Insect Science最新文献

Insects, the most diverse group of animals, inhabit almost all environments on Earth. They are susceptible to a wide range of parasites, including entomopathogenic protozoans, nematodes, and ectoparasitic mites. These parasites manipulate host physiology via immunomodulation, endocrine disruption, and metabolic reprogramming. The long-term coexistence of insects and parasites has driven the evolution of intricate survival strategies. Insects deploy morphological, physiological, and behavioral adaptations to mitigate infection risks, whereas parasites counter with sophisticated mechanisms enhancing transmission and reproductive success. Emerging evidence indicates symbiotic microbiota as critical mediators in this evolutionary arms race, modulating infection outcomes through microbial-host-parasite crosstalk. Here, we review recent research progress on the effects of parasites on the development, reproduction, immunity, and behavior of insect hosts; the evolutionary dynamics between insects and parasites; and the interactions of host-parasite-microbiota in insects. Compared to mammals, insects provide a simple model system for elucidating conserved molecular mechanisms underlying host-parasite-gut microbiota interactions. This paradigm not only advances fundamental understanding of evolutionary parasitology but also pioneers microbial-based biocontrol approaches, offering sustainable alternatives for agricultural pest management and economic insect conservation.

Nodulation is an efficient innate immune regulatory mechanism primarily mediated by hemocytes, which aids insects in effectively capturing and eliminating pathogens following their invasion into the hemocoel. Hemocytin is a crucial protein that mediates the nodulation process, synthesized and secreted by granulocytes, facilitating the aggregation of hemocytes. However, the mechanisms underlying the synthesis and release of Hemocytin in granulocytes, as well as the molecular mechanisms regulating nodule formation, remain unclear. In this study, we constructed a yeast library and used Hemocytin as the bait protein, combined with SPR molecular interaction experiments, to identify a trypsin-like serine protease (SP) that interacts with Hemocytin. Through localization studies, we found that SP and Hemocytin co-localize in the granules of granulocytes and are co-released into the hemolymph. Additionally, enzymatic cleavage experiments confirmed that SP can cleave the propeptide portion of Hemocytin. Destruxin A, a Hemocytin-targeting drug, modulates the interaction between SP and Hemocytin, thereby influencing insect immune responses. This, together with functional studies of SP, confirms that SP plays a key role in regulating Hemocytin-mediated hemocyte aggregation and nodulation. These findings will enhance our understanding of the molecular mechanisms by which Hemocytin mediates nodulation and deepen our comprehension of the nodule formation process.

Chemosensory proteins (CSPs) are small soluble proteins that play various roles in insects. The non-sexual parthenogenetic females (virginoparae) of Rhopalosiphum padi can transition to sexual reproduction and produce sexual females (oviparae) when exposed to short photoperiods and low temperatures. To date, research on the distinct roles of chemosensory proteins in sexual versus parthenogenetic female aphids remains scarce. In this study, we investigated the roles of RpCSP8 in R. padi. Among the eight RpCSPs, RpCSP8 exhibited a 3.81 fold higher expression in the oviparae compared to virginoparae. Across developmental stages and tissues, RpCSP8 showed the highest expression in the fourth-instar nymphs and adults, as well as in the salivary glands of oviparae. In contrast, it exhibited the highest expression in adults and the antennae of virginoparae. In oviparae, knockdown of RpCSP8 significantly impaired reproductive performance: fecundity decreased by over 80%, and lifespan was reduced by more than 50%. RpVg (vitellogenin) expression declined by 37.1%, although no significant differences in egg morphology were detected. Electrical penetration graph (EPG) recordings revealed that RpCSP8 knockdown in oviparae significantly reduced phloem ingestion duration, indicating impaired feeding behavior. In virginoparae, knockdown of RpCSP8 showed no significant changes in fecundity, lifespan, or feeding behavior. These results demonstrate different roles for RpCSP8 in regulating both reproductive output and host plant utilization in the oviparae and virginoparae of R. padi. This study reveals the non-chemosensory functions of insect CSP and provides new insights into the adaptive mechanisms underlying reproductive mode transitions and host switching in R. padi.

