Tenebrio Molitor Research Articles

Stenotrophomonas maltophilia Isolated from the Gut Symbiotic Community of the Plastic-Eating Tenebrio molitor.

Polyvinyl chloride (PVC) waste is a major environmental challenge. In this study, we found that a PVC-eating insect, Tenebrio molitor, could survive by consuming PVC as a dietary supplement. To understand the gut symbiotic community, metagenomic analysis was performed to reveal the biodiversity of a symbiotic community in the midgut of Tenebrio molitor. Among them, seven genera were enriched from the midgut of the insect under culture conditions with PVC as carbon source. A strain of Stenotrophomonas maltophilia was isolated from the midgut symbiotic community of the plastic-eating Tenebrio molitor. To unravel the functional gene for the biodegradation enzyme, we sequenced the whole genome of Stenotrophomonas maltophilia and found that orf00390, annotated as a hydrolase, was highly expressed in the PVC culture niche.

The Nutritional Value of Mealworm (Tenebrio molitor), its Breeding and its Perspective Application in Nutrition

Summary Ensuring a high‐protein diet in the human population and important farm animals is closely related to looking for new protein sources intended for food and feed production. Quantitative and qualitative proteins are one of the basic components for human nutrition and farm animal nutrition. Under European conditions, there is a lack of production of protein raw material, especially those intended for livestock nutrition. Therefore, the European Agriculture policy also focuses on looking for and producing local non‐traditional protein components. One possibility for animal protein production is producing invertebrate proteins. There are currently a number of invertebrate taxa that can be used in human and animal nutrition, as illustrated by the study conducted in 2017 on the “Nutritional Value of Invertebrates and Their Application in Nutrition (present and perspectives)”. Currently, the larval stage of the Tenebrio molitor species seems to be promising, with fast use time. The presented study deals with the nutrition values of the produced biomass of Tenebrio molitor.

In silico identification and expression analysis of glutathione S‐transferase in Tenebrio molitor

AbstractSelective herbicides are used to control undesirable vegetation or weeds in fields without harming crops. Herbicide use for weed management can directly impact the densities of insect pests in agricultural communities as a result of insect mortality during and immediately after application. In insects, the glutathione S‐transferase (GST) enzyme is involved in both the detoxification process and the defense of cellular membranes against oxidative damage. In this study, two TmGSTs (TmGST‐iso1 and TmGST‐iso2) were identified and characterized to elucidate the GST family in Tenebrio molitor. Among the developmental stages of T. molitor, eggs had the highest expression levels of TmGST‐iso1. TmGST‐iso2 expression was highest in the pre‐pupal stage. TmGST‐iso1 expression was high in the guts of early and late larvae, whereas TmGST‐iso2 expression was not observed in early larvae. Adults, both male and female, had the highest levels of TmGST‐iso1 mRNA expression in the gut and reproductive organs, and the highest levels of TmGST‐iso2 expression in the reproductive organs. Quantitative polymerase chain reaction was used to investigate the impact of treatment with butachlor on the mRNA expression of TmGST‐iso1 and TmGST‐iso2 in larvae. TmGST‐iso1 expression increased in the butachlor‐treated group after 3 and 24 h, whereas TmGST‐iso2 expression peaked at 24 h after treatment. This study provides vital information about the detoxifying activities of T. molitor.

Enhanced parasitisation of caterpillars and aphids on field‐grown Brassica oleracea plants upon soil amendment with insect exuviae

