Ultrastructure of male accessory glands of Chrysomya megacephala (Fabricius) (Diptera: Calliphoridae)

The ultrastructure of the male accessory glands of the blow fly, Chrysomya megacephala (Fabricius), was presented using light microscopy (LM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). A pair of accessory glands was separated at opposite sites. Morphometric results using LM yield evidenced no significant difference in the median of either length or width of the left and right glands. A significant increment in both length and width was seen to plateau between three to six days. SEM observation showed that the surface of the glands revealed a faint irregular groove pattern throughout, and it was occasionally penetrated by tracheoles. Each gland was a slender, elongated sac‐like tubule having apical rounded ends, with a slight constriction at the sub‐apical part of the gland being observed occasionally. TEM analyses of three‐day‐old males showed that the glands consisted of external capsular cells with a basement membrane underneath, glandular cells, and gland lumen. The capsular cell was flat and contained a nucleus with electron dense material in the nuclear envelope. The glandular cell, appearing as columnar, consisted of a vacuolated component that contained a large oval nucleus centrally or sub‐basally located, with dense mitochondria, numerous rough endoplasmic reticulum, and secretory vesicles containing electron‐lucent materials. In the gland lumen, the cross‐section through the middle portion revealed dense secretory materials, characterized by electron‐dense materials. Some sections revealed a large lumen where secretion accumulates within the delicate sac. The seven‐day‐old glands exhibited a remarkable change in the lumen, where the whole space contained a large amount of secretory materials, with the electron‐dense materials being characterized as similar to those observed in three‐day‐old glands. About four prominent types of secretions were observed on the basis of difference in electron‐density.     

Visual and olfactory factors interaction in resource-location by the blowfly, Chrysomya megacephala (Fabricius) (Diptera: Calliphoridae), in natural conditions

The interaction between olfactory and visual cues in the landing responses of Chrysomya megacephala (Fabricius) was analyzed in a natural environment (grass) using three plain cardboard circles with the colors white, black and other being the own grass (control) with 30 cm in diameter. The circles were divided in four quadrants and five sectors using as bait 80 mg of carcass of fish and minced flesh put in the center. To check the interaction between visual and olfactory factors, we analyzed the relation among the direction of wind and the sectors, the quadrants and the color of circle where C. megacephala adults landed. In the presence of the black and white circles, flies landed closer to the central release point of the bait when the wind was present compared with the other control circle. The results show that while odor cues may enhance the induction of landing by C. megacephala, visual cues are important when selecting a final landing site. Improved understanding of this interaction may allow the development of more effective traps or targets, enhancing the control efficiency of these control devices.     

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。     

Sexual size dimorphism decreases with temperature in a blowfly,Chrysomya megacephala (Fabricius) (Diptera: Calliphoridae)

1. There is wide intra‐specific variation in sexual size dimorphism (SSD). Much of this variation is probably as a result of sexual differences in the selective pressure on body size. However, environmental variables could affect males and females differently, causing variation in SSD. 2. We examined the effects of two temperatures (20 and 30 °C) on SSD in six populations of the blowfly, Chrysomya megacephala. 3. We found that body size increased with temperature in all the populations studied, and the sexes differed in phenotypic plasticity of body size in response to rearing temperature. This created substantial temperature‐induced variation in SSD (i.e. sex × temperature interaction). Males were often smaller than females, but the degree of dimorphism was smaller at the higher temperature (30 °C) and larger at the lower temperature (20 °C). This change in SSD was not because of a gender difference in the effect of temperature on development time. Further studies should address whether this variation can be produced by adaptive canalisation of one sex against variation in temperature, or whether it may be a consequence of non‐adaptive developmental differences between the sexes. 4. Although most studies assume that the magnitude of SSD is fixed within a species, the present study demonstrates that rearing temperature can generate considerable intra‐specific variation in the degree of SSD.     

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.     

