Solanum Nigrum Fruit Extract Increases Toxicity of Fenitrothion-A Synthetic Insecticide, in the Mealworm Beetle Tenebrio Molitor Larvae

Effects of agricultural microplastics in multigenerational tests with insects; mealworms Tenebrio molitor

Mulching films, widely used in agriculture, are a large source of microplastics (MPs) to soil. However, there is little knowledge on the long-term effects of agricultural MPs on soil invertebrates. We investigated the effects of MPs from conventional non-biodegradable, fossil-based, low-density polyethylene (PE) and biodegradable fossil-based poly(butylene adipate-coterephthalate) (starch-PBAT blend) mulching films on two generations of the mealworm Tenebrio molitor. No effects of MPs (0.005 %-5 %, w/w dry food) on mealworm development and survival were observed until the end of the experiments (12 weeks for the first generation, nine weeks for the second generation), but effects on their moulting and growth were observed. These were most evident for PE MPs (5 %, w/w), where a decrease in larval growth and moulting was noted in the first generation. On the contrary, PBAT MPs (5 %, w/w) significantly induced the growth of mealworms in the second generation. In addition, there was a non-significant trend towards increased growth at all other PBAT MP exposure concentrations. Increased growth is most likely due to the biodegradation of starch PBAT MPs by mealworms. Overall, these data suggest that PE and PBAT MPs do not induce significant effects on mealworms at environmentally relevant concentrations, but rather only at very high exposure concentrations (5 %).

[A Pilot Test of Olive Weevil Repellents in an Olive Orchard]

Recently, feeding damage by the olive weevil Pimelocerus (Dyscerus) perforatus Roelofs, which utilizes olive trees (Olea europaea Linne) as a host plant, has become the biggest obstacle to olive cultivation in Japan. We previously identified several volatile plant-derived natural products that exhibit repellent activity against olive weevils. In this study, we conducted a pilot test of repellents in an olive orchard along with the use of insecticide. During three consecutive years from 2021 to 2023, the first year was the observation period, and the second and third years were set aside for a trial period for o-vanillin and geraniol as repellents, respectively. Using o-vanillin, the number of adult olive weevil outbreaks decreased to almost half a year in the experimental area, the use of geraniol then resulted in a drastic reduction of the number of individual olive weevils in the experimental area. In contrast, adults and larvae outbreaks increased in the control area without a repellent, despite the use of insecticide. These results indicate that the volatile repellents drove the olive weevils away and kept them at bay in the field. Based on the observations, we will be able to provide a new approach for the control of olive cultivation, including fruit and leaves used for commercial purposes, following integrated pest management (IPM) practices, such as reducing environmental poisoning from intense insecticides, and returning olive weevils to their original habitat outside of olive orchards.

Atomic force microscopy study of the complexation of sterols and the glycoalkaloid α-tomatine in Langmuir-Blodgett monolayers

Glycoalkaloids are secondary metabolites produced by plants that aid in their protection from pathogens and pests. They are known to form 1:1 complexes with 3β-hydroxysterols such as cholesterol causing membrane disruption. So far, the visual evidence showcasing the complexes formed between glycoalkaloids and sterols in monolayers has been mainly restricted to some earlier studies using Brewster angle microscopy which were of low resolution showing the formation of floating aggregates of these complexes. This study is aimed at using atomic force microscopy (AFM) for topographic and morphological analysis of the aggregates of these sterol-glycoalkaloid complexes. Langmuir-Blodgett (LB) transfer of mixed monolayers of the glycoalkaloid α-tomatine, sterols, and lipids in varying molar ratios onto mica followed by AFM examination was performed. The AFM method allowed visualization of the aggregation of sterol-glycoalkaloid complexes at nanometer resolution. While aggregation was observed in mixed monolayers of α-tomatine with cholesterol and in mixed monolayers with coprostanol, no sign of complexation was observed for the mixed monolayers of epicholesterol and α-tomatine, confirming their lack of interaction found in prior monolayer studies. Aggregates were observed in transferred monolayers of ternary mixtures of α-tomatine with cholesterol and the phospholipids 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) or egg sphingomyelin (egg SM). The formation of aggregates was found to be less prevalent for mixed monolayers of DMPC and cholesterol containing α-tomatine than it was for mixed monolayers containing egg SM and cholesterol with α-tomatine. The observed aggregates were generally elongated structures, of a width ranging from about 40-70 nm.

