A mortality cost of virginity at older ages in female Mediterranean fruit flies

Overwintering potential of the Mediterranean fruit fly (Diptera: Tephritidae) in Austria

The Mediterranean fruit fly (medfly), Ceratitis capitata (Wiedemann), one of the most important invasive pests of fresh fruits and vegetables from the coastal Mediterranean habitats, is expanding its current geographic distribution to cooler more temperate areas of Europe. Every year since 2010 the fly is detected in the area of Vienna, Austria. However, whether it can establish permanent populations is not known. In this current paper, the capacity of C. capitata to overwinter in Vienna, Austria (48.1° northern latitude) was studied over 2 consecutive winter seasons (2020-2022). Overwintering trials with different life stages (larva, pupa, and adult) of C. capitata were performed in the open field and in the protected environment of a basement without a heating system. Control flies were kept under constant conditions in a climate chamber (25 °C, 60% RH, 14:10 L:D). Our data showed that no life stage of the Mediterranean fruit fly was able to survive the Austrian winter in the open field. However, in the protected environment C. capitata outlived the winter months in all studied life stages at least in small numbers and several surviving females were able to lay eggs at the time of the following fruiting season. Implications of these findings for the ongoing geographic range expansion of the pest in temperate European countries are discussed.

Olfactory sensitivity to major, intermediate and trace components of sex pheromone in Ceratitis capitata is related to mating and circadian rhythm

The Mediterranean fruit fly, Ceratitis capitata Wied., is a worldwide pest of several fruits given its extremely wide host range which includes more than 250 different species of fruits and vegetables. Its high biological potential is mainly due both to its ability to readily adapt to new environments and its high reproductive capacity as it completes multiple generations each year. Since sexually mature males emit a sex pheromone to call both other males for "lekking" and receptive females for mating, many studies have been directed to characterize the chemical composition of the sex pheromone. Besides, the release of sex pheromone appears to be modulated both by mating and time of day. Based on these considerations, we measured the olfactory sensitivity of antennae and palps of C. capitata to six volatiles of the male sex-pheromone: α-farnesene and geranyl acetate (major components), linalool and β-myrcene (intermediate components), β-farnesene and 2,3-butanediol (minor/trace components). The electroantennogram (EAG) and electropalpogram (EPG) responses were evaluated in both sexes, at different physiological states (virgin and mated), and at different times of the day (morning and afternoon). The results show that the EAG amplitude values in response to all stimuli are higher in the morning than in the afternoon for both sexes and in both virgin and mated insects. Furthermore, in both sexes, the olfactory sensitivity of virgin insects is higher than in mated ones. The EPG amplitude in response to all stimuli is higher in the morning in mated females than in virgin females and higher in the morning than in the afternoon in both mated sexes. By gaining knowledge on the effects of sex, physiological state and time of day on the olfactory sensitivity of C. capitata, one could better understand the medfly reproductive behavior.

Demographic Analysis of Sex Ratio on Population Growth of Bactrocera dorsalis (Diptera: Tephritidae) With Discussion of Control Efficacy Using Male Annihilation

The life table data for the oriental fruit fly, Bactrocera dorsalis (Hendel), at different adult sex ratios (1♀: 1♂, 1♀: 50♂, 50♀: 1♂ free-choice mating, and 50♀: 1♂ no-choice mating) were collected to determine the effects of sex-ratio manipulation on current pest control procedures. At 1♀: 1♂, females mated, on average, 2.3 times during their lifetime with a mean fecundity (F) of 1,122 eggs. The net reproductive rate (R0), intrinsic rate of increase (r), finite rate (λ), and mean generation time (T) were 561.0 offspring, 0.1693 d- 1, 1.1844 d- 1, and 37.4 d, respectively. At 50♀: 1♂ free-choice mating, males mated 46.7 times during their lifetime, while at 50♀: 1♂ no-choice mating, males mated on average 50 times during their lifetime, and all females mating only once in both treatments. The values for F, r, and λ were significantly lower for both 50♀: 1♂ treatments than those in the 1♀: 1♂ group; the R0 values, however, were either equal to or even higher than those in the 1♀: 1♂ treatment. In the male-biased sex ratio (1♀: 50♂), fecundity was the highest (1,610 eggs) and female average life span the longest (166 d), while the R0 was the lowest (31.6 offspring) among all treatments. Population projections showed that even at a sex ratio of 50♀: 1♂, B. dorsalis could still produce a large number of offspring. These findings demonstrate that management strategies for controlling B. dorsalis could be properly evaluated by using demographic methods. Because female annihilation appears to be a more effective control strategy, it should be considered as a viable alternative.

