Changes in the circadian flight activity of the mosquito Anopheles stephensi associated with insemination, blood-feeding, oviposition and nocturnal light intensity

Abstract. The circadian activity patterns of Anopheles stephensi Liston were examined before and after mating and throughout the gonotrophic cycle. In LD 12:12h, males and virgin females are active at dusk. After insemination, females are active at dusk and also for short bursts during much of the night. After blood-feeding, inseminated females are inactive for two nights. On becoming gravid, these females become highly active at dusk and, to a lesser extent, are also active later in the night. In contrast, blood-feeding and egg maturation have minimal effects on the activity pattern of virgin females, who continue to fly only during dusk periods, i.e. virgins continue with the activity pattern which would most likely lead to mating encounters. After oviposition, parous females resume the activity pattern characteristic of inseminated nulliparous females. In a light regime which simulates moonlit nights and normal days, inseminated females are more active overall and flight-burst durations are much longer than in LD 12:12h.     

Genetic manipulation of the circadian clock's timing of sexual behaviour in the Queensland fruit flies, Dacus tryoni and Dacus neohumeralis

ABSTRACT. Mating in Dacus tryoni is restricted to dusk, whereas that of a sibling species, Dacus neohumeralis , occurs in the middle of the day. The timing of sexual behaviour in both species is determined by an interaction between a circadian clock and light intensity. In D. tryoni peak mating responsiveness is at the time of dusk, and the optimal light intensity for mating is approximately 91x. In D.neohumeralis peak responsiveness is in the middle of the day, and the optimal light intensity for mating is greater than 10 000 lx. The two species were crossed and the time of mating and response to light intensity of F₁, F₂ and backcross progeny determined. The circadian clock set a mating phase ('gate') as narrow in F₁ flies as in their parents, suggesting the circadian timing mechanism to be common between the two species. The results indicate that the genetic mechanism controlling timing is independent of that controlling response to light intensity, and that both genetic mechanisms are complex.     

Prolonged mating in the melon fly,Dacus cucurbitae (Diptera: Tephritidae): Competition for fertilization by sperm-loading

Summary Males of the melon flyDacus cucurbitae mate with females for 10 hours or more, usually starting at dawn and terminating at dusk. We tested the sperm-loading hypothesis (Dickinson, 1986) that males remaining with females for long periods of time benefit by numerically overwhelming the sperm of their competitors. The amount of sperm transferred to a female increased with time after mounting. The number of feamles which laid eggs at least once during experimental periods was positively correlated with mating duration. Oviposition rate was positively correlated with mating duration, as well. Egg hatchability was not influenced by mating duration. Mating duration was a major determinant of paternity when females were doubly mated with one male for 6 hours and another male for 2 hours. Females whose first matings were longer showed first male sperm predominance, while females whose second matings were longer showed last male sperm predominance. The adaptive significance of prolonged mating by male melon flies is discussed.     

Female spawning migrations of the protogynous wrasse,Halichoeres marginatus

Spawning sites and spawning migration paths of tagged females of the protogynous wrasse,Halichoeres marginatus, were studied on the shallow reefs at Kuchierabu-jima Island, Japan. Males set up mating territories above prominent rocks on the offshore reef slope in the late afternoon, and pair-spawned with females, which had migrated there from their home ranges located in inshore areas. Small females migrated to the spawning sites near their home ranges, whereas large females migrated to various spawning sites located within a wide area, including downcurrent sites. Spawning at the downcurrent sites favors transport of eggs offshore, thereby increasing the female’s fitness. The spawning sites where an individual had spawned as a female were subsequently used for mating after it had changed sex. It is suggested that the wide migration of females to various spawning sites, enables the storing up of information on those sites, which later helps in the acquisition of mating territories after changing sex.     

