Age, sex, adult and larval diet shape starvation resistance in the Mediterranean fruit fly: an ecological and gerontological perspective.

The ability of an animal to withstand periods of food deprivation is a key driver of invasion success (biodiversity), adaptation to new conditions, and a crucial determinant of senescence in populations. Starvation resistance (SR) is a highly plastic trait and varies in relation to environmental and genetic variables. However, beyond Drosophila, SR has been studied poorly. Exploiting an interesting model species in invasion and ageing studies-the Mediterranean fruit fly (Ceratitis capitata)- we investigated how age, food and gender, shape SR in this species. We measured SR in adults feeding in rich and poor dietary conditions, which had been reared either on natural hosts or artificial larval diet, for every single day across their lifespan. We defined which factor is the most significant determinant of SR and we explored potential links between SR and ageing. We found that SR declines with age, and that age-specific patterns are shaped in relation to adult and larval diet. Females exhibited higher SR than males. Age and adult diet were the most significant determinants of SR, followed by gender and the larval diet. Starvation resistance proved to be a weak predictor of functional ageing. Possible underlying mechanisms, ecological and gerontological significance and potential applied benefits are discussed

POPULATION ECOLOGY Threshold Temperature for Post-Diapause Development and Degree-Days to Hatching of Winter Eggs of the European Red Mite (Acari: Tetranychidae) in Northern Greece Downloaded from

ABSTRACT The threshold temperature for postdiapause development in overwintering eggs of the European red mite, Panonychus ulmi (Koch), was determined after exposing the eggs to various constant temperatures (5, 10, 15, 20, and 25ЊC) in the laboratory. The mean number of days to 50% hatch in each temperature was Ͼ120, 44.5, 22.0, 14.5, and 8.1 d, respectively. From the regression of postdiapause developmental rate to temperature, it was estimated that 50% of egg hatch coincides with the accumulation of 154.6 degree-days (DD) above the threshold of 7.4ЊC. In the Þeld (1991 and 1993Ð1996), 50% egg hatch occurred from the end of March to 20 April after the accumulation of a mean sum of 129.4 Ϯ 4.5 DD above the threshold of 7.4ЊC from 10 February onward. The starting date of 10 February for heat accumulation was chosen because earlier experiments had shown that diapause is terminated in 50% of the eggs in the Þrst half of February. Using the theoretical sum of 154.6 DD, the predicted dates for 50% egg hatch deviated from Þeld observations by an average of 3.7 Ϯ 0.5 d over the 5 yr of experiments. KEY WORDS Panonychus ulmi, European red mite, degree-days, hatching, winter eggs THE EUROPEAN RED mite, Panonychus ulmi (Koch), is an important foliar pest of apple trees feeding on the palisade and spongy mesophyl cells and causing a reduction in the photosynthetic rates of the plant Application of chemical acaricides early in spring against newly hatched larvae is a widely used method for the control of this mite. The development of a degree-day (DD) model for predicting the time of egg hatch in the Þeld could be a useful tool for the proper timing of acaricide applications. In the current study we determined the threshold temperature for postdiapause development and subsequently using laboratory and Þeld data estimated a sum of degree-days for predicting the time of egg hatch. The accuracy of the degree-day model for predicting egg hatch was validated under Þeld conditions. Materials and Methods Threshold Temperature for PostDiapause Development. Twigs bearing diapause-eggs were cut from an apple orchard in the area of Alexandria (Northern Greece) in the second half of February of 1994, and subsequently transferred to the laboratory. The course of diapause termination in the Þeld was determined in earlier experiments by transferring diapause eggs during winter and early spring for 4 yr (1992Ð 1996) from the same and other apple orchards to short days (a photoperiod of 8:16 [L:D] h) at 20ЊC where percentages of diapause termination were determined Every third day the percentage of eggs hatch at each temperature was determined. The data were then used to estimate the mean number of days required for 50% egg hatch (t 50% ) at each temperature. The reciprocal, 1/t 50% , represented the daily rate of postdiapause embryonic development. The threshold temperature for postdiapause development was estimated by the x-intercept metho

Financing micro-entrepreneurs for poverty alleviation: a performance analysis of microfinance services offered by BRAC, ASA, and Proshika from Bangladesh

Microfinance services have emerged as an effective tool for financing microentrepreneurs to alleviate poverty. Since the 1970s, development theorists have considered non-governmental microfinance institutions (MFIs) as the leading practitioners of sustainable development through financing micro-entrepreneurial activities. This study evaluates the impact of micro-finance services provided by MFIs on poverty alleviation. In this vein, we examine whether microfinance services contribute to poverty alleviation, and also identify bottlenecks in micro-finance programs and operations. The results indicate that the micro-loans have a statistically significant positive impact on the poverty alleviation index and consequently improve the living standard of borrowers by increasing their level of income

Cross-talk between high light stress and plant defence to the two-spotted spider mite in Arabidopsis thaliana