Abstract Multitrophic plant–insect interactions are mediated by plant volatiles. The emission of herbivore‐induced plant volatiles is influenced by environmental conditions, such as soil microbes and nutrient composition, with consequences for above‐ground trophic interactions. Here, we investigated whether insect exuviae in the soil alter the plant's volatile blend and attraction of parasitoids in the laboratory and whether this attraction also occurs in the field. We studied the effects of soil amendment with exuviae originating from three insect species, Tenebrio molitor, Acheta domesticus and Hermetia illucens, on the proportion of parasitised Plutella xylostella caterpillars and Brevicoryne brassicae aphids in the field in three consecutive years. In the laboratory, we collected and analysed the volatile blend of amended plants infested with caterpillars or aphids. The attraction of the parasitoids Diadegma semiclausum and Diaeretiella rapae, respectively, towards these volatile blends was assessed in an olfactometer. Our study shows that insect exuviae‐amended soil enhanced the proportion of parasitised herbivores of two species in the field. Relative amounts of several components of the plant volatile blend were affected by soil amendment. Soil amendment with Acheta domesticus or Tenebrio molitor exuviae resulted in an increased attraction of the two parasitoid species in the olfactometer. Soil amendment with insect exuviae altered the plant volatile blend leading to enhanced attraction of parasitoids in laboratory assays. These effects were sustained under the complex and variable biotic and abiotic conditions in the field. Our results underline the importance of belowground processes, such as the decomposition of insect exuviae, on aboveground volatile‐mediated multitrophic interactions. Read the free Plain Language Summary for this article on the Journal blog.

In silico identification and expression analyses of peroxidases in Tenebrio molitor.

Human advancements in agriculture, urbanization, and industrialization have led to various forms of environmental pollution, including heavy metal pollution. Insects, as highly adaptable organisms, can survive under various environmental stresses, which induce oxidative damage and impair antioxidant systems. To investigate the peroxidase (POX) family in Tenebrio molitor, we characterized two POXs, namely TmPOX-iso1 and TmPOX-iso2. The full-length cDNA sequences of TmPox-iso1 and TmPox-iso2 respectively consisted of an open reading frame of 1815 bp encoding 605 amino acids and an open reading frame of 2229 bp encoding 743 amino acids. TmPOX-iso1 and TmPOX-iso2 homologs were found in five distinct insect orders. In the phylogenetic tree analysis, TmPOX-iso1 was clustered with the predicted POX protein of T. castaneum, and TmPOX-iso2 was clustered with the POX precursor protein of T. castaneum. During development, the highest expression level of TmPox-iso1 was observed in the pre-pupal stage, while that of TmPox-iso2 expression were observed in the pre-pupal and 4-day pupal stages. TmPox-iso1 was primarily expressed in the early and late larval gut, while TmPox-iso2 mRNA expression was higher in the fat bodies and Malpighian tubules. In response to cadmium chloride treatment, TmPox-iso1 expression increased at 3 hours and then declined until 24 hours, while in the zinc chloride-treated group, TmPox-iso1 expression peaked 24 hours after the treatment. Both treated groups showed increases in TmPox-iso2 expression 24 hours after the treatments.

EFFECT OF POLYSTYRENE PAPER STYROFOAM FEED ON SURVIVORSHIP AND GROWTH OF Tenebrio molitor L.

Polystyrene Paper Styrofoam (PSP) styrofoam waste is one of the plastic waste that is difficult to degrade. However, from the recently research reported that the PSP styrofoam can be degradated by Tenebrio molitor L. The degradation depends on composition of PSP styrofoam as a part of feeding. This research was aimed to get the composition of good feed to increase the degradation rate of the PSP styrofoam waste, but it still had a good effect on the survivorship and growth of T molitor L. larvae. This research was an experimental laboratory and designed using a control and seven treatments with 3 replications. The parameters observed were survivorship, growth in body length, biomass, and waste degradation rate. The data obtained was analysed using Anova and Duncan test. The results showed that differences in PSP styrofoam waste feed had a significant effect on survivorship (p=0.00), on the growth of body length (p=0.002) and biomass (p=0.00), and waste degradation rate (p=0.02). The research revealed that lower the composition of PSP styrofoam and higher the composition of concentrate combination effected on increasing the survivorship, growth, and waste degradation rate. The result shows that 1 kg T molitor L. larvae can degrade 0.25 kg of PSP styrofoam waste for 60 days. The finding can be used to solve the problem according to the styrofoam pollution.

Exploiting Agri-Food Waste as Feed for Tenebrio molitor Larvae Rearing: A Review.

