The Impact of Drying Methods on the Quality of Blanched Yellow Mealworm (Tenebrio molitor L.) Larvae.

The growing world population necessitates the implementation of appropriate processing technologies for edible insects. The objective of this study was to examine the impact of distinct drying techniques, including convective drying at 70 °C (70CD) and 90 °C (90CD) and freeze-drying (FD), on the drying kinetics, physical characteristics (water activity, color), chemical characteristics (chemical composition, amino acid profile, oil properties, total polyphenol content and antioxidant activity, mineral composition, FTIR), and presence of hazards (allergens, microorganisms) of blanched yellow mealworm larvae. The freeze-drying process results in greater lightness and reduced moisture content and water activity. The study demonstrated that the freeze-dried insects exhibited lower contents of protein and essential amino acids as compared to the convective-dried insects. The lowest content of total polyphenols was found in the freeze-dried yellow mealworm larvae; however, the highest antioxidant activity was determined for those insects. Although the oil isolated from the freeze-dried insects exhibited the lowest acid and peroxide values, it proved to have the lowest PUFA content and oxidative stability. All the samples met the microbiological criteria for dried insects. The results of the study demonstrate that a high temperature during the CD method does not result in the anticipated undesirable changes. It appears that freeze-drying is not the optimal method for preserving the nutritional value of insects, particularly with regard to the quality of protein and oil.

Oven-drying and decontamination effects on crude protein concentration and in vitro crude protein digestibility of yellow mealworm (Tenebrio molitor) (Coleoptera: Tenebrionidae).

The study aims to assess the impact of oven-drying and decontamination on crude protein concentration and in vitro crude protein digestibility of yellow mealworms. Two kilograms of 12-wk-old mealworm larvae were subjected to freezing prior to the drying process. Approximately 1.5 kg of mealworm larvae were divided into 3 groups and exposed to oven-drying at temperatures of 50 °C for 36 h, 60 °C, and 70 °C for 24 h each. At intervals of 2 h, sets of 3 replicates were withdrawn to record water loss. Consistent weight stabilization was observed at 36 h for 50 °C (T50), 18 h for 60 °C (T60), and 14 h for 70 °C (T70). The remaining 0.5 kg of mealworm larvae was divided and dried under treatments T50, T60, and T70. Each treatment was then split into 2 portions, with one portion subjected to 90 °C for 15 min (denoted as T50-90, T60-90, T70-90) to eliminate microbial contamination. The 6 treatments were then used to determine concentrations of dry matter, crude ash, crude protein, pre-caecal protein digestibility, and dry matter residues after neutral detergent fiber, acid detergent fiber, and acid detergent lignin treatments. No interaction was observed between drying and decontamination treatments (P > 0.17). Pre-caecal crude protein digestibility increased with decreasing temperature (T50: 58% crude protein; T60: 51% crude protein; T70: 50% crude protein). Therefore, lower temperatures for longer times preserve crude protein digestibility. These findings are crucial for understanding how drying temperature and time impact protein bioavailability.

Design of eco-friendly antifreeze peptides as novel inhibitors of gas-hydration kinetics.

In this study, peptides designed using fragments of an antifreeze protein (AFP) from the freeze-tolerant insect Tenebrio molitor, TmAFP, were evaluated as inhibitors of clathrate hydrate formation. It was found that these peptides exhibit inhibitory effects by both direct and indirect mechanisms. The direct mechanism involves the displacement of methane molecules by hydrophobic methyl groups from threonine residues, preventing their diffusion to the hydrate surface. The indirect mechanism is characterized by the formation of cylindrical gas bubbles, the morphology of which reduces the pressure difference at the bubble interface, thereby slowing methane transport. The transfer of methane to the hydrate interface is primarily dominated by gas bubbles in the presence of antifreeze peptides. Spherical bubbles facilitate methane migration and potentially accelerate hydrate formation; conversely, the promotion of a cylindrical bubble morphology by two of the designed systems was found to mitigate this effect, leading to slower methane transport and reduced hydrate growth. These findings provide valuable guidance for the design of effective peptide-based inhibitors of natural-gas hydrate formation with potential applications in the energy and environmental sectors.