Mating behaviour and chemical communication in the invasive Chinese mitten crab Eriocheir sinensis

Mating in the Chinese mitten crab (Eriocheir sinensis) was examined; in particular the nature of mating and the role of sex pheromones. A semi-lunar periodicity (16.8 days and 14.5 days, respectively) was observed in the mating frequencies in two consecutive breeding seasons (2001-2002 and 2002-2003). This semi-lunar rhythm coincided with spring tides (full and new moon), and activity peaked in November. Observation of the progression of specific behaviour types in mating and non-mating pairs revealed that pairs which would go on to complete mating progressed from fighting to mating behaviour significantly faster than non-mating pairs. These findings indicate that mate recognition occurs only after physical contact. Reproductively active pairs (ascertained from mating experiments) were then used for several bioassays aiming to assess under which conditions pheromones may be released by females. Firstly, male E. sinensis were exposed to female smell in an actograph experiment and secondly, male antennule flick rate was recorded before and after exposure to the urine of a sexually active female. In both cases no change in male E. sinensis behaviour was observed. Both experiments used females which had not had immediately prior exposure to males. However, in further experiments using water where mating had occurred, a significant response in antennule flick rate was triggered. Finally, a sponge assay was used in order to test the male attraction to a sponge injected with a water sample of varying concentrations (0.5×, 1×, 3×, 4.5×, 9×) of female smell. These samples were conditioned using a female immediately following a mating attempt. Males tried to grasp the sponge at 3× increased concentrations or higher. In conclusion, this study found no indication that E. sinensis females release a distance pheromone, but instead that mate recognition occurs after physical contact between male and female, most likely via a contact pheromone.     

Swarming and mating behavior in Ephemera orientalis Mclachlan, 1875 (Ephemeroptera: Ephemeridae) with morphological analyses

Swarming and mating behaviors of a mayfly species, Ephemera orientalis Mclachlan, 1875 were observed in 2015, 2016, and 2018 at a river bank of the Asahi River, Japan. Males started to make swarms between late April and middle May in 2016 and 2018. The numbers of mated pairs in a swarm correlated with the numbers of flying males in a swarm in 2016 and 2018. Swarms were formed during a limited period at dusk most probably because that interval is free from natural enemies. Males competed with each other to copulate with females in swarms. We clarified the function of the forelegs of males, which are significantly longer than those of females. Males used their forelegs to hold up a female from below. Besides forelegs, males have longer tails than females. We will discuss why sexual differences are found in these traits. Our results represent the first observation of swarm mating behavior in E. orientalis.     

Temporal modulation and adaptive control of the behavioural response to odours in Rhodnius prolixus

It has been demonstrated in several insect species that a circadian clock makes the whole of antennal chemoreceptors more sensitive during a particular temporal window every day. This assessment raises the question about how insects exhibiting bimodal activity handle their sensitivity to odours which are relevant at different moments of the day. To shed some light on this problem, we studied in Rhodnius prolixus the daily dynamics of their responsiveness to CO₂ (host-associated cue) and aggregation cues (refuge-associated), which are relevant at dusk and dawn, respectively. We analysed: (1) whether a temporal modulation of the responsiveness to odours does exist in R. prolixus, (2) if this modulation is a general one or it is specific for each type of volatile, and (3) if it is controlled by exogenous or endogenous mechanisms. We found that the responsiveness to CO₂ only occurs at dusk and that to assembling odours is restricted to dawn. Experiments under free-running conditions revealed that only the responsiveness to CO₂ is controlled by a circadian clock, but not that to assembling signals. Thus, by combining endogenous and exogenous mechanisms, sensitivities to different odours are adjusted according to their associated behavioural context and moment of the day.     

Night-interruption experiments and action spectra for dawn and dusk in relation to the photoperiodic clock of the cabbage whitefly,Aleyrodes proletella (Homoptera: Aleyrodidae)

The dark period (scotophase) is the most photoperiodically important part of a light-dark cycle in Aleyrodes proletella. Night-interruption studies have revealed three distinct dark stages: the photosensitive stage 1 lasts for about 3 h after dusk and 1-h light breaks both stop and re-set the photoperiodic clock; stage 2 also lasts about 3 h, but is photorefractory to some degree; stage 3 is photosensitive, but short light breaks do not re-set the clock although a 4-h light break (equivalent to a main photophase) does restore the capacity to respond to a normal critical night length in the post-interruption scotophase.Action spectra revealed peak photoperiodic sensitivity to blue light (410–430 nm) with 50% responses., at 1.5 μWcm⁻² and 2.5 μWcm⁻² for the dusk and dawn peaks respectively. These data are consistent with the view that the photopigment is a carotenoprotein.The results are interpreted in terms of the photoperiodic clock in A. proletella operating on the hour glass principle.     