The agri-food industry generates substantial amounts of waste, including by-products and residues. The increasing demand for sustainable and eco-friendly practices in the agri-food sector has sparked an interest in finding alternative uses for such waste materials. One promising approach is the utilization of waste from the agri-food industry as feed for the rearing of mealworms (Tenebrio molitor). Since agri-food waste is rich in proteins, carbohydrates, lipids, and vitamins, as well as other bioactive compounds, all of which are essential for insect growth and development, incorporating such waste into the diet of mealworms promotes sustainable insect production, reducing the economic and environmental problems associated with waste disposal. This practice can also be beneficial for the rearing of mealworms since their nutritional value can also be enhanced. To this end, various waste materials, such as fruit and vegetable peels, spent grains, and food processing residues, have been investigated as potential feed sources, leading to increased mass production, lower cost, and enhanced nutritional value. This review aims to highlight the potential of agri-food waste as a feed source for mealworms, as well as their potential to enhance their nutritional value. Furthermore, the potential applications of mealworms reared on agri-food waste are highlighted, including their potential as a sustainable protein source for human consumption and as feed ingredients in the livestock and aquaculture sectors.

Improving Yellow Mealworm (Tenebrio molitor) Utilization with Sodium Butyrate in Nile Tilapia Diets: Effects on Growth Performance, Intestinal Histology, Antioxidative Response, and Blood Biomarkers

Yellow mealworm (Tenebrio molitor) meal was introduced to aquafeed as a suitable protein source to replace fish meal (FM) and soybean meal and, thereby, consistent aquaculture production. However, mealworms should be added at adequate levels due to the presence of antinutritional factors such as chitin. Consequently, sodium butyrate (SB) is suggested to improve feed quality and ensure aquatic animals’ productivity and welfare. In this study, parallel with the protein source (T. molitor meal or FM), dietary supplementation of SB (1 g/kg) is involved as a factor in the 2 × 2 factorial study. The first and the second diets were formulated using FM as a protein source with or without SB, while the third and fourth diets were prepared by replacing FM with T. molitor meal with or without SB supplementation. After 60 days, fish fed with FM or T. molitor and SB showed improved final body weight and weight gain, while those fed with T. molitor without SB had a reduced protein efficiency ratio. Histological analysis revealed that dietary SB improved intestinal histological features by increasing the height and branching of intestinal villi and immune cell infiltration near intestinal crypts in Nile tilapia-fed FM or T. molitor. Furthermore, fish-fed FM or T. molitor and SB had higher Hb, red blood cells, PCV, total protein, and globulin levels than fish-fed respective test diets without SB supplementation. Dietary SB addition to FM or T. molitor-based diets also significantly enhanced blood lysozyme and phagocytic activities, catalase, superoxide dismutase, glutathione peroxidase, and reduced MDA levels. Our results demonstrate that T. molitor meal can replace FM without compromising Nile tilapia’s growth performance and health status. Additionally, SB supplementation improved T. molitor meal utilization by Nile tilapia, thereby significantly enhancing the growth, digestion capacity, intestinal histological features, and antioxidative and immune responses. Consequently, dietary T. molitor meal reduces the reliance on FM and improves the sustainability and efficiency of Nile tilapia production.

Nutritional Composition and Safety Parameters of Mealworms (Tenebrio molitor) Reared on Substrates Derived from By-Products

