Dietary glycerol and adult access to water: effects on fecundity and longevity in the almond moth

The role of condition on sexual selection in the seed bug Lygaeus simulans

Organism condition plays an important role in sexual selection. Sexual ornaments and displays can be condition-dependent, reflecting either underlying genetic quality, experience of environmental stressors, or both. As such, the phenotypic expression of such traits, and the resulting patterns of mate choice acting on them, may be shaped by intrinsic genetic quality and the environment. Moreover, condition may also influence the choosing individual in mate choice, influencing their ability to invest in mate discrimination, or changing what traits of the chosen, including resources, are most preferred. Here we consider sexual selection and condition in the seed bug Lygaeus simulans, a species characterised by strong post-copulatory sexual selection, but rather limited pre-copulatory discrimination. We manipulated short-term condition in both males and females by restricting access to water for 24 h. Water is particularly important in these bugs, given their feeding ecology and physiology. We found that water-deprived males proved less likely to mate, while copulation duration with water-deprived females was significantly reduced. Given the importance of copulation duration for the successful transfer of sperm by males to females, the data suggest cryptic male choice acting against water-deprived females. These data add to those suggesting that cryptic male choice for fecund females plays an important role in sexual selection in this species. More generally, our results support the widespread importance of condition in terms of mating dynamics and sexual selection.

Polyols induce acute oxidative stress and mortality in Indian malaria vector Anopheles stephensi (Diptera: Culicidae): potential for use as sugar-cum-toxin source in toxic sugar baits

BACKGROUND

Development of insecticide resistance in the major malaria vectors has necessitated the development of novel vector control tools. One such strategy involves the use of toxic sugar baits that targets the sugar-feeding behaviour of mosquito vectors. In this study, we investigated the potential of polyols, as a toxic food (sugar) source in toxic sugar baits against the malaria vector Anopheles stephensi Liston. We examined the acute toxicity of six polyols, namely, erythritol, glycerol, mannitol, propylene glycol (PG), sorbitol, and xylitol on adult female An. stephensi mosquitoes at two different concentrations - 2% and 10%. We also studied changes in fecundity, egg hatchability and mid-gut peroxide levels induced by polyol exposure.

RESULTS

Among the six polyol compounds tested, PG was most toxic and lethal followed by glycerol and erythritol (P < 0.001) compared to the control (sucrose). PG induced acute mortality at different tested concentrations. In the erythritol- and glycerol-fed groups, a dose-dependent effect on mortality was observed. Glycerol evidently reduced fecundity and egg-hatchability in gonotrophic cycles G1 and G2. Sucrose was the preferred food source (48%), followed by erythritol (18%), PG (10%) and glycerol (8%). Ingestion of polyols increased peroxide levels in mosquito guts, which persisted for extended durations ultimately resulting in rapid mortality (P < 0.05).

CONCLUSION

The present study highlights the usefulness of sugar polyols for the development of toxic sugar baits with minimal yet effective ingredients. Further research could be focused on field experiments and on the exploration of synergistic effects of different polyols for optimization of field applications. © 2024 Society of Chemical Industry.

How does access to water at different life-stages affect male investment in reproduction and survival?

Holometabolous insects have four distinct life-stages – eggs, larvae, pupae and adults. Active resource acquisition generally occurs during either or both the larval and adult stages. Previous research on the acquisition of food resources in holometabolous insects, has shown that resources acquired during each of these life-stages can differ in how they are allocated to different traits, and how they affect fitness. In addition to food, water is also an essential resource needed for a range of biological processes that enhance fitness. Yet, how water acquired at different life-stages affects key fitness traits is still not clear. Here, we manipulated both developmental and adult water availability of male seed beetles (Callosobruchus maculatus) to explore how water acquired at each life-stage affects a range of fitness related traits, including body mass, ejaculate weight, mating behavior and lifespan. Our results indicate that the juvenile environment had little effect on body weight, ejaculate weight, ejaculate replenishment or lifespan, but did influence male mating behavior in both early and late adult life. This contrasts with the adult environment, which had strong effects on weight loss, ejaculate size and lifespan but little effect on mating behavior. Males with access to water during adulthood transferred larger ejaculates during their first mating, lost less weight as they aged, and lived longer. These results suggest that water acquired during development and adulthood are allocated differently to a variety of fitness traits across life.