The effect of dusk and dawn on the locomotor activity rhythm of Talitrus saltator (Montagu) (Crustacea: Amphipoda)

Entrainment of the nocturnal, endogenous locomotor activity rhythm of Talitrus saltator (Montagu) by the natural light-dark cycle is non-parametric, the phase of the rhythm shifting only in response to changes in the time of an experimentally simulated ‘dawn’ transition. The difference in response to light at ‘dusk’ and ‘dawn’ illustrates a phase-dependent responsiveness common to endogenous rhythms. Activity begins after complete darkness, with cessation always occurring during the ‘dawn’ transition and never continuing past the onset of total experimental illumination. The point of activity cessation is taken to be the position of a synchronizing cue controlling entrainment. The ‘dawn’ cue appears to be an absolute irradiance level of approximately 1.5 × 10^?4 W/m² (1.5 lux). The implications of such a cue are discussed in relation to field behaviour.     

Light,predation and the lekking behaviour of the ghost swift Hepialus humuli (L.) (Lepidoptera,Hepialidae)

We examined the timing of the crepuscular lekking flight of male ghost swift moths in southern Sweden with respect to variations in: (i) the quality of the visual mating signal; and (ii) the behaviour of potential vertebrate predators (mainly bats). The moths'' display flights started ca. 57 min after sunset, and occurred during 20–30 min at incident light intensities between 10.0 and 2.0 lux. Owing to the falling and more shortwave ambient light after sunset, the brightness contrast between the moth wings and the background (grass) increased steeply at the time of display onset. The silvery white male wing colour thereby seems to maximize conspicuousness, and may be a secondary adaptation that facilitates visibility at low light intensities. The display timing itself is probably determined by other factors, possibly predation. By displaying only for a short period at dusk, the moths seem to avoid most birds, which normally do not forage at these light levels, and gleaning bats, which typically do not start to feed until the light intensity has fallen even further. Nevertheless, aerial-hawking bats were often (54% of the evenings, n = 22) seen at the leks, and one species (Eptesicus nilssonii) frequently fed on the displaying moths (22% of the moths observed, n = 83). H. humuli represents an ancient clade among the Lepidoptera. By restricting its sexual behaviour to a short time window at dusk, when predation risk may be minimized (but still high), it may to some extent compensate for the lack of sophisticated predator defence systems such as aposematic or mimetic coloration, manoeuvrable flight, and ultrasonic hearing, which predominate among the more recent Lepidopteran clades. However, the time window solution restricts the moths'' activities considerably and the lack of defence still carries a considerable cost in terms of predation.     

Influence of Host Plant Structure and Microclimate on the Abundance and Behavior of a Tephritid Fly

Microclimate and host plant architecture significantly influence the abundance and behavior of insects. However, most research in this field has focused at the invertebrate assemblage level, with few studies at the single-species level. Using wild Solanum mauritianum plants, we evaluated the influence of plant structure (number of leaves and branches and height of plant) and microclimate (temperature, relative humidity, and light intensity) on the abundance and behavior of a single insect species, the monophagous tephritid fly Bactrocera cacuminata (Hering). Abundance and oviposition behavior were signficantly influenced by the host structure (density of foliage) and associated microclimate. Resting behavior of both sexes was influenced positively by foliage density, while temperature positively influenced the numbers of resting females. The number of ovipositing females was positively influenced by temperature and negatively by relative humidity. Feeding behavior was rare on the host plant, as was mating. The relatively low explanatory power of the measured variables suggests that, in addition to host plant architecture and associated microclimate, other cues (e.g., olfactory or visual) could affect visitation and use of the larval host plant by adult fruit flies. For 12 plants observed at dusk (the time of fly mating), mating pairs were observed on only one tree. Principal component analyses of the plant and microclimate factors associated with these plants revealed that the plant on which mating was observed had specific characteristics (intermediate light intensity, greater height, and greater quantity of fruit) that may have influenced its selection as a mating site.     

