Insect Science最新文献

Many animals display physiological and behavioral activities limited to specific times of the day. Certain insects exhibit clear daily rhythms in their mating activities that are regulated by an internal biological clock. However, the specific genetic mechanisms underlying this regulation remain largely unexplored. Mating in the fruit fly Bactrocera dorsalis exhibits a daily rhythm and is dependent on sex pheromones produced in the male rectum. We used transcriptome sequencing and clustered regularly interspaced short palindromic repeats (CRISPR) / CRISPR-associated nuclease 9 techniques to understand whether the daily rhythmicity of mating in B. dorsalis and sex pheromone production in the rectum are regulated by clock genes. The results showed that the production of sex pheromones by B. dorsalis males is rhythmic (low during the day and high at night) and is influenced by clock genes. Knockout of the clock genes cryptochrome 1 (cry1) and timeless (tim) reduced the production of sex pheromones and significantly impaired mating ability in males. In addition, quantitative polymerase chain reaction results from 5 different tissues showed cry1 was highly expressed in the head, whereas tim was highly expressed in both the head and rectum (a key site for male sex pheromone production). Transcriptome analysis confirmed that cry1 (head) and tim (head and rectum) exhibit rhythmic expressions consistent with sex pheromone rhythmicity. These results suggest that cry1 may be related to a central clock neuron (like the suprachiasmatic nucleus), whereas the rhythmic expression of tim in the rectum indicates the potential presence of peripheral oscillators. Our study reveals new targets and ideas for improved control of the fruit fly.

Reproductive diapause is an insect survival strategy in which reproduction temporarily halts in response to adverse environmental changes. This process is characterized by arrested ovarian development and lipid accumulation in females. A reduction in juvenile hormone (JH) biosynthesis is known to initiate reproductive diapause, but its regulatory mechanism remains unclear. Seven up (Svp), a transcription factor from the nuclear receptor family, plays a crucial role in various developmental processes in insects. In this study, using the cabbage beetle Colaphellus bowringi as a model, we observed higher expression of Svp in the heads of female adults under reproductive photoperiodic conditions (short-day [SD]) compared to diapause conditions (long-day [LD]). RNA interference-mediated knockdown of Svp in SD females induced typical diapause phenotypes, including ovarian arrest and lipid accumulation. The application of methoprene (ME), a JH receptor agonist, reversed these diapause phenotypes and restored reproduction, indicating that Svp's regulation of reproductive diapause is dependent on JH signaling. Additionally, Svp knockdown led to the downregulation of JH pathway genes and a reduction in JH titers. Further evidence suggested that Svp regulates the expression of JHAMT1, a critical gene in JH biosynthesis, which determines diapause entry in C. bowringi. These findings suggest that diapause-inducing photoperiods suppress Svp expression, blocking JH production and triggering diapause. This work reveals a critical transcription factor that regulates reproductive diapause initiation through modulating JH production, providing a potential target for controlling pests capable of entering reproductive diapause.

Respiration is a vital process essential for organism survival, with most terrestrial insects relying on a sophisticated tubular tracheal network. In the current study, a gene with repetitive sequence was identified within the silkworm genome. Designated as BmMuc91C, it contains a dozen repeated motifs "PSSSYGAPX" and "GGYSSGGX" in its sequence. BmMuc91C exhibits specific expression in the tracheal system of silkworm larvae, with significantly higher expression levels during the molting stage. Overexpression of BmMuc91C in individual silkworms resulted in a marked increase in tracheal diameter, particularly during the molting stage. Immunofluorescence staining using a BmMuc91C antibody revealed a noticeable thickening of the apical extracellular matrix in the trachea. Tensile testing confirmed a considerable enhancement in tracheal elasticity. Additionally, a BmMuc91C mutation strain of silkworms was generated using the clustered regularly interspaced short palindromic repeats (CRISPR) / CRISPR-associated nuclease 9 system. Although no significant differences were observed in the growth, development, and molting of BmMuc91C mutant silkworms, mechanical tests demonstrated a decrease in tracheal elasticity. Transcriptomic techniques revealed that a significant number of cuticular and chitin-binding proteins were among the differentially expressed genes between mutant and wild-type silkworms. Furthermore, the recombined BmMuc91C protein was successfully expressed using the Escherichia coli system. Cross-linking experiments with horseradish peroxidase demonstrated the formation of macromolecular complexes of BmMuc91C, which exhibited spontaneous luminescent properties under ultraviolet light. This research sheds light on the role of elastic proteins in insect tracheae and provides valuable insights for the development of elastic biomaterials.