Mealworms provide a viable option for transforming agricultural and food processing by-products that can be converted into a valuable source of high-quality protein and fat suitable for both animals and humans. Hence, our investigation was aimed at employing sprouted and green potatoes, wheat bran, and by-products from brewers’ production as a comprehensive substrate for rearing mealworms. The nutritional value (fat and protein content) and composition of amino acids (AAs) and fatty acids (FAs) were tested in lyophilized and milled larvae. The results showed that the highest amount of protein was detected in sample 3L (59.18 ± 007%), grown on brewers’ spent grain, whereas sample 2S (with wheat bran) comes out with the highest fat content (34.22 ± 0.491%). It was found that the amount of FAs in the larvae depended on the substrate used: the statistically highest amount of monounsaturated FAs was detected in the sample with sprouted potatoes (1L), the highest content of omega-3 FAs was found in the control sample (4CL), with agar–agar gels, and the sample with brewers spent grains (3L) showed a statistically higher amount of oleic acid. Meanwhile, the highest content of total polyunsaturated FAs (36.23%) was detected in the sample with wheat bran (2L). During the study, 16 distinct AAs have been analyzed, and sample 3L has demonstrated the highest content in 11 instances. It is noteworthy that the sample containing brewers’ spent grain exhibited the highest peroxide levels, indicating oxidation. Meanwhile, the determined number of volatile fatty acids did not exceed the regulatory limits for meat. In summary, it can be asserted that adjusting the substrate is essential for extracting specific amino acids and FAs. However, this could potentially affect the content of peroxides. This adaptation enables the desired chemical composition in larvae, making it suitable for specific purposes such as animal or human nutrition and health enhancement.

Bridging the Gap: Scaling Up the Sustainable Production of the Yellow Mealworm with Agricultural By-Products—Insights into Larval Growth and Body Composition

Amidst the escalating global demand for protein-rich livestock feed, there’s an urgent call to explore innovative alternatives. Insects, renowned for their rich protein, lipid, and nutrient profiles, offer a sustainable solution. Integrating agricultural waste into insect diets emerges as a promising strategy to alleviate rearing costs. However, large-scale investigations into by-product valorization remain limited. Thus, our study aims to evaluate Greek agricultural by-products—brewer’s spent grains, rice bran, oat and maize by-products, and animal feed mill leftovers—as potential feedstock for Tenebrio molitor larvae, an insect species that is authorized by the European Union for both livestock feed and human consumption. In this study, the larval growth and body composition were assessed in commercial trays, unveiling optimal performance with rice bran and brewer’s spent grains. Conversely, larvae fed with animal feed mill leftovers and maize by-products displayed suboptimal outcomes. These findings underscore the potential efficacy of integrating locally produced agricultural by-products into T. molitor commercial production. Such an approach not only addresses the growing demand for protein-rich livestock feed but also offers a sustainable solution to agricultural waste management. In conclusion, our research contributes valuable insights towards developing economically viable insect farming.

Quality Characteristics of Meat Analogs through the Incorporation of Textured Vegetable Protein and Tenebrio molitor Larvae in the Presence of Transglutaminase.

Alternative protein sources with greater nutritional value and a lower environmental footprint have recently attracted interest in the production of meat substitutes. However, it is required that these alternatives mimic the texture and structure of meat. This study investigated varying ratios of textured vegetable proteins (TVP) to Tenebrio molitor larvae (brown mealworm; TM) with the addition of transglutaminase (TG) to determine the quality characteristics of these emulsions. The results demonstrated low protein solubility of the emulsions as TVP content increased. Furthermore, when the proportion of TM was high, the TG-treated emulsion had a low pH. Additionally, when there was a high TM ratio to TVP in the TG treatment, the emulsions demonstrated better thermal stability and water holding capacity. Regarding the rheological properties of the emulsion, both the frequency-dependent storage modulus (G') and loss modulus (G'') increased as the proportion of TVP in the emulsion increased with and without the addition of TG. Differential scanning calorimetry analyses demonstrated two protein denaturation peaks in all treatments, with high peak temperatures for both treatments with a high proportion of TM. The hardness and chewiness of the emulsion were highest in the treatment (T6 and T8) with TG, and the gumminess of the emulsion was greatest when TM only or when equal ratios of TVP and TM were treated with TG, respectively. In conclusion, the addition of TM to TVP with TG improves the overall texture of the protein mixture, making it a suitable meat alternative.