Effect of Diets with the Addition of Edible Insects on the Development of Atherosclerotic Lesions in ApoE/LDLR-/- Mice.

Foods enriched with insects can potentially prevent several health disorders, including cardiovascular diseases, by reducing inflammation and improving antioxidant status. In this study, Tenebrio molitor and Gryllus assimilis were selected to determine the effect on the development of atherosclerosis in ApoE/LDLR-/- mice. Animals were fed AIN-93G-based diets (control) with 10% Tenebrio molitor (TM) and 10% Gryllus assimilis (GA) for 8 weeks. The nutritional value as well as antioxidant activity of selected insects were determined. The lipid profile, liver enzyme activity, and the fatty acid composition of liver and adipose tissue of model mice were evaluated. Quantitative analysis of atherosclerotic lesions in the entire aorta was performed using the en face method, and for aortic roots, the cross-section method was used. The antioxidant status of the GA cricket was significantly higher compared to the TM larvae. The results showed that the area of atherosclerosis (en face method) was not significantly different between groups. Dietary GA reduced plaque formation in the aortic root; additionally, significant differences were observed in sections at 200 and 300 µm compared to other groups. Furthermore, liver enzyme ALT activity was lower in insect-fed groups compared to the control group. The finding suggests that a diet containing edible insect GA potentially prevents atherosclerotic plaque development in the aortic root, due to its high antioxidant activity.

Preparation of chitosan/Tenebrio molitor larvae protein/curcumin active packaging film and its application in blueberry preservation.

With growing concerns about postharvest spoilage of fruits, higher requirements have been placed on high-performance and sustainable active packaging materials. In this study, we prepared curcumin-based functional composite films using chitosan (CS) and Tenebrio molitor larvae protein (TMP) as the substrates. The effects of curcumin concentration on the structural and physicochemical properties of the composite films were determined. Curcumin was equally distributed in the polymer film through physical interactions. Furthermore, the curcumin composite film with 0.3 % addition exhibited a 27.39 % increase in elongation at break (EBA), a 37.04 % increase in the water vapor barrier, and strong UV-blocking properties and antioxidant activity compared with the control film (CS/TMP). The degradation experiment of the composite film on natural soil revealed that the composite film exhibited good biodegradability and environmental protection. Furthermore, the applicability of functional composite films for preserving blueberries was investigated. Compared with the control film and polyethylene (PE) films, the prepared composite films packaging treatment reduced the decay rate and weight loss rate of blueberries during storage, delayed softening and aging, and maintained the quality of blueberries. Using sustainable protein resources (TMP) and natural polysaccharides as packaging materials provides an economically, feasible and sustainable way to achieve the functional preservation of biomass materials.

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 %).

Sphingobacterium tenebrionis sp. nov., isolated from intestine of mealworm.

A bacterial strain designated PU5-4T was isolated from the mealworm (the larvae of Tenebrio molitor) intestines. It was identified to be Gram-stain-negative, strictly aerobic, rod-shaped, non-motile, and non-spore-forming. Strain PU5-4T was observed to grow at 10-40 °C, at pH 7.0-10.0, and in the presence of 0-3.0 % (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain PU5-4T should be assigned to the genus Sphingobacterium. The 16S rRNA gene sequence similarity analysis showed that strain PU5-4T was closely related to the type strains of Sphingobacterium lactis DSM 22361T (98.49 %), Sphingobacterium endophyticum NYYP31T (98.11 %), Sphingobacterium soli NCCP 698T (97.69 %) and Sphingobacterium olei HAL-9T (95.73 %). The predominant isoprenoid quinone is MK-7. The major fatty acids were identified as iso-C15 : 0, iso-C17 : 03-OH and summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c) and summed feature 9 (iso-C17 : 0 ω9c). The polar lipids are phosphatidylethanolamine, one unidentified phospholipid, and six unidentified lipids. The genomic DNA G+C content of strain PU5-4T is 40.24 mol%. The average nucleotide identity of strain PU5-4T exhibited respective values of 73.88, 73.37, 73.36 and 70.84 % comparing to the type strains of S. lactis DSM 22361T, S. soli NCCP 698T, S. endophyticum NYYP31T and S. olei HAL-9T, which are below the cut-off level (95-96 %) for species delineation. Based on the above results, strain PU5-4T represents a novel species of the genus Sphingobacterium, for which the name Sphingobacterium temoinsis sp. nov. is proposed. The type strain is PU5-4T (=CGMCC 1.61908T=JCM 36663T).