C-banding and FISH in chromosomes of the blow flies Chrysomya megacephala and Chrysomya putoria (Diptera, Calliphoridae)

The blow flies Chrysomya putoria and C. megacephala have 2n=12 chromosomes, five metacentric pairs of autosomes and an XX/XY sex chromosome pair. There are no substantial differences in the karyotype morphology of these two species, except for the X chromosome which is subtelocentric in C. megacephala and metacentric in C. putoria and is about 1.4 times longer in C. putoria. All autosomes were characterized by the presence of a C band in the pericentromeric region; C. putoria also has an interstitial band in pair III. The sex chromosomes of both species were heterochromatic, except for a small region at the end of the long arm of the X chromosome. Ribosomal genes were detected in meiotic chromosomes by FISH and in both species the NOR was located on the sex chromosomes. These results confirm that C. putoria was the species introduced into Brazil in 1970s, and not C. chloropyga as formerly described.     

Base-line susceptibility of the oriental latrine fly, Chrysomya megacephala (Diptera: Calliphoridae), to five insecticides

Susceptibility to five insecticides was assessed on seven colonies of the oriental latrine fly, Chrysomya megacephala (Fabricius), originating from Japan, Hong Kong, Philippines, Indonesia and Papua New Guinea, and on C. saffranèa (Bigot) from PNG. All the colonies were susceptible to fenitrothion, diazinon, dichlorvos, permethrin and gamma-HCH, although the Jakarta, Manila and Tokyo colonies of C.megacephala were least susceptible (most tolerant) to diazinon, dichlorvos and permethrin. Feral forms of both Chrysomya species were 4-5-fold more susceptible to permethrin at the LD50 level than were all six colonies of the synanthropic form of C.megacephala.     

Study on ascending and descending vertical dispersal behavior of third instar larvae of Chrysomya megacephala (Fabricius) (Diptera:Calliphoridae): An evidence that blowflies survive burial

Although the pupation behavior of blowflies has been widely studied, this preliminary study was done on the vertical dispersal behavior (both ascending and descending) and fly emergence rate of third instar larvae of Chrysomya megacephala (Fabricius) to evaluate weather immature stages of blowflies survive burial and emerge out as adult. Third instar larvae of Chrysomya megacephala were placed at three different depths (5 cm, 25 cm and 45 cm) of soil under laboratory conditions to determine the impact of soil depth on the ascending and descending vertical dispersal behavior and the subsequent emergence of adults. The results of this study, although preliminary, but valuable to the field of forensic entomology because they provide new information about both ascending and descending vertical dispersal behavior of Chrysomya megacephala forensically important species of blowfly. In all the cases, maximum number of pupae recovered at the depth of 0 to 5 cm are 35.5 ± 4.5, 34 ± 1, 25 ± 5, when food was located at 5 cm, 25 cm and 45 cm depth respectively. This means that maximum no of larvae reached to the depth of 0 to 5 cm by ascending dispersal irrespective of at which depth they are placed. Paramount pupae were recovered from shallow burial depth of 0–5 cm in ascending dispersal and showed highest eclosion success i.e. 90.1% followed by 25 cm and 45 cm i.e. 71.7% and 55% respectively. While the number of pupae recovered as well as eclosion success was less in descending dispersal with an average of 62.8%, 39.25% and 33.9% at depths of 5, 25 and 45 cm respectively. This manifest if larvae disperse ascendingly, it increases their chance of survival.     

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。     

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.     

温度对大头金蝇生长发育的影响及其用于PMI推断的探讨

分别在22℃、25℃、28℃恒温下,用处死家兔的肌肉饲养大头金蝇Chrysomya megacephala初孵幼虫,研究温度对大头金蝇生长发育的影响及其在法医学中推断死者死后间隔时间(postmortem interval,PMI)方面的应用.结果显示,不同温度下,幼虫体长、体重分别与取食时间呈线性相关(R2>0.96,R2>0.92),可用于推断PMI.另外,蛹长、蛹重、发育历期可作为辅助指标,提高推断的准确性.随温度升高,大头金蝇的生长发育明显加快.不同温度的大头金蝇生长发育差异显著,28℃下的大头金蝇发育历期为187.2 h,22℃下为279 h,比22℃发育时间缩短了91.8 h;28℃下的大头金蝇幼虫、蛹的体长和体重与处于25℃、22℃的大头金蝇也有明显差异.     

