Feeding, fecundity and lifespan in female Drosophila melanogaster

Male seminal fluid proteins induce a profound remodelling of behavioural, physiological and gene signalling pathways in females of many taxa, and typically cause elevated egg production and decreased sexual receptivity. In Drosophila melanogaster, these effects can be mediated by an ejaculate 'sex peptide' (SP), which, in addition, contributes significantly to the cost of mating in females. Recent research has revealed that SP can stimulate female post-copulatory feeding, raising the possibility that the widespread female cost of mating could be due to over-feeding. In this study, we used D. melanogaster as a model to test this hypothesis. We first show that elevated post-mating feeding is dependent upon egg production and does not occur in sterile ovoD1 mutant females. This conclusion was also supported by the increase in feeding of virgin females whose egg production was experimentally elevated. We then demonstrated that sterile ovoD1 and fertile females experienced identical survival costs of mating, related to their frequency of mating and not to female feeding rate or to egg production. We conclude that female mating costs are not the result of over-feeding, but may be due to other, potentially more direct, effects of ejaculate molecules.     

Mating increases starvation resistance and decreases oxidative stress resistance in Drosophila melanogaster females

Mating stimulates complex physiological changes in females of Drosophila melanogaster. Long-term effects of mating are manifested in increased fecundity and shortened lifespan. It is not clear how mating affects stress resistance in fly females. We addressed this question here and found that mated and highly fecund wild-type D. melanogaster females have significantly higher resistance to starvation throughout their lifetime than age-matched virgin females. Mean survival time under starvation was age dependent with maximum survival time observed in 15-day-old mated females. Mating-induced increase in starvation resistance was associated with significantly higher fat reserves stored as triacylglycerols. While mated females had higher resistance to starvation, their resistance to oxidative stress was significantly lower than in age-matched virgins. Our study revealed that mating leads to an opposing relationship between resistance to starvation and resistance to oxidative stress in Drosophila females. Thus, shortened lifespan of mated females is associated with their high-fat content and greater susceptibility to oxidative stress.     

Enhanced cost of mating in female sterile mutants of Drosophila melanogaster

In Drosophila females, mating is known to cause a reduction in life span, which is referred to as 'the cost of mating'. Since mating enhances oogenesis and oviposition, the cost of mating may be regarded as a trade-off between reproduction and longevity. We examined whether the cost of mating exists in mutant females that are unable to produce eggs. Three different mutant alleles of ovarian tumors (otu) and an allele of dunce (dnc(M11)) of Drosophila melanogaster were used to sterilize females. For all the female sterile mutants tested, mating dramatically decreased the life span of homozygous sterile females. Even more extreme shortening of life spans were observed when the sex peptide gene (Acp70A) was expressed in homozygous otu females, though they were virgin, indicating that the shortening in life span is due to seminal factors. These results indicate that the cost of mating is greater in females defective in oogenesis than that in normally fertile females.     

Cost of reproduction in the Queensland fruit fly: Y-model versus lethal protein hypothesis

The trade-off between lifespan and reproduction is commonly explained by differential allocation of limited resources. Recent research has shown that the ratio of protein to carbohydrate (P : C) of a fly''s diet mediates the lifespan–reproduction trade-off, with higher P : C diets increasing egg production but decreasing lifespan. To test whether this P : C effect is because of changing allocation strategies (Y-model hypothesis) or detrimental effects of protein ingestion on lifespan (lethal protein hypothesis), we measured lifespan and egg production in Queensland fruit flies varying in reproductive status (mated, virgin and sterilized females, virgin males) that were fed one of 18 diets varying in protein and carbohydrate amounts. The Y-model predicts that for sterilized females and for males, which require little protein for reproduction, there will be no effect of P : C ratio on lifespan; the lethal protein hypothesis predicts that the effect of P : C ratio should be similar in all groups. In support of the lethal protein hypothesis, and counter to the Y-model, the P : C ratio of the ingested diets had similar effects for all groups. We conclude that the trade-off between lifespan and reproduction is mediated by the detrimental side-effects of protein ingestion on lifespan.     