Lie to me to lay with me: Females deceive males via terminal investment.

Historically, males have frequently been portrayed as the manipulative and deceptive gender, while females are often seen as adopting a coy and passive role. In this context, it is proposed that males use a terminal investment strategy, misleading females about their true poor condition, while females passively opt to mate with these deceptive males. However, we hypothesize that females in suboptimal condition may also engage in a terminal investment strategy by mimicking or enhancing their attractiveness to match that of females in better conditions. We studied this hypothesis in Tenebrio molitor, by subjecting females to three varying doses of lipopolysaccharides of Escherichia coli (LPS; 0.25, 0.5, or 1 mg ml-1), or three doses of the pro-oxidant Paraquat (PQ; 20, 40 or 80 mM), and subsequently assessing their survival and attractiveness to males. The LPS treatments and 20 mM of PQ had no significant effect on the survival or attractiveness of the females. However, females treated with 40 or 80 mM PQ survived fewer days compared to the control group. Those injected with 40 mM were more attractive than their control counterparts, while those treated with 80 mM were less attractive. Since the identical doses of LPS, which induce terminal investment in males, had no effect on females, we suggest sexual dimorphism in terminal investment. Furthermore, similar to males, if the stressor reaches a sufficiently high level, the signal becomes honest. These findings highlight how the quantity of stressors influences support for the terminal investment strategy in both males and females. Notably, this study challenges prevailing notions regarding gender roles in sexual selection, indicating that females, not just males, conceal their poor condition to attract mating partners.

Insects as a Prospective Source of Biologically Active Molecules and Pharmaceuticals-Biochemical Properties and Cell Toxicity of Tenebrio molitor and Zophobas morio Cell-Free Larval Hemolymph.

Insects are of great interest as novel sources of alternative proteins and biologically active compounds, primarily anticancer agents. Protein-rich insect larval hemolymph is a prospective candidate for pharmaceutical and food industry-related research. In this study, selected biochemical properties and cell toxicity of larval hemolymph from two mealworm species, Tenebrio molitor and Zophobas morio, were analyzed. Total proteins and carbohydrates, antioxidant capacity, and the level of lipid peroxidation were determined. Human cancer (U-87) and normometabolic (MRC-5) cells were treated with different concentrations of larval hemolymph proteins, and the effects on cell viability were assayed 24, 48, and 72 h after treatments. Z. morio hemolymph was shown to be richer in total proteins, showing a higher antioxidant capacity and lipid peroxidation level than T. molitor hemolymph, which was richer in total carbohydrates. Cytotoxicity assays showed that T. molitor and Z. morio hemolymphs differently affect the viability of U-87 and MRC-5 cells in cell type-, dose-, and time-dependent manners. Hemolymph from both species was more cytotoxic to U-87 cells than to MRC-5 cells, which was particularly prominent after 48 h. Additionally, a more potent cytotoxic effect of Z. morio hemolymph was observed on both cell lines, likely due to its higher antioxidant capacity, compared to T. molitor hemolymph.

Analysis of glycoalkaloid distribution in the tissues of mealworm larvae (Tenebrio molitor).

