Mitochondrial genomes of the sheep blowfly, Lucilia sericata, and the secondary blowfly, Chrysomya megacephala

This paper presents complete mitochondrial genomes for the sheep blowfly, Lucilia sericata (Meigen), and the secondary blowfly, Chrysomya megacephala (Fabricius). Both L. sericata and C. megacephala had standard dipteran-type mitochondrial genome architectures and lengths of 15 945 bp and 15 831 bp, respectively. Additionally, C. megacephala possessed a tRNA duplication either side of the D-loop, as previously reported in another Chrysomya species, C. putoria; this duplication appears to be synapomorphic for the genus Chrysomya. As in other insect mitochondrial genomes, base compositions had a high AT content, with both genomes more than 76% AT-rich.     

盐酸吗啡对大头金蝇生长发育的影响及其对死者死亡时间推断的意义

用盐酸吗啡注射家兔,处死后用家兔的不同组织饲养大头金蝇 Chrysomya megacephala初孵幼虫,研究吗啡剂量对大头金蝇幼虫生长的影响及其在法医学中推断死者死亡时间方面的应用。结果显示,在28℃下,取食处理组兔肉和肝脏的大头金蝇幼虫的体长和体重均于孵化后28 h开始在不同程度上大于对照组幼虫,这种趋势一直持续到幼虫末期。在实验的剂量范围内（2.67～10.66 mg/kg）,吗啡可促进大头金蝇幼虫的生长。根据大头金蝇幼虫体长和体重推断死者死亡时间时,吗啡的这种影响可使推断值产生的最大偏差达18h。     

Eicosanoids mediate nodulation reactions to bacterial Escherichia coli K 12 infections in larvae of the oriental blowfly, Chrysomya megacephala

Abstract  Nodulation is the predominant cellular defense reaction to bacterial challenges in insects. In this study, third instar larvae of Chrysomya megacephala were injected with bacteria, Escherichia coli K 12 (10⁶ CFU/mL, 2 μL), immediately prior to injection of inhibitors of eicosanoid biosynthesis, which sharply reduced nodulation response. Test larvae were treated with specific inhibitors of phospholipase A₂ (dexamethasone), cyclo-oxygenase (indomethacin, ibuprofen and piroxicam), dual cyclo-oxygenase/lipoxygenase (phenidone) and lipoxygenase (esculetin) and these reduced nodulation except esculetin. The influence of bacteria was obvious within 2 h of injection (5 nodules/larva), and increased to a maximum after 8 h (with 15 nodules/larva), and then significantly reduced over 24 h (9 nodules/larva). The inhibitory influence of dexamethasone was apparent within 2 h of injection (4 vs. 5 nodules/larva), and nodulation was significantly reduced, compared to control, over 24 h (5 vs. 8 nodules/larva). Increased dosages of ibuprofen, indomethacin, piroxicam and phenidone led to decreased numbers of nodules. Nodules continued to exist during the pupal stage. However, the effects of dexamethasone were reversed by treating bacteria-injected insects with an eicosanoid-precursor polyunsaturated fatty acid, arachidonic acid. These findings approved our view that eicosanoid can mediate cellular defense mechanisms in response to bacterial infections in another Dipteran insect C. megacephala .     

大头金蝇的综合利用研究进展

大头金蝇Chrysomya megacephala是重要的法医昆虫、资源昆虫和卫生害虫。大头金蝇的各个发育阶段与人类活动关系密切。本文简要介绍了大头金蝇的分布、分类鉴定及生物学背景,着重从法医学应用、幼虫在有机废弃物转化中的应用、幼虫的活性物质及成虫传粉应用4个方面总结其在资源综合利用方面的研究进展,并讨论了大头金蝇其幼虫和成虫存在的风险及可能的控制方法。新型法医学手段的开发拓宽了大头金蝇在法医领域的应用范围;大头金蝇幼虫能够有效地转化粪便、餐厨垃圾、污泥等多种有机废弃物创造环境和经济效益;幼虫具有多种活性物质,有利于其高附加值产品的开发;虽然成虫的自然传粉效果好,但是其作为传粉昆虫人工释放仍有局限性,仅适用可控空间内。大头金蝇的病媒特性仍是限制其广泛应用的绊脚石,这一问题的解决,有赖于多种技术的有机结合。     

Development of two forensically important blowfly species (Chrysomya megacephala and Chrysomya rufifacies) (Diptera: Calliphoridae) at four temperatures in India