Quantitative food utilization and reproductive allocation by adult milkweed bugs, Oncopeltus fasciatus

ABSTRACT. Age-specific and lifetime dry mass budgets were estimated for mated and virgin adult milkweed bugs, Oncopeltus fasciatus (Dallas) Hemiptera: Lygaeidae), fed air-dried milkweed seeds ( Asclepias syriacd ) in the laboratory at LD 14:10 and 23°C. Relative consumption rate (RCR) of all bugs was high during the first 8 days posteclosion (teneral period) as their fresh weight, dry weight, and fat content increased. Thereafter, the physiological syndrome associated with reproduction in mated females was indicated by their higher RCR, earlier and greater rate of egg production, greater lifetime relative metabolic rate and higher net and gross production efficiencies than virgin females and males. Males tended to live longer than virgin and mated females, which had similar lifespans. Mated females weighing less at eclosion remained lighter in weight on the day of mean peak weight, but food consumption, egg production and lifespan were independent of body-weight over a 25% range. Input of nymphal reserves or male reproductive secretions to egg production is probably minor in comparison with the adult female's food budget. The high proportion of the food budget allocated to egg production by mated females of O.fasciatus is consistent with its migratory, colonizing lifestyle.     

Female Gryllus vocalis Field Crickets Gain Diminishing Returns from Increasing Numbers of Matings

Although female insects generally gain reproductive benefits from mating frequently, females do not mate unlimited numbers of times. This study asks whether the limit on female mating rate is imposed by trade‐offs between reproduction and survival. Female Gryllus vocalis were given the opportunity to mate 5, 10, or 15 times with novel males, and the effects on daily fecundity (egg production), fertility (proportion of eggs that were fertilized), and female post‐experimental longevity were measured. Females that mated 10 times laid more eggs and had a higher proportion of fertile eggs than females that mated 5 times. However, females that mated 15 times did not lay significantly more eggs or have a higher proportion of fertile eggs than females that mated 10 times. Although number of matings did not affect the date that females laid their last egg, mating more times was associated with a prolonged period of laying fertile eggs. Number of matings did not affect female post‐experimental longevity. Thus, there was no trade‐off between female reproductive effort and survival, even when females mated very large numbers of times. When females were allowed to mate ad libitum, the average number of times that females mated was greater than the number of times that confers maximal fitness. The lack of cost to mating explains why females might be willing to mate beyond the point of diminishing reproductive returns.     

Costs of mating and egg production in female Callosobruchus chinensis

Costs of reproduction include the costs of mating and egg production. Specific techniques such as irradiation or genetic mutation have been used to divide the expense into costs of mating and egg production in previous studies. We tried to divide the costs in the adzuki bean beetle, Callosobruchus chinensis (Coleoptera: Bruchidae), which needs some kinds of bean as an oviposition substrate. Mated females that were not allowed to lay eggs had a shorter life span than virgin females, but they had a longer life span than mated females that were allowed to lay eggs. The results showed two independent significant costs, mating and egg production, on the life span in C. chinensis. Costs of mating, however, include the costs of sexual harassment by males and copulation itself, and we need further studies to divide the costs. The present method for dividing the cost of reproduction into costs of mating and egg production can be applied to a broad taxonomic range of insect species, and thus it will be a useful model system for inter-specific comparisons of costs of mating and egg production.     

Effects of delayed mating and male mating history on the reproductive potential of Leucoptera coffeella (Lepidoptera: Lyonetiidae)

Abstract 1 Despite the importance of Leucoptera coffeella (Guérin‐Mèneville) in coffee production worldwide, there is a lack of information on its reproduction. This knowledge will help in mass rearing, and support the development of behavioural control techniques for this insect. The present study determined the effects of delayed mating and previous matings of male L. coffeella on fecundity, egg viability and frequency of female remating. 2 The highest levels of fecundity and egg viability were obtained from matings of 1–3‐day‐old females. When females mated at 5 days of age, there were reductions of 40% in oviposition and of 43% in egg viability. 3 Females mated with 2‐day‐old virgin males were more fecund than those mated with older males; egg viability was also low (18%) from females mated with older males. 4 Virgin females that mated with virgin males laid a greater number of eggs than those mated with previously copulated males. Egg viability decreased with the increase in the number of previous male matings. 5 Five‐day‐old females remated in greater proportion than 2–3‐day‐old females. Females that copulated with males that had previously mated three times had higher rates of remating than those that copulated with virgin males. 6 The results obtained indicate that 1–3 days after emergence is the optimum age for mating. The implications of these findings for the control of L. coffeella by synthetic sex pheromone are discussed.     