Solanine (SOL) and chaconine (CHA) are glycoalkaloids (GAs) produced mainly by Solanum plants. These plant secondary metabolites affect insect metabolism; thus, they have the potential to be applied as natural plant protection products. However, it is not known which GA concentration induces physiological changes in animals. Therefore, the aim of this study was to perform a quantitative analysis of SOL and CHA in the larvae of Tenebrio molitor using LC‒MS to assess how quickly they are eliminated or metabolised. In this experiment, the beetles were injected with 2 µL of 10-5 M SOL or CHA solution, which corresponds to a dosage range of 0.12-0.14 ng/mg body mass. Then, 0.5, 1.5, 8, and 24 h after GA application, the haemolymph (H), gut (G), and the remainder of the larval body (FB) were isolated. GAs were detected in all samples tested for 24 h, with the highest percentage of the amount applied in the FB, while the highest concentration was measured in the H sample. The SOL and CHA concentrations decreased in the haemolymph over time, while they did not change in other tissues. CHA had the highest elimination rate immediately after injection, while SOL slightly later. None of the GA hydrolysis products were detected in the tested samples. One possible mechanism of the detoxification of GAs may be oxidation and/or sequestration. They may be excreted by Malpighian tubules, with faeces or with cuticles during moulting. The results presented are significant because they facilitate the interpretation of studies related to the effects of toxic substances on insect metabolism.

Study on the mechanism of mitigating radiation damage by improving the hematopoietic system and intestinal barrier with Tenebrio molitor peptides.

Research on plant and animal peptides has garnered significant attention, but there is a lack of studies on the functional properties of Tenebrio molitor peptides, particularly in relation to their potential mitigating effect on radiation damage and the underlying mechanisms. This study aims to explore the protective effects of Tenebrio molitor peptides against radiation-induced damage. Mice were divided into five groups: normal, radiation model, and low-, medium-, and high-dose Tenebrio molitor peptide (TMP) groups (0.15 g per kg BW, 0.30 g per kg BW, and 0.60 g per kg BW). Various parameters such as blood cell counts, bone marrow DNA content, immune organ indices, serum levels of D-lactic acid, diamine oxidase (DAO), endotoxin (LPS), and inflammatory factors were assessed at 3 and 15 days post gamma irradiation. Additionally, the intestinal tissue morphology was examined through H&E staining, RT-qPCR experiments were conducted to analyze the expression of inflammatory factors in the intestine, and immunohistochemistry was utilized to evaluate the expression of tight junction proteins ZO-1 and Occludin in the intestine. The findings revealed that high-dose TMP significantly enhanced the hematopoietic system function in mice post radiation exposure, leading to increased spleen index, thymus index, blood cell counts, and bone marrow DNA production (p < 0.05). Moreover, TMP improved the intestinal barrier integrity and reduced the intestinal permeability. Mechanistic insights suggested that these peptides may safeguard intestinal barrier function by downregulating the gene expression of inflammatory factors TNF-α, IL-1ß, and IL-6, while upregulating the expression of tight junction proteins ZO-1 and Occludin (p < 0.05). Overall, supplementation with TMP mitigates radiation-induced intestinal damage by enhancing the hematopoietic system and the intestinal barrier, offering valuable insights for further investigations into the mechanisms underlying the protective effects of these peptides against ionizing radiation.

Beyond carrots: Evaluation of gelling agents as wet feeds for Tenebrio molitor L. (Coleoptera: Tenebrionidae) larvae.

Previous studies have shown that larvae of the yellow mealworm, Tenebrio molitor L. (Coleoptera: Tenebrionidae), need a source of moisture to grow and perform well. Currently, much research has been oriented towards the effect of dry feed on larval growth and performance. The effect of different wet feeds as moisture source on the performance traits of T. molitor larvae has not been thoroughly investigated yet. This study aims to investigate in laboratory trials the effect of various gelling agents (agar, carrageenans, guar gum, xanthan gum, sodium alginate, modified starch, and pectin) on the growth and performance of T. molitor larvae. A number of 50 newly emerged larvae obtained from the rearings of the LEAZ were inserted in plastic vials together with 4 g of wheat bran as dry feed. Additionally, 1 g of gelling agents was provided 3 times per week as moisture sources. Carrot slices served as control. Larval survival and weight were recorded weekly until the appearance of the first pupa. Dry feed was replenished when depleted. Our data showed that gelling agents efficiently supported the growth of T. molitor larvae, in terms of larval survival and weight, as well as feed utilization expressed as FCR. Interestingly, carrageenans seem to be the most appropriate gelling agent for T. molitor larvae rearing as it can enhance their weight and is also able to reduce their development time and their specific growth rate.