The development of the Oriental latrine fly, Chrysomya megacephala (Fabricius), and hairy maggot blowfly, C. rufifacies (Macquart) (Diptera: Calliphoridae), was studied at four different temperatures (22°C, 25°C, 29°C and 31°C) in order to draw correlations between larval age, body length and body dry weight. The mean larval body length increased steadily from a minimum of 1.4 mm for C. megacephala and 1.8 mm for C. rufifacies to a maximum of 17.4 mm for C. megacephala and 15.9 mm for C. rufifacies at different temperatures. Similarly, the mean dry weight increased steadily from a minimum of 0.0007 g for C. megacephala (second instar) and 0.0008 g for C. rufifacies (second instar) to a maximum of 0.0290 g for C. megacephala and 0.0270 g for C. rufifacies at different temperatures. Entomological evidence is often used to estimate the minimum postmortem interval (mPMI) and both of these species are important from a forensic point of view. Graphs of age of larvae vs. body length and age of larvae vs. dry body weight at different temperatures can be used to estimate the larval age of these two species.     

家蝇和大头金蝇在麦麸和猪瘦肉上的产卵选择和发育差异

在中国许多地区, 大头金蝇Chrysomya megacephala F.已侵入过去由家蝇Musca domestica L.占绝对优势的垃圾生态位, 逐渐成为城市蝇类的优势种. 为了解单独和混合饲养时食物种类对家蝇和大头金蝇幼虫生长发育的影响, 在室内观察了野外大头金蝇和家蝇F1代在湿麦麸、猪瘦肉以及两者混合物上的产卵选择和生活史. 结果显示: (1)大头金蝇嗜在含有猪瘦肉的基质上产卵, 而家蝇嗜在含有麦麸的基质上产卵;(2)初孵家蝇和大头金蝇幼虫都能在含有瘦肉的食物上发育至成虫. 在麦麸上, 初孵家蝇幼虫能发育至成虫, 而初孵和2龄大头金蝇幼虫在进入下一龄期前全部死亡, 但少数3龄大头金蝇幼虫能发育至成虫;(3)等量初孵家蝇与大头金蝇在含有猪瘦肉的食物上共同生长时, 与家蝇相比, 大头金蝇的发育历期较短、存活率较高. 与家蝇在麦麸上共同生长时, 与在麦麸上独立生长的同龄大头金蝇相比, 大头金蝇的发育历期较短、存活率较高. 这些结果表明, 共生时家蝇可促进大头金蝇对植物质营养的利用, 这也许是大头金蝇能成功侵入家蝇占绝对优势的垃圾生态位的一个重要原因.     

特种五谷虫脂肪酸的体外抗肿瘤、抗HIV-1整合酶活性及组成分析

为研究特种五谷虫(大头金蝇Chrysomya megacephala蝇蛆的俗称)脂肪酸的体外抗肿瘤、抗HIV-1整合酶活性,并确定其组分构成,通过溶剂萃取和油脂酶解获得2种脂肪酸FA1和FA2,采用MTT法/SRB法测定其体外抗人白血病细胞HL-60/人肺癌细胞A-549活性,以及采用Biotin-ELISA法检测其对HIV-1整合酶的抑制作用;并由GC-MS分析确定其脂肪酸组成。结果表明：FA1和FA2对人白血病细胞/人肺癌细胞均有显著的抑制活性,其IC₅₀值在35～65 μg/mL;对HIV-1整合酶同样具有强烈的抑制活性,IC₅₀值分别为86.7 μg/mL和98.5 μg/mL。GC-MS分析表明,FA1和FA2化学组成相似,均含有15%～16%的多不饱和脂肪酸（PUFA),其中有2个组分为ω-6 PUFA。提示特定培养的五谷虫,其脂肪酸成分具有显著的体外抗肿瘤、抗HIV-1整合酶活性,其中含有的PUFA,尤其ω-6 PUFA,可能是主要活性组分;FA2在来源上和FA1存有相关性。     

Molecular identification of some forensically important blowflies of southern Africa and Australia

One major aspect of research in forensic entomology is the investigation of molecular techniques for the accurate identification of insects. Studies to date have addressed the corpse fauna of many geographical regions, but generally neglected the southern African calliphorid species. In this study, forensically significant calliphorids from South Africa, Swaziland, Botswana and Zimbabwe and Australia were sequenced over an 1167 base pair region of the COI gene. Phylogenetic analysis was performed to examine the ability of the region to resolve species identities and taxonomic relationships between species. Analyses by neighbour-joining, maximum parsimony and maximum likelihood methods all showed the potential of this region to provide the necessary species-level identifications for application to post-mortem interval (PMI) estimation; however, higher level taxonomic relationships did vary according to method of analysis. Intraspecific variation was also considered in relation to determining suitable maximum levels of variation to be expected during analysis. Individuals of some species in the study represented populations from both South Africa and the east coast of Australia, yet maximum intraspecific variation over this gene region was calculated at 0.8%, with minimum interspecific variation at 3%, indicating distinct ranges of variation to be expected at intra- and interspecific levels. This region therefore appears to provide southern African forensic entomologists with a new technique for providing accurate identification for application to estimation of PMI.     

