Physicochemical structure of chitin in the developing stages of black soldier fly.

Black soldier fly can convert organic wastes into their own functional biological macromolecules i.e. chitin that has great potential for biotechnological, biomedical and cosmetic application. The variation in the physiochemical structure of chitin was proved for several insects during metamorphosis stages whereas, it remains unknown for black soldier fly (BSF), a recognized resource insect for industrial production and organic waste management. The current work noted results on how the chitin matrix can undergo physicochemical changes during the developmental phases (larvae, prepupa, puparium, and adults) of BSF. Chitin content was determined around 3.6%, 3.1%, 14.1% and 2.9%, respectively. Fourier transform infrared spectroscopy, thermogravimetric analysis and x-ray diffraction analysis showed that chitin from BSF different stages was all α-chitin with similar thermal stability. The chitin crystalline index increased gradually with development from larvae to adult, 33.09%, 35.14%, 68.44% and 87.92%, respectively. Moreover, it was observed by scan electron microscopy that surface morphology characteristics of chitin vary significantly in developmental phases. These results confirmed that Hermetia illucens is promising for converting organic wastes into valuable biopolymers i.e. chitin and its physiochemical properties in various developmental stages help to determine the related biomedical, biotechnological, cosmetic and functional food utilization potential.

Bacillus thuringiensis subsp. israelensis and its dipteran-specific toxins.

Bacillus thuringiensis subsp. israelensis (Bti) is the first Bacillus thuringiensis to be found and used as an effective biological control agent against larvae of many mosquito and black fly species around the world. Its larvicidal activity resides in four major (of 134, 128, 72 and 27 kDa) and at least two minor (of 78 and 29 kDa) polypeptides encoded respectively by cry4Aa, cry4Ba, cry11Aa, cyt1Aa, cry10Aa and cyt2Ba, all mapped on the 128 kb plasmid known as pBtoxis. These six δ-endotoxins form a complex parasporal crystalline body with remarkably high, specific and different toxicities to Aedes, Culex and Anopheles larvae. Cry toxins are composed of three domains (perforating domain I and receptor binding II and III) and create cation-selective channels, whereas Cyts are composed of one domain that acts as well as a detergent-like membrane perforator. Despite the low toxicities of Cyt1Aa and Cyt2Ba alone against exposed larvae, they are highly synergistic with the Cry toxins and hence their combinations prevent emergence of resistance in the targets. The lack of significant levels of resistance in field mosquito populations treated for decades with Bti-bioinsecticide suggests that this bacterium will be an effective biocontrol agent for years to come.

[First description of the Prosimulium candicans Rubzov, 1956 males (Diptera: Simuliidae)].

First description of the previously unknown Prosimulium candicans males is given. Belonging of this species to the genus Prosimulium Roubaud, 1906 rather than to the genus Taeniopterna Enderlein, 1925 is confirmed.

Ecdysteroids and oocyte development in the black fly Simulium vittatum.

BACKGROUND: Oocyte development was studied in the autogenous black fly, Simulium vittatum (Diptera, Nematocera), a vector of Onchocerca volvulus, the causative agent of onchocerciasis. RESULTS: Oocyte growth was nearly linear between adult eclosion and was complete by 72 hours at 21 degrees C. The oocyte became opaque at 14 hours after eclosion indicating the initiation of protein yolk deposition. The accumulation of vitellogenin was measured using SDS-PAGE. The density of the yolk protein bands at about 200 and 65 kDa increased during the first and second days after eclosion. The amount of protein in the 200 kDa band of vitellogenin, determined using densitometry, rapidly increased between 12 and 25 hours after eclosion. Ecdysteroid levels were measured using a competitive ELISA. Ecdysteroid levels increased rapidly and subsequently declined during the first day after eclosion. CONCLUSION: These data show a correlation between the appearance of vitellogenin in the oocyte, and the rise in ecdysteroids. A possible relationship to molting of the nematode, Onchocerca volvulus, is discussed.

Dormancy, embryogenesis, and hatching of eggs of Prosimulium kiotoense (Diptera: Simuliidae) under natural and experimental conditions.

The egg dormancy and embryogenesis of the univoltine black fly, Prosimulium kiotoense Shiraki, in southwestern Japan were examined under natural and laboratory conditions. Eggs laid in April remained dormant until August (approximately 14 wk after oviposition). Hatching commenced in early October (after 23 wk), when air and water temperatures decreased to 20 and 15 degrees C, respectively, and continued until mid-December (32 wk) in the field. Laboratory experiments showed that lower temperatures (10 and 14 degrees C) supported embryogenesis similar to that observed in the field. In contrast, higher temperatures (18 and 22 degrees C) retarded or completely suppressed embryogenesis after the termination of dormancy. However, completion of dormancy was accelerated when eggs were exposed experimentally to these higher temperatures for 3-12 wk, then returned to a constant low temperature (14 degrees C). Daylength did not affect the maintenance and termination of dormancy. Therefore, temperature played an important role differentially affecting completion of dormancy and postdormancy development. Variable lengths of developmental periods among egg batches under the same conditions indicated possible genetic control of dormancy intensity.