Effects of the Replacement of Dietary Fishmeal by the Blend of Tenebrio molitor Meal, Chlorella Meal, Clostridium Autoethanogenum Protein, and Cottonseed Protein Concentrate on Growth, Protein Utilization, and Intestinal Health of Gibel Carp (Carassius gibelio, CAS Ⅴ)

The trial was conducted to investigate the effects of the replacement of dietary fishmeal (FM) by the blend of Tenebrio molitor meal (TMM), Chlorella meal (CM), Clostridium autoethanogenum protein (CAP), cottonseed protein concentrate (CPC) on growth, protein utilization and intestinal health of gibel carp (Carassius gibelio, CAS Ⅴ). The FM-based diet was used as the control, and the blended proteins (TMM: CM: CAP: CPC) at ratios of 1 : 1:8 : 2 (BLEND A), 1 : 1:6 : 4 (BLEND B), and 1 : 1:4 : 6 (BLEND C) were used to replace FM at three levels (33%, 67%, 100%), respectively. The results showed that, compared to the control group, growth performance increased significantly when dietary FM was fully replaced by BLEND B (P<0.05), while decreased by BLEND A (P<0.05). The complete substitution of FM with BLEND B significantly upregulated the mRNA expression of intestinal proinflammatory cytokines, anti-inflammatory cytokines, and tight junction-related genes (P<0.05), improving intestinal tissue morphology and health. And it also significantly increased intestinal trypsin activity (P<0.05), upregulated the mRNA expression of amino acid sensory receptor-related and amino acid or peptide transport-related genes (P<0.05), increased protein apparent digestibility coefficient (P<0.05). The 100% substitution of FM with BLEND A significantly upregulated the mRNA expression of intestinal proinflammatory cytokines and downregulated the mRNA expression of anti-inflammatory cytokine il-10 (P <0.05), reduced intestinal villus height (P<0.05), and decreased protein apparent digestibility coefficient (P<0.05). In conclusion, BLEND B could completely substitute dietary FM and was beneficial to the growth and health of gibel carp. Dietary digestible essential amino acids index (DEEAI) was found as an important indicator and should be higher than 79.5% to meet the maximum growth of fish.

Extended Temperature Range of the Ice-Binding Protein Activity.

Ice-binding proteins (IBPs) are expressed in various organisms for several functions, such as protecting them from freezing and freeze injuries. Via adsorption on ice surfaces, IBPs depress ice growth and recrystallization and affect nucleation and ice shaping. IBPs have shown promise in mitigating ice growth under moderate supercooling conditions, but their functionality under cryogenic conditions has been less explored. In this study, we investigate the impact of two types of antifreeze proteins (AFPs): type III AFP from fish and a hyperactive AFP from an insect, the Tenebrio molitor AFP, in vitrified dimethylsulfoxide (DMSO) solutions. We report that these AFPs depress devitrification at -80 °C. Furthermore, in cases where devitrification does occur, AFPs depress ice recrystallization during the warming stage. The data directly demonstrate that AFPs are active at temperatures below the regime of homogeneous nucleation. This research paves the way for exploring AFPs as potential enhancers of cryopreservation techniques, minimizing ice-growth-related damage, and promoting advancements in this vital field.

Diet replacement with whole insect larvae affects intestinal morphology and microbiota of broiler chickens

Insect-based diets are gaining interest as potential ingredients in improving poultry gut health. This study assessed the dietary treatment with whole dried Tenebrio molitor larvae (TM) on broiler chickens’ gut microbiota and morphology. 120 Ross-308 broilers received treated diets with 5% (TM5) and 10% (TM10) replacement ratio in a 35-day trial. Intestinal histomorphometry was assessed, as well as claudin-3 expression pattern and ileal and caecal digesta for microbial community diversity. Null hypothesis was tested with two-way ANOVA considering the intestinal segment and diet as main factors. The TM5 group presented higher villi in the duodenum and ileum compared to the other two (P < 0.001), while treated groups showed shallower crypts in the duodenum (P < 0.001) and deeper in the jejunum and ileum than the control (P < 0.001). Treatments increased the caecal Firmicutes/Bacteroidetes ratio and led to significant changes at the genus level. While Lactobacilli survived in the caecum, a significant reduction was evident in the ileum of both groups, mainly owed to L. aviarius. Staphylococci and Methanobrevibacter significantly increased in the ileum of the TM5 group. Results suggest that dietary supplementation with whole dried TM larvae has no adverse effect on the intestinal epithelium formation and positively affects bacterial population richness and diversity.

