not show any biases for domesticated or wild-derived males. Behavioural observations indicated that the wild-derived females were distressed, which explains their lack of attraction to males. In summary, domesticated female zebrafish discriminated the sexes using both visual (body colour) and olfactory cues; however, wild-derived zebrafish were too distressed for behavioural experiments under these laboratory conditions.