Proximate Composition of Thai and Cambodian Ready-to-Eat Insects

Samples of ready-to-eat snacks based on Lethocerus indicus, Gymnogryllus vietnamensis, Tarbinskiellus portentosus, Teleogryllus mitratus, Bombyx mori, Omphisa fuscidentalis, and Cybister limbatus were purchased in Cambodia and Thailand, and their proximate chemical composition (including Na and Cl) was analysed. Comparing the results with the few existing references from the literature (based on unprocessed specimens), marked differences occurred. This was expected as the insect chemical composition varies strongly intra- and interspecifically due to taxon, feeding, instar, and processing, among others. In general, the insects mainly consisted of fat (35 to 60%) and protein (25 to 38%), with 2 to 16% nitrogen-free extract, 2 to 15% fibre, 3 to 5% ashes, 0.4 to 1.6% Na, and 0.6 to 1.4% Cl (dry matter base). In this way, this contribution adds to the compositional knowledge about traditional insect-based foodstuffs. The combination of high fat and protein with low carbohydrates makes them suitable to combat nutrition disorders.

The myosin II coiled-coil domain atomic structure in its native environment

The atomic structure of the complete myosin tail within thick filaments isolated from Lethocerus indicus flight muscle is described and compared to crystal structures of recombinant, human cardiac myosin tail segments. Overall, the agreement is good with three exceptions: the proximal S2, in which the filament has heads attached but the crystal structure doesn’t, and skip regions 2 and 4. At the head–tail junction, the tail α-helices are asymmetrically structured encompassing well-defined unfolding of 12 residues for one myosin tail, ∼4 residues of the other, and different degrees of α-helix unwinding for both tail α-helices, thereby providing an atomic resolution description of coiled-coil “uncoiling” at the head–tail junction. Asymmetry is observed in the nonhelical C termini; one C-terminal segment is intercalated between ribbons of myosin tails, the other apparently terminating at Skip 4 of another myosin tail. Between skip residues, crystal and filament structures agree well. Skips 1 and 3 also agree well and show the expected α-helix unwinding and coiled-coil untwisting in response to skip residue insertion. Skips 2 and 4 are different. Skip 2 is accommodated in an unusual manner through an increase in α-helix radius and corresponding reduction in rise/residue. Skip 4 remains helical in one chain, with the other chain unfolded, apparently influenced by the acidic myosin C terminus. The atomic model may shed some light on thick filament mechanosensing and is a step in understanding the complex roles that thick filaments of all species undergo during muscle contraction.

Practices of entomophagy and entomotherapy in Bangladesh

Aspects of entomophagy and entomotherapy of ethnic people in Bangladesh are documented as this practice is believed to ensure future food security. A comprehensive survey was conducted involving six insect-consuming ethnic groups: Garo, Chakma, Tanchangya, Marma, Mro, and Tripura. A total of 36 insect species of 19 families and 7 orders were consumed by them. In terms of species, those of the Coleoptera ranked highest (14), followed by Hymenoptera (7), Orthoptera (5), Hemiptera (5) and Blattodea (3 species); one species each belonged to Ephemeroptera and Odonata. The field cricket (Brachytrupes sp.), short-horned grasshopper (Oxya sp.) and giant water bug (Lethocerus indicus) were most preferred, reaching respective acceptance levels of 84, 83, and 79% by the respondents of all ethnic groups taken together. The total number of species used as human food by the Chakma, Marma, Mro, Tanchangya, Tripura, and Garo was 32, 22, 29, 21, 26, and 14, respectively. Nine species were used to treat coughs, fevers, nocturnal emissions, burning and gastroenteritis. People gathered the insects mainly from the insects’ natural habitat and consumed them as snacks or part of a meal. The availability of edible insects depended on the season. Despite consumer demand, insect consumption is decreasing, apparently due to the unavailability of insects because of the random application of pesticides and fertilisers. The top three entomophagy constraints include lack of knowledge to farm insects, to harvest them, and to effectively store and preserve them. By overcoming these constraints, practices of entomophagy might play additional role in increasing future food security in Bangladesh through developing edible insect industry.

CryoEM structure of Drosophila flight muscle thick filaments at 7 Å resolution

Striated muscle thick filaments are composed of myosin II and several non-myosin proteins. Myosin II’s long α-helical coiled-coil tail forms the dense protein backbone of filaments, whereas its N-terminal globular head containing the catalytic and actin-binding activities extends outward from the backbone. Here, we report the structure of thick filaments of the flight muscle of the fruit fly Drosophila melanogaster at 7 Å resolution. Its myosin tails are arranged in curved molecular crystalline layers identical to flight muscles of the giant water bug Lethocerus indicus. Four non-myosin densities are observed, three of which correspond to ones found in Lethocerus; one new density, possibly stretchin-mlck, is found on the backbone outer surface. Surprisingly, the myosin heads are disordered rather than ordered along the filament backbone. Our results show striking myosin tail similarity within flight muscle filaments of two insect orders separated by several hundred million years of evolution.

CryoEM Structure of Drosophila Flight Muscle Thick Filaments at 7Å Resolution

Striated muscle thick filaments are composed of myosin II and several non-myosin proteins. Myosin II’s long α-helical coiled-coil tail forms the dense protein backbone of filaments while its N-terminal globular head containing the catalytic and actin binding activities extends outward from the backbone. Here we report the structure of thick filaments of the flight muscle of the fruit fly Drosophila melanogaster at 7 Å resolution. Its myosin tails are arranged in curved molecular crystalline layers identical to flight muscles of the giant waterbug Lethocerus indicus. Four non-myosin densities are observed, three of which correspond to ones found in Lethocerus; one new density, possibly stretchin-Mlck, is found on the backbone outer surface. Surprisingly, the myosin heads are disordered rather than ordered along the filament backbone. Our results show striking myosin tail similarity within flight muscle filaments of two insect orders separated by several hundred million years of evolution.Significance StatementMyosin thick filaments are one of striated muscle’s key structures, but also one of its least understood. A key question is how the myosin a-helical coiled-coil tail is arranged in the backbone. At 7Å resolution, sufficient to resolve individual a-helices, the myosin tail arrangement in thick filaments from the flight muscle of the fruit fly Drosophila melanogaster is strikingly similar to the myosin tail arrangement in flight muscles of the giant waterbug Lethocerus indicus. Nearly every other thick filament feature is different. Drosophila and Lethocerus evolved separately >245 million years ago suggesting myosin tail packing into curved molecular crystalline layers forms a highly conserved thick filament building block and different properties are obtained by alterations in non-myosin proteins.