Renewal of sexual receptivity in mated female mosquitoes, Aedes aegypti

ABSTRACT. Females of Aedes aegypti (L.) (Diptera, Culicidae) were not receptive to mating 1 h after the initial insemination or at later times throughout the first gonotrophic cycle. A significant proportion of these females (75–90%) were inseminated again prior to the second gonotrophic cycle. Insemination was determined by the detection in females of sperm labelled with ³ H(G)-adenine or ³²PO₄ after matings with radiolabeled males. Females deprived of males after the first insemination displayed an abnormal reduction in fertility throughout successive gonotrophic cycles.     

The programming of circadian flight-activity in relation to mating and the gonotrophic cycle in the mosquito, Aedes aegypti

ABSTRACT. The circadian flight activity of female Aedes aegypti (L.) changes after insemination and during the course of the gonotrophic cycle. Virgin females attain a high level of spontaneous activity within 3–4 days of adult emergence; in LD 12:12 there are peaks of activity at the beginning and end of the light phase. Inseminated females are less than 20% as active as virgins, but exhibit a similar daily pattern. After blood-feeding, inseminated females become almost totally inactive for about 48h and then show a unimodal pattern of activity which is consistent with oviposition behaviour; after oviposition they revert to the basic inseminated pattern and level of activity. Blood-fed virgin females continue to show a high level of spontaneous activity. It is suggested that insemination has the general effect of raising the threshold for activity and that it is necessary before blood-fed females can switch to the gravid behaviour programme. Blood-fed uninseminated females thus continue with behaviour which will maximize the probability of insemination.     

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.     

A survival and reproduction trade-off is resolved in accordance with resource availability by virgin female mosquitoes

The first 2-4 days after an Anopheles gambiae female mosquito emerges are critical to her survival and reproductive success. Yet, the order of behavioural events (mating, sugar feeding, blood feeding) during this time has received little attention. We discovered that among female cohorts sampled from emergence, sugar feeding had a higher probability than blood feeding of occurring first, and mating rarely occurred before a meal was taken. The night after emergence, 48% of females fed on sugar in mesocosms, and 25% fed on human blood; in the absence of sugar, 49% of females fed on human blood. After 5 days, 39% of the sugar-supplied females had blood fed and mated, and were fructose negative, whereas only 8% of the sugar-denied females had both blood fed and mated by this time. The model that best explained the transitions suggests that females made use of two distinct behavioural pathways, the most common one being to sugar-feed, then mate, and then seek blood. Other females sought blood first, then mated, and forwent a sugar meal. Lipid levels were higher in females with access to sugar than in females without access to sugar, particularly for those in later gonotrophic stages, while glycogen levels in the sugar-supplied group were higher throughout. In single-night experiments with females having had access to sucrose since emergence, those given a blood meal 1 day before spending a night with males had higher insemination rates than those not receiving the blood meal. These results indicate that the trade-off between survival and immediate reproduction is resolved by young adult females in accordance with availability of resources and gonotrophic state.     

Nectar feeding by mosquitoes in Sweden, with special reference to Culex pipiens and Cx torrentium

1. Nectar feeding by mosquitoes collected from tansy (Tanacetum vulgare) flowers was studied in July and August 1983-85 at two sites in central and south-western Sweden. Prior to fructose analysis, gonotrophic state and parity was determined. 2. A total of 1010 mosquitoes (70% males) of eighteen species was collected. Fructose was detected in 75% of the males and 78% of the females. Most (86%) mosquitoes collected belonged to Culex pipiens and Cx torrentium. 3. Among 219 Cx pipiens females, for most of which the abdomen appeared gravid (52%) or empty (42%), 81% were fructose-positive. Females of other species were also proved to have fed on plant sugars in both early and later stages of the gonotrophic cycle. 4. In Cx pipiens and males of Cx torrentium peak nectar feeding occurred between 22.00 and 04.00 hours. Data for males of both species suggested a V-shaped pattern of nectar feeding activity during the night. 5. At about 16 degrees C nearly all mosquitoes became fructose-negative in the anthrone test within 20 h after collection from tansy flowers. 6. At least 44% of Cx pipiens females that were attracted to a dove-baited trap had fed on plant sugars shortly before.     