Cannibalistic Behavior and Functional Response in Chrysomya albiceps (Diptera: Calliphoridae)

Chrysomya albiceps is a facultative predator and cannibal species during the larval stage. Very little is known about cannibalism and prey size preference, especially in blowflies. The purpose of this investigation was to determine the influence of prey size and larval density on cannibalism by third-instar larvae of C. albiceps under laboratory conditions. Our results indicate that no cannibalism occurs by third-instar larvae on first- and second-instar larvae, but third-instar larvae do eat second-instar larvae. The functional response on second-instar larvae is consistent with Holling type II. The consequences of consuming second-, compared to first- or third-, instar larvae as well as the implications of cannibalism for the population dynamics of C. albiceps are discussed.     

Prey choice by facultative predator larvae of Chrysomya albiceps (Diptera: Calliphoridae)

In this study we investigated predation rates on third instar larvae of Chrysomya putoria and C. megacephala by third instar larvae of C. albiceps in a two-choice situation. The highest predation rate occurred on C. putoria larvae and this result is compared to previous experiments, in which C. macellaria larvae were present. Our results suggest that, when C. macellaria is absent C. albiceps larvae attack more C. putoria than C. megacephala larvae. Prey choice decisions and its implications for introduced and native blowflies are discussed.     

Development of female accessory glands of Chrysomya putoria (Wiedemann) (Diptera: Calliphoridae) during oogenesis

Females of Chrysomya putoria (Diptera: Calliphoridae) have two sexual accessory glands, which are tubular and more dilated at the distal extremity. The glands open independently into the common oviduct. Two morpho-physiological regions were distinguished in the longitudinal semi-thin sections of the glands. The secretory region is constituted by three layers: a cuticular intima, lining the lumen, followed by a layer of small cells, and then a layer of very large secretory cells. The ductal region of the gland presents only two layers: the cuticular intima and a cellular layer. In both regions a basement membrane is present. Each secretory cell has in its apical region a reservoir, which enlarges throughout oogenesis; in its basal region there is a large nucleus. The ductal cells are cylindrical and smaller than the secretory cells. The glandular secretion is synthesized in the cytoplasm of the secretory cells, stored and/or modified in the reservoir, then drained to the lumen through an end apparatus seen in the apical region of the secretory cell. Histochemical tests indicate that this secretion is a glycoprotein. Measurements of the glands from females at different physiological conditions and fed on different diets correlate with the results obtained for changes in the ovary during oogenesis. Cell number averaged 561.2 ± 77.54 per gland. There was no increase in cell number during oogenesis.     

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。     

Sensitivity of last larval stadium of Chrysomya megacephala (Fabricius) to anti-allatin ageratochromene Precocene II

Treatment of early and late third instar larvae of economically important insect C. megacephala with the ageratochromene precocene II resulted into precocious metamorphosis. The other effects included mortality, production of pupal-adult mosaics, reduction in percentage of adult emergence and formation of non-viable deformed adults that died after a few hours of emergence. The application of precocene II adversely hampered the normal growth, development and metamorphosis of the insect and the results show that precocene II has vast potential for excellent control of this insect of medico-veterinary importance and can be used in insect pest management programs.     

Characterization of polymorphic microsatellite markers for the blowfly Chrysomya albiceps (Diptera: Calliphoridae)

Chrysomya albiceps is a blowfly of great medical, sanitary and forensic importance widely distributed in the Afrotropical, southern Palaearctic, northern Oriental regions and, recently, in Central and South Americas. Here, we report the characterization of 13 polymorphic microsatellite markers for C. albiceps. The number of alleles ranged from three to 13 alleles with expected heterozygosities ranging from 0.4668 to 0.8408. These markers will be extremely useful for investigating many important aspects of this species such as population structure, dispersal and colonization dynamics.