An Evaluation of Differentially Spliced Genes as Markers of Sex for Forensic Entomology,,

Blow flies (Calliphoridae) are important medically and economically and are commonly used in forensics as temporal markers in death investigations. While phenotypic traits in adult flies can be sexually dimorphic, sex identification in immatures is difficult. Consequently, little is known about how sex may result in developmental disparities among sexes even though there are indications that they may be important in some instances. Since genetic mechanisms for sex are well studied in model flies and species of agricultural and medical importance, we exploit the sex-specifically spliced genes transformer (tra) and doublesex (dsx) in the sex determination pathway to optimize a sex identification assay for immatures. Using known primer sets for tra and with a novel one for dsx, we develop PCR assays for identifying sex in four forensically relevant Calliphoridae species: Lucilia sericata (Meigen), Lucilia cuprina (Wiedemann), Cochliomyia macellaria (Fabricius), and Chrysomya rufifacies (Macquart) and evaluated their performance. Band detection rates were found to range from 71 to 100%, call rates ranged from 90 to 100%, and no error was found when bands could be called. Such information is informative for purposes of testimony and in preparation for development studies. The developed assays will assist in further differentiating sexually dimorphic differences in development of the Calliphoridae and aid in more accurately estimating insect age when age predictive markers (size, development time, molecular expression) are sexually dimorphic.     

NCBI数据库在常见嗜尸性蝇类种属鉴别中的应用

目的探讨NCBI数据库比对分析对常见嗜尸性蝇类种属鉴别中的应用价值。方法收集2009年1月至2012年12月重庆市常见嗜尸性蝇类不同发育历期2科5属7种样本52份,采用Chelexl00法提取mtDNA,利用2对引物扩增细胞色素C氧化酶辅酶I基因,分别截取498bp和841bp相同长度的序列,采用MEGA软件计算种内及种间进化分歧情况,并分别在NCBI数据库进行序列BLAST搜索种属同源性比对分析。结果所得序列种内进化分歧均数在0％～0．7％之间,种问进化分歧均数在7．5％～16．1％之间;7个种属的样本序列Ⅰ和序列Ⅱ分别有5个和6个种属完全比对正确,样本总体的正确率分别达到96．15％和98．08％,Maxident值均在97％以上。结论采用序列同源性比对分析,并借助NCBI数据库强大的检索分析功能,可准确进行常见嗜尸性蝇类的种属鉴定,为法医学死亡时间推断提供重要参考依据。     

呼和浩特夏秋季嗜尸性苍蝇群落组成与演替

目的研究呼和浩特夏秋季常见嗜尸性苍蝇生态群落组成与演替规律。方法连续3年用观察法研究7—10月份,家兔、狗尸体、鸡、鱼内脏等试验材料上的嗜尸性苍蝇生态群落组成与演替。结果该地区上述尸体上出现的双翅目嗜尸性苍蝇是最先到达尸体上的昆虫,而且在尸体上出现时间及部位表现出很强的生态群落演替规律性。结论研究结果可成为在呼和浩特地区对尸体进行死亡时间、死亡地点推断的依据。     

四季尸食性蝇类参与尸体软组织分解过程初探

目的观察了解四季尸食性蝇类参与尸体软组织分解过程的规律。方法在室外自然环境中设置尸体,分别在春、夏、秋、冬季节,用肉眼观察尸体每一时段的变化及尸食性蝇类参与尸体分解的现象。结果在4个不同的季节中,尸体软组织分解过程中尸食性蝇类参与种类及虫态各不相同。通过观察获得尸体变化各阶段的大体历期,尸体变化各阶段常见的尸食性蝇种及虫态资料。结论观察所得资料可为推测晚期尸体的死亡时间提供参考。     

潍坊地区六种常见嗜尸性蝇类mtDNA COI区序列研究

目的解决蝇类成虫、蛹和蛆快速、准确鉴定的难题。方法随机采集潍坊地区人尸周围环境中的蝇类成虫、蛹和蛆,提取其mtDNA,经PCR扩增、产物检测与纯化、测序等,比较其序列差异。结果六种常见嗜尸性蝇类相互之间序列差异明显,同一种蝇的成虫、幼虫、蛹之间未见差异。结论mtDNACOI区序列分析可作为法医学嗜尸性蝇类种属鉴别的可靠方法。     

Some notes on the nocturnal larviposition by two species of Sarcophaga (Diptera: Sarcophagidae)

Experiments in the month of September 2005 were performed to study nocturnal larviposition by the flesh flies (Diptera: Sarcophagidae). Two species namely Sarcophaga albiceps Meigen and Sarcophaga hirtipes Wiedemann were observed to deposit their larvae during night time as well. Therefore, possibility of night larviposition by flesh flies should always be taken into consideration while determining age of maggots.     

