Physiological Entomology最新文献

Honeybees are important insects, both economically and as pollinators. While foraging, bees can come in contact with environmental pollutants such as pesticides, possibly in combination with other xenobiotic compounds that may compromise bee health. Our current study investigated the acute exposure to nanosized titanium dioxide, a common additive in food, cosmetics, paints and agricultural products, along with deltamethrin (DLT), a well-known pyrethroid pesticide. The effects of binary exposure to titanium dioxide nanoparticles (TiO₂-NPs) nanoparticles at concentrations of 25, 50, 75 and 100 μg/mL with DLT were noted on Apis mellifera brain histology along with their possible synergism. In DLT- and combined TiO₂-NP-DLT treated bees, survival rates were lowered and several histological alterations were observed including an increased number of cells with pyknotic nuclei, along with cytoplasmic vacuolization, chromatin compaction and degeneration indicating autophagic activity and a decrease in the cross-sectional area of nanoparticle-treated mushroom body calyces. A synergistic relationship between TiO₂-NPs and DLT was revealed, while LD₅₀ for combined TiO₂-NP-DLT treatment was 0.101, 0.09 and 0.02 μg/bee at 24, 48 and 72 h, respectively. In summary, results demonstrate that TiO₂-NP and DLT co-exposure can induce damage in bee brain structures at higher concentrations, which indicates an additional risk factor for bee health in the field.

Tribolium castaneum (Herbst) and Tribolium confusum (Jacquelin du Val) are common and damaging pests of stored grain flours in several homes and flour mill industries worldwide. This study examines how food, species, concentration, and exposure time affect the susceptibility and nutritional physiology of T. castaneum and T. confusum when exposed to partially purified methanolic fruit extract of Dennettia tripetala (G. Baker) and two of its major active compounds (linalool and 2-phenylnitroethane). Gas chromatography–mass spectrometry was used to evaluate the chemical profile of the partially purified plant extract. Thirty-two compounds were found in the plant, including established insecticidal and insectifuge compounds such as linalool, cis-vaccenic acid, 2-phenylnitroethane, and linoleic acid, among others. The interactions among the factors have a differential impact on the susceptibility and nutritional indices of both Tribolium species to D. tripetala, linalool and 2-phenylnitroethane. According to LC₅₀ values, linalool and 2-phenylnitroethane were the most and least toxic to both beetles, respectively. With increasing extract concentrations, all nutritional indices except feeding deterrence decreased. Relative to controls, linalool and 2-phenylnitroethane evoked the highest and least reduction, respectively, in beetles' nutritional indices. Treated corn discs deterred both species over treated wheat discs, regardless of insecticide type. T. castaneum had a higher overall food consumption than T. confusum. Regardless of insecticide type, the relative growth rate was higher in T. confusum and T. castaneum fed with treated corn and wheat discs, respectively. D. tripetala extract, linalool, and 2-phenylnitroethane showed higher post-ingestion toxicity to T. castaneum than T. confusum. This study emphasises the importance of certain intrinsic factors, like beetles' species and cereal food types, when managing Tribolium species with plant-based insecticides. The various data obtained from this study will help researchers and pesticide manufacturers formulate effective biopesticides from linalool and 2-phenylnitroethane to control Tribolium species on corn and wheat flours.

Nutrition is vital to health, but while the link between diet and body nutritional composition is well explored in humans and other vertebrates, this information is not well understood in insects, despite the vital roles they play in ecosystems, and their increasing use as experimental models. Here we used Nutritional Geometry to explore the rapid physiological response to ingested nutrients in the haemolymph nutritional profile of Spodoptera littoralis caterpillars. We ask whether blood nutrients are maintained homeostatically in the face of variable nutritional intake, or if regulation is more flexible for some nutrients than others (allostasis), which allows animals to adapt to stress by responding in a way that prioritises efficiency of responses in the face of trade-offs. Caterpillars were placed on 1 of 20 diets, systematically varying in their nutrient ratios (protein: carbohydrate) and density (calorie content), and their consumption was measured. After 48 h, caterpillars were bled, and the macronutrient (protein, carbohydrates and lipids) and nutrient metabolite (amino acids and simple sugars) content of the haemolymph was measured. Proteins comprised 93% of the haemolymph macronutrient pool on average and their concentration increased with protein eaten. The amino acid (AA) pool was dominated by five AAs, and the total pool increased with total nutrient intake. However, the ratio of essential to non-essential AAs increased as the proportion of protein consumed increased. Carbohydrates were tightly controlled, increasing only on the most extreme carbohydrate intakes. Simple sugars were dominated by glucose and trehalose, and overall, the simple sugar pool showed high levels of homeostasis. Rather than strict homeostasis of blood nutritional properties, an allostatic model seemed to be a better fit for blood nutrient regulation in this generalist herbivore. This flexibility in response to the nutritional composition of the diet may, in part, explain how this species has evolved to extreme dietary generalism and may play a role in its worldwide pest status. Given the range of fitness-related processes affected by the haemolymph, future studies should examine the physiological impacts of blood nutrient variation on reproduction, growth and response to infection and the trade-offs between them.

