Physiological Entomology最新文献

Insects encounter variable temperature conditions in their natural habitats. Under non-optimal temperatures, they experience thermal stress and oxidative damage, which are mitigated by antioxidant enzymes like superoxide dismutase (SOD), catalase (CAT) and lipid peroxidation (LPO). While short-term effects of thermal stress on antioxidant enzyme activities in insects are well understood, the long-term effects are less explored. We investigated both short-term (3 and 6 h) and long-term (24 h) effects of thermal stress on SOD, CAT and LPO activities in the Parthenium beetle, Zygogramma bicolorata Pallister at cold (15°C), control/optimal (25°C) and hot (35°C) temperatures. Although Z. bicolorata is an effective biocontrol agent for noxious Parthenium weed, no prior study assessed the impact of thermal stress on antioxidant enzyme activities in this beetle. Our results revealed that antioxidant enzymes activities increased above control levels in both larvae and adults when exposed to thermal stress for short durations. Under long-term thermal stress, CAT and LPO activities decreased below control levels, while SOD activity increased. Regardless of temperature conditions, early larval instars exhibited higher enzyme activities compared to later instars. In adults, males showed higher SOD and CAT activities, whereas LPO activity did not differ significantly between sexes. Our findings suggest that short-term thermal stress can stimulate protective enzyme activity in these beetles and help them adapt to suboptimal temperatures. However, prolonged exposure may lead to excessive stimulation, potentially inhibiting protective enzyme activity and causing the beetles to activate alternative pathways to manage thermal stress. Moreover, fourth instars and adult females are the most thermal stress-tolerant stages for Parthenium biocontrol.

The presence of environmental microplastics (MPs) poses a significant threat to terrestrial and aquatic animals, including insects such as blood-sucking mosquitoes. The paper reports on the laboratory study of the effect of three different types of MPs, including fragmented high-density polyethylene (HDPE), polypropylene (PP) and polystyrene (PS), on the viability, innate immune responses, activity of detoxifying enzymes and malondialdehyde (MDA) concentration in Aedes aegypti (Linnaeus, 1762). The results showed that dietary administration of microfragments of PP, PS and HDPE at low concentrations (4 mg/L) had no effect on the survival rate of mosquito larvae, but was observed to suppress the larval immune response. The addition of MPs to the diet resulted in a significant suppression of phenoloxidase activity compared to the control. A decrease in the activity of the detoxifying enzymes glutathione-S-transferase and non-specific esterase was observed. Dietary administration of MPs did not cause any significant change in alkaline proteolytic enzyme activity in larvae compared to the control. However, we observed a twofold increase in the activity of acid proteolytic enzymes in all experiments compared to the control (p < 0.05). MDA levels in larval homogenates remained unchanged, while lysozyme-like activity showed a slight decrease compared to the control. The observed processes may be a consequence of intestinal obstruction by MPs, which may cause microtraumas to intestinal tissues and changes in the structure and composition of the microbiota. These changes may have a profound effect on the resistance of mosquito larvae to insecticides and pathogens.

Triacylglycerides (TAGs) are neutral lipids and are one of the major energy storage forms in an insect aiding in normal physiology including reproduction of the organism. Importance of TAG metabolism in gametogenesis has been investigated in insects like mosquitoes, silkworm and Drosophila. However, a direct association between TAG levels and egg-to-adult viability has not been explored. In this study, we have assessed both stored and circulating TAG levels and egg-to-adult viability in Drosophila melanogaster lines with varying genetic backgrounds established through inbreeding and recombinant inbreeding strategies. We found noticeable variation in egg-to-adult viability and in both stored and circulating TAG levels in D. melanogaster lines. Apparently the D. melanogaster lines with higher levels of circulating TAG also had a higher egg-to-adult viability. To validate this, analysis of these variations through supervised correlation and unsupervised K-means clustering showed that levels of circulating TAG are positively associated with egg-to-adult viability irrespective of gender. The findings suggest that levels of circulating TAG promotes successful transition of egg to an adult. Taken together, the findings not only have a potential application in husbandry of ecologically and economically important insects but also holds importance in translational research in fertility of vertebrates including humans.

Wildlife faces an increasing threat from extreme climatic events, such as heatwaves, which can have a severe impact on various species, including crucial pollinators like bumblebees. Bumblebees are cold-adapted and heterothermic, possessing the ability to regulate their internal temperature. The impact of heat stress seems species specific in bumblebees. While most species are impacted, some bumblebee species manage to survive, potentially by employing physiological mechanisms, including the modulation of their protein profile (e.g. Heat Shock Proteins). However, there is limited understanding of how their protein profiles are associated with heat exposure. In this study, we examined the global variation in the protein profile of males from two bumblebee species sampled in the wild: the heat-tolerant Bombus terrestris and the heat-sensitive Bombus magnus. After subjecting them to heat stupor at 40°C in controlled condition, it was observed that nearly all B. terrestris survived the stress, while over 50% of B. magnus individuals succumbed to the heat exposure. Through off-gel bottom-up proteomics and LC–MS/MS analysis of the hemolymph proteome, we identified 164 proteins in both species with a large part of differentially expressed proteins after heat exposure. Additionally, quantitative analysis of fat bodies revealed that the relative mass was stable in B. terrestris, while it was significantly lower in B. magnus exposed to heat stress. Our data suggest that compared with B. magnus, B. terrestris displays a higher adaptability of its hemolymph proteome in response to heat stress. This adaptability could be a key factor contributing to the high physiological resistance of B. terrestris and its ability to adapt to new, stressful environments expected due to climate change. Understanding these mechanisms of protein regulation in bumblebees could provide valuable insights into their resilience and vulnerability facing environmental stresses.