Swarming and mating of Aedes communis mosquitoes in nature

The date of the beginning of mating behaviour in males and females, the rate of insemination and the increasing of bloodsucking activity of females were studied in natural environments. Over 80% of females mated on the 3-4th day after emergence; after fertilization their behaviour changed from looking for males for coupling to looking for ones for a prey. The male swarming began on the 5th day after emergence and simultaneously the appearance of inseminated females was observed. The places of mating of males and females were investigated. It was established that coupling took place in swarms with swarming males and out of swarms with freely flying males.     

Lipid metabolism during sequential gonotrophic cycles in large and small female Aedes aegypti

The lipid metabolism was investigated during six gonotrophic cycles of Aedes aegypti. Females of constant body size were analyzed for their total lipid content: large females with a body size of 41.06 (wing length cubed) and small females with 15.63. Their lipid contents at eclosion were compared to lipid values after two days of sugar-feeding, shortly before a blood meal, after oviposition, of their total egg batches, and again before the next blood meal, with intermittent access to sugar for two days for six gonotrophic cycles.Large females transferred most of their pre-blood meal lipid into the ovaries. Their low lipid content after oviposition was restored by synthesis from intermittent sugar meals. After the third gonotrophic cycle, they withheld more and more of the resynthesized lipid in their fat body, thus gradually reducing their fecundity. Since blood consumption was not altered significantly during these six cycles, age-related reduction of fecundity was clearly caused by limitations of yolk lipid.Small females transferred a considerably smaller, but constant segment of sugar-derived lipids to the ovaries. In both size classes, lipid content per oocyte was constant throughout all cycles with 9 mcal/oocyte in large and 7 mcal/oocyte in small females. Total fecundity reached 450 eggs in large and 280 eggs in small females. Large females that were maintained on water without sucrose took large blood meals from which part of the yolk lipid was synthesized. Extrapolations suggest that only one or two additional gonotrophic cycles would be possible without additional carbohydrate sources, despite lipogenesis from blood protein.     

Age effects on the insemination rate ofAnopheles gambiae s.l. in the laboratory

Age effects on the insemination rate of the Galisua strain ofAnopheles gambiae s.s. (Diptera: Culicidae) and of the Nyanza strain ofAn. arabiensis were investigated in the laboratory. Batches of 7-day old males and females were kept together for 24 h with batches of mosquitoes of the opposite sex of ages ranging from 1–7 days. Males and females were also kept together continuously from emergence. The effect of increasing male/female ratios on the insemination rate was investigated as well. The insemination rate ofAn. arabiensis in the laboratory (96%) was similar to that found in nature, whereas that of our strain ofAn. gambiae s.s. was consistently low (maximum 72%), particularly after females had been together with males for a 24 h period only. The optimum age for insemination was 7 days for males and females of both species. The insemination rate of our strain ofAn. arabiensis was significantly higher at all ages than that of our strain ofAn. gambiae s.s.. The latter strain became inseminated at the earliest when 4 days old. An increase in the male/female ratio significantly enhanced the insemination rate in both strains. It was found that motility of spermatozoa inside the spermatheca, once in contact with saline, could be used as a marker for the approximate time of insemination. It is concluded that the relatively low insemination rate of the Galisua strain ofAn. gambiae s.s. is unlikely to be caused by the rearing conditions. Other factors that may be responsible are discussed.     