Effects of alloferon and its analogues on reproduction and development of the Tenebrio molitor beetle.

As the most numerous group of animals on Earth, insects are found in almost every ecosystem. Their useful role in the environment is priceless; however, for humans, their presence may be considered negative or even harmful. For years, people have been trying to control the number of pests by using synthetic insecticides, which eventually causes an increased level of resistance to applied compounds. The effects of synthetic insecticides have encouraged researchers to search for alternatives and thus develop safe compounds with high specificity. Using knowledge about the physiology of insects and the functionality of compounds of insect origin, a new class of bioinsecticides called peptidomimetics, which are appropriately modified insect analogues, was created. One promising compound that might be successfully modified is the thirteen amino acid peptide alloferon (HGVSGHGQHGVHG), which is obtained from the hemolymph of the blue blowfly Calliphora vicinia. Our research aimed to understand the physiological properties of alloferon and the activity of its peptidomimetics, which will provide the possibility of using alloferon or its analogues in the pharmaceutical industry, as a drug or adjuvant, or in agriculture as a bioinsecticide. We used alloferon and its three peptidomimetics, which are conjugates of the native peptide with three unsaturated fatty acids with various chain lengths: caprylic, myristic, and palmitic. We tested their effects on the morphology and activity of the reproductive system and the embryogenesis of the Tenebrio molitor beetle. We found that the tested compounds influenced the growth and maturation of ovaries and the expression level of the vitellogenin gene. The tested compounds also influenced the process of egg laying, embryogenesis, and offspring hatching, showing that alloferon might be a good peptide for the synthesis of effective bioinsecticides or biopharmaceuticals.

The allatotropin/orexin system as an example of immunomodulatory properties of neuropeptides.

The central nervous system (CNS) plays a critical role in signal integration in animals and allows the orchestration of life processes to maintain homeostasis. Current research clearly shows that inflammatory processes can also be modulated by the CNS via the neuroendocrine system. One of the neuropeptide families that participate in vertebrates in this process is orexins (OXs). Interestingly, our previous results suggested that a similar dependency may also exist between neuropeptides and immune system activity in insects. Due to the structural homology of orexin and allatotropin receptors and the functional similarity between these two neuropeptide families, the main aim of this research was to perform a complex analysis of the relationships between allatotropin (AT) and the insect immune response. Our results revealed functional similarities between vertebrate OXs and insect ATs. Similar effects were observed in the profile of the expression level of the gene encoding the AT precursor in the Tenebrio molitor nervous system and in the general action of Tenmo-AT on selected immune parameters of the tested beetles. Moreover, for the first time in insects, we confirmed the role of cytokines in the modulation of neuroendocrine system by determining the effect of Spätzle-like protein injection on the expression of genes encoding AT precursor and receptor. All these results are important for understanding the evolutionary basis of hormonal regulation of the immune response.

Edible insects: Understanding benzo(a)pyrene toxicokinetics in yellow mealworms for safe and sustainable consumption.

The global interest in edible insects as sustainable protein sources raises concerns about the bioaccumulation of contaminants, including polycyclic aromatic hydrocarbons (PAHs), to problematic levels. Understanding the accumulation dynamics of PAHs in edible insects is highly relevant due to the widespread sources and toxicological profiles; however, the bioaccumulative potential of PAHs in edible insects is unexplored. This study examined the uptake and elimination dynamics of benzo(a)pyrene (B(a)P), a representative and carcinogenic PAH, in yellow mealworm larvae (YMW, Tenebrio molitor). Larvae were exposed to feeding substrate with varying B(a)P concentrations (0.03, 0.3, and 3 mg kg-1), and uptake (21 days in B(a)P-contaminated substrate) and elimination (21 days in B(a)P-free substrate) kinetics were subsequently assessed. The results showed that YMW can eliminate B(a)P, revealing dose-dependent B(a)P bioaccumulation in these insects. Larvae fed on a substrate with 0.03 mg kg-1 accumulated B(a)P over 21 days, presenting values of 0.049 (Standard deviation - 0.011) mg kg-1 and a kinetic-based (BAFkinetic) of 1.93 g substrate g organism-1, exceeding the EU regulatory limits for food. However, with a B(a)P half-life (DT50) of 4.19 days in the larvae, an EU legislation safety criterion was met after a 13-day depuration period in clean substrate. Larvae exposed to substrates with 0.3 and 3 mg kg-1 showed B(a)P accumulation, with BAFkinetic values of 3.27 and 2.09 g substrate g organism-1, respectively, not meeting the current legal standards for food consumption at the end of the exposure to B(a)P. Although the B(a)P half-life values after 35 days were 4.30 and 10.22 days (DT50s), the larvae retained B(a)P levels exceeding permitted food safety limits. These findings highlight a significant oversight in regulating PAHs in animal feed and the need for comprehensive safety evaluations of PAH hazards in edible insects for improved PAH feeding guidelines.