Vitellogenin and egg production in the moth,Heliothis virescens

The characteristics of vitellogenin (Vg) and the relationship between Vg production and egg production in the tobacco budworm, Heliothis virescens, were studied. The relationship between Vg production and juvenile hormone (JH) and the impact of mating on Vg and egg production were also investigated. Vg appears in the hemolymph of H. virescens about 6 h after moth eclosion. Vg may be separated into two apoproteins (ApoVg-I and ApoVg-II) by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The molecular weights were calculated to be 156,065 ± 800 for ApoVg-I and 39,887 ± 323 for ApoVg-II. SDS-PAGE analysis revealed that the female hemolymph Vg polypeptides appear to be identical to those from eggs but are absent in male hemolymph. Vg concentration was significantly higher in mated females than in virgin females of the same age at 48 h after emergence. Rates of egg production increased as Vg production increased; rates of egg production in mated females were significantly higher than those of virgin females at 48, 72, 96, and 120 h postemergence. Vg production is dependent on JH, because hemolymph from decapitated females lacked Vg while that of decapitated females treated with synthetic JH had Vg at levels comparable to similarly aged, normal H. virescens females. Hemolymph JH titers in mated females were significantly higher compared with those in virgin females at all sampling periods. The high JH level in mated females may explain the high Vg and egg production in mated H. virescens. Arch. Insect Biochem. Physiol. 34:287–300, 1997. © 1997 Wiley-Liss, Inc.     

Combinative stimulation inactivates sex pheromone production in the silkworm moth, Bombyx mori.

Mating results in a strong suppression of sex pheromone (bombykol) production in the female silkworm moth, Bombyx mori. The mechanical stimulation from the insertion of a penis, inflation of the bursa copulatrix (BC), or copulation with the sterile male whose penis was removed in order to prevent ejaculation (pr-male) induced only a partial decline in bombykol production. Artificial insemination stimulates oviposition of fertilized eggs as does normal mating. However, bombykol production did not decline in artificially inseminated females. When females were artificially inseminated before or after mating with pr-males, some females had a small amount of bombykol, similar to females mated with normal males, while other females had a large amount of bombykol similar to virgin females. The former usually laid fertilized eggs, while the latter laid only unfertilized eggs though semen filled their spermatophores and spermathecae. The mechanical stimulation caused by mating with a pr-male could be replaced by covering the abdominal tip with melted paraffin. Neither implantation of the BC obtained from mated females, nor injection of the spermatophore extract, into a female mated with a pr-male could inactivate bombykol production. Injection of hemolymph from a mated female into a virgin also failed to affect bombykol production These results indicate that a combination of both the tactile stimulation of the abdominal tip and the arrival of fertile spermatozoa in the vestibulum trigger a neural inactivation mechanism of bombykol production after mating.     

Male age affects female mating preference but not fitness in the monandrous moth Dendrolimus punctatus Walker (Lepidoptera: Lasiocampidae)

It is widely accepted that male age can influence female mating preference and subsequent fitness consequences in many polyandrous species, yet this is seldom investigated in monandrous species. In the present study, we use the monandrous pine moth Dendrolimus punctatus to examine the effects of male age on female mating preference and future reproductive potential. In multiple male trials, when permitted free mating from an aggregation consisting of virgin males aged 0 (young), 2 (middle-aged) and 4 (old) days, virgin females preferentially mate with young and middle-aged males, although mating latency and mating duration are independent of male age. In single male trials, when virgin females are randomly assigned single virgin males of known age, a negative correlation is found between mating success and male age in this species. However, we find that male age also has no effect on mating latency and mating duration. Further fitness analysis reveals that females do not receive benefits in terms of oviposition period, total egg production, average daily egg production, percentage of egg hatching, longevity, expected reproduction and relative expected reproduction from mating with young and middle-aged males compared with mating with old males. The results of the present study are the first demonstrate that females mated preferentially with younger males but gain no apparent fitness benefits in a monandrous moth species.     