The production of cloned fish in the medaka (Oryzias latipes)

The measurement of cellular DNA content by DNA microfluorometry revealed that medaka embryos that were fertilized with normal sperm and exposed to heat shock (41 degrees C for 3 min) or hydrostatic pressure (700 kg/cm2 for 10 min) at 85-95 min after insemination were tetraploid. Embryos fertilized with normal sperm and exposed to heat shock (41 degrees C for 2 min at 2-3 min after insemination) were triploid. These results suggest that heat shock or hydrostatic pressure at 85-95 min after insemination arrests the first cleavage, while heat shock at 2-3 min after insemination arrests the second meiotic division. Medaka clones have been produced by the following method: Eggs from orange-red or variegated variety were activated by UV-irradiated, genetically impotent sperm of wild-type fish (UV sperm). The haploid eggs obtained were diploidized by preventing the first cleavage with heat shock or hydrostatic pressure to produce homozygous females. Each of the two homozygous females was mated with vasectomized male in isotonic balanced salt solution to collect unfertilized eggs. The collected eggs were activated with UV sperm and converted from haploid to diploid by arrest of the second meiotic division with heat shock. Hatched fry of each homozygous diploid (all females) were fed with a methyltestosterone-containing diet (40 micrograms/gm diet) to produce sex-reversed males, which were mated with brood females, and thus two cloned lines were obtained.     

Nectar feeding by the early-spring mosquito Aedes provocans

Abstract. Nectar feeding by males and females of the mosquito Aedes provocans was studied at a site near Belleville, Ontario, Canada. Canada plum, Prunus nigra , and especially pin cherry, P. pensylvanica , bloomed contemporaneously with the emergence of Ae. provocans and were important nectar sources for adult mosquitoes during their first week of life. Blossoms of P. pensylvanica shielded for 24 h from foragers produced an average of 0.14 mg of sugar (≅ 2.3 J). This nectar was avidly sought by both sexes of Ae.provocans; > 97% of the blossoms were visited by mosquitoes in the first few days of blooming. Young adult mosquitoes were found on blossoms at all hours of the day and night; feeding on P. nigra was strongly eocrepuscular, whereas on P.pensylvanica feeding was much less strongly periodic. Adults foraged for nectar in an energy-conserving, pedestrian strategy, devoting 56% (females) and 68% (males) of their time on blossoms to nectar feeding during foraging bouts that lasted a median of 5.3min. Both sexes sought nectar soon after emergence - males before they had completed hypopygial rotation or swarmed, and females before mating or host seeking. Female Ae.provocans sought nectar in all stages of oogenesis, but primarily at the initiation of a gonotrophic cycle. Energy stores in the crop averaged 18 J per female, with a distribution that depended on gonotrophic age and parity.     

Sperm transport after insemination in the Alpine newt (Triturus alpestris, Caudata, Salamandridae)

The goal of this study was to test if sperm transport to the spermathecae in the Alpine newt (Triturus alpestris) requires active co-operation of the female. Artificial insemination of anaesthetised female newts was conducted using spermatophores collected from courting males and with sperm duct contents collected from sacrificed males. Sperm was present in the spermathecae of 9 out of 10 females inseminated with the spermatophores but in only 1 out of 8 females inseminated with sperm duct contents. The females of both groups laid some eggs after insemination, and a portion of these eggs in group of females inseminated with spermatophores were fertilized. However, the number of eggs produced by the females was much lower than typical egg-production in newts. The presence of sperm in the spermathecae of females inseminated with spermatophores and lack of sperm in the spermathecae of females inseminated with sperm duct contents suggests that sperm transport is either induced by the substances present in spermatophores and/or that sperm from the sperm duct is not fully mobile in comparison with sperm from the spermatophores.     