Polyphagous insect species develop using multiple host plants. Often considered beneficial, polyphagy can also be costly as host nutritional quality may vary. Drosophila suzukii (Matsumura) is an invasive species that can develop on numerous fruit species over the annual cycle. Here, we assessed the contribution of winter-available fruit to the development of seasonal populations of D. suzukii, under fluctuating late winter/early spring temperature regimes. We infested an artificial diet and three suitable fruit species available in winter/early spring (Aucuba japonica, Elaeagnus ×submacrophylla, Viscum album) with D. suzukii larvae under three temperature regimes: constant 20 °C, fluctuating controlled regime of 8-15 °C (12 h of light at 8 °C and 12 h of dark at 15 °C), and uncontrolled outdoor regime during spring. As expected, fly performance was impaired by early spring-like environmental conditions, whatever the development diet, and the winter fruit were suboptimal diets compared to the artificial diet, whatever the thermal regime. However, under cold fluctuating temperature regimes, the ranking of fruit supporting the best performance changed, highlighting the occurrence of physiological trade-offs. Winter-acclimated females preferentially oviposited in A. japonica and/or E. ×submacrophylla, whatever the thermal regime, which does not support the preference-performance hypothesis. This finding is also discussed in the context of D. suzukii management strategies.

Jewel beetles pose significant threats to forestry, and effective traps are needed to monitor and manage them. Green traps often catch more beetles, but purple traps catch a greater proportion of females. Understanding the function and mechanism of this behavior can provide a rationale for trap optimization. Jewel beetles possess UV-, blue-, green-, and red-sensitive photoreceptors, and perceive color differently from humans. Jewel beetle photoreceptor signals were calculated for tree leaf and tree bark stimuli, representing feeding and oviposition sites of adult jewel beetles respectively. Artificial neural networks (ANNs) were trained to discriminate those stimuli using beetle photoreceptor signals, providing in silico models of the neural processing that might have evolved to drive behavior. ANNs using blue-, green-, and red-sensitive photoreceptor inputs could classify these stimuli with very high accuracy (>99%). ANNs processed photoreceptor signals in an opponent fashion: increasing green-sensitive photoreceptor signals promoted leaf classifications, while increasing blue- and red-sensitive photoreceptor signals promoted bark classifications. Trained ANNs were fed photoreceptor signals calculated for traps, wherein they always classified green traps as leaves, but often classified purple traps as bark, indicating that these traps share salient features with different classes of tree stimuli from a beetle's eye view. A metric representing the photoreceptor opponent mechanism implicated by ANNs then explained catches of emerald ash borer, Agrilus planipennis, at differently colored traps from a previous field study. This analysis provides a hypothesized behavioral mechanism that can now guide the rational selection and improvement of jewel beetle traps.

Water striders inhabit the elastic surface tension film of water, sharing their environment with other aquatic organisms. Their survival relies heavily on swift maneuverability and navigation around floating obstacles, which aids in the exploration of their habitat and in escaping from potential threats. Their high agility is strongly based on the ability to execute precise turns, enabling effective directional control. This paper investigates the intricate coordination of leg movements essential for initiating and sustaining turning maneuvers in water striders. We elucidate the distinct roles of each leg in modulating posture and stability during turns, with a focus on the pivotal role of the midlegs in maintaining directional movement. Through analysis of leg accelerations, decelerations, and load distribution, we unveil the spatiotemporal dynamics governing successful turns. Our findings reveal refined turning strategies employed by water striders in varying situations, from narrow to wide turns, characterized by adaptations in their locomotor system, particularly in the widening of the sculling field. Additionally, we report the phenomenon of reverse sculling, a novel escape tactic of water striders. By shedding light on the maneuverability of water striders, this study contributes to a deeper understanding of animal locomotion strategies in aquatic environments.

