Research on possible medical use of silk produced by caddisfly larvae of Hydropsyche angustipennis (Trichoptera, Insecta)

Characterization of the primary structure of the major silk gene, h-fibroin, across caddisfly (Trichoptera) suborders

Larvae of caddisflies (Trichoptera) produce silk to build various underwater structures allowing them to exploit a wide range of aquatic environments. The silk adheres to various substrates underwater and has high tensile strength, extensibility, and toughness and is of interest as a model for biomimetic adhesives. As a step toward understanding how the properties of underwater silk evolved in Trichoptera, we used genomic data to identify full-length sequences and characterize the primary structure of the major silk protein, h-fibroin, across the order. The h-fibroins have conserved termini and basic motif structure with high variation in repeating modules and variation in the percentage of amino acids, mainly proline. This finding might be linked to differences in mechanical properties related to the different silk usage and sets a starting point for future studies to screen and correlate amino acid motifs and other sequence features with quantifiable silk properties.

Nutritional Composition, Health Benefits, and Application Value of Edible Insects: A Review

For thousands of years, edible insects have been used as food to alleviate hunger and improve malnutrition. Some insects have also been used as medicines because of their therapeutic properties. This is not only due to the high nutritional value of edible insects, but more importantly, the active substances from edible insects have a variety of biofunctional activities. In this paper, we described and summarized the nutritional composition of edible insects and discussed the biological functions of edible insects and their potential benefits for human health. A summary analysis of the findings for each active function confirms that edible insects have the potential to develop functional foods and medicines that are beneficial to humans. In addition, we analyzed the issues that need to be considered in the application of edible insects and the current status of edible insects in food and pharmaceutical applications. We concluded with a discussion of regulations related to edible insects and an outlook on future research and applications of edible insects. By analyzing the current state of research on edible insects, we aim to raise awareness of the use of edible insects to improve human health and thus promote their better use and development.

Sericulture and the edible-insect industry can help humanity survive: insects are more than just bugs, food, or feed

The most serious threat which humans face is rapid global climate change, as the Earth shifts rapidly into a regime less hospitable to humans. To address the crisis caused by severe global climate change, it will be necessary to modify humankind's way of life. Because livestock production accounts for more than 14.5% of all greenhouse gas (GHG) emissions, it is critical to reduce the dependence of humans on protein nutrients and calories obtained from livestock. One way to do so is to use insects as food. Compared with typical livestock, farming edible insects (or "mini-livestock") produce fewer GHG emissions, require less space and water, involve shorter life cycles, and have higher feed conversion rates. It has been recently reported that consumption of certain insects can prevent or treat human diseases. This review goes beyond entomophagy to entomotherapy and their application to the food industry.

Fine structure of the silk spinning system in the caddisworm, Hydatophylax nigrovittatus (Trichoptera: Limnephilidae)

Silk is produced by a variety of insects, but only silk made by terrestrial arthropods has been examined in detail. To fill the gap, this study was designed to understand the silk spinning system of aquatic insect. The larvae of caddis flies, Hydatophylax nigrovittatus produce silk through a pair of labial silk glands and use raw silk to protect themselves in the aquatic environment. The result of this study clearly shows that although silk fibers are made under aquatic conditions, the cellular silk production system is quite similar to that of terrestrial arthropods. Typically, silk production in caddisworm has been achieved by two independent processes in the silk glands. This includes the synthesis of silk fibroin in the posterior region, the production of adhesive glycoproteins in the anterior region, which are ultimately accumulated into functional silk dope and converted to a silk ribbon coated with gluey substances. At the cellular level, each substance of fibroin and glycoprotein is specifically synthesized at different locations, and then transported from the rough ER to the Golgi apparatus as transport vesicles, respectively. Thereafter, the secretory vesicles gradually increase in size by vesicular fusion, forming larger secretory granules containing specific proteins. It was found that these granules eventually migrate to the apical membrane and are exocytosed into the lumen by a mechanism of merocrine secretion.

Molecular cloning, gene expression analysis, and recombinant protein expression of novel silk proteins from larvae of a retreat-maker caddisfly, Stenopsyche marmorata

Retreat-maker larvae of Stenopsyche marmorata, one of the major caddisfly species in Japan, produce silk threads and adhesives to build food capture nets and protective nests in water. Research on these underwater adhesive silk proteins potentially leads to the development of new functional biofiber materials. Recently, we identified four major S. marmorata silk proteins (Smsps), Smsp-1, Smsp-2, Smsp-3, and Smsp-4 from silk glands of S. marmorata larvae. In this study, we cloned full-length cDNAs of Smsp-2, Smsp-3, and Smsp-4 from the cDNA library of the S. marmorata silk glands to reveal the primary sequences of Smsps. Homology search results of the deduced amino acid sequences indicate that Smsp-2 and Smsp-4 are novel proteins. The Smsp-2 sequence [167 amino acids (aa)] has an array of GYD-rich repeat motifs and two (SX)4E motifs. The Smsp-4 sequence (132 aa) contains a number of GW-rich repeat motifs and three (SX)4E motifs. The Smsp-3 sequence (248 aa) exhibits high homology with fibroin light chain of other caddisflies. Gene expression analysis of Smsps by real-time PCR suggested that the gene expression of Smsp-1 and Smsp-3 was relatively stable throughout the year, whereas that of Smsp-2 and Smsp-4 varied seasonally. Furthermore, Smsps recombinant protein expression was successfully performed in Escherichia coli. The study provides new molecular insights into caddisfly aquatic silk and its potential for future applications.