An Analysis of Forensically Important Insects Associated with Human Remains in Indiana,U.S.A.*

Research documenting insect colonization of human remains is limited in North America, and currently nonexistent for the American Midwest. Such research is essential for forensic entomologists to identify species of research interest in a region. In this study, we collected insects from human remains in 24 cases across Indiana from June 2016 through September 2018. We analyzed species composition across scene type and season. Eight species of blow flies were collected as larvae from human remains, with Phormia regina and Lucilia sericata as the two predominant colonizers. Phormia regina was the most numerous species collected from outdoor scenes (73.6% of total collections) while L. sericata was the most numerous from the indoor scenes (60.4% of total collections). With scene types pooled, Calliphora vicina and Cochliomya macellaria were the predominant species in the fall (55.6% and 42.2%, respectively); P. regina was the dominant colonizer in the spring (68.6%); and P. regina and L. sericata were the predominant colonizers (46.5% and 44.4%, respectively) in the summer. In addition to these findings, we confirmed the first record of Lucilia cuprina colonizing human remains in Indiana having collected this species from three cases. A single adult Chrysomya megacephala was collected from an indoor scene in southern Indiana, which represents its second collection in the state. Beetles belonging to the families Staphylinidae, Silphidae, Histeridae, Cleridae, Trogidae, Dermestdae, and Nitidulidae were also collected from two outdoor scenes. This study provides important baseline data for forensic entomologists in Indiana, as well as surrounding states with similar environments.     

Eristalinus arvorum (Fabricius, 1787) (Diptera: Syrphidae) in Human Skull: A New Fly Species of Forensic Importance

A body of an unknown adult female was found within a shallow burial ground in Malaysia whereas the skull was exposed and visible on the ground. During autopsy examination, nine insect larvae were recovered from the interior of the human skull and subsequently preserved in 70% ethanol. The larvae were greyish in appearance, each with a posterior elongated breathing tube. A week after the autopsy, more larvae were collected at the burial site, and some of them were reared into adults. Adult specimens and larvae from the skull and from the burial site were sequenced to obtain DNA barcodes. Results showed all adult flies reared from the burial site, as well as the larvae collected from the skull were identified as Eristalinus arvorum (Fabricius, 1787) (Diptera: Syrphidae). Here, we report the colonization of E. arvorum larvae on a human corpse for the first time.     

DNA‐Based Identification of Forensically Important Lucilia (Diptera: Calliphoridae) in the Continental United States*

Abstract: Correct species identification is critical when dipteran larvae are used for inference of the postmortem interval. To facilitate DNA‐based identification of forensically important flies of the genus Lucilia in the continental United States, we develop a vouchered reference collection and DNA sequence database. A total of 122 specimens were collected for nine of the 10 species of Lucilia reported to occur in the continental United States. Using the polymerase chain reaction and DNA sequencing, data were obtained for an 1100‐bp region of the mitochondrial gene encoding cytochrome oxidase I (COI). We consider a species suitable for DNA‐based identification if it is exclusively monophyletic in >95% of bootstrap pseudoreplicate phylogenetic analyses. Seven of the nine species meet that criterion. Two species (Lucilia coeruleiviridis and Lucilia mexicana) share COI sequence and cannot be distinguished using our reference database. We conclude that DNA‐based identification is likely to be successful for the other seven species.     

利用16S rDNA序列鉴定常见嗜尸性蝇类种属

目的通过分析16S rDNA 551bp基因序列,鉴定常见嗜尸性蝇类种属。方法随机采集17个地区放置于室外草地的家兔尸体上7个种24只嗜尸性苍蝇样本,经形态学鉴定种类后,提取胸肌DNA,对16S rDNA 551bp基因片段进行PCR扩增,产物纯化、测序后上传GenBank;利用MEGA 4.0软件构建序列间的系统发育树,分析建立种内及种间进化分歧表。结果 24只样本16S rDNA序列分析显示7种蝇类可以较好聚类;其中棕尾别麻蝇种内进化分歧整体均数为2.8%,家蝇为1.5%,丽蝇科的5个种均在0.7%以内。上述7个蝇种的种间进化分歧均数在1.6%～7.1%之间。其中,棕尾别麻蝇、家蝇与其它蝇类的种间分歧均数在4.0%～7.1%之间。结论本文分析结果显示,蝇种间同源性相差明显,采用mtDNA 16S rDNA中551bp基因序列分析,可进行蝇种鉴定。