Additive and interactive effects of nutrient classes on longevity, reproduction, and diet consumption in the Queensland fruit fly (Bactrocera tryoni)

Insect lifespan is often closely linked to diet, and diet manipulations have been central to studies of ageing. Recent research has found that lifespan for some flies is maximised on a very low yeast diet, but once all yeast is removed, lifespan drops precipitously. Although effects of yeast availability on lifespan are commonly interpreted in terms of protein, yeast is a complex mix of nutrients and provides a rich source of vitamins, minerals and sterols. Elucidating which components of yeast are involved in this lifespan drop provides insights into more specific nutritional requirements and also provides a test for the commonplace interpretation of yeast in terms of protein. To this end, we fed Queensland fruit flies (Bactrocera tryoni) one of eight experimental diets that differed in the nutrient group(s) found in yeast that were added to sucrose: none, vitamins, minerals, amino acids, cholesterol, vitamin+mineral+cholesterol (VMC), vitamin+mineral+cholesterol+amino acids (VMCA), and yeast. We measured survival rates and egg production in single sex and mixed sex cages, as well as nutrient intake of individual flies. We found that the addition of minerals increased lifespan of both male and female flies housed in single sex cages by decreasing baseline mortality. The addition of just amino acids decreased lifespan in female flies; however, when combined with other nutrient groups found in yeast, amino acids increased lifespan by decreasing both baseline mortality and age-specific mortality. Flies on the yeast and VMCA diets were the only ones to show significant egg production. We conclude that the drop in lifespan observed when all yeast is removed is explained by missing micronutrients (vitamins, minerals and cholesterol) as well as the absence of protein in females, whereas minerals alone can explain the pattern for males. These results indicate a need for caution when interpreting effects of dietary yeast as effects of protein.

Gender separation increases somatic growth in females but does not affect lifespan in Nothobranchius furzeri

According to life history theory, physiological and ecological traits and parameters influence an individual's life history and thus, ultimately, its lifespan. Mating and reproduction are costly activities, and in a variety of model organisms, a negative correlation of longevity and reproductive effort has been demonstrated. We are employing the annual killifish Nothobranchius furzeri as a vertebrate model for ageing. N. furzeri is the vertebrate displaying the shortest known lifespan in captivity with particular strains living only three to four months under optimal laboratory conditions. The animals show explosive growth, early sexual maturation and age-dependent physiological and behavioural decline. Here, we have used N. furzeri to investigate a potential reproduction-longevity trade-off in both sexes by means of gender separation. Though female reproductive effort and offspring investment were significantly reduced after separation, as investigated by analysis of clutch size, eggs in the ovaries and ovary mass, the energetic surplus was not reallocated towards somatic maintenance. In fact, a significant extension of lifespan could not be observed in either sex. This is despite the fact that separated females, but not males, grew significantly larger and heavier than the respective controls. Therefore, it remains elusive whether lifespan of an annual species evolved in periodically vanishing habitats can be prolonged on the cost of reproduction at all.

A new cultivation system for studying chemical effects on the lifespan of the fruit fly

A side-by-side comparison was made between a conventional vial system and a novel bottle system for cultivating flies and testing the effect of chemical exposure on the lifespan of the flies. While the two cultivation systems yielded very similar results for the effect of DEHP (di[2-ethylhexyl] phthalate) on reducing the lifespan of fruit fly Drosophila melanogaster, the new bottle system has many advantages over the conventional vial system. The bottle system allowed long-term cultivation of flies in the same bottle and thus eliminated the need for transferring of flies between vials. Foods/nutrients were provided as fresh moisture medium coated on a glass slide vertically hanged in the center of the bottle. Fly discharges and dead flies were collected onto a draw horizontally inserted into the bottom of the bottle. These features have resulted in great convenience for cultivating flies and reduced labor and media cost. The effective separation of food from discharge may allow accurate mass balance measurement and thus yield more definitive observations for understanding the actual role of calorie restriction (CR) or dietary-restriction (DR) in fly metabolism and longevity.

