No abstract

The invasive red palm weevil, Rhynchophorus ferrugineus Olivier (Coleoptera: Curculionidae), is considered one of the world's most devastating insect pests to palm trees. It was observed that larvae of this pest are able to inhibit microbial growth on the rearing media when they start feeding and this observation has led us to study the effect of red palm weevils on various microbial species. The antimicrobial effect of extracts from different parts of the alimentary canal on Gram positive bacteria (Enterococcus faecalis and Staphylococcus aureus), Gram negative bacteria (Escherichia coli and Klebsiella spp.), Candida albicans, and Penicillium sp. was tested using the agar well diffusion method. All extracts inhibited the tested microbial species. Foregut extracts had the greatest zones of growth inhibition. Enterococcus faecalis, Staphylococcus aureus, and Penicillium sp. were significantly sensitive to the extracts and had the largest growth inhibition zones. It is concluded that the gut extracts contain potent antimicrobial activity and may provide a new source of antimicrobial peptides.

Like other Lepidoptera, the silkworm (Bombyx mori) has both nucleated eupyrene and anucleated apyrene sperm that are derived from the same spermatocysts. The former type is responsible for egg fertilization, while the function of the latter is still uncertain. Many hypotheses have been presented concerning the role of the apyrene sperm in mating and fertilization, but none is supported by a convincing experimental approach. The aim of the present study was to enhance the production of apyrene sperm in vitro by using different concentrations of fetal bovine serum (FBS), namely 20%, 30% and 40%, in the culture medium used for cultivating the naked spermatocysts isolated from the silkworm testes at 0 hr, 120 hr, and 192 to approximately 360 hr after the fourth molt. Cultivation of 0-hr spermatocysts was not successful. The development of spermatocysts into eupyrene and apyrene sperm bundles was slightly slower in vitro than in vivo. The overall growth percentage of both eupyrene and apyrene bundles was satisfactory when the spermatocysts were cultivated in TC-100 culture medium containing 30% FBS.

In vitro study was conducted to explore antibacterial properties of the larval gut extracts of Rhynchophorus ferrugineus (Red Palm Weevil) Oliver. Larval gut extracts were tested against salivary bacteria causing dental carries using the agar well diffusion method. The gut extracts significantly affected the growth of both Klebsiella spp. and Streptococcus viridans. The two bacterial species revealed significant differences in their sensitivity to the extract. The extract efficacy depended upon the concentration and time of exposure. When using 100%concentration of the extract, the mean of inhibition zones for S. viridans and Klebsiella spp. at 24 h after treatment were 1.61 mm and 2.50 mm, respectively. At 48 h post-treatment, the mean of inhibition zones for S. viridans and Klebsiella spp. were 1.96 mm and 2.66 mm. After 72 hours, the means zones were 2.28 mm and 2.91 mm, respectively. Electron microscopic examinations showed morphological changes of the outer membrane of bacteria with a noticeable damage as a result of exposure to the gut extract. The results suggest potential use of these extracts against dental caries bacteria.

The present study was conducted to evaluate the performance of five mulberry varieties used for rearing the bivoltine race (EJ) of mulberry silkworm. Nutritional composition of the leaves was determined. Carbohydrate/protein (C/N) ratios were focused. Also, leaf/cocoon ratios and its suitability for judging the mulberry leaves efficiency were determined.The results show significant differences between varieties. Kokuso-27 and Kearyang-Seoban-3 show higher nutritional components followed by Josaengrok-2. While the lowest value were recorded in Morittiana and Kokuso-20 varieties. Kokuso-27 and Kearyang-Seoban-3 recorded lowest values in C/N ratio and in leaf/cocoon ratio, and therefore, Kokuso-27 and Kearyang-Seoban-3 give more superiority over other varieties, they can be used as criteria for comparing the different mulberry varieties.The biological and economic characters of silkworm were reflection of higher values of leaf nutritional contents, lower values of carbohydrate/ protein ratio and leaf /cocoon ratio.