Solanum nigrum Fruit Extract Modulates Immune System Activity of Mealworm Beetle, Tenebrio molitor L

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.

Solanaceae glycoalkaloids: α-solanine and α-chaconine modify the cardioinhibitory activity of verapamil

CONTEXT

Solanaceae glycoalkaloids (SGAs) possess cardiomodulatory activity.

OBJECTIVE

This study investigated the potential interaction between verapamil and glycoalkaloids.

MATERIAL AND METHODS

The cardioactivity of verapamil and glycoalkaloids (α-solanine and α-chaconine) was tested in adult beetle (Tenebrio molitor) myocardium in vitro using microdensitometric methods. The myocardium was treated with pure substances and mixtures of verapamil and glycoalkaloids for 9 min with saline as a control. Two experimental variants were used: simultaneous application of verapamil and glycoalkaloids or preincubation of the myocardium with one of the compounds followed by perfusion with a verapamil solution. We used 9 × 10^-6-5 × 10^-5 M and 10^-9-10^-5 M concentration for verapamil and glycoalkaloids, respectively.

RESULTS

Verapamil, α-solanine and α-chaconine showed cardioinhibitory activity with IC₅₀ values equal to 1.69 × 10^-5, 1.88 × 10^-7 and 7.48 × 10^-7 M, respectively. When the glycoalkaloids were applied simultaneously with verapamil, an antagonistic effect was observed with a decrease in the maximal inhibitory effect and prolongation of t₅₀ and the recovery time characteristic of verapamil. We also confirmed the expression of two transcript forms of the gene that encodes the α1 subunit of L-type calcium channels in the myocardium and brain with equal transcription levels of both forms in the myocardium and significant domination of the shorter form in the brain of the insect species tested.

DISCUSSION AND CONCLUSIONS

The results show that attention to the composition of the daily diet during therapy with various drugs is particularly important. In subsequent studies, the nature of interaction between verapamil and SGAs on the molecular level should be checked, and whether this interaction decreases the efficiency of cardiovascular therapy with verapamil in humans.

Solanum nigrum Extract and Solasonine Affected Hemolymph Metabolites and Ultrastructure of the Fat Body and the Midgut in Galleria mellonella

Glycoalkaloids, secondary metabolites abundant in plants belonging to the Solanaceae family, may affect the physiology of insect pests. This paper presents original results dealing with the influence of a crude extract obtained from Solanum nigrum unripe berries and its main constituent, solasonine, on the physiology of Galleria mellonella (Lepidoptera) that can be used as an alternative bioinsecticide. G. mellonella IV instar larvae were treated with S. nigrum extract and solasonine at different concentrations. The effects of extract and solasonine were evaluated analyzing changes in carbohydrate and amino acid composition in hemolymph by RP-HPLC and in the ultrastructure of the fat body cells by TEM. Both extract and solasonine changed the level of hemolymph metabolites and the ultrastructure of the fat body and the midgut cells. In particular, the extract increased the erythritol level in the hemolymph compared to control, enlarged the intracellular space in fat body cells, and decreased cytoplasm and lipid droplets electron density. The solasonine, tested with three concentrations, caused the decrease of cytoplasm electron density in both fat body and midgut cells. Obtained results highlighted the disturbance of the midgut and the fat body due to glycoalkaloids and the potential role of hemolymph ingredients in its detoxification. These findings suggest a possible application of glycoalkaloids as a natural insecticide in the pest control of G. mellonella larvae.