Interactions of mating,egg production and death rates in females of the Mediterranean fruit fly,Ceratitis capitata.

Costs of reproduction include costs of producing eggs and of mating itself. In the present study, we made an experimental investigation of costs of reproduction in the Mediterranean fruit fly (medfly, Ceratitis capitata). We demonstrated that virgins live longer than non-virgin females. However, in strong contrast to most findings within the Diptera, non-virginity had no detectable effect on egg production. Therefore the increased longevity of the virgin females cannot be attributed to an increase in egg production in non-virgin females, and instead indicates a cost of mating. A comparison of the life spans of normal females and those sterilized by low doses of X-irradiation, revealed an additional cost of egg production. There were no significant differences in remating levels between females that did and did not lay eggs, showing that the cost of producing eggs is independent of mating frequency. Medfly females therefore suffer a decrease in survival as a result of egg production and of mating, and these costs are independent of one another. To put our results into context, we reviewed the existing literature on the effects of mating on longevity, egg production and sexual receptivity for 64 species of Diptera, and examined the pattern of mating effects that emerged.     

A cost of maternal care in the dung beetle Onthophagus taurus?

Parental care theory assumes that investment in current offspring will trade against future investment. A number of field studies on birds have used clutch size manipulations to demonstrate a survival cost to chick rearing. However, such studies do not account for costs accrued during earlier stages of reproduction because not all aspects of reproductive effort are manipulated by varying the number of nestlings. In this study, we investigate the effect of reproductive effort on female survival in the dung beetle, Onthophagus taurus. By experimentally manipulating mating status and dung availability, we demonstrate that virgin females survive longer than mated females and that the survival of mated females was negatively associated with the number of brood masses produced. Using a novel manipulation of the mating system, we separated the effects of egg production and maternal care on female survival. Previously, we have shown that females provisioning with the assistance of a major male provide relatively less care than unassisted females. However, paternal assistance did not alter the number of brood masses produced and hence the amount of reproductive effort that was allocated to egg production. Therefore, our finding that female survival was increased when receiving paternal assistance provides, to our knowledge, the first definitive evidence that maternal care reduces female lifespan. These results are of major importance to theoretical models on the evolution of parental care.     

Biotin deficiency decreases life span and fertility but increases stress resistance in Drosophila melanogaster

Biotin deficiency is associated with fetal malformations and activation of cell survival pathways in mammals. In this study we determined whether biotin status affects life span, stress resistance, and fertility in the fruit fly Drosophila melanogaster. Male and female flies of the Canton-S strain had free access to diets containing 6.0 (control), 4.8, 2.5, or 0 pmol biotin/100 mg. Biotin concentrations in diets correlated with activities of biotin-dependent propionyl-CoA carboxylase and biotin concentrations in fly homogenates, but not with biotinylation of histones (DNA-binding proteins). Propionyl-CoA carboxylase activities and biotin concentrations were lower in males than in females fed diets low in biotin. The life span of biotin-deficient males and females was up to 30% shorter compared to biotin-sufficient controls. Exposure to oxidative stress reversed the effects of biotin status on survival in male flies: survival times increased by 40% in biotin-deficient males compared to biotin-sufficient controls. Biotin status did not affect survival of females exposed to oxidative stress. Exposure of flies to cold, heat, and oxidative stress was associated with mobilization of biotin from yet unknown sources. Biotin deficiency decreased fertility of flies. When biotin-deficient males and females were mated, the hatching rate (larvae hatched per egg) decreased by about 28% compared to biotin-sufficient controls. These findings are consistent with the hypothesis that biotin affects life span, stress resistance, and fertility in fruit flies.     

