Fahd A. Al-Mekhlafi

Cryomazine concentration and host type effects on the biology of the southern cowpea weevil Callosobruchus maculatus F.

In this study we investigated the effects of different cryomazine concentrations and host type on the biology of the southern cowpea weevil Callosobruchus maculatus F. (Coleoptera: Bruchidae). Our results showed that increasing cryomazine concentration led to the increase in the average incubation period of eggs and low hatching rate, reaching the highest average of egg incubation period 13.25 days for insects reared on a mung beans treated with cryomazine concentration of 3 and 5%. The lowest average for incubation period reached 9.25 days when insects reared on cowpea treated with 1% concentration of cryomazine. Insect reared on peas treated with 5% cryomazine concentration had a lower average percentage of hatching eggs, 1.25% in comparison with the control (67.25%). The maximum average rate of eggs hatching reached 55% of insects reared on mung beans treated with 1% cryomazine concentration compared with the control (75%). High cryomazine concentration reduced the percentage of pupation and adult emergence; the average percentage reached 19.83 and 27.08%, compared with the control 87.33 and 88.5% respectively. Thus, increasing cryomazine concentration not only led to the increase in the average duration of larvae and pupae of insects bred to all nutritional hosts except peas where the insect was unable to complete its life cycle but also led to reduction in the percentage of pupation and adult emergence.

Biological activity of Xanthium strumarium seed extracts on different cancer cell lines and Aedes caspius, Culex pipiens (Diptera: Culicidae)

Effects of methanol extracts of Xanthium strumarium on different cancer cell lines and on the mortality rates of Aedes caspius, Culex pipiens (Diptera: Culicidae) were investigated. Among the cell lines tested, the Jurkat cell line was the most sensitive to the methanol extract and ethyl acetate fraction, with reported LC50 values of 50.18 and 48.73 μg/ml respectively. Conversely, methanol extracts were not that toxic to the A549 cell line though the toxicity increased on further purification. The percentage of growth inhibition was dose dependent for the methanol extract and ethyl acetate fraction. The ethyl acetate fraction showed higher toxicity to all cell lines tested when compared to the methanol extract. The results showed that methanol extracts of plant seeds caused 100% mortality of mosquito larvae at a concentration of 1000 μg/ml after 24 h of treatment. The LC50 and LC90 values of X. strumarium were found to be 531.07 and 905.95 μg/ml against Ae. caspius and 502.32 and 867.63 μg/ml against Cx. Pipiens, respectively. From the investigations, it was concluded that the crude extract of X. strumarium showed a weak potential for controlling the larval instars of Ae. caspius and Cx. pipiens. However, on further purification the extract lost the larvicidal activity. The ethyl acetate fraction showed higher toxicity to all cell lines tested when compared to the methanol extract. The ethyl acetate fraction investigated in this study appears to have a weak larvicidal activity but a promising cytotoxic activity. Future studies will include purification and investigation in further detail of the action of X. strumarium on Cancer Cell Lines and mosquitoes.

Differential Diptera Succession Patterns on Decomposed Rabbit Carcasses in Three Different Habitats

Abstract This study describes for the first time the necrophagous Diptera attracted to rabbit carcasses in three distinct habitats in Riyadh, Kingdom of Saudi Arabia (KSA). A mean number of 1,427 flies belonging to 8 families and 16 species were collected during the decomposition process of the rabbits at the three different sites. Carcasses in the agricultural habitat attracted 1,146 flies from 7 families and 14 species, compared to carcasses in the urban site, which attracted 249 flies from 5 families and 9 species. Carcasses in the desert site attracted the lowest number (28 flies from 4 families and 5 species). In the agricultural and desert sites, flies were represented at all decomposition stages. Also, in the urban site, flies were represented at all stages except the fresh and dry stages. Lucilia sericata Meigen was the most abundant species occurring in both the agricultural and desert sites, while Musca domestica L. was the most abundant species occurring in the urban site. The evidence presented here, therefore, suggests that L. sericata and M. domestica are potentially useful species for estimating minimal postmortem intervals in this region of KSA.