The environment surrounding invertebrates can influence the physiology of larval offspring. Dung beetles provide several significant ecological functions, including dung breakdown, fly control and nutrient cycling. Cattle diet influences the chemical and physical constituents of dung, of which pH is considered critical. Few studies have assessed this, though a pH of 6.3 is the lowest threshold for dung beetle reproduction. We investigated the effects of an introduced and widespread dung beetle (Onthophagus binodis) on cattle dung pH (7.3, 6.0 and 5.0) and pH on O. binodis reproduction, offspring phenotypic traits and development time. Dung beetle presence increased the Δ pH (more alkaline) within dung pads after 96 h. Dung beetles produced broods in dung with a pH of 5.0, though in fewer numbers compared with the other pH treatments. Larval development was delayed in pH 5.0 with an average of 50 days compared with 44 days in dung with pH 6, 7, and the control (7.3). Smaller broods (ellipsoid volume [mm³]) were produced in dung with a pH of 5.0 compared with pH 6.0 and 7.0, and offspring emerging from broods produced from dung with a pH of 6.0 were larger compared with the other pH treatments. Our results show that dung pH is important for brood production and progeny phenotypic traits of O. binodis, an agricultural ecosystem engineer and that there is no experimental evidence to support the suggestion that dung pH influences the provisioning of broods in this species.

Understanding and characterizing how insects tolerate low temperatures is important for predicting their overwintering survival and subsequent geographic spread. This study characterized the cold tolerance of two members of the Rhagoletis genus (Diptera: Tephritidae) in Colorado, USA. Pupae were collected from the infested fruits in late summer and early fall. For the first time, we show that the rosehip fly Rhagoletis basiola Osten Sacken is freeze-avoidant; overwintering pupae could supercool to temperatures as low as −26°C and survive. Interestingly, the temperature at which ice forms (supercooling point; SCP) did not vary between R. basiola at high (c. 2900 m above sea level [m a.s.l.]) and lower (c. 1650 m a.s.l.) elevations. We also report the apple maggot R. pomonella Walsh infesting an unusual host fruit, the Dolgo crabapple, in close proximity to infested hawthorn trees. R. pomonella infesting hawthorn fruits and crabapples had similar SCPs and survived temperatures as low as −21°C. Pupae from both host fruits also survived prolonged exposure (2 weeks or more) to mild low temperatures (0 to −5°C). Further study into the mechanisms underlying the impressive and conserved cold tolerance of R. pomonella and R. basiola is an interesting avenue for future research.

Climate change is associated with increased mean temperatures and amplitudes manifesting both acutely and chronically, triggering organism stress responses that confer fitness costs and/or benefits. The larger grain borer (LGB), Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) is an invasive postharvest agricultural pest. While host shift is its well-known potential invasive mechanism, how repeated intergenerational stress environments may influence offspring phenotypes is largely unknown. We thus evaluated physiological and ecological performance of LGB following repeated intergenerational acute heat acclimation to insinuate its likely responses to projected increased bouts of heat stress associated with climate change. Parental colonies were acutely heat-acclimated separately at 35°C and 38°C; 80% RH for 2 h in climate chambers and released onto sterilized maize grain at optimal conditions (32°C, 80% RH). The F₁ progenies were, respectively, acclimated at the same conditions and incubated to F₂ generation. We then evaluated physiological and ecological performance under optimal conditions across parental, F₁ and F₂ generations. Our results showed that plasticity was highly trait dependent, and that acclimation did not affect F₁ and F₂ critical thermal maxima, but did improve critical thermal minima. However, while acclimation improved heat knockdown time at F₁, repeated acclimation significantly reduced heat knockdown times at F₂, suggesting plasticity erosion with generational repeated acclimations. Acute acclimation negatively affected ecological performance of F₁ generations although this was restored with repeated acclimation in F₂ populations. Our results suggest that the LGB may inflict more economic damage with repeated heat stress due to generational adaptation to temperature stress. The results contribute to knowledge on pest forecasting modelling under changing climates and provides a framework for phytosanitary adjustments in heat treatment protocols for international grain trade.