Biochemical differentiation of lone star tick,Amblyomma americanum (L), salivary glands: Effects of attachment,feeding and mating

Salivary glands of female Amblyomma americanum (L.) are stimulated to differentiate by attachment to a host, subsequent feeding and mating. Incorporation of [³H]uridine into ribosomal and transfer RNAs as well as the synthesis of poly(A⁺)mRNA and protein parallel the pattern of increasing enzymatic activity and secretory ability of the glands. Unfed ticks contained 3.5 ± 0.47 ng poly(A⁺)mRNA/gland pr. By the second day of feeding this had increased more than 5-fold. The greatest amount of poly(A⁺)mRNA found in rapid-feeding phase females (body wt > 100 mg) was 370 ± 80 ng/gland pr. Poly(A⁺)mRNA mass doubles on the final day of feeding, just as the ticks exceeded 100 mg in wt. Ticks attached 1 to 10 days had increasingly greater amounts of salivary monosomes, 60 and 40S ribosomal subunits, and polysomes. Polysomal mass/gland pr also attained its maximum above 100 mg tick wt at the slow/rapid-feeding phase boundary; exceeding by 20 times that of unfed ticks. Degenerating glands from replete ticks continued to synthesize protein. In vitro incorporation of [³H]leucine was greatest within 24 h of attachment. Fluorographs of [³H]leucine labeled protein showed that mating caused a drop in incorporation after the 4th day of feeding. Glands from unmated females attached the same number of days continued to incorporate [³H]leucine at higher levels than those from mated females.     

Spawning behavior of the collared knifefish, Cymolutes torquatus (Labridae) in Papua New Guinea

A colony of about 10 males and nearly 50 females of Cymolutes torquatus was found living over a sandy substrate on the northwest coast of Normanby Island, Papua New Guinea at depths 14.6 to 18.3 m. Each male appeared to maintain a harem territory, approximately 10 to 14 m², with 4 or 5 females living in sub-units of this territory. Eleven matings of 4 males with 2 to 4 females each were observed on 9 and 10 April 1993. The broadcast spawning of C. torquatus is similar to that of razorfishes in the genus Xyrichtys, but in contrast to most tropical sand-dwelling fishes which mate at dawn or dusk, C. torquatus mated mid-morning between 9:38 to 10:50 h. Sexual dichromatism, color changes during mating, and cleaning of C. torquatus by juvenile Halichoeres zeylonicus are documented with color photographs.     

Extrinsic and Intrinsic Factors Influencing the Emerging and Burrowing Behaviors of Reproductively Active Adults of the White Grub Beetle, Dasylepida ishigakiensis

The subtropical scarab beetle, Dasylepida ishigakiensis, has a two-year life cycle. This study showed the time of adult emergence from the soil relative to the time of dusk and the presence of the female sex pheromone. Beetles collected on Miyako Island were transported to Tsukuba where they were immediately placed under natural day lengths in February. They exhibited two emergence peaks that corresponded to the times of dusk in Tsukuba and on the island, respectively. Males emerged precociously if a lure containing synthetic female sex pheromone was placed in their container, whereas the females’ behavior was unaffected. Previous observations that mated females dig deeper in the soil than virgin females, males or mated males were confirmed. To explore the underlying mechanism controlling the behavioral change associated with mating, liquid material derived from the male accessory glands, seminal vesicles and female bursa copulatrix was injected into beetles, but without any significant influence on burrowing behavior. No significant influence was also observed in beetles injected with anisomycin, an inhibitor of protein synthesis related to memory in other animals.     

蝇蛹金小蜂的交配行为及雄蜂交配次数对雌蜂繁殖的影响

多数昆虫能够进行多次交配,随寄生蜂雄蜂交配次数的增加,雄蜂体内精子减少,雌蜂获得的精子数量减少,产下更多的单倍体卵,发育为雄性后代;一些单寄生性的寄生蜂雌蜂一生仅能够交配1次。描述了蝇蛹金小蜂雌雄蜂的交配行为,探讨了雄蜂交配次数对雌蜂后代产量等的影响以及雌蜂的可交配次数。结果表明,交配过程包括求偶、交尾前期、交尾和交尾后期;雄蜂已交配的次数并不能够显著影响其配偶的寿命、产卵期和后代总数量,但显著影响到其配偶的雌、雄后代数量和性比。随雄蜂交配次数的增加,与之交配的雌蜂的后代雄性百分比显著增大,雌蜂在产卵期内更早地出现较多雄性后代,体内精子不足的现象更加明显。无论已交配的蝇蛹金小蜂雌蜂在产卵期中是否出现精子不足,均不能再次完成交配。     