Diversity of soil fungi and entomopathogenic fungi in subtropical mountain forest in southwest China.

Till now, the diversity of entomopathogenic fungi in subtropical mountain forest was less studied. Here, the vertical distribution of forest soil fungi, entomopathogenic fungi, and their environmental influencing factors in a subtropical mountain in western China were investigated. Soil samples were collected from four elevations in a subtropical forest in Shaanxi. The results indicated a greater richness of soil fungi at middle elevations and soil fungi were more even at low elevation. Soil pH, available iron, available potassium, total potassium, and available zinc were the most important influencing factors affecting this vertical distribution of fungi. Interestingly, the Isaria genus was predominant while Metarhizium and Beauveria showed decreasing abundance. The presence of Isaria showed a significant positive correlation with both total phosphorus and available iron, while, available zinc was negatively correlated. Metarhizium was influenced by elevation, pH, available phosphorus, and available copper and Beauveria was influenced by soil organic carbon, total nitrogen, total potassium, available potassium, and available zinc. Overall, as environmental factors affecting soil fungi, elevation, and plant species diversity were less important than soil physical and chemical properties. The virulence of isolated entomopathogenic fungi were tested against larvae of Tenebrio molitor, with mortality ranging from 31.11% to 100%. The above findings provide valuable data to deepen our understanding of the diversity of entomopathogenic fungi in subtropical mountain forests.

Development of a lexicon for the sensory description of edible insects commercially available in Australia.

Sensory lexicons provide an important tool for describing the sensory properties of emerging, unfamiliar foods such as edible insects. This study sought to establish and validate a sensory lexicon for the description and differentiation of edible insects commercially available in Australia and prepared using common preservation and cooking methods (freeze-drying, hot-air drying, roasting, sautéing and deep-frying). Five species were evaluated, including house crickets (Acheta domesticus), yellow mealworm larvae (Tenebrio molitor), king mealworm larvae (Zophobas morio), tyrant ants (Iridomyrmex spp.) and green tree ants (Oecophylla smaragdina). Following generic descriptive sensory analysis methods, a trained panel (n=8) developed a sensory lexicon of 29 aroma and flavour descriptors, and 16 texture descriptors. Vocabulary were then categorised and ordered to generate a sensory wheel. Due to a lack of cross-over in sensory attributes between species, sub-categories of species-specific vocabulary were also generated for each insect. The lexicon enabled sensory profiling of commercially available edible insect samples which revealed large variation in aroma, flavour, and texture attributes due to both species and preparation method. This work provides a platform for development of a globally relevant edible insect sensory lexicon. International collaboration will enable expansion of the lexicon for use with other insect species and preparation methods, insect-derived ingredients (such as insect powder, defatted insect powder and textured insect protein) and in different cultural settings. As the industry grows, the applicability of vocabulary for differentiating within species and between competitive products should also be assessed.

Multitrait genetic parameter estimates in a Tenebrio molitor reference population: high potential for breeding gains.