Direct and indirect top‐down effects of previous contact with an enemy on the feeding behavior of blowfly larvae

We investigated the addition of a trophic level to a simple food web. Direct and indirect effects caused by the presence of a new species in the food web were quantified by estimating survival and consumption rates on the basal resource. We focused on a blowfly intraguild prey–predator system with various ecological interactions taking place during the larval period. The experiments were designed to set Chrysomya megacephala (Fabricius) (Diptera: Calliphoridae) as the intraguild prey and Chrysomya albiceps (Wiedemann) as the intraguild predator and/or cannibal. The generalist pupal parasitoid Nasonia vitripennis (Walker) (Hymenoptera: Pteromalidae) was introduced into the system during a non‐susceptible life stage of the interacting blowfly species. The cascading parasitoid effects induced behavioral changes in the blowfly larvae, increasing the impact of intraguild predation and cannibalism on blowfly survival. The results suggest that blowfly larvae can change their feeding behavior in response to the presence of a parasitoid.     

Effect of diets on the developmental rate of calliphorid fly of forensic importance Chrysomya megacephala (Fabricius, 1794)

The aim of this study was to compare the effect of diets on the morphological parameters of different developmental stages of blowflies Chrysomya megacephala (Fabricius, 1794). Adult C. megacephala flies were collected from a goat cadaver and reared in the laboratory when the max and min temperature were 32 and 24 °C and the relative max and min humidity were ranged between 55 and 31% respectively. Blowflies at various feeding stages (first-, second-, and third-instar larvae) received different types of diets (meat, liver, fats, and mixed). The effects of the different diets on the life cycle duration and the morphological parameters of various stages were observed. The results revealed that the fat diet prolonged the post-mortem interval (PMI) up to 298.5 ± 1.15 hrs, whereas the mixed food diet shortened PMI to the 243.67 ± 0.12 hrs. Significant variation were observed at level (F = 740.71 df = 3P < 0.001). Furthermore, the mixed food diet significantly increased the morphological parameters (length, width, and weight) for almost all stages during the life cycle of blowflies. In contrast, the fat diet decreased these parameters to the lowest level. The present findings may provide a scientific basis for the determination of PMI.     

四川西部丽蝇科4蝇种昼夜活动节律的研究

首次记录四川西部雅安市丽蝇科(Calliphoridae)4蝇种昼夜活动节律的初步研究,结果表明,蝇类这一具有白昼活动、夜间蛰伏的生物生态特性的昆虫群体,对光照度和光照时间表现出异常敏感的行为反应;在地理生态环境中,对于影响蝇类行为活动诸因素如气温、光照、晴、阴、雨等气候现象,文中予以讨论。     

Effects of temperature and photoperiod on development and oviposition of the legume flower thrips, Megalurothrips sjostedti

Chrysomya albiceps, the larvae of which are facultative predators of larvae of other dipteran species, has been introduced to the Americas over recent years along with other Old World species of blowflies, including Chrysomya megacephala, Chrysomya putoria and Chrysomya rufifacies. An apparent correlate of this biological invasion has been a sudden decline in the population numbers of Cochliomyia macellaria, a native species of the Americas. In this study, we investigated predation rates on third instar larvae of C. macellaria, C. putoria and C. megacephala by third instar larvae of C. albiceps in no-choice, two-choice and three-choice situations. Most attacks by C. albiceps larvae occurred within the first hour of observation and the highest predation rate occurred on C. macellaria larvae, suggesting that C. albiceps was more dangerous to C. macellaria than to C. megacephala and C. putoria under these experimental conditions. The rates of larvae killed as a result of the predation, as well as its implications to population dynamics of introduced and native species are discussed.     