Insects attach to various surfaces that differ, among others, in roughness and wettability. Identifying surface characteristics that allow or prevent insects from attaching are an important research avenue of pest control. Here we take an experimental approach to analyse the attachment of common bed bugs, Cimex lectularius Linnaeus (1758), to Perspex (PMMA) substrates. We construct a reliable centrifuge device that allows the measurement of attachment forces at substrate roughnesses, Ra, between 0.02 and 1.3 μm and at two wettabilities. Our results suggest that bed bug attachment to surfaces is minimal at a substrate roughness of 0.2 and 0.4 μm on normal PMMA, where the lowest attachment force was 0.8 mN and the safety factor 15. At lower and higher roughness, attachment forces were higher and the safety factor increased to a maximum of 133. On PMMA that was made superhydrophobic by spray-coating, attachment was lowest (0.2 mN) at the lowest roughness and continuously increased with increasing roughness, reaching 2.5 mN and a safety factor of 46. For every roughness, attachment forces were lower on superhydrophobic than on normal PMMA. This knowledge may inspire the development of repelling substrates for bed bug control.

Colours in nature can be pigmentary, structural or a combination of both. The prevalence, function and nanostructural origin of structural coloration in eggs is largely unknown. Stick and leaf insect eggs display a wide variety of colours, most of which are produced by pigments. The eggs of Myronides glaucus (Phasmida: Lonchodidae; Hennemann, 2021), however, show a clear purple to green iridescence. Here, we use micro-spectrophotometry, Fourier-transform infrared reflectance, transmission- and scanning electron microscopy, atomic force microscopy, finite-difference time-domain optical simulations and experimental approaches to elucidate the mechanism for iridescence in M. glaucus eggshells, which together reveal that iridescence is caused by thin-film interference by a 200- to 450-nm-thick outermost layer. These results highlight the diversity of phasmid eggs and the need to study the different mechanisms and functions of structural coloration.

Ingested toxins formulated as baits can be effective in the management of insect pests, but their efficacy may be influenced by insect foraging alongside active ingredients. There are several components that might influence insect consumption of toxic baits, one of which being prior nutritional exposure. In our study, we investigated how protein deprivation following adult emergence influences lethal and sublethal effects of boric acid on the pest tephritid melon fly, Zeugodacus cucurbitae. We performed a series of experiments to address the impact of prior diet on mortality, diet consumption, enzymes involved in detoxification and antioxidation and fly activity. Newly emerged melon fly adults were provided either diet containing 3:1 sucrose/yeast hyrdrolysate or just sucrose for three days prior to bioassays. Overall, protein deprivation had a strong effect on fly interactions with boric acid. In two separate experiments (continuous exposure and short duration feeding), insects only pre-fed sucrose had significantly higher mortality compared with those pre-fed protein. Insects that were pre-fed only sucrose removed more liquid diet over the same duration of the experiments, suggesting compensatory foraging behaviours. Adults pre-fed sucrose had higher catalase (1.5×) and superoxide dismutase (1.7×) activities compared with adults pre-fed sucrose-yeast, but we found no effect of boric acid on their activity or that of glutathione-S-transferase or acetylcholinesterase activity. Boric acid consumption also significantly reduced the activity of melon flies. Overall, our results demonstrate that prior diet in fly adulthood can impact subsequent exposure to and efficacy of ingested toxicants.

Vitellogenin (Vg) has been recognized as a co-opted gene involved in social colonies where it is associated with reproduction in the queen and task transitions in workers. The Solenopsis invicta genome harbours four Vg genes, Vg1, Vg2, Vg3 and Vg4, and this study explored the regional expression of these genes in the brain and head of the worker caste in different subcaste and social contexts. Transcriptomic analyses of the worker brain while in the presence or absence of brood revealed differential expression of genes involved with social behaviours. Among these, we found higher expression of Vg2 and Vg3 in the brains of workers in the absence of brood. The influence of brood on expression of Vg between worker castes was also investigated. RT-qPCR revealed higher expression of Vg in the head of workers in the absence of brood. Further studies demonstrated that Vg was also differentially expressed in the heads of workers conducting specific tasks and differing between subcastes. Nurses maintained higher Vg expression than foragers. We conclude worker Vg expression may be linked to the brood and/or nutritional state. Vg expression changes when workers are deprived of protein suggesting it is regulated by nutritional signalling and the presence of brood.

Opisthoplatia orientalis Burmeister is a traditional medicinal insect in China that is mass-produced by entrepreneur farmers. However, low temperatures pose a serious threat to the survival and quality of this insect, causing economic losses to the farmers. This study aimed to test the hypothesis that low temperatures induce a trade-off between immunity and physical condition of O. orientalis. The phenoloxidase activity and hemocyte concentration of O. orientalis under 25°C and 5°C were measured by micro-determination and haemocytometre, respectively. The immunocompetence of the insect was also evaluated by inoculating it with Metarhizium anisopliae M11, an entomopathogenic fungus. The physical factors (protein content, fatty acid content and body weight) of O. orientalis were determined accordingly. The results showed that phenoloxidase activity and hemocyte concentration increased from 9.21 mOD/min and 122.30 hemocyte/ml to 3.64 mOD/min and 55.70 hemocyte/ml when temperature down-regulated from 25 to 5°C. However, the insects at 5°C had higher protein and fatty acid content, but lower body weight, than those at 25°C. Moreover, there was a significant negative correlation between immunity and protein or fatty acid content, indicating a trade-off between immunity and physical condition in O. orientalis under low temperatures. This study provides useful insights for improving the efficiency of insect breeding and enhancing the quality of this medicinal insect.