Samsum ant, Brachyponera sennaarensis (Formicidae: Ponerinae): Distribution and abundance in Saudi Arabia

Invasive species are capable of causing considerable damage to natural ecosystems, agriculture and economies throughout the World. Samsum ant, Brachyponera (Pachycondyla) sennaarensis has been a reason for medical implication and social nuisance through its poisonous and severely painful sting causing anaphylactic shock in many cases. We surveyed for the presence of the samsum ant in various provinces of Saudi Arabia. B. sennaarensis was the abundant Ponerinae species in human settlements. In the Eastern provinces, however, few samples were collected, and none were found in the Northern and Western provinces. Infestations of B. sennaarensis were particularly severe in the spring and summer seasons, when the ants make nests in moist areas and in cracks in cemented structures, whereas the extent of infestation reduced in winter seasons.

Brevibacillus laterosporus isolated from the digestive tract of honeybees has high antimicrobial activity and promotes growth and productivity of honeybee’s colonies

The development of novel antimicrobial drugs, as well as the discovery of novel compounds able to promote honeybee’s growth, represents major challenges for modern entomology. The main aim of this study was to investigate whether Brevibacillus laterosporus isolated from the digestive tract of Saudi honeybees, Apis mellifera, was able to stimulate colony strength parameters of honeybees and to evaluate its ability to produce antimicrobial agents. Honeybees were collected in Dirab, Riyadh Region, Saudi Arabia, and microorganisms were isolated and identified by 16S ribosomal RNA analysis. Microscopic identification of the microorganism in its native state was facilitated by atomic force microscopy at high-resolution imaging. Active biological compounds were produced by submerged fermentation with B. laterosporus. The fermented broth was subjected to extraction and purification, and then semi-pure compounds were analyzed by gas chromatography–mass spectrometry. The effectiveness of the crude extract and semi-pure compounds as antimicrobial agents was evaluated by susceptibility assays. More than 22% of the microorganisms isolated from the digestive tract of healthy honeybees have been identified as B. laterosporus, this kind of species has a unique shape and morphological structure. The cyclic dipeptide cyclo(Leu-Pro) produced by B. laterosporus showed biological activity against several pathogenic microorganisms. Furthermore, the total counts of workers, closed brood, and open brood, as well as the production of bee pollen and honey, were better in honeybees treated with a B. laterosporus suspension. The data indicated that the B. laterosporus strain isolated from a healthy honeybee might be a novel probiotic and a producer of important biological compounds.

Larvicidal, ovicidal activities and histopathological alterations induced by Carum copticum (Apiaceae) extract against Culex pipiens (Diptera: Culicidae)

An experiment was carried out, firstly, to determine the possible toxicity of Carum copticum (Apiaceae) extract against Culex pipiens (Diptera: Culicidae), and, secondly, to study the histopathological alterations in the midgut of Cx. pipiens as a result of treatment with C. copticum extract. Larvicidal and ovicidal activities of C. copticum extract against the larvae of Cx. pipiens was determined according to World health organization (WHO). The inhibition effect of C. copticum was assessed by determining the mortality of the treated larvae and eggs. The histopathological effect of the C. copticum extracts on midgut epithelium of the larvae was examined under both light and transmission electron microscopy. The crude extract of C. copticum exerted 100% mortality for Cx. pipiens after 24 h at 200 μm/ml, and zero hatchability (100% mortality) at 150 μm/ml for Cx. pipiens. The histopathological study showed that larvae treated with C. copticum extract had cytopathological alterations of the midgut epithelium. The study provided information on various effects of C. copticum extract against Cx. pipiens.