Effect of Temperature on the Nutritional Quality and Growth Parameters of Yellow Mealworm (Tenebrio molitor L.): A Preliminary Study

The nutritional quality of insects is related to many factors, including their rearing conditions. In this study, the effects of temperature on the contents of crude protein, lipids, ash, and amino acids and the body size and weight of Tenebrio molitor larvae were analysed. The larvae were reared with the occurrence of the first 20 pupae in a laboratory incubator at temperatures of 22, 25, and 28 °C. The results revealed that the weight (from 0.09 to 0.15 g), dry matter (DM) content (from 30.72 to 36.55 g/100 g), and fat concentration (from 22.46 to 36.01 g/100 g DM) of the larvae increased with increasing rearing temperature. In contrast, the crude protein content significantly decreased (from 64.33 to 54.41 g/100 g DM). Methionine was the limiting amino acid. The essential amino acid index ranged from 37% to 45%. Information about the effect of temperature on the growth and nutritional parameters of mealworms may contribute to the optimisation of mealworm-rearing technology.

Rearing methods of four insect species intended as feed, food, and food ingredients: a review.

Over the past 2 decades, the potential of insects as food and feed has been recognized globally. Insects as feed ingredients can improve sustainability because of their lower greenhouse gas emissions and their potential to transform organic wastes into high-quality feed rich in nutrients. However, currently, the practical use of insects as food or feed is limited by the high costs of insect production. A great deal of effort is required to improve the rearing technology necessary to establish the principles of insect farming. Several insect species have become industrialized using existing methods of production. The most common industrialized insect species intended as feed and food include the yellow mealworm, Tenebrio molitor L. (Coleoptera: Tenebrionidae); the house cricket, Acheta domesticus L. (Orthoptera: Gryllidae); the black soldier fly, Hermetia illucens L. (Diptera: Stratiomyidae); and the house fly, Musca domestica L. (Diptera: Muscidae). This review focuses on describing the existing rearing methods for these 4 insect species, which may provide a basis for future research to enhance insect production capabilities.

Density-dependent development of the yellow mealworm Tenebrio molitor (Coleoptera: Tenebrionidae)

Abstract The increasing global population has led to high food demand and the interest for alternative resources is highly topical. The interest in utilizing insects as a source of food and feed has been rapidly increasing, as the on-growing population has made the need for protein even more demanding. Insect rearing is economically viable, since they can be fed with organic waste and agricultural by-products. The inclusion of bioactive compounds and active ingredients in insect diets has been identified as a potential key factor for enhancing their growth and performance. The aim of this study was to evaluate the effect of a diet enriched with functional ingredients of medicinal and aromatic plants and agricultural by-products of the Greek flora on the growth, survival and development of larvae of the yellow mealworm, Tenebrio molitor (Coleoptera: Tenebrionidae), in the context of larval density-induced stress. Wheat bran enriched with 5%, 10% or 20% of a prepared mixture containing post-distillation residues of medicinal and aromatic plants of the Greek flora (oregano, thyme, sage and rosemary, linseed oil, rock-samphire, industrial cannabis, and olive paste by-product) was evaluated as insect feeding substrate, whereas wheat bran alone (0% enrichment) served as control. Groups of 25, 50, 75 and 100 first instar larvae were separately collected, weighed, and put in cylindrical plastic cups to test if larval density had any effect on survival and development. According to our results, the final larval weight of T. molitor is significantly affected by the density of larvae but not by the rearing substrate. The highest individual weight among all tested substrates was achieved at the density of 25 larvae. Individual weights were highest when larvae were reared on 5% mixture. The weight of those reared on the control substrate was slightly lower, followed by the 10% and 20% mixtures. Larvae fed with 10% enriched substrate showed the highest survival rate, followed closely by those fed with the control and 5% substrates. Our results clearly demonstrate that larval survival is not density dependent, but density is important in the case of individual larval weight.