Little is known about how plants deal with arthropod herbivores under the fluctuating light intensity and spectra which occur in natural environments. Moreover, the role of simultaneous stress such as excess light (EL) in the regulation of plant responses to herbivores is poorly characterized. In the current study, we focused on a mite-herbivore, specifically, the two-spotted spider mite (TSSM), which is one of the major agricultural pests worldwide. Our results showed that TSSM-induced leaf damage (visualized by trypan blue staining) and oviposition rate (measured as daily female fecundity) decreased after EL pre-treatment in wild-type Arabidopsis plants, but the observed responses were not wavelength specific. Thus, we established that EL pre-treatment reduced Arabidopsis susceptibility to TSSM infestation. Due to the fact that a portion of EL energy is dissipated by plants as heat in the mechanism known as non-photochemical quenching (NPQ) of chlorophyll fluorescence, we tested an Arabidopsis npq4-1 mutant impaired in NPQ. We showed that npq4-1 plants are significantly less susceptible to TSSM feeding activity, and this result was not dependent on light pre-treatment. Therefore, our findings strongly support the role of light in plant defence against TSSM, pointing to a key role for a photo-protective mechanism such as NPQ in this regulation. We hypothesize that plants impaired in NPQ are constantly primed to mite attack, as this seems to be a universal evolutionarily conserved mechanism for herbivores

Effects of exposure to citrus compounds on male sexual signaling.

<p>Overall levels of sexual signalling activity (mean number of males signalling through the ages of 6 to 10 days old and 16 days old) of Vienna 8 GSS sterilized males medflies that were exposed during day 4 and 5 of adult life to orange essential oil, limonene, and a mixture of 5 pure compounds (limonene, linalool, myrcene, <i>α</i>-pinene and <i>β</i>-myrcene 1:1:1:1:1 ratio) or left unexposed (control) fed on (A) yeast hydrolyzate & sugar (YS) and (B) sugar only (S). On each day of age, observations took place hourly from 07:00 to 20:45 hours in 10 cages (replicates) containing 10 males each. Values on y-axis are mean numbers (±SE) of males signalling per cage per hour observation. Means followed by the same lowercase letter are not significantly different (P>0.05, Tukey’s HSD test).</p

Daily pattern on male sexual siganlling.

<p>Daily rhythm of sexual signalling on adult day 6 of sterilized male <i>C</i>. <i>capitata</i> of the Vienna 8 GSS in four different exposure compounds (orange oil, limonene, mixture of 5 pure compounds and control) on yeast hydrolyzate & sugar (YS, left column) and sugar only (S, right column). Values on y axis indicate the mean number (±SE) of males signalling per cage. Ten cages were considered containing 10 males each.</p

Repeated measures ANOVA on the effect of exposure compound (orange oil, limonene, mixture of 5 pure compounds and control), food (yeast hydrolyzate and sugar and sugar only) and time of day (repeated factor) on daily rhythms of sexual signalling on sterilized (Vienna 8 GSS) <i>C</i>. <i>capitata</i> males.

<p>Times of the day between 07:00 and 20:45 hours of adult day 6 were considered in the analysis.</p

Age specific ratio on male sexual signaling.

<p>Ratio between signalling rates of Vienna 8 GSS sterilized male medflies fed on either yeast hydrolyzate & sugar (YS) or sugar only (S) in relation to age. Males had been exposed during day 4 and 5 of adult life to orange essential oil, limonene, and a mixture of 5 pure compounds (limonene, linalool, myrcene, <i>α</i>-pinene and <i>β</i>-myrcene, 1:1:1:1:1 ratio) or left unexposed (control). On each day of age, observations took place hourly from 07:00 to 20:45 hours in 10 cages (replicates) containing 10 males each. The ratio was estimated considering the average calling for each day of the observation during 07:00 to 20:45 for protein and sugar treatments.</p

Diet specific effects on male sexual signaling.

<p>Effect of yeast hydrolyzate and sugar (YS) and sugar only (S) on the overall levels of sexual signalling activity (mean daily activity through the ages of 6 to 10 days old and 16 days old) of Vienna 8 GSS sterilized male medflies, that were exposed during day 4 and 5 of adult life to orange essential oil, limonene and a mixture of 5 pure compounds (limonene, linalool, myrcene, <i>α</i>-pinene and <i>β</i>-myrcene, 1:1:1:1:1 ratio) or left unexposed (control). On each day of age, observations took place hourly from 07:00 to 20:45 hours in 10 cages (replicates) containing 10 males each. Values on y-axis are mean numbers (±SE) of males signalling per cage per hour observation (** P<0.001, *P<0.01, <i>t</i>-test YS vs S in each treatment).</p

Longevity parameters of adult medflies that were exposed and non-exposed to the aroma of citrus oil and held in diet restriction (sugar fed only) and in full diet (yeast and sugar fed) food conditions.

<p>Within diet regime, numbers followed by different letters are significantly different (pairwise comparisons log-rank test, P < 0.05).</p