Insecticidal Effect of Solenostemma argel Extracts Against Culex pipiens

Of the various plant extracts from 10 plant species tested against larvae of Culex pipiens in the laboratory, only extracts from Solenostemma argel exhibited larvicidal activity. A chloroform leaf extract of S. argel exhibited relatively high activity with a lethal concentration causing 50% mortality (LC50) of 15.89 ppm, while chloroform and ethyl acetate extracts of S. argel fruits were 19.70 and 19.52 ppm, respectively. The chloroform fruit extract at 10 ppm reduced the hatchability of Cx. pipiens eggs by 20%, whereas the chloroform leaf extract was found to be less effective (5% reduction). At 10 ppm, adult emergence was reduced by 84% and 75% for chloroform and ethyl acetate extracts of fruits, respectively. Metamorphosis of larvae exposed to chloroform fruit extract (10 ppm) was extended to 15 days, as compared to 10 days for control larvae. It took 12 days at 1 ppm, and 15 days at 6 and 10 ppm for chloroform fruit extract-treated embryos to develop into adult mosquito while it took 10 days in the control treatment. However, 100% toxicity was observed in the embryos of zebrafish, Danio rerio, treated with the ethyl acetate fruit extracts (LC50 of 20 ppm and LC100 of 40 ppm) and chloroform leaf extract (LC50 of 30 ppm and LC100 of 60 ppm). These findings emphasize the need to further isolate the bioactive molecules in S. argel crude extracts that may still be mosquitocidal but produce no, or minimal, adverse effects on nontarget organisms such as zebrafish.

Larvicidal potency of selected xerophytic plant extracts on Culex pipiens (Diptera: Culicidae): Effect of Plant Extracts on Culex pipiens

Chemical insecticides released into the environment may have adverse biological effects. Therefore, there is a need for ecofriendly insecticides for mosquito control. Xerophytic plant extracts that may provide more ecofriendly active component were evaluated against Culex pipiens 4th instars. Plant extracts prepared using different solvents with a Soxhlet apparatus and different concentrations were tested against Culex pipiens larvae. The effects were observed at 24 h and 72 h intervals and LD50 and LD90 values determined. Chloroform (CHCl3) and ethyl acetate (EtOAc) extracts of Althaea ludwigii were the most effective against Cx. pipiens 4th instars, but were highly dependent on extract concentrations and exposure time. Results suggest that A. ludwigii extracts contain bioactive compounds, such as phenols and saponins, that may provide effective Cx. pipiens larval control. However, the extract was found to be toxic to zebrafish larvae, and may be toxic to other aquatic fauna. Further studies to determine the active components and toxicity to other fauna are needed.

Larvicidal activity of some fungal extracts on Aedes caspius and Culex pipiens (Diptera: Culicidae)

A preliminary study was conducted to evaluate the effects of nine methanol fungal extracts on fourth instar larvae of Aedes caspius and Culex pipiens (Diptera: Culicidae). None of the extracts tested showed larvicidal activity except for the Paecilomyces lilacinus extract, which showed 100 % mortality against the larvae of Ae caspius after 24 h. The LC50 values of the P. lilacinus extract after 24 h were 190.66 μg/mL against Ae. caspius and 254.25 μg/mL against Cx. pipiens, respectively. After 48 h, meanwhile, the LC50 values were 65.70 and 164.13 μg/mL, respectively. Histological analysis of the midgut of the treated larvae of Ae. caspius and Cx. pipiens revealed changes such as cell destruction, spacing between the cells and disruption of the microvilli, resulting in an appearance of vacuolization in the midgut. This article is the first report of the use of P. lilacinus extract for the control of Ae. caspius and Cx. pipiens larvae and the data obtained may help to provide a better understanding of the mode of action of P. lilacinus as an insecticide against mosquito larvae.

Efficacy of entomopathogenic fungi isolated from the nest of the samsum ant, Pachycondyla sennaarensis against larvae of the mosquitoes Aedes caspius and Culex pipiens

The use of entomopathogenic fungi is a promising alternative to chemical control against mosquitoes. In February 2013, two fungi were isolated from the Samsum ant, Pachycondyla sennaarensis, Mayr, (Hymenoptera: Formicidae) collected in Riyadh, KSA. One of these fungi, identified as Fusarium solani was highly pathogenic against larvae of the mosquito, Aedes caspius (Diptera: Culicidae). F. solani killed 100% of Ae. caspius within 5 days of exposure to the concentration of 5 × 107 cfu/ml. Also, results indicated that F. solani was more virulent to the mosquito larvae than F. chlamydosporum at the concentration of 8 × 107 cfu/ml. The histopathological examination indicated that spores of F. solani are invasive to the wall of Ae. caspius larvae. Both F. solani and F. chlamydosporum were not affected against Ae. caspius and Culex pipiens. These results suggested that F. solani could be an effective tool to manage Ae. caspius proliferation and hence diseases transmission.