Arkadiusz Urbański

Background: Burying beetles (Coleoptera: Nicrophorus spp.) are necrophagous insects well known for their highly developed parental care, which in many respects resembles the reproductive behaviour of birds. As in many other taxa, to avoid intense competition, different sympatric Nicrophorus species occupy distinct habitats and show variation in both seasonal and daily activity. Although niche partitioning is known to influence eye and head morphology in insects, this has been poorly studied in burying beetles. Because these beetles show sexual dimorphism in head size, we hypothesized that eye morphology may also differ between sexes and be linked to the morphology of other head structures. Results: In most species, eye length increased more slowly than width, so larger individuals had relatively wider eyes; only N. humator was near isometry. The strongest negative allometry of eye size vs. body size occurred in N. humator , while N. interruptus and N. vespilloides were close to isometry. Eye aspect ratio (eye length-to-width) changed little with body size, except for notable differences in N. interruptus . PCA indicated that most variation reflects body size change as well. PC2 captured sex and eye–head relationships: females have consistently higher PC2 scores than males, driven by consistent sexual dimorphism in interocular distance and postocular area length. Larger eyes were associated with a smaller postocular area, distinguishing N. humator from other species in PC2. Eye size scales similarly in females and males. The extent of sexual dimorphism, however, depended on species and trait. It is stronger in head structures than eyes, most evident in N. interruptus and N. vespilloides , where it involves an enlarged postocular area, greater interocular distance, and positive eye-size allometry in males. Conclusions: The main finding of our study is that burying beetle species differ in morphological scaling patterns and head shape. Variation and dimorphism are concentrated mainly in head structures other than the eyes, supporting the view of the head as a complex modular system. Compared with other head structures, scaling of the eyes appears more evolutionarily conserved, showing weaker sexual dimorphism and more stable allometric relationships. However, among the studied species, N. humator is distinct and its eye morphology may be linked to a nocturnal lifestyle. These findings provide a basis for future studies on the role of vision in carcass detection, competition, and parental behaviour in burying beetles.

The immunomodulatory properties of transient receptor potential (TRP) channels in insects are poorly understood. Here, we provide evidence of the immunoregulatory role of one of the TRPA (transient receptor potential ankyrin) channels, Painless, in the mealworm beetle ( Tenebrio molitor ), an economically important insect species. Our research revealed that the expression patterns of Painless gene vary across different phases of the immune response. Additionally, we show that the cytokine Spätzle-like protein significantly influences the expression of Painless gene. Furthermore, we report that an allyl isothiocyanate (AITC), TRPA channel agonist which may activate the Painless channel, increases calcium level in T. molitor haemocytes which leading to changes in the expression of immune-related genes. On the basis of the results of the dsRNA experiment, our research also suggested that the link between Painless channel activity and immune pathways is likely mediated by Calcineurin, a calcium-activated serine/threonine phosphatase. Importantly, coinjection of AITC with Escherichia coli significantly improved beetle survival, indicating a functional role in host defense. The results of physiological experiments and phylogenetic analysis suggest that the modulation of Painless channel activity can be a valuable tool for pest control and large-scale T. molitor production.

Introduction: Insects possess a well-developed innate immune system, which encompasses both cellular and humoral mechanisms. On the basis of the similarities in neuropeptide actions between insects and vertebrates, we assume that neuropeptides such as tachykinin-related peptides ( TRP s) regulate insect immune responses and are themselves modulated following infection. Methods: In this study, we examined how immune activation affects the expression of genes encoding TRP precursors and receptors ( TRP and TRPR ) and whether TRPs directly modulate selected immune mechanisms in the pest species Tenebrio molitor . In our experiment, we combined cytokine stimulation, genetic knockdown, pharmacological inhibition, immune profiling, and survival analysis to dissect neuropeptide function. Results: Our results revealed two important insights. First, after activation of the immune system, TRP and TRPR genes were significantly downregulated in the nervous system and immune-related cells. These changes are closely correlated with the changes of the expression level of immune genes. We then show, using Spantide II, a potent antagonist of TRPR, and RNAi knock down of TRP and TRPR , the modulation of key processes of the T. molitor humoral response. This includes the over expression of genes encoding antimicrobial peptides and the important arthropod immune effector phenoloxidase activity. Discussion: Our findings highlight a compelling association between the TRP and immune regulation in Tenebrio and provide insights into the hormonal regulation of physiological processes in insects. Our research also provides novel insights that can contribute to the development of sustainable pest control strategies amid increasing insecticide resistance.