Glucose enrichment impair neurotransmission and induce Aβ oligomerization that cannot be reversed by manipulating O-β-GlcNAcylation in the C. elegans model of Alzheimer's disease

Amyloid beta (Aβ) plaques formation and impaired neurotransmission and neuronal behaviors are primary hallmarks of Alzheimer's disease (AD) that are further associated with impaired glucose metabolism in elderly AD's patients. However, the exact role of glucose metabolism on disease progression has not been elucidated yet. In this study, the effect of glucose on Aβ-mediated toxicity, neurotransmission and neuronal behaviors has been investigated using a C. elegans model system expressing human Aβ. In addition to regular diet, worms expressing Aβ were supplemented with different concentrations of glucose and glycerol and 5 mM 2-deoxyglucose to draw any conclusions. Addition of glucose to the growth medium delayed Aβ-associated paralysis, promoted abnormal body shapes and movement, unable to restore impaired acetylcholine neurotransmission, inhibited egg laying and hatching in pre-existing Aβ-mediated pathology. The harmful effects of glucose may associate with an increase in toxic Aβ oligomers and impaired neurotransmission. O-β-GlcNAcylation (O-GlcNAc), a well-known post-translational modification is directly associated with glucose metabolism and has been found to ameliorates the Aβ- toxicity. We reasoned that glucose addition might induce O-GlcNAc, thereby protect against Aβ. Contrary to our expectations, induced glucose levels were not protective. Increasing O-GlcNAc, either with Thiamet-G (TMG) or by suppressing the O-GlcNAcase (oga-1) gene does interfere with and, therefore, reduce Aβ- toxicity but not in the presence of high glucose. The effects of glucose cannot be effectively managed by manipulating O-GlcNAc in AD models of C. elegans. Our observations suggest that glucose enrichment is unlikely to be an appropriate therapy to minimize AD progression.

Biology of Anthonomus testaceosquamosus Linell, 1897 (Coleoptera: Curculionidae): A New Pest of Tropical Hibiscus

Simple Summary

Although native to northeastern Mexico and southern Texas, the hibiscus bud weevil (HBW), Anthonomus testaceosquamosus Linell 1897, was recently discovered infesting hibiscus in south Florida in 2017. During outbreak events, HBW feeding on hibiscus buds has been found to significantly affect the marketability of the crop. Therefore, it is vital that an integrated pest management (IPM) program be developed for this pest in order to mitigate the economic loss to the hibiscus industry of south Florida. However, a comprehensive understanding of the HBW’s biology is critical to the development of such a program. In this study, we sought to determine how temperature and diet affect the life history of the HBW. Four temperatures were tested 10, 15, 27 and 34 °C. Life cycle completion was found to only occur at 27 °C, but weevils developed equally as fast on hibiscus buds as on an artificial diet. Adult HBW could survive solely on pollen, but reproduction did not occur. Without water at 27 °C, HBW survived for ≈15 days; survival times reached nearly 30 days when water was accessible. Our results suggest that if left unmanaged, the HBW may cause significant economic damage to the hibiscus industry. We provide a foundation for future research endeavors that aim to better manage this weevil in south Florida.

Abstract

Originating in northeastern Mexico and southern Texas, the hibiscus bud weevil (HBW), Anthonomus testaceosquamosus Linell 1897, was discovered infesting China rose hibiscus (Hibiscus rosa-sinensis L.) in south Florida in May 2017. Although the biologies of the congeneric boll weevil, A. grandis Boheman 1843, and pepper weevil, A. eugenii Cano 1894 are well documented, no data are available regarding the biology of HBW. Here, we present a comprehensive study on the biology of this pest when reared at 10, 15, 27 and 34 °C and on different food sources. This weevil has three larval instars and its life cycle was completed only at 27 ± 1 °C. Weevil development was similar on an artificial diet when compared with a diet of hibiscus buds. Adult HBW could survive solely on pollen, but reproduction did not occur. Without water, HBW survived for ≈15 days; survival times reached nearly 30 days when water was accessible. Our results suggest that if left unmanaged, HBW has the potential to cause significant economic damage to the hibiscus industry. Given that a comprehensive understanding of a pest’s biology is critical for development of effective integrated pest management, our results provide a foundation for future research endeavors to mitigate the impact of this weevil in south Florida.