To address multiple issues impacting the climate imbalance, insects, and in particular Tenebrio molitor, represent now a promising alternative for producing high-quality protein products with low environmental impact. As with any new species farmed on an industrial scale, insect breeding production must be improved through the accumulation of knowledge on rearing techniques and genetic management. Little information on the inheritance of agronomically interesting traits, dedicated to Tenebrio molitor, is available. This study aims to decipher the genetic parameters (heritability and genetic correlations) of reproduction, larval growth and survival, pupation rate and developmental time from a reference population made up of 1 931 sib-groups reared under pedigree, in controlled and stable environments and generated with single pair mating. Considering all sib-groups, 29 599 offspring have been generated and phenotyped over four generations to support this study and provide enough data to estimate, under linear animal models, the additive genetic and common environmental effects. Phenotypic analyses underlined an important variability among sib-groups and individuals, as for the total oviposition during 4 weeks counting (0-680 eggs, min - max, respectively) or larval body mass 63 days posteclosion (36.3-206.8 mg, min - max, respectively). Moderate to important heritability values have been obtained and ranged from 0.17 to 0.54 for reproduction phenotypes, 0.10-0.44 for growth parameters, 0.06-0.22 for developmental time and 0.10-0.17 for larval survival rates. The proportion of phenotypic variance explained by the environmental part varyies from 0.10 to 0.36 for reproductive traits, from 0.17 to 0.38 for growth parameters, from 0.06 to 0.36 for developmental time and 0.17-0.22 for survival rates. Genetic correlations underline relationships among phenotypes such as the trade-off between developmental time from egg to pupae and pupae weight (r2 = 0.48 ± 0.06). These important phenotypic variations coupled with promising heritability values pave the road for future breeding programs in Tenebrio molitor.

The Set of Serine Peptidases of the Tenebrio molitor Beetle: Transcriptomic Analysis on Different Developmental Stages.

Serine peptidases (SPs) of the chymotrypsin S1A subfamily are an extensive group of enzymes found in all animal organisms, including insects. Here, we provide analysis of SPs in the yellow mealworm Tenebrio molitor transcriptomes and genomes datasets and profile their expression patterns at various stages of ontogeny. A total of 269 SPs were identified, including 137 with conserved catalytic triad residues, while 125 others lacking conservation were proposed as non-active serine peptidase homologs (SPHs). Seven deduced sequences exhibit a complex domain organization with two or three peptidase units (domains), predicted both as active or non-active. The largest group of 84 SPs and 102 SPHs had no regulatory domains in the propeptide, and the majority of them were expressed only in the feeding life stages, larvae and adults, presumably playing an important role in digestion. The remaining 53 SPs and 23 SPHs had different regulatory domains, showed constitutive or upregulated expression at eggs or/and pupae stages, participating in regulation of various physiological processes. The majority of polypeptidases were mainly expressed at the pupal and adult stages. The data obtained expand our knowledge on SPs/SPHs and provide the basis for further studies of the functions of proteins from the S1A subfamily in T. molitor.

Structure information analysis and relative content determination of protein and chitin from yellow mealworm larvae using Raman spectroscopy.

Insect protein extract is one of the high-quality protein sources and is frequently viewed as a potential nutrition alternative. However, a more precise method for protein measurement is still needed due to protein overestimation by the Kjeldahl method due to the presence of a large amount of chitin in insects. Therefore, we demonstrated the monitoring of chitin and protein extracted from yellow mealworm larvae through the information on molecular vibration obtained using Raman spectroscopy and infrared (IR) spectroscopy. The NH vibration at 3475 cm-1 is the characteristic peak of chitin in defatted product observed in the Raman spectra. The nitrogen-to-protein conversion factor in protein extracted from larvae by the Raman method was determined based on the NH vibration and found to be 5.66 ± 0.01. We also compared these experimental data to theoretical Raman and IR spectra and determined the possible reasons for why nitrogen elements in chitin affect the determination of protein content. The method of sequentially removing fat and protein could provide more accurate quantification of protein and chitin. Raman spectroscopy is feasible for various types of insects with high chitin content. Compared with the Kjeldahl method, the Raman method is a faster and more accurate measurement method. Moreover, it provides the content of impurities, purity, and structural information.