Calcitonin-like diuretic hormone (CT/DH) is a pleiotropic neuropeptide in insects that plays a role in regulating diuresis in Rhodnius prolixus, a blood-feeding insect and a vector of Chagas' disease. Here, we examine the role of this neuropeptide in another feeding-dependent event, that of reproduction in female R. prolixus. CT/DH-like immunoreactivity is present in the female reproductive system, including cells of the tropharium and pedicel of the ovariole, and nerve processes over the oviducts and calyx; tissues involved in egg maturation, ovulation, and egg laying. qPCR analysis reveals that the transcripts for the Rhopr-CT/DH receptors, Rhopr-CT/DH-R-1B/C and Rhopr-CT/DH-R-2B are present in reproductive tissues and fat body, and appear to be regulated post blood meal, a stimulus that triggers diuresis and reproduction. Knockdown of the two receptors using RNA interference reduces the number of eggs produced and their hatching rate. Downregulation of Rhopr-CT/DH-Rs does not alter protein levels, including vitellogenin, in the fat body or hemolymph and does not change transcript expression of RhoprVg1 in the fat body. Knockdown does lead to a decrease in transcript expression of RhoprVg1 and the Vg receptor, RhoprVgR, in the ovaries. In vitro analyses show that incubation of tissues with Rhopr-CT/DH leads to a notable but not significant increase in transcript expression of RhoprVg1 and a significant increase in RhoprVgR in the ovaries but has no effect on fat body RhoprVg1 or vitellogenin release. Rhopr-CT/DH causes a dose-dependent increase in phasic contraction of the oviducts and increases the amplitude and frequency of intrinsic rhythmic contractions. Collectively, these results suggest the involvement of Rhopr-CT/DH in coordinating aspects of reproduction in female R. prolixus.

The molecular mechanisms by which insects perceive and behaviorally adapt to host plant nutritional variation constitute a fundamental question in insect-plant coevolution. The brown planthopper (Nilaparvata lugens, BPH), a monophagous pest of rice (Oryza sativa), exhibits striking wing dimorphism that directly governs its outbreak patterns: long-winged morphs (LW) initiate migration to escape low-quality hosts, while short-winged morphs (SW) drive local population explosions, thriving in high-quality hosts. However, the mechanism underlying this migration-residence behavior in response to host plant senescence remains unclear. Here, we identified early 4th and early 5th instars as sensitive stages in response to the yellow-ripe rice, a phenological stage marking the onset of host plant senescence that must be promptly avoided. High-performance liquid chromatography (HPLC) revealed that serotonin (5-HT) levels were significantly increased in BPHs during the sensitive stages. Exogenous administration of 5-HT and its precursor 5-hydroxytryptophan (5-HTP) significantly promoted long-winged morph development, whereas pharmacological inhibition with α-methyltryptophan (AMTP, a serotonin synthesis inhibitor) attenuated the wing dimorphism response to yellow-ripe rice. Identification and functional analysis of 5-HT synthesis pathway enzymes suggested that tryptophan hydroxylase (NlTRH) and aromatic L-amino acid decarboxylase (NlAADC) regulated the expression of insulin-like peptide 3 (NlIlp3), subsequently regulating the expression of insulin receptors 1 and 2 (NlInR1, NlInR2), which control wing dimorphism. In contrast, phenylalanine hydroxylase (NlPAH) showed no involvement. This study highlights the vital role of serotonin in wing dimorphism of BPH in response to host plant senescence and offers new targets for sustainable control of the pest.

Neoseiulus barkeri Hughes, a widely used biological control agent for small pests, relies on its sophisticated olfactory system for key behaviors such as foraging, prey location, and mating. While herbivore-induced plant volatiles (HIPV) are well-studied in other insects and large natural enemies, the olfactory mechanisms of phytoseiid mites like N. barkeri remain largely uncharacterized, hindering advances in biological control. This study investigated the potential function of foreleg tarsal sensory organs of the phytoseiid mites in HIPV recognition. The results showed N. barkeri females and males were both attracted to the full blend and six individual volatile originated from cowpea leaves infested by Tetranychus urticae Koch. N. barkeri females no longer showed odor preferences once tarsi of leg I were excised, but attraction was not affected when tarsi of leg IV were excised. SEM analysis characterized the setae types in the distal part of tarsi in leg I as stout peg-shaped structures without sockets, identified as olfactory sensilla. Excising tarsi of legs did not affect predation or copulation in N. barkeri, but reduced its walking speed and mate-searching efficiency. Expression of three Niemann-Pick type C2 genes in excised tarsi of leg I was significantly down regulated when induced by ocimene. These results suggest that tarsi of forelegs of phytoseiids are involved in the perception of HIPV, as well as in discrimination of odor signals. Our study provides a foundation for further elucidation of effective control strategies against small insect and mite pests with predators and HIPV-based components as attractants or repellents.