Productive performance, egg quality, and hatching traits of Japanese quail reared under different levels of glycerin

This study evaluated subsequent effects of glycerin on productive performance, egg quality, and hatching traits in Japanese quail. A total of 200 birds was arranged according to a completely randomized design into 5 treatment groups having 5 replicates of 8 birds each (6 females and 2 males). Treatments consisted 5 levels of glycerin, i.e., 2.5, 5, 7.5, and 10% and the control group. Birds were fed with different levels of glycerin during a rearing period of 6 wk and their subsequent effects on productive performance, egg quality, and hatching traits were observed. Data were collected regarding productive performance for 16 wk; however, egg quality and hatching traits were recorded during pre-peak (at fourth wk), peak (at 12th wk), and post peak (at 16th wk) phase. Productive performance, egg quality, and hatching traits did not differ significantly throughout the experimental period. It was concluded that glycerin can be used as a replacement energy source, having no effect on productive and reproductive performance in Japanese quail.

Food source affects the expression of vitellogenin and fecundity of a biological control agent, Neoseiulus cucumeris

Neoseiulus cucumeris (Oudemans) (Acari: Phytoseiidae) is one of the most widely used and important biological control agents for thrips and other small pests worldwide. In the present study, we cloned two cDNAs of vitellogenins (Vgs, NcVg1 and NcVg2) and analyzed the effect of food source on the expression of both Vgs and fecundity in female adults. NcVgs showed higher sequence similarity to Vgs from Parasitiformes. Both neighbor-joining and maximum likelihood methods for phylogenetic analysis of NcVgs yielded similar topologies and showed that the Parasitiformes except Haemaphysalis longicornis segregated into a single clade that was separated into two subclades including one of both Vgs from N. cucumeris. Both transcripts, NcVg1 and NcVg2 revealed similar trends during developmental periods and reached the maximum level at the pre-oviposition period. When fed with different food sources, both NcVg1 and NcVg2 of female adults demonstrated a significant difference (P < 0.05) during the pre-oviposition period. Meanwhile, a positive correlation between the expression of Vgs and fecundity was observed. Therefore, the nutrients provided by the food sources affected fecundity resulting in differential expression of Vgs. Vitellogenin expression can be used as a molecular marker of fecundity of N. cucumeris.

Dual fitness benefits of post-mating sugar meals for female hawkmoths (Hyles lineata)

The white-lined sphinx moth (Hyles lineata: Sphingidae) is the most widespread and abundant hawkmoth pollinator in North America and plays a major role in the reproductive biology of many plant species. H. lineata visits a wide range of plants, which differ in the quality and quantity (e.g. caloric content, volume) of the nectar reward that they offer in exchange for pollination services. Some of these plants represent a suitable oviposition substrate as well as a profitable nectar source, allowing mated H. lineata females to mix foraging and oviposition bouts. We investigated the effects of post-mating nectar intake on the reproductive success of female H. lineata. While all experimental females had access to a 20% sucrose solution during the pre-mating phase (avg. 2.7 days) we manipulated the post-mating diet, assigning mated females to three experimental groups (sucrose fed, water fed, or unfed). Mated females with access to sucrose lived twice as long and produced more fertile eggs at double the rate of control moths that were starved or water-fed after mating. Thus, the sugar component of floral nectar positively affects the physiology of mated H. lineata at multiple levels, which translates into strong selection for mated females to continue nectar foraging during or between oviposition bouts.

Experimental evidence for nutrition regulated stress resistance in Drosophila ananassae

Background

The amount and quality of nutrients consumed by organisms have a strong impact on stress resistance, life-history traits and reproduction. The balance between energy acquisition and expenditure is crucial to the survival and reproductive success of animals. The ability of organisms to adjust their development, physiology or behavior in response to environmental conditions, called phenotypic plasticity, is a defining property of life. One of the most familiar and important examples of phenotypic plasticity is the response of stress tolerance and reproduction to changes in developmental nutrition. Larval nutrition may affect a range of different life-history traits as well as responses to environmental stress in adult.

