Physiological Entomology最新文献

For over a century, the role of acoustic communication in the sensory ecology of bark beetles (Scolytinae) has been recognized. However, their ‘world of sound’ remains largely unexplored. Here, we review 153 years of bark beetle bioacoustics publications to summarize current knowledge, identify gaps and suggest future research directions. Our survey identified 117 publications covering 170 species. Morphological reports revealed five stridulatory organs across 125 species, with elytro-tergal, gular-prosternal and vertex-pronotum mechanisms being the most prevalent for sound production. However, confirmed sound recordings exist for only 40 species. Acoustic signalling in adults is proposed to function in avoiding enemies, pair formation, sexual selection and spacing, while in juveniles, vibratory communication is proposed for gallery spacing. However, experimental evidence supporting these functions is lacking. Acoustic sensory organs remain unidentified, and comprehension of signal transmission—whether through airborne sounds or solid-borne vibrations (or both)—is limited. Bioacoustic technologies have emerged as tools for potential management practices and are also discussed. Based on these findings, we recommend three directions for future research: (1) characterize acoustic morphology and behaviours in more species, particularly unrepresented taxa, with recordings in various contexts, preferably under natural conditions; (2) test hypotheses to explain the functions of acoustic communication through experimental and comparative phylogenetic methods and (3) investigate how sounds or vibrations are transmitted and received through behavioural and neurophysiological experiments. Advancements in bark beetle acoustic sensing and communication research will enhance our understanding of their sensory ecology and facilitate potential control measures of these fascinating insects.

The invasive avian vampire fly, Philornis downsi, Dodge and Aitken (Diptera: Muscidae) is a threat to the long-term conservation of Darwin's finches and other landbirds in the Galapagos Islands. Adult flies feed on fermented fruit, but their larvae are obligate parasites that feed on, and often cause the mortality of, the developing nestlings. Various techniques for the control of this parasite are currently under study, but the inability to rear flies in captivity has slowed progress. To help understand the reproductive behaviour of P. downsi, in this study, we measured the reproductive organs of male and female flies to determine the age flies mature physiologically, as well as the influence of the larval and adult diets on this process. Both females and males reared from larvae that had developed in the wild on live birds reached physiological maturity at 6 days; in the males, this was associated with increased pigmentation of the testes and the presence of free sperm, and in the females, mature eggs. Females reared in the laboratory on an artificial diet produced mature eggs at 6 days. However, the ovaries of laboratory-reared females were statistically smaller than those of wild females, suggesting that egg production was affected by larval diet. Physiological maturity was delayed in laboratory-reared males, taking twice as long. The testes of these males had more unpigmented areas and deformities indicating that the artificial larval diet was insufficient. Enrichment of the adult diet could help compensate for this. The addition of methoprene (M) to the diet was found to have a positive effect on the sexual development of the flies. In females, a diet of sugar + yeast hydrolysate (YH) in a 3:1 ratio combined with M favoured the development of larger ovaries and the production of mature eggs at an earlier age (3 days). In the case of males, a diet with YH increased testis size and M accelerated the growth of testis length even when males were fed only with sugar and without YH. Additional studies are recommended for improving the diets for mass-rearing this highly harmful fly.

The effect of the particle size of the feed on the larval growth and feed utilization parameters of two mealworm species, Alphitobius diaperinus (Panzer) and Tenebrio molitor L. (Coleoptera: Tenebrionidae), was examined under laboratory conditions. Wheat bran of four different particle sizes (100–250, 500–650, 850–1000 and >2000 μm) was provided as feed to larvae of both species. The larval growth and survival, as well as time to pupation and the amount of feed consumed, were monitored to determine differences among the wheat bran particle sizes within each insect species. Our research results suggest that a finely ground feed with a particle size below 650 μm significantly impact the growth and development of A. diaperinus, as opposed to a feed containing particles larger than 850 μm. Contrariwise, the larvae of T. molitor exhibited no discernible response to the various feed particle sizes that were evaluated. Overall, it was observed that the two mealworm species did not exhibit identical responses for the tested feed particle size, suggesting that this factor is species dependent.