Micromelalopha sieversi (Staudinger) (Lepidoptera: Notodontidae) is a destructive defoliator of poplar (Populus sp.) trees in China. In prior study, (13Z,15E)-octadeca-13,15-dienal (Z13,E15-18:Ald) (I) and (13Z,15Z)-octadeca-13,15-dienal (Z13,Z15-18:Ald) (II) were identified from the sex pheromone glands of M. sieversi females. Although traps baited with Z13,E15-18:Ald (I) captured M. sieversi males, the attractiveness was inferior to that of unmated females. Moreover, male moths exhibited distinct mate-selection and mating behaviors, suggesting the production of unidentified bioactive components by the sex pheromone glands of females. Gas chromatography-electroantennographic detection and gas chromatography-mass spectrometry were used to identify two additional minor components, (13E,15Z)-octadeca-13,15-dienal (E13,Z15-18:Ald) (III) and (13E,15E)-octadeca-13,15-dienal (E13,E15-18:Ald) (IV), in the sex pheromone gland extracts from M. sieversi females. The four geometric isomers of 13,15-octadecadienal were present in a relative ratio of 100 : 13.43 : 5.27: 20.04. A wind tunnel assay and field tests demonstrated that E13,Z15-18:Ald (III) played a pivotal role in the "short-range" localization of females by male moths, and exhibited a synergistic effect with Z13,E15-18:Ald (I). In contrast, Z13,Z15-18:Ald (II) and E13,E15-18:Ald (IV) had antagonistic effects. Gas chromatographic analysis revealed that the proportion of Z13,Z15-18:Ald (II) in the sex pheromone gland extracts increased markedly after mating. Furthermore, application of exogenous Z13,Z15-18:Ald (II) to the terminal segment of unmated female moths reduced mating rates, suggesting its potential role in the mating decision-making processes of M. sieversi. By clarifying the specific functional roles of minor pheromone components, this study provides a practical approach for development of precise pheromone-based control strategies against M. sieversi.

Insect pests are remarkably successful in evolving resistance to management tactics while facing multiple sources of stress in modern agroecosystems. One possible explanation for this success is that repeated exposure to insecticides may enable pests to tolerate additional stressors through cross-protection. Using the Colorado potato beetle (CPB), Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae), we tested whether selection for imidacloprid tolerance influences responses to multiple stressors. We compared imidacloprid-selected and unselected beetles exposed to sublethal imidacloprid (LD₁₀), high temperature (40 °C), or their combination, measuring effects on mobility, herbivory, development, fecundity, and mortality. Compared to unselected beetles, imidacloprid-selected beetles exhibited 35% lower mobility and 30% lower survival to adulthood under combined stress. Under high temperature alone, mobility in selected beetles was 27% lower, and under imidacloprid alone, mobility was 17% lower than in unselected beetles. Herbivory was reduced in both beetle groups under all stressor treatments, though no significant differences were detected between groups for the combined treatment. Development time and reproductive output were unaffected by any stressor treatment. Independent Action model predictions indicated that combined stress caused greater-than-expected reductions in survival in imidacloprid-selected beetles, suggesting synergistic effects. These findings suggest that selection for insecticide tolerance may create vulnerabilities to environmental stress, a dynamic that could inform pest management strategies under climate change.

The involvement of circadian clock genes in diapause induction has been demonstrated across various insect species, yet the downstream effector molecules mediating this process remain largely uncharacterized. In the bivoltine strain of the silkworm Bombyx mori, embryonic diapause is regulated through the perception of temperature and photoperiod cues perceived by circadian clock genes during a critical environmental-sensitive window of maternal embryogenesis. In this study, we used a knockout mutant (Tim^-/-) of Timeless, a core circadian clock gene, which disrupts diapause induction, as a model system. Employing label-free quantitative (LFQ) proteomics on embryonic heads from wild-type Dazao eggs incubated at 25°C (diapause) and 15 °C (non-diapause), alongside Tim^-/- embryos, we identified differentially expressed proteins (DEPs) associated with diapause fate determination. Comparative analysis revealed significant downregulation of BmaaNAT (B. mori arylalkylamine N-acetyltransferase) in destined diapause egg producers compared to destined non-diapause egg producers. Dual luciferase assays confirmed direct transcriptional activation of BmaaNAT by the CLOCK/CYCLE (CLK/CYC) heterodimer binding to the fourth E-box element of its promoter. Functional validation demonstrated that BmaaNAT knockout shortened larval duration and disturbed diapause occurrence, while overexpression extended larval development, and partially restored diapause capacity in Tim^-/- mutants. This study establishes BmaaNAT as a critical effector linking circadian clock outputs to diapause regulation, uncovering a novel molecular mechanism underlying seasonal adaptation in insects.