Increased female age at mating is considered a detrimental factor on reproductive output and fitness in insects, even if the impact is rather species specific. The effect of delayed mating on reproductive output has been widely studied in pest species controlled with mating disruption, as if the method is not fully effective in suppressing matings, it could still delay them, limiting female fitness and pest damage. Female mating delay, however, may also occur in natural habitats without invoking mating disruption. We studied the effect of female delayed mating in Cerambyx welensii (Küster) (Coleoptera: Cerambycidae), an oak-living sapro-xylophagous longhorn beetle considered a critical factor in oak decline. Several life history and ecological traits may potentially delay mating, including low abundance, (re)colonisation processes, sexual communication channel, host-produced kairomones, operational sex ratio, reproductive interference and adverse weather conditions. We conducted laboratory tests to assess the impact of mating delays (0-, 10-, 20- and 30-day post-emergence) on reproductive output. Data showed that mating delay until at least 20 days of age had a limited effect on mating success, lifetime fecundity, longevity and fertility. The daily fecundity pattern depended on mating delay, and virgin females showed ovarian retention. We conclude that C. welensii females have evolved physiological adaptations to overcome mating delays and optimise fitness. We discuss our results from an evolutionary perspective, considering specifically the risk of early predation and egg-laying time limitation. We hypothesise that unpredictable recurrent stochastic variation in male availability could act as an additional driver selecting for synovigeny in this longhorn species.

Juvenile diet can profoundly affect subsequent adult development, morphology and reproductive investment. Yet, little is known about how juvenile diet affects adult investment into chemical-based sexual signalling, perhaps due to the historical assumption that pheromone production is not costly. We explored how juvenile diet influenced the reproductive investment of adults in the gumleaf skeletonizer moth, Uraba lugens. Juveniles were reared on different host plant species (Eucalyptus camaldulensis and Eucalyptus moorei) and on E. moorei host plants with different fertilizer treatments (fertilized and non-fertilized). These juvenile diets differ in foliage carbon and nitrogen content. Several adult life history traits were influenced by juvenile diet, including body size in females, and longevity in males. However, we found no evidence from Y-maze olfactometer assays that diet affected the attractiveness of female pheromones to males. Finally, host plant species affected male pre-copulatory investment: males reared on E. moorei had longer antennae, but less dense sensilla. Combined, our experiments suggest that the effects of juvenile diet on investment in reproductive traits, including those associated with signalling, differ between males and females. Females allocate nutrients to adult body size, which determines fecundity. In contrast, males allocate nutrients to adult longevity and antennae size, both of which improve mate search and mating success.

Investigations of age-based food conversion and utilization efficiencies in phytophagous insects are very few. Studies examining the effects of age, sex and mating status on biochemical assimilation of macronutrients by phytophagous insects are scarce as well. Hence, we designed the present study to evaluate the combined effect of age, sex and mating status on food consumption and utilization efficiencies, and the assimilation of macronutrients by the Parthenium beetle, Zygogramma bicolorata Pallister (Coleoptera: Chrysomelidae), on the invasive weed, Parthenium hysterophorus Linnaeus (Asterales: Asteraceae). We hypothesized that mated adults would consume and utilize more food than unmated adults, that assimilation of nutrients by old adults would be lower than young adults and that females would consume and utilize food more efficiently than males. However, our results revealed that as adults aged, their food consumption and utilization efficiencies decreased, and they assimilated less proteins and glucose in their body. Despite that, their mean body biomass and assimilation of triglycerides increased. While mated adults had higher food utilization efficiencies and increased assimilation of triglycerides and glucose, unmated adults assimilated more proteins. Females had higher food consumption rates and increased assimilation of nutrients, whereas males had higher food conversion efficiencies and growth rates. Furthermore, middle-aged adults had higher food utilization efficiencies and they assimilated more nutrients than young and old adults. Our results therefore suggest compensatory feeding in adults of Z. bicolorata with ageing. We also recommend the release of more numbers of mated middle-aged females to control P. hysterophorus in agro-ecosystems.

We analysed the influence of laboratory domestication, under relaxed conditions, on the courtship behaviour of the fruit fly species Anastrepha obliqua, an important agricultural pest. We compared the temporal patterns of pheromone emission (Calling behaviour) and the frequencies and sequences of the courtship behavioural units of males of a laboratory lineage and a wild lineage. Our results indicated similarities in the temporal behavioural patterns of calling, the durations of their behavioural sequences, the final sequences of courtships resulting in copulation, of wild and laboratory males. Differences, however, were observed between the two populations in terms of the frequencies of the behavioural units executed and the initial sequence of courtship. Differences were noted in the presence or absence of some behavioural units within the courtship behavioural repertoires of the laboratory-reared and wild. The wild males did not show units such as Alignment, Contact, Fighting and Marking Leaf that were observed in the laboratory males' courtship behaviour under laboratory conditions; on the other hand, laboratory males did not show the Abdominal movements and Oscillation observed in the courtship behaviour of wild males. The rearing of A. obliqua males under relaxed conditions in the laboratory provides an environment adequate for the preservation of behavioural characteristics relevant to the successful mating, such as Movement, Arrowhead 1, and Attempt, and in temporal patterns of pheromone emission.