Feeding and molting are particularly important physiological processes for insects, and it has been reported that neuropeptides are involved in the nervous regulation of these 2 processes. Sulfakinin (SK) is an important neuropeptide that is widely distributed among insects and plays a pivotal role in regulating feeding, courtship, aggression, and locomotion. In this study, we investigated the involvement of SK in feeding and molting on a highly notorious pest insect, the fall armyworm, Spodoptera frugiperda. SK transcript levels were found in all larval stages and there was a predominant expression of SK in the brain of 5th instar larvae. By immunostaining, SK was detected in 2 pairs of cells in the median protocerebrum. But during prolonged periods of starvation, there was a significant reduction in SK messenger RNA levels; however, subsequent refeeding led to a notable increase. To investigate the role of SK in feeding and molting, SK was silenced in S. frugiperda larvae through RNA interference. This resulted in a significant increase in food intake, weight gain, and the molting process happened more rapidly in the double-stranded SK-treated larvae compared to the controls. Conversely, injection of sulfated SK peptide (sSK) caused opposite effects. Interestingly, SK-knockdown in larvae resulted in increased levels of 20-hydroxyecdysone and also of the expression of some of it signaling pathway genes. Altogether, this study highlights the important role played by SK in regulating feeding and molting in S. frugiperda.

As the catalytic subunit of the Elongator complex, Elongator protein 3 (Elp3) plays a crucial role in multiple physiological processes, including growth, development and immune responses. Previous studies on Elp3 have focused on Caenorhabditis elegans, Drosophila melanogaster, Homo sapiens (human) or Mus musculus (mouse), whereas there are few reports on Elp3 in agricultural pests. Here, the role of TcElp3 in reproduction in the red flour beetle, Tribolium castaneum, was investigated, and the underlying mechanisms were explored. The results showed that RNA interference (RNAi)-mediated knockdown of TcElp3 in female pupae led to decreased fecundity in female adults. Consistently, the injection of dsTcElp3 into female pupae decreased the mRNA levels of the vitellogenin (Vg)-encoding genes TcVg1 and TcVg2 in female adults. Notably, knockdown of TcElp3 upregulated the expression of forkhead box protein O (FOXO) at both the mRNA and the protein level in T. castaneum, and promoted the nuclear translocation of TcFOXO. Additionally, TcElp3 directly interacts with TcFOXO and the silencing of TcElp3 significantly decreased the acetylation level of TcFOXO. Overall, our studies reveal that Elp3 regulates beetle reproduction by interacting with FOXO and modulating its acetylation status.

Succession is one of the most extensively studied ecological phenomena, yet debates persist about the importance of dispersal and external factors in driving this process. We aimed to quantify the influence of these factors by investigating how wing-related traits evolve across succession of blowfly (Diptera: Calliphoridae) communities in South Brazil. Rat carrion was placed in both forest and grassland habitats, and the associated blowfly communities were documented throughout the decomposition process. Using morphometric analysis, we measured wing and thorax traits and assessed trait changes over succession through mixed models. Our findings revealed that carrion succession follows distinct trajectories in forest and grassland environments. Specifically, we observed that Calliphora lopesi predominantly visited carcasses during the final phase of decomposition, resulting in significant differences in species composition and wing size between habitats. In forests, wing size increased toward the later stages of succession, whereas an opposite trend was observed in grasslands. Notably, these trait patterns were only evident at the species level, indicating that intraspecific trait variation is irrelevant. Stronger dispersers tend to arrive during the later stages of succession, suggesting that dispersal has a negligible role in shaping successional dynamics. Instead, environmental differences between habitats drive trait patterns throughout succession. Our results suggest that community composition in ephemeral resources is governed by deterministic processes and that successional stages can be predicted based on blowfly wing traits. Specifically, the presence of the large-winged C. lopesi indicates late decay, while the small-winged Chrysomia albiceps and Lucilia eximia are indicative of early decay.