Contrasting responses to object orientation and illumination by the blowflies Chrysomya chloropyga and Lucilia sericata

The alighting response of two species of blowfly, Chrysomya chloropyga (Weidemann) and Lucilia sericata(Meigen) (Diptera: Calliphoridae), were considered in relation to the orientation and illumination of a flat, oblong visual object. A strong response to orientation was displayed by L. sericata with the greatest number alighting on the vertical object; there was no significant effect of orientation on the number of C. chloropyga which alighted. Both species alighted preferentially on the more strongly illuminated side of a vertical object. With the object horizontal and more strongly illuminated from below, C. chloropygaagain landed on the most brightly illuminated side. In contrast, reducing the brightness on the upper surface of the horizontally-suspended object reduced the number of L. sericataalighting on the upper surface but also reduced the overall catch, suggesting that for L. sericata the response to the illumination of a surface does not outweigh its response to its orientation. The implications of these results for the development of trapping technology for the monitoring or control of these economically important pest species is discussed.     

Effects of natural and commercial diets on the fatty acid content of European grayling

Eicosaenoic acid (20:1ω9) and docosaenoic acid (22:1ω11) levels were about 10 and 100 times higher in food pellets fed to cultured grayling than in the insect larvae on which wild grayling fed. Among the PUFA, docosahexaenoic acid (DHA) was very high in the pellets, resulting in an unnaturally elevated, and probably unbalanced, ω3/ω6 ratio of 7–13 in the cultured fish whereas the same ratio varied only from 4 to 6 in the wild fish. Despite very low DHA levels in the native food, wild grayling muscle tissue contained relatively high amounts of DHA. DHA is probably not essential in the diet of grayling.     

Recent African derivation of Chrysomya putoria from C. chloropyga and mitochondrial DNA paraphyly of cytochrome oxidase subunit one in blowflies of forensic importance

Chrysomya chloropyga (Wiedemann) and C. putoria (Wiedemann) (Diptera: Calliphoridae) are closely related Afrotropical blowflies that breed in carrion and latrines, reaching high density in association with humans and spreading to other continents. In some cases of human death, Chyrsomya specimens provide forensic clues. Because the immature stages of such flies are often difficult to identify taxonomically, it is useful to develop DNA-based tests for specimen identification. Therefore we attempted to distinguish between C. chloropyga and C. putoria using mitochondrial DNA (mtDNA) sequence data from a 593-bp region of the gene for cytochrome oxidase subunit one (COI). Twelve specimens from each species yielded a total of five haplotypes, none being unique to C. putoria. Therefore it was not possible to distinguish between the two species using this locus. Maximum parsimony analysis indicated paraphyletic C. chloropyga mtDNA with C. putoria nested therein. Based on these and previously published data, we infer that C. putoria diverged very recently from C. chloropyga.     

不同食料对野蚕黑卵蜂卵巢发育和卵子发生的影响

以20%浓度蜂蜜、蔗糖、葡萄糖、果糖、甘露糖为食料,研究了它们对野蚕黑卵卵巢发育和卵子发生的影响。结果表明,与对照相比(蒸馏水),蜂蜜、蔗糖、葡萄糖和果糖能促进野蚕黑卵蜂雌蜂卵巢发育和卵子发生,可使其卵巢管中较高的成熟卵量维持较长时间,即可延缓该蜂的卵子重吸收。甘露糖对野蚕黑卵蜂的卵子形成有一定的促进作用,但其所起的作用显然不如蜂蜜及其它3种糖类,并且也不能延缓该蜂的卵子重吸收。     

Evaluation of some adhesives for collecting Musca domestica and Chrysomya megacephala adults or mosquito larvae in sticky traps

1. Seven types of water-insoluble adhesives were evaluated in sticky traps for collecting adults of Musca domestica L. and Chrysomya megacephala (Fabricius) or mosquito larvae (Aedes aegypti (L.) and Culex quinquefasciatus Say). 2. Adhesive viscosity affected the tackiness of the glues and this determined their trapping efficiency in air or water. 3. From the 'Hyvis' range of adhesives tested, 'Hyvis 200' was most effective for trapping adult flies. 4. With 24 h exposure to fourth instar Ae.aegypti larvae in tapwater, submerged plates coated with 'Hyvis 10', 'Hyvis 30' or 'Hyvis 200' formulations trapped the majority of larvae. In polluted water the highest rates of trapping were 17.3% of Ae.aegypti and 18.7% of Cx quinquefasciatus with 'Hyvis 200'. Floating traps were consistently less productive than submerged traps under laboratory conditions. 5. In a heavily polluted natural breeding-site of Cx quinquefasciatus, floating traps were more productive than submerged sticky traps with four of seven adhesives tested, the most efficient being 'Hyvis 200' (4.2 mosquitoes per hour) and Hyvis:polyethylene 90:10 (4.5/h). Despite the relative inefficiency of aquatic traps, emergent adults, pupae and second to fourth instars of larvae were collected quickly from the habitat.