Prolongevity effects of an oregano and cranberry extract are diet dependent in the Mexican fruit fly (Anastrepha ludens)

Botanicals have numerous health benefits. Here, we used the Mexican fruit fly to screen 14 compounds and botanicals for their prolongevity effects and found an oregano and cranberry mixture (OC) improved survival. We then evaluated prolongevity effects of OC within the context of diet composition. Individual flies were fed 0%, 1%, or 2% OC in one of the three diets containing sugar and yeast extract (SY) at a ratio of 3:1, 9:1, or 24:1. We found that prolongevity effects of OC depended upon dose, gender, and diet composition. The greatest increase in longevity was observed in females fed the SY24:1 diet with 2% OC compared to the non-supplemented diet. OC did not reduce egg laying and, hence, did not compromise fecundity under any dietary condition tested here. This study reveals the prolongevity effects of OC and supports the emerging view that benefits of botanicals on aging depend on diet composition and gender.

Environmental effects on the expression of life span and aging: an extreme contrast between wild and captive cohorts of Telostylinus angusticollis (Diptera: Neriidae)

Most research on life span and aging has been based on captive populations of short-lived animals; however, we know very little about the expression of these traits in wild populations of such organisms. Because life span and aging are major components of fitness, the extent to which the results of many evolutionary studies in the laboratory can be generalized to natural settings depends on the degree to which the expression of life span and aging differ in natural environments versus laboratory environments and whether such environmental effects interact with phenotypic variation. We investigated life span and aging in Telostylinus angusticollis in the wild while simultaneously estimating these parameters under a range of conditions in a laboratory stock that was recently established from the same wild population. We found that males live less than one-fifth as long and age at least twice as rapidly in the wild as do their captive counterparts. In contrast, we found no evidence of aging in wild females. These striking sex-specific differences between captive and wild flies support the emerging view that environment exerts a profound influence on the expression of life span and aging. These findings have important implications for evolutionary gerontology and, more generally, for the interpretation of fitness estimates in captive populations.

Quantitative trait loci and interaction effects responsible for variation in female postmating mortality in Drosophila simulans and D. sechellia introgression lines

Mating appears to inflict a cost to Drosophila females, resulting in a reduction of their lifespan shortly after mating. Males from different chromosome extracted lines differ significantly in their detrimental effects on postmating female survival, and seminal fluid proteins produced in the male accessory glands are at least partially responsible for the effect. This suggests that there is a genetic basis underlying the male inflicted effect on female's postmating mortality. However, the genes responsible for this effect remain elusive. Using males from introgression lines between D. simulans and D. sechellia genomes and a quantitative trait locus (QTL) mapping approach, we identified chromosomal regions that affect postmating mortality of females. We found a second chromosome QTL with an effect on average female lifespan after mating and a third chromosome QTL with an effect on postmating female mortality rate. Under the general observation of a faster divergence of sex-related genes among closely related species, it is predicted that genes for reproductive traits other than hybrid sterility will show evidence of epistatic effects when brought into a heterospecific background. We detected a significant epistatic genetic effect on postmating female mortality rate that supports this prediction.

Shall we dance or shall we fight? Using DNA sequence data to untangle controversies surrounding sexual selection

Population and evolutionary genetics studies have largely benefitted from advances in DNA manipulation and sequencing, as well as DNA data analysis techniques. Molecular evolution studies of male reproductive genes show a pattern of rapid evolution shaped, in some cases, by an adaptive selective process. Despite the large body of data on male reproductive genes, the female side of the story has remained unexplored. The few cases of female egg receptors analyzed also show rapid evolution. However, to disentangle between competing hypotheses on how selection operates on male × female molecular interaction leading to fertilization, we need to find male and female molecules that are partners in fertilization. A conflict model of sexual selection (similar to a host-parasite model) assumes a male-driven system where females are being forced under suboptimal conditions. This predicts that the amount of divergence at a female receptor depends on the amount of divergence among the male reproductive proteins that it binds (i.e., males are leading). Under a classical model of runaway sexual selection, female protein receptors might be the key to the rapid molecular changes observed in male reproductive proteins and higher divergence should be expected among female receptors than among their respective male binding proteins.Key words: Reproductive genes, DNA sequence data, sexual selection, coadaptation, conflict.