Chemical insecticides play a crucial role in securing global food production but have also caused serious environmental and health problems due to their persistence and low target specificity. In response, insect neuropeptides, which are biological macromolecules that act as key regulators of development, metabolism, reproduction, and behavior, are being explored as potential environmentally friendly alternatives for pest control. This review evaluates the prospects and limitations of using neuropeptides and their synthetic analogues as bioinsecticides. We discuss their mechanisms of action, challenges in increasing biostability, and the risks of affecting nontarget species. Strategies to improve, introduce and increase their applicability usage include peptide modification, targeted delivery systems, and the use of molecular techniques such as RNA interference (RNAi) and CRISPR-Cas9 to disrupt neuropeptide signaling pathways with high specificity. Advances in omics technologies and artificial intelligence are accelerating the discovery and design of novel neuropeptide-based agents. Nonetheless, regulatory challenges, high production costs, limited ecological impact data, and the potential for resistance development remain key obstacles. The integration of neuropeptide-based approaches with existing pest control methods, particularly within genetically modified crops and integrated pest management (IPM), could enhance both efficacy and environmental sustainability. Although the direct application of neuropeptides is still limited, targeting neuropeptide-related genes appears to be a promising and practical direction for the future of biological pest control.

Insects possess a well-developed innate immune system, which encompasses both cellular and humoral mechanisms. On the basis of the similarities in neuropeptide actions between insects and vertebrates, we assume that neuropeptides such as tachykinin-related peptides (TRPs) regulate insect immune responses and are themselves modulated following infection. In this study, we examined how immune activation affects the expression of genes encoding TRP precursors and receptors ( TRP and TRPR ) and whether TRPs directly modulates selected immune mechanisms in the pest species Tenebrio molitor . Our results revealed two important insights. First, after activation of the immune system, TRP and TRPR genes were significantly downregulated in the nervous system and immune-related cells. These changes are closely correlated with the changes of the expression level of immune genes. We then show using Spantide II, a potent antagonist of TRPR, and RNAi knock-down of TRP and TRPR the modulation of key processes of the T. molitor humoral response. This includes the over-expression of genes encoding antimicrobial peptides and the important arthropod immune effector phenoloxidase activity. Our findings highlight a compelling association between the TRP and immune regulation in Tenebrio and provide insights into the hormonal regulation of physiological processes in insects. Our research also provides novel insights that can contribute to the development of sustainable pest control strategies amid increasing insecticide resistance.

Phoretic dispersal is critical in low-mobile invertebrates because it enables feeding, breeding, and gene flow. Phoresy may have serious evolutionary consequences for species in highly specific interactions. Mites within the Uroobovella nova species complex have a narrow range of carriers limited to burying beetles. Nicrophorus vespilloides, a model organism used in behavioural studies, is a common carrier of U. nova, but this interaction remains underexplored. This study investigated how carrier sex, body size, season, and year affect the relationship between U. nova and N. vespilloides. We tested the hypotheses that mite infestation is sex-biased because of differences in parental care between females and males and that larger individuals carry more mites. Mite prevalence was affected only by season. A slightly higher mite load was found in females than in males, and mites showed a significant but weak preference for beetle body size. Considerable temporal differences in mite load were found. Deutonymphs were highly specific when selecting attachment sites, irrespective of the carrier sex, and appeared on some body parts when the preferred sites had already been infested. The low specificity of U. nova towards N. vespilloides individuals and the high selectivity of attachment sites seem to increase the probability of colonising beetle brood chambers.

The short neuropeptide F (sNPF) family of peptides is a multifunctional group of neurohormones involved in the regulation of various physiological processes in insects. They have been found in a broad spectrum of species, but the number of isoforms in the precursor molecule varies from one to four. The receptor for sNPF (sNPFR), which belongs to the G protein-coupled receptor family, has been characterized in various insect orders and was shown to be an ortholog of the mammalian prolactin-releasing peptide receptor (PrPR). The sNPF signaling pathway interacts with other neurohormones such as insulin-like peptides, SIFamide, and pigment-dispersing factors (PDFs) to regulate various processes. The main physiological function of sNPF seems to be involved in the regulation of feeding, but the observed effects are species-specific. sNPF is also connected with the regulation of foraging behavior and the olfactory system. The influence of sNPF on feeding and thus energy metabolism may also indirectly affect other vital processes, such as reproduction and development. In addition, these neurohormones are involved in the regulation of locomotor activity and circadian rhythm in insects. This review summarizes the current state of knowledge about the sNPF system in insects.

Here, we report the first evidence concerning the modulation of insect immune system activity after applying Solanum nigrum fruit extract (EXT). We focused on two main issues: (1) is EXT cytotoxic for Tenebrio molitor haemocytes? and (2) how EXT affects the basic immune mechanisms of T. molitor. The results indicate cytotoxic action of 0.01 and 0.1% EXT on beetle haemocytes. Both the injection of EXT and incubating haemocytes with the EXT solution on microscopic slides significantly increased the number of apoptotic cells. However, 24 h after injection of 0.1% EXT cytotoxic effect of the tested extract probably was masked by the increased number of circulating haemocytes. Application of 0.01 and 0.1% EXT led to impairment of the activity of basic immune mechanisms such as phenoloxidase activity and the lysozyme-like antimicrobial activity of T. molitor haemolymph. Moreover, the EXT elicited significant changes in the expression level of selected immune genes. However, some of the immunomodulatory effects of EXT were different in beetles with and without an activated immune system. The obtained results are an essential step toward a complete understanding of the EXT mode of action on the T. molitor physiology and its potential usage in pest control.