First copulation increases longevity and fecundity of <Emphasis Type="Italic">Histiostoma feroniarum</Emphasis> (Acari: Astigmata: Acaridida) females

I investigated the influence of insemination at different life stages on female fitness in the mite Histiostoma feroniarum. In this species, males guard immature females at the tritonymph stage to inseminate them immediately after the last moulting. Four groups of females were studied (1) females inseminated naturally, i.e. mating occurred immediately after guarding, and then the male was removed (IF/0M), (2) naturally inseminated females, where after insemination the male was replaced by two additional males (IF/2M), (3) virgin females reared without males (VF/0M) and (4) mature, virgin females to which two virgin males were added 3 days after last moulting (VF/2DM). The results show that females inseminated naturally (IF/0M) have higher longevity and fecundity than either virgin (VF/0M) or late-inseminated females (VF/2DM). Furthermore, longevity and fecundity of the former (IF/0M) was also greater than that of females naturally inseminated and subsequently exposed to males (IF/2M). One may suggest that seminal fluids have a positive effect on female fitness. When delayed insemination occurs, such positive effect may not be observed due to a change in features of the sperm access system. Harassment may explain decreased longevity and fecundity of females inseminated naturally compared to females that received additional males.This revised version was published online in May 2005 with a corrected cover date.     

Multiple traumatic insemination events reduce the ability of bed bug females to maintain water balance

To examine how traumatic insemination, a wounding process to females inflicted by males during copulation, reduces the longevity of females of the bedbug, Cimex lectularius, we assessed if multiple bouts of mating impact water relations of females by measuring net transpiration water loss rates. Our studies show that net transpiration rate of females correlates with frequency of mating (small increase after exposure to low numbers of males; large increase after exposure to large numbers of males), and this is reflected by reduced female survivorship for as much as 22 days at 75% RH, 25°C. Water loss occurs up to 28% more rapidly in females after being held with large groups of males. Females that were exposed to males having their paramere removed, females exposed only to other females, and females kept in isolation (unmated) exhibited no reduction in ability to retain water, indicating that traumatic insemination was responsible for the net transpiration rate increase. Mechanical piercing of the female’s abdominal wall leads to increased net transpiration rates for longer periods than puncturing the ectospermalege (regular mating site), implying that inaccurate copulation by males is extremely detrimental to the water balance of females and that the ectospermalege is uniquely modified to seal off more quickly to prevent excess water loss. Mating frequency and the associated increased water loss is considerably reduced by the addition of bed bug alarm pheromone components. Thus, females experience elevated water stress due to traumatic insemination, especially at high levels and when males fail to pierce the ectospermalege, and water loss prevention, likely by more rapid sealing of the wound, is a novel function of the ectopsermalege.     

Effects of Plasmodium yoelii nigeriensis infection on Anopheles stephensl egg development and resorption

Abstract It has been shown previously that infection with Plasmodium yoelii nigeriensis reduces the number of eggs produced by female Anopheles stephensi. Here we examine the mechanism underlying fecundity reduction. Ovaries from infected and uninfected (control) female mosquitoes were examined12, 24 or 36 h after blood-feeding during the first gonotrophic cycle (replicated) or the second gonotrophic cycle (unreplicated). Follicular development was assessed according to Christophers' stages and the proportions of developing and resorbing follicles per ovary were determined. Resorption of some follicles commenced within 12h of blood-feeding, affecting significantly more follicles in the infected females: 1.1% v. 3.2%. The difference was greatest 36h after blood-feeding: 25% reduction (10 v. 35%) in the first cycle; 16% reduction (9 v. 25%) in the second gonotrophic cycle. The mean speed of oogenesis was also found to be significantly retarded in infected mosquitoes. During the second gonotrophic cycle, for example, only 92–94% of follicles reached stage III by 24 h and stage IV by 36 h in infected females, whereas all the developing follicles of uninfected females reached these stages more or less synchronously in the time specified.     