Principal Findings

Here we investigate the effect of larval nutrition on desiccation, starvation, chill-coma recovery, heat resistance as well as egg to adult viability, egg production and ovariole number in Drosophila ananassae. We raised larvae on either protein rich diet or carbohydrate rich diet. We found that flies consuming protein rich diet have higher desiccation and heat shock resistance whereas flies developed on carbohydrate rich diet have higher starvation and cold resistance. Egg production was higher in females developed on protein rich diet and we also found trade-off between egg production and Egg to adult viability of the flies. Viability was higher in carbohydrate rich diet. However, sex specific viability was found in different nutritional regimes. Higher Egg production might be due to higher ovariole number in females of protein rich diet.

Conclusion

Thus, Drosophila ananassae adapts different stress tolerance and life-history strategies according to the quality of the available diet, which are correlated with phenotypic adjustment at anatomical and physiological levels.

The influence of larval diet on adult feeding behaviour in the tobacco hornworm moth, Manduca sexta

Lab-reared sphingid and noctuid moths appear to feed less than wild moths, and often are starved to enhance responsiveness in feeding assays. To measure the impact of larval nutrition on adult feeding, we raised a model sphingid species, Manduca sexta, on control or modified diets (reduced sugar, protein or water, supplemented beta-carotene) or cut tobacco leaves, then conducted feeding assays with artificial flowers. Behaviour was scored and analysed in a double-blind manner. Larval diet affected adult eclosion time, size and fat content, the latter of which was inversely proportional to moth approaches to the floral array in a flight cage. In contrast, behaviours refractory to feeding (sitting, escaping) were associated with sex and barometric pressure, but not with diet or fat content. Frequency of floral approaches and probing was not associated with any variable. However, moths reared on beta-carotene-supplemented diet were 2-3 times more likely to feed, and significantly less likely to sit or show "escape" behaviour than were moths from most other treatments. Our results suggest that decreased visual sensitivity, rather than increased fat content, accounts for reduced adult feeding by lab-reared M. sexta.

The effect of diet quality on physiological and life-history traits in the harvestman Pachylus paessleri

The balance between energy acquisition and expenditure is critical to the survival and reproductive success of animals. Here we investigate the long-term effects of diet quality on physiological and life-history flexibility in the harvestman, Pachylus paessleri. We used cow meal as a protein-rich diet and potatoes as a carbohydrate-rich diet in order to reproduce two extreme conditions regarding food quality in harvestmen natural habitat. As proxy variables of the energy expenditure process, we quantified standard metabolic rate (maintenance), changes in body mass (somatic condition), and fecundity (reproduction). We found that animals consuming the protein-rich diet were able to increase both their body condition and fecundity. However, the increment in these two life-history traits was correlated with higher maintenance costs. In contrast, the carbohydrate-rich diet did not provide enough specific nutrients for reproductive events, although it may have allowed animals to survive for a long time. Thus, according to the quality of the diet available in the environment, harvestman females can adopt different life-history strategies correlated with phenotypic adjustments at anatomical and physiological levels. In the Mediterranean region, spatial and temporal changes in food quality are typical, so greater phenotypic flexibility is expected to cope with this kind of environmental variation.

Reduction in an almond moth Ephestia cautella (Lepidoptera: Pyralidae) population by means of mating disruption

Pheromone-based mating disruption of the almond moth (Ephestia cautella) (Walk.) (Lepidoptera: Pyralidae) was carried out in a chocolate factory in Sweden. Population monitoring was conducted with pheromone-baited traps and water traps. Pheromone traps showed a 94% catch reduction, and monitoring with water traps showed a significant decrease in total catch (5.0 and 1.6 individuals per trap per week before and during treatment respectively). The significance of the results was tested by fitting the observed data to a first-order autoregressive model. This made it possible to test the data with a 95% confidence interval, comparing trap catches before mating disruption treatment with trapping data during the experiment. It is suggested that this statistical approach may be used more frequently in mating disruption experiments where it is extremely difficult to control external factors and therefore equally difficult to use a comparable control plot to evaluate the treatment.