Deleterious effect of suboptimal diet on rest-activity cycle in Anastrepha ludens manifests itself with age.

Activity patterns and sleep-wake cycles are among the physiological processes that change most prominently as animals age, and are often good indicators of healthspan. In this study, we used the video-based high-resolution behavioral monitoring system (BMS) to monitor the daily activity cycle of tephritid fruit flies Anastrepha ludens over their lifetime. Surprisingly, there was no dramatic change in activity profile with respect to age if flies were consistently fed with a nutritionally balanced diet. However, if flies were fed with sugar-only diet, their activity profile decreased in amplitude at old age, suggesting that suboptimal diet affected activity patterns, and its detrimental effect may not manifest itself until the animal ages. Moreover, by simulating different modes of behavior monitoring with a range of resolution and comparing the resulting conclusions, we confirmed the superior performance of video-based monitoring using high-resolution BMS in accurately representing activity patterns in an insect model

Diet Shapes Mortality Response to Trauma in Old Tephritid Fruit Flies.

Despite the importance of trauma in healthspan and lifespan in humans as well as in non-human species, with one important exception the literature in both gerontology and ecology contains virtually no experimental demographic studies concerned with trauma in any species. We used dietary manipulation [full diet (F) versus sugar-only (S)] to produce four levels of frailty in 55-day old tephritid fruit flies (Anastrepha ludens) that were then subject to the trauma of cage transfer stress (n = 900/sex in each of the 4 treatments). The key results included the following: (1) there is a trauma effect caused by the transfer that depends on previous diet before transfer, new diet after transfer and gender of the fly; (2) males are more vulnerable than females; (3) if initial diet was F, flies are relatively immune against the trauma, and the subsequent diet (F or S) does not matter; (4) however if initial diet was S, then the effect of the trauma depends largely on the diet after the transfer; (5) flies transferred from S to F diets do very well in terms of remaining longevity (i.e. greatest remaining longevity), while flies transferred from S to S diet do poorly (i.e. shortest remaining longevity). We discuss both the strengths and weaknesses of this study and implications of the results

Host-specific demography of Utetes anastrephae (Hymenoptera, Braconidae), a native parasitoid of Anastrepha spp. fruit flies (Diptera, Tephritidae)

The braconid Utetes anastrephae (Viereck, 1913) (Hymenoptera: Braconidae) is a larva-pupal parasitoid of fruit flies of the genus Anastrepha Schiner, commonly associated with Anastrepha obliqua (Macquart, 1835) (Diptera: Tephritidae), the most important pest of mango (Mangifera indica L., 1753) in Mexico. This parasitoid was established in a laboratory colony using larvae of Anastrepha ludens (Loew, 1873) as host. Here we describe a demographic study to compare the reproductive and population parameters of this parasitoid reared on A. obliqua and A. ludens under laboratory conditions. Two U. anastrephae cohorts of 30 individual pairs each were set up, one was reared on A. obliqua larvae and the other one on A. ludens. Every day, 30 third instar larvae of each host species were exposed to an adult pair through the lifespan of the female. Daily mortality and fecundity were recorded. Life tables were constructed and sex ratios, parasitism rates, survival, reproductive and population parameters were estimated. Higher survival of U. anastrephae females was observed in females from A. obliqua (mean live expectancy of 22.4 days), but higher fecundity and parasitism occurred in females from A. ludens (net fecundity of 62.61 daughters/ female and 16.72% parasitism rate). The intrinsic rate of increase (r = 0.128 and r = 0.134 for A. obliqua and A. ludens respectively), mean generation time (27.88 and 28.30 days) and population doubling time (5.42 and 5.16 days) were similar in both cohorts, as well as the sex ratio (73 and 69% of females). These results suggest that A. ludens as host increase the production rates; however, any one of these two species could be used as host for mass rearing purposes

Longevity-Fertility Trade-offs in the Tephritid Fruit Fly, \u3ci\u3eAnastrepha ludens\u3c/i\u3e, across Dietary-restriction Gradients