Oxidative damage and plasma antioxidant capacity in relation to body size,age, male sexual traits and female reproductive performance in the collared flycatcher (<Emphasis Type="Italic">Ficedula albicollis</Emphasis>)

The study of oxidative stress is a potential tool for studying the functional interactions among life history traits, sexual traits and physiological status in animals. In this study, we investigated relationships between measures of plasma oxidative status and male sexual traits, female reproductive investment and three other life history traits, in a wild population of collared flycatchers (Ficedula albicollis). Flycatcher males with a larger white forehead patch had higher level of plasma antioxidant capacity. For females, clutch size was not associated with plasma oxidative status, but egg size was positively correlated with antioxidant capacity. The relationship between age and levels of plasma oxidative damage remains controversial in this species: young female flycatchers showed higher levels of hydroperoxides compared to antioxidants, whereas age did not predict oxidative status of males. Males had higher levels of oxidative damage than females, although the concentration of antioxidant compounds was similar between the sexes. Females that mated with more ornamented males had higher plasma antioxidant capacity. Our results suggest that, for males and females, greater investment in sexual signal and reproduction, respectively, does not reduce the capacity for self-maintenance or avoidance of oxidative stress. Finally, our data support indirectly the occurrence of assortative mating in our species, since females with higher plasma antioxidant capacity mated with more ornamented males.     

Juvenile hormone biosynthesis,oocyte growth and vitellogenin accumulation in Choristoneura fumiferana and C. rosaceana: a comparative study

We assessed the effects of age and mating status on in vitro juvenile hormone (JH) biosynthesis, oocyte growth, egg production and vitellogenin (Vg) accumulation in the tortricid moths, Choristoneura fumiferana and C. rosaceana. To determine whether vitellogenesis is dependent on the presence of JH, we also examined the effects of decapitation and JH analog treatments on egg production. In both species, the corpora allata (CA) of adult females released fmol quantities of JH, with JH II being the major homolog produced. The CA began producing detectable quantities of JH around the time of emergence. Full activation of the CA was observed a few hours sooner in C. fumiferana than in C. rosaceana. In pharate adults and young virgin females of both species, growth of the basal oocyte reflected changes in CA activity. Decapitation of newly emerged females significantly reduced egg production, but treatment of decapitated females with the JH analog methoprene resulted in egg production that was similar to (C. fumiferana) or greater than (C. rosaceana) that of controls, indicating that JH is required for oocyte maturation. Vg was first observed in the hemolymph before the presumptive time of CA activation, suggesting that the synthesis of this protein is not dependent on JH. The presence of normal quantities of Vg in the hemolymph of pupae decapitated before CA activation confirmed this hypothesis. The Vg titer underwent a transient decline following CA activation and was significantly lower in mated than in virgin females of both species 3 and 5 days after copulation. Since CA activation at emergence and mating are both expected to cause a rise in the JH titer, we suggest that the declines in the levels of Vg result from JH-enhanced Vg uptake by the developing oocytes. Mating induced a significant increase in egg production but had no measurable impact on rates of JH biosynthesis in vitro.     

Single and multiple mating reduces longevity of female dumpling squid (Euprymna tasmanica)

For many species, mating is a necessary yet costly activity. The costs involved can have an important influence on the evolution of life histories and senescence. Females of many species mate multiply, and this behaviour can inflict a longevity cost. Most studies investigating the effects of multiple mating on female survival have been conducted on insects, and the effects in other taxa are largely unknown. We investigate the effects of both a single mating and a second mating on longevity in female dumpling squid (Euprymna tasmanica), a species in which both sexes mate multiply. Through comparing the longevity of virgin, once‐mated and twice‐mated females, we found that a single mating reduced female life span by 15 days on average. A second mating resulted in an additional 8 day (on average) longevity cost, despite no difference in total clutch mass, number of clutches, single egg mass or number of eggs per clutch between once‐mated and twice‐mated females. This demonstrates a cost to multiple mating which may be independent of the cost of egg production. Furthermore, total clutch mass and female life span were positively correlated, whereas female life span decreased with increasing average water temperature. The presence of an additive effect of reproduction on longevity suggests that multiple mating in cephalopods may have benefits that outweigh these costs, or that there is a conflict in optimal mating frequency between males and females.     

Seasonal dimorphism of foliage in Californian coastal sage scrub

Summary An experiment was conducted to examine the relationship between reproduction and longevity in an annual iteroparous species of grasshopper, Melanoplus sanguinipes. Two hypotheses derived from life history theory were tested. These included: 1) virgin females produce fewer eggs and live longer than mated females, and 2) the rate of egg production and longevity are negatively related. The results of this study indicated that there is no trade-off between reproduction and longevity in this species of grasshopper. It is suggested that other factors, such as male-female interactions, may be more important in affecting female survival than reproduction.