Bean Sprouts, Lettuce, and Milk as Water Sources in Tenebrio molitor Larval Growth.

The Tenebrio molitor larva (yellow mealworm) holds great potential as a sustainable ingredient in food and feed. Optimizing its growth under mass farming requires careful water management. However, the availability and cost of fresh fruit and vegetables, which are the most widely used sources of water, can vary geographically, which calls for the search for relatively affordable, effective, and readily available alternatives. We evaluated the effect of three water sources (bean sprouts, lettuce leaves, and milk) as well as their quantity on weights and nutrient profiles of reared T. molitor larvae. Newly hatched mealworm larvae were maintained in controlled conditions of 25 °C and 60% relative humidity under a 12-h light-dark cycle for 15 weeks. When provided as sole-supplements, bean sprouts induced the highest larval weight gains compared to fresh lettuce leaves, which in turn performed better than milk and water. However, the addition of milk to the vegetable supplements enhanced growth. Furthermore, doubling the level of water supply resulted in 70% higher larval weights by week 14 post hatching. Moreover, water sources did not change the nutrient content of the harvested larvae. These findings suggest that mealworm productivity can be enhanced by increasing water feed levels and that bean sprouts may be a superior alternative to lettuce.

To live free or being a parasite: The optimal foraging behavior may favor the evolution of entomopathogenic nematodes.

Facultative parasites can alternate between a free-living and a parasitic existence to complete their life cycle. Yet, it remains uncertain which lifestyle they prefer. The optimal foraging theory suggests that food preferences align with fitness benefits. To test this hypothesis, we investigated the facultative parasite nematode Rhabditis regina, assessing its host preference and the associated benefits. Two experiments were conducted using wild nematode populations collected from Phyllophaga polyphylla, their natural host. In the first experiment, we used a behavioral arena to assess host preference between the natural host and two experimental hosts: Spodoptera frugiperda which is an alternative host and dead Tenebrio molitor, which simulates a saprophytic environment. In the second experiment, we subjected wild nematodes to "experimental evolution" lasting 50 generations in S. frugiperda and 53 generations in T. molitor carcass. We then compared life history traits (the size, survival, number of larvae, and glycogen and triglycerides as energy reserves) of dauer larvae with those nematodes from P. polyphylla (control group). We found a significant preference for P. polyphylla, which correlated with higher values in the nematode's life history traits. In contrast, the preference for S. frugiperda and the saprophytic environment was lower, resulting in less efficient life history traits. These findings align with the optimal foraging theory, as the nematode's parasitic preferences are in line with maximizing fitness. This also indicates that R. regina exhibits specificity to P. polyphylla and is better adapted to a parasitic lifestyle than a free-living one, suggesting an evolutionary pathway towards parasitism.

Farmed Insect Frass as a Future Organic Fertilizer

The aim of this incubation experiment was to evaluate the effect of Tenebrio molitor L. frass on selected chemical and microbiological properties of acid peat. The optimal rate of mealworm frass in the substrate for growing ornamental trees and shrubs was determined. Acid peat was fertilized with frass or urea at five nitrogen (N) rates: 0, 50, 100, 200, and 400 mg dm−3. Mineral N content and electrical conductivity increased, and calcium content decreased in peat with increasing N rates. Similarly to urea, frass increased the ammonification rate at the beginning of incubation and the nitrification rate from the second week of incubation. Higher frass rates increased the abundance of plant-available nutrients (N, P, Mg, K, and Na) in acid peat. Frass undesirably decreased the counts of bacteria with antagonistic activity against soil-borne plant pathogens. Regarding the abundance of functional genes, the optimal N rate was 100 mg dm−3, which promoted the growth of N-fixing and chitinolytic bacteria. Higher N rates promoted the development of aerobic spore-forming bacteria, which produce antibiotics that can be used as biocontrol agents. Moderate fertilizer rates contributed to N accumulation in bacterial biomass. These preliminary findings, which indicate that insect frass can partially replace mineral fertilizers, are promising and can be used in pot and field experiments testing various plant species.