Although it is widely known that dietary restriction (DR) not only extends the longevity of a wide range of species but also reduces their reproductive output, the interrelationship of DR, longevity-extension and reproduction is not well understood in any organism. Here we address the question: “Under what nutritional conditions do the longevity-enhancing effects resulting from food restriction either counteract, complement or reinforce the mortality costs of reproduction? To answer this question we designed a fine-grained DR study involving 4,800 individuals of the tephritid fruit fly Anastrepha ludens in which we measured sex-specific survival and daily reproduction in females in each of 20 different treatments (sugar:yeast ratios) plus 4 starvation controls. The database generated from this 3-year study consisted of approximately 100,000 life-days for each sex and 750,000 eggs distributed over the reproductive lives of 2,400 females. The fertility and longevity-extending responses were used to create contour maps (X-Y grid) that show the demographic responses (Z-axis) across dietary gradients that range from complete starvation to both ad libitum sugar-only and ad libitum standard diet (3:1 sugar-to-yeast). The topographic perspectives reveal demographic equivalencies along nutritional gradients, differences in the graded responses of males and females, egg production costs that are sensitive to the interaction of food amounts and constituents, and orthogonal contours (equivalencies in longevity or reproduction) representing demographic thresholds related to both caloric content and sugar-yeast ratios. If general, the finding that lifespan and reproductive maxima occur at much different nutritional coordinates poses a major challenge for the use of food restriction (or a mimetic) in humans to improve health and extend longevity in humans. PubMed Central version Supplementary material is attached below

Life History Response of Mediterranean Fruit Flies to Dietary Restriction

The purpose of this study was to investigate medfly longevity and reproduction across a broad spectrum of diet restriction using a protocol similar to those applied in most rodent studies. Age-specific reproduction and age of death were monitored for 1,200 adult males and 1,200 females, each individually maintained on one of 12 diets from ad libitum to 30% of ad libitum. Diet was provided in a fixed volume of solution that was fully consumed each day, ensuring control of total nutrient consumption for every fly. Contrary to expectation and precedence, increased longevity was not observed at any level of diet restriction. Among females, reproduction continued across all diet levels despite the cost in terms of increased mortality. Among males, life expectancy exceeded that of females at most diet levels. However, in both sexes, mortality increased more sharply and the pattern of survival changed abruptly once the diet level fell to 50% of ad libitum or below, even though the energetic demands of egg production has no obvious counterpart in males. We believe that a more complete picture of the life table response to dietary restriction will emerge when studies are conducted on a wider range of species and include both sexes, more levels of diet, and the opportunity for mating and reproduction

Female Sensitivity to Diet and Irradiation Treatments Underlies Sex-Mortality Differentials in the Mediterranean Fruit Fly

Large-scale experiments on medflies that were subjected to sterilizing doses of ionizing radiation (plus intact controls) and maintained on either sugar-only or full, protein-enriched diets revealed that, whereas the mortality trajectories of both intact and irradiated male cohorts maintained on both diets are similar, the mortality patterns of females are highly variable. Mean mortality rates at 35 days in male cohorts ranged from 0.2 to 0.3 but in female cohorts ranged from 0.09 to 0.35, depending on treatment. The study reports three main influences: (a) qualitative differences exist in the sex–mortality response of medflies subjected to dietary manipulations and irradiation, (b) the female mortality response is linked to increased vulnerability due to the nutritional demands of reproduction, and (c) female sensitivity to environmental changes underlies the dynamics of the sex-mortality differential

A Mortality Cost of Virginity at Older Ages in Female Mediterranean Fruit Flies

Mortality rates were measured over the lifetime of 65,000 female Mediterranean fruit flies, Ceratitis capitata, maintained in either all-female (virgin) cages or cages with equal initial numbers of males, to determine the effect of sexual activity and mating on the mortality trajectory of females at older ages. Although a greater fraction of females maintained in all-female (virgin) cages survived to older ages, the life expectancy of the surviving virgins was less than the life expectancy of surviving non-virgins at older ages. This was due to a mortality crossover where virgin flies experience lower mor-tality than mated flies from eclosion to Day 20 but higher mortality thereafter. These results suggest that there are two consequences of mating—a short-term mortality increase (cost) and a longer term mortality decrease (benefit)