Biosynthesis and titre of juvenile hormone during the first gonotrophic cycle in isolated and crowded Locusta migratoria females

Basal oöcyte length, corpus allatum volume and “in vitro” juvenile hormone biosynthesis were measured in isolated and crowded Locusta migratoria females at selected times during the first gonotrophic cycle. Using gas chromatography-mass spectrometry with selected ion monitoring, the juvenile hormone titre in the haemolymph of isolated and crowded females was also determined 1 and 4 days after fledging. The rate of oöcyte growth was more rapid in isolated females and a significant (P < 0.01) difference in mean length was apparent as early as 3 days after fledging. This early manifestation of a difference in rate of oöcyte growth was correlated with a difference in haemolymph juvenile hormone titre between isolated and crowded females. Whilst there was no difference in titre 1 day after fledging, by day 4 the juvenile hormone titre in isolated females was found to be approximately twice that in crowded females. There was no significant difference in the rates of juvenile hormone biosynthesis by corpora allata from isolated and crowded females on days 0 through to 6 after fledging. On day 8, however, the rates of juvenile hormone biosynthesis of corpora allata from isolated females were very high (mean value = 136 pmol/h/pair) and were significantly (P < 0.002) greater than those of corpora allata from crowded females. Day 8 was also the point in the first gonotrophic cycle at which the difference in the mean basal oöcyte length in isolated and crowded females was at a maximum. The mean volume of corpora allata from isolated females was greater than that of corpora allata from crowded females at all points at which measurements were taken during the first gonotrophic cycle.     

Sexual size dimorphism and sexual selection in turtles (order testudines)

Summary This paper combines published and original data on sexual size dimorphism, reproductive behavior, and habitat types in turtles. Our major finding is that observed patterns of sexual size dimorphism correlate with habitat type and male mating strategy. (1) In most terrestrial species, males engage in combat with each other. Males typically grow larger than females. (2) In semiaquatic and bottom-walking aquatic species, male combat is less common, but males often forcibly inseminate females. As in terrestrial species, males are usually larger than females. (3) In truly aquatic species, male combat and forcible insemination are rare. Instead, males utilize elaborate precoital displays, and female choice is highly important. Males are usually smaller than females.We interpret these correlations between sexual behavior and size dimorphism in terms of sexual selection theory: males are larger than females when large male size evolves as an adaptation to increase success in male combat, or to enable forcible insemination of females. In contrast, males are usually smaller than females where small size in males evolves to increase mobility (and hence, ability to locate females), or because selection for increased fecundity may result in increased female size. In turtle species with male combat or forcible insemination, the degree of male size superiority increases with mean species body size.     

Female Choice and the Consistency of Courtship Feeding in Black-horned Tree Crickets Oecanthus nigricornis Walker (Orthoptera: Gryllidae: Oecanthinae)

Courtship feeding in insects is often strongly correlated with insemination duration and therefore provides a potential postcopulatory episode of sexual selection. We tested whether courtship feeding and other courtship traits in the black-horned tree cricket Oecanthus nigricornis showed sufficient consistency potentially to respond to sexual selection by testing whether they differed significantly among males. Duration of courtship feeding differed among males when measured repeatedly and this caused significant differences in the duration of spermatophore attachment, a trait that determines the maximum duration of insemination and thus has important fitness consequences in crickets. We also partitioned variance in courtship behaviour between the sexes to test whether differences in courtship behaviour were attributable primarily to males, females or both sexes. Duration of spermatophore attachment was controlled by females and therefore represents a mechanism of female mate choice. Significant variation in duration of spermatophore attachment was associated with differences between individuals of both sexes. Differences among males indicate that females agree in their preference of certain males whereas differences among females indicate that females differ in their receptivity to postcopulatory courtship and insemination. The fact that differences among males in duration of spermatophore attachment were due to significant differences solely in the period of courtship feeding indicates that postcopulatory female choice was mediated through courtship feeding. Whether males manipulate female choices by allocating more or fewer resources requires further testing, but we found that males court some females more vigorously than others after females dismount. The number of previous mates had opposite effects on the duration of courtship feeding for the sexes, decreasing it for males but increasing it for females, and we discuss the possible causes of these results.     