The etiological agent of cytoplasmic incompatibility in Culex pipiens

All individuals of Culex pipiens (wide sense) which have been examined were infected with Wolbachia pipientis. Larvae reared in tetracycline were freed of these symbiotes and remained free (aposymbiotic) in future generations. When males were freed of their symbiotes, they no longer displayed incompatibility. Aposymbiotic males were compatible with all females, whether infected or not. Aposymbiotic females, on the other hand, laid fertile eggs after mating with aposymbiotic males, but not after mating with normal males. Most eggs laid by aposymbiotic females after mating with normal males showed no development at all, even though the females had been inseminated.     

Age Influence on Sexual Behavior of the Lesser Cornstalk Borer, <Emphasis Type="Italic">Elasmopalpus lignosellus</Emphasis> (Zeller) (Lepidoptera: Pyralidae)

The objective of this work was to evaluate the reproductive behavior and response of Elasmopalpus lignosellus (Zeller) males to calling females. Frequency of mating was recorded in couples during the first 7 days of the adult stage. Calling behavior of females was observed during the first 4 days of the adult stage and responses of males, in the same age intervals, to calling females were recorded in wind tunnel bioassays. The maximum number of matings occurred when the couple was between 24 and 48 h old. The scotophase period significantly influenced mating behavior, which peaked between 6 and 8 h of darkness and the mean mating duration was 93.9 ± 4.2 min. Calling females, when evaluated in a wind tunnel, attracted significantly more males than in bioassays with clean air (control). The number of individuals in calling behavior was significantly lower for females that were between 0 to 24 h old compared to the other females evaluated, but this did not influence male response. A lower proportion of males between 48 to 72 h old responded to calling females and these responses were delayed in comparison with males of other ages (0 to 24, 24 to 48, and 72 to 96 h old). These results indicate that the age of E. lignosellus males influences the response to conspecific calling females.     

Semi-monthly reproductive cycles in male and female fiddler crabs, Uca pugnax

In the fiddler crab, Uca pugnax, numbers of displaying males, numbers of burrows with half-dome superstructures (hoods), numbers of females with decalcified vulvar opercula, and numbers of females hatching their eggs, all follow a semi-monthly cycle with peaks near the time of the spring tides. These are all aspects of reproduction in Uca. Decalcification of female opercula, although necessary for mating and egg deposition, is neither necessary nor sufficient for behavioural response to courting males. In fact, behavioural responsiveness to males probably precedes decalcification in most cases. The different aspects of the reproductive cycle are coordinated so that females and males are ready to mate at about the same time near one spring tide, and the resulting eggs will be ready to hatch on the next spring tide. Two decalcified females which were kept isolated from males produced fertile clutches, suggesting that stored sperm from a previous mating may fertilize eggs in a later cycle. This may be one reason for the relative rarity of observed matings or precopulatory behaviour in Uca.     

The biosynthesis of the male housefly accessory secretion and its fate in the mated female

Autoradiographic studies of ejaculatory ducts from male houseflies, Musca domestica, previously injected with either tritiated arginine, lysine, or histidine showed that only arginine and lysine were incorporated into the stored accessory secretion. Scintillation spectrophotometry indicated that the amount of [³H] arginine incorporated into the duct correlated with the number of times the male had previously copulated. Cycloheximide and actinomycin D were effective in inhibiting the uptake of [³H] arginine in the ejaculatory ducts of newly emerged males, but only cycloheximide was an effective inhibitor in older males that had mated repeatedly. Autoradiography and electron microscopy showed that during mating the accessory secretion was transferred to the vaginal pouches of the female and that within 10 min after mating began, it was penetrating the intimal lining of the pouches. Cytolysis of many of the cells of these pouches was correlated to the transfer of the secretion during mating. This transfer of the secretion apparently terminated about 40 min after copulation began, although mating usually continued for an additional 10 to 20 min. The amount of ³H-labelled material in the haemolymph of the females increased until the completion of mating and then decreased about 60 per cent after 8 hr.