A Mortality Cost of Virginity at Older Ages in Female Mediterranean Fruit Flies

Mortality rates were measured over the lifetime of 65,000 female Mediterranean fruit flies, Ceratitis capitata, maintained in either all-female (virgin) cages or cages with equal initial numbers of males, to determine the effect of sexual activity and mating on the mortality trajectory of females at older ages. Although a greater fraction of females maintained in all-female (virgin) cages survived to older ages, the life expectancy of the surviving virgins was less than the life expectancy of surviving non-virgins at older ages. This was due to a mortality crossover where virgin flies experience lower mor-tality than mated flies from eclosion to Day 20 but higher mortality thereafter. These results suggest that there are two consequences of mating—a short-term mortality increase (cost) and a longer term mortality decrease (benefit)

Food Pulses Increase Longevity and Induce Cyclical Egg Production in Mediterranean Fruit Flies

1. Inasmuch as virtually all studies on mortality and reproduction in insects are conducted under conditions in which food availability is constant, little is known about the demographic response of insects to variable food environments. For example, it is not known if and to what extent the life expectancy of insects subjected to shortages of high-quality food will increase and/or whether this increase is associated with major decreases in lifetime reproduction. 2. Therefore cohorts of 100 individual female medflies were subjected to different sets of conditions of protein availability (interspersed with sugar-only diets) including ad libitum sugar-only (no protein), ad libitum protein and full (protein) diet either every 2nd, 4th, 6th, 11th, or 21st day, as well as two lag-treatments (1 day full diet followed by 30 days sugar-only, followed by one of two cyclical treatments). 3. Both life expectancy and lifetime reproduction were strongly affected by specific treatments. Specifically (i) mortality was inversely related to frequency of protein availability whereas lifetime reproduction was directly related; (ii) distinct cycles in reproduction began to appear when food pulse cycles were as short as every 4 days. However, egg-laying peaks and troughs were particularly pronounced in the 10- and 20-day food pulse cycles; (iii) the peak and trough levels were inversely related to cycle length; and (iv) the within-cycle height was independent of cycle length, occurring 4 days after protein food was made available to the cohort whether the cycle length was 5, 10 or 20 days. 4. The results shed new light on the within- and between-cycle and lifetime dynamics of reproduction when insects are subjected to variable food environments and indicate that medfly females track food level very closely

Bioprospección de receptores de insulina a partir de ARN mensajero en Brevicoryne brassicae L. (Hemiptera: Aphididae)

Suppression of messenger ribonucleic acid (mRNA) molecules by RNA interference (RNAi) has been proposed as a method for controlling insect pests. RNAi impedes the morphological and functional development of insects and is considered highly specific. In this study, insulin receptors (InR) were searched for in Brevicoryne brassicae L. (Hemiptera: Aphididae) from aphid mRNA, as a first step for further design of RNAi targeting InR suppression. From complementary deoxyribonucleic acid (cDNA) and by means of nested PCR, the region corresponding to InR was amplified with two pairs of primers designed for Nilapavata lugens (Homoptera: Delphacidae). InRs could not be identified. However, the presence of the follistatin-binding receptor protein Dip2A (FS) was predicted from the regions of similarity with the InRs that are involved in signal translation in insects. We recommend continuing the search for aphid specific InRs, as well as possible primers for Dip2A regions, to identify a highly specific RNAi.La supresión de moléculas de ácido ribonucleico mensajero (ARNm) mediante ARN interferente (ARNi) se ha propuesto como método de control de insectos plagas. El ARNi impide el desarrollo morfológico y funcional de los insectos y se considera altamente específico. En este estudio se buscaron receptores de insulina (InR) en Brevicoryne brassicae L. (Hemiptera: Aphididae) a partir del ARNm de pulgones, como primer paso para el diseño posterior de ARNi dirigido a la supresión de InR. A partir del ácido desoxirribonucleico complementario (ADNc) y mediante PCR anidada, se amplificó la región correspondiente a InR con dos pares de cebadores diseñados para Nilaparvata lugens (Homoptera: Delphacidae). No se logró identificar InR, en su lugar se predice la presencia de la proteína receptora Dip2A de unión a folistatina (FS) debido a que comparten regiones proteicas similares con los InR, involucradas en la traducción de señales en los insectos. Se sugiere continuar con la búsqueda de InR específicos para el pulgón, así como posibles cebadores para regiones de Dip2A, para lograr un ARNi altamente específico