Several studies have implicated the L3 auditory interneuron in the regulation of syllable period selective phonotaxis in female cricket Acheta domesticus. The L3's response to model calls of conspecific males comprises of an immediate and a prolonged response. The kinetics of activation of these electrical activities are consistent with sequential activation of ionotropic and metabotropic mechanisms. In this study, we used electrophysiological and pharmacological tools to investigate the cellular mechanisms underlying L3's response. Bath application of the synthetic protein kinase inhibitor 1-(5-isoquinolinesul-fonyl)-2-methylpiperazine (H7), results in the suppression of L3's spiking response, and this effect can be reversed by saline wash. Additionally, when female A. domesticus that were previously nano-injected with H7 were tested for phonotaxis on a non-compensating treadmill, they demonstrated suppression of syllable period-dependent phonotaxis. These findings implicate protein kinase in the regulation of L3's spiking rhythm and the associated phonotaxis in A. domesticus.

Non-linear immune response is one of the causes of multi-stability of infection outcomes. In order to avoid the uncertainty caused by multi-stability in experiments, one needs to quantitatively measure immune response and other traits as well. Here, we took a quantitative approach, which combines mathematical model and time-series data, to measure the immune response of the Tenebrio moliter challenged by non-replicative immune inducers. The results showed that the host immunity that characterized by in-vitro bacterial killing rapidly mounted after immune challenging, then slowly declined to an undetectable level within 100 h. We then quantified the immunity at 15 h after challenging. The results showed that immune response was non-linearly correlated with the titter of inducer, which fits well to a Hill-like function. Our results have verified the non-linear immune response with respect to amount of invading pathogens and may also help to rigorously test the concepts and theories in host–pathogen interaction, such as resistance and tolerance.

Organisms subjected to periodic nutrient limitation early in life exhibit improvements in aspects of survival, including resistance to some environmental stressors. Recent findings indicate that forms of periodic fasting, such as intermittent fasting and time-restricted feeding, can improve starvation resistance. However, it remains unclear to what extent this survival improvement persists across different genetic backgrounds. In this study, we examine fasting-induced starvation resistance across a broad survey of wild-derived lineages and document genetic variation within this trait. We adopt a standard dietary intervention and show improvement in starvation resistance within a common laboratory lineage, replicating previous results. Next, we examine fasting-induced starvation resistance across isofemale lines collected across latitudes and in different seasons, and among inbred lines derived from flies collected on different continents. We discover genetic variation of fasting-induced starvation resistance and show that fasting improved starvation resistance as often as it worsened starvation resistance. Fasted flies generally showed reduced fat concentration, and their starvation survival varied with sex, season of collection and geographic origin. While specific lineages common to the laboratory can show a specific fasting-induced phenotype, we show that this result is not consistent across genetic backgrounds, reinforcing the idea that phenotypes observed in historic laboratory strains may not be conserved across a species.

Elevated concentrations of atmospheric carbon dioxide (CO₂), a consequence of anthropogenic global change, may profoundly interfere with natural ecological processes, perhaps even interactions across trophic levels. Even the survival prospects of organisms at higher trophic levels could be affected, as follows. We showed previously that the endoparasitoid Diaeretiella rapae, a specialized parasitoid of the cabbage aphid Brevicoryne brassicae, exposed to elevated CO₂ concentrations (800 ppm) for up to 10 weeks, performed far worse (e.g., lower survival and parasitism rates) compared with ambient CO₂ (400 ppm). To investigate whether these CO₂-related effects in the parasitoids were mediated by changes in the quality of the aphids as hosts, we measured the nutritional and energy content of cabbage aphids under the above conditions. Specifically, we measured lipid, protein and water-soluble carbohydrate concentrations. We tested the hypothesis that when insects feed from plants with altered nutritional content, they incur a cost in dealing with such biotic stresses. That cost reduces their metabolic well-being and, thus, reduces their nutritional status with respect to parasitoids developing at their expense. We found that CO₂ had significant effects on aphid body mass (i.e., wet weight) and chemical composition, with elevated CO₂ concentrations reducing aphid mass by more than 50%. Aphids grown under elevated CO₂ also had significantly reduced soluble carbohydrates but significantly more lipids, on a weight-per-weight basis, than aphids grown under ambient CO₂. A significant decrease in total energy reserves (i.e., the sum of total proteins, lipids, and water-soluble carbohydrates) thus typified aphids grown under elevated CO₂. Our results contribute to explaining the impaired performance of the aphid B. brassicae and its parasitoid D. rapae previously reported under elevated CO₂, and provide evidence that under future climate change, host plants might affect the development and performance of parasitoids through their impacts on the nutritional quality of their herbivorous hosts.

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.