Intromission Induces and Insemination Reduces Female Immune Response in the Medfly

Sexual reproduction exposes females to immune threats. The immune response of females to these threats may conflict with male reproductive interests. We examine the hypothesis that in the Mediterranean fruit fly, Ceratitis capitata, female immune activity during and after copulation reflects this conflict, and its resolution. By comparing the temporal changes in immune status of females paired with normal males to virgin females of the same age, or to those paired with surgically altered males (that perform normal courtship without intromission), we determined the specific effects of courtship, intromission and insemination on female immune response. At the initiation of mating, levels of the immune enzyme Phenoloxidase (PO) were higher in mated females compared to virgin females. Females who copulated with normal males, compared to females paired with males lacking external genitalia, had significantly higher levels of PO. However, 2 h after the beginning of mating PO levels decreased significantly, and increased again 24 h later. These changes may be interpreted as a sequential resolution of the ongoing conflict of interest between males and females, with the advantage shifting from one sex to another.     

栗山天牛成虫取食、交配和产卵行为

通过室内配对饲养和野外观察,本文研究了栗山天牛成虫的取食、交配和产卵行为。结果表明:栗山天牛成虫吸食从栎树树皮受伤处溢出的汁液补充营养。栗山天牛雄成虫比雌成虫更具攻击性,在取食和交配中的雄成虫易发生争斗,交配中的雄成虫攻击性最强。其攻击方式主要是用上颚咬住对手的触角或者足进行拖拽。70%的栗山天牛雄成虫争斗是为了争夺配偶,其次是为了争夺食物资源。栗山天牛成虫完成一次完整的交配经过4个阶段,即:识别、追逐-攀附、抚慰-插入输精-交尾间歇、配后保护。整个交配过程最长可达2 h。试探性插入、插入输精和输精后保护是整个交配过程的重点,持续时间长短不一。雄成虫输入精子的次数与交配持续的时间成正比。雄成虫每次插入输精持续的时间与次数成反比,每次输精间歇时间与次数成正比。雄成虫输入精子之后会再次插入保护,平均持续约1 min。栗山天牛雌成虫产卵于寄主树皮裂缝中。以上研究为了解栗山天牛成虫的行为及其防治提供参考。     

Transcervical artificial insemination in the domestic ferret (Mustela putorius furo)

The research was undertaken to develop a successful nonsurgical procedure for artificially inseminating ferrets. A fiberoptic endoscope used in conjunction with a specially designed speculum and catheter permitted cervical catheterization and intrauterine insemination. Sperm were collected from the cauda epididymides of 10 discarded breeder males; the number of sperm in diluted samples used for insemination ranged from 4.4–13.6 × 10⁶/100 μl with progressive motility of sperm ranging from 40 to 60%. Sperm collected from each male were diluted with an egg-yolk extender (TEST) and used to inseminate 8–12 females, with deposition of sperm intravaginally or transcervically into the uterine body 0 or 24 hr after an ovulatory injection of human chorionic gonadotropin (hCG). The vaginal inseminations were used as a control, and no pregnancies resulted after insemination of 26 females. Intrauterine inseminations resulted in 4/24 (17%) of the ferrets pregnant when hCG administration was coincident with insemination, and 19/24 (79%) of the ferrets were pregnant when inseminations were done 24 hr after hCG administration. All inseminated females were euthanized on day 20 after insemination to count fetuses. The mean number of fetuses was 3.1 (range, 1–8). The number (millions) of motile sperm inseminated (X) had a significant effect on the percentage of fetuses (Y). Regression analysis indicated a linear relationship between the two variables, with an R² value of 0.99 and a line of best fit described by the equation Y = 0.029 + 0.034 X. This paper is the first report of transcervical artificial insemination in the domestic ferret (Mustela putorius furo). The method can serve as a model for application to ferrets and other mammals, particularly endangered species. Zoo Biol 17:393–404, 1998. © 1998 Wiley-Liss, Inc.