Bernhardt Victoria, Hannig Laura, Kinast Ronja, Verhoff Marcel A, Rothweiler Florian, Zehner Richard, Amendt Jens
Institute of Legal Medicine, University Hospital Frankfurt, Goethe-University, Kennedyallee 104, D-60596 Frankfurt am Main, Germany.
Institute of Legal Medicine, University Hospital Frankfurt, Goethe-University, Kennedyallee 104, D-60596 Frankfurt am Main, Germany.
J Insect Physiol. 2017 Apr;98:356-359. doi: 10.1016/j.jinsphys.2017.03.002. Epub 2017 Mar 4.
Age estimation of adult flies could extend the possible window of time for calculating the minimal postmortem interval (PMI) by means of entomological methods. Currently, this is done by estimating the time required by necrophagous Diptera to reach certain juvenile developmental landmarks, and the method only works until the end of metamorphosis and emergence of the adult fly. Particularly at indoor crime scenes, being able to estimate the age of trapped adult flies would be an important tool with which to extend the calculable PMI beyond the developmental period. Recently, several promising age-dependent morphological and physiological characteristics of adult insects have been investigated in medical and forensic entomology, but the results are still preliminary and restricted to a few species. We examined adults of the forensically relevant blow fly species Calliphora vicina and investigated the fluorescence levels of pteridine, a group of metabolites that accumulates in the eyes during aging. From Day 1 to Day 25 post-emergence, flies were kept at three different temperature regimes (20°C, 25°C, and fluctuating temperatures in the context of a field study) and 12:12 L:D. From Day 1 until Day 7, the fluorescence of pteridine was determined on a daily basis, and thereafter, every three days. The achieved fly age was multiplied with the relevant temperature and converted into accumulated degree-days (ADD). The fluorescence level of pteridine increased linear with increasing ADD (females: R=0.777; males: R=0.802). The difference between sexes was significant (p<0.001). Neither head weight nor temperature had an effect on pteridine fluorescence. Because the variation in pteridine fluorescence increased with increasing ADD, it seems favorable to combine several aging methods for more precise results. In context, we emphasize that different body parts of the same specimen can be used to analyze cuticular hydrocarbons (legs), pteridine fluorescence (head/eyes), and gonotrophic stage (female abdomen).
成年苍蝇的年龄估计可以通过昆虫学方法延长计算最短死后间隔时间（PMI）的可能时间窗口。目前，这是通过估计食尸性双翅目昆虫达到某些幼虫发育里程碑所需的时间来完成的，而该方法仅在变态结束和成年苍蝇羽化之前有效。特别是在室内犯罪现场，能够估计被困成年苍蝇的年龄将是一个重要工具，可将可计算的PMI延长到发育阶段之后。最近，医学和法医昆虫学研究了成年昆虫一些有前景的与年龄相关的形态和生理特征，但结果仍处于初步阶段，且仅限于少数物种。我们检查了法医相关的丽蝇物种红头丽蝇的成虫，并研究了蝶啶的荧光水平，蝶啶是一组在衰老过程中在眼睛中积累的代谢产物。羽化后第1天到第25天，苍蝇被置于三种不同的温度条件下（20°C、25°C以及在野外研究环境中的波动温度），光照周期为12:12（光:暗）。从第1天到第7天，每天测定蝶啶的荧光，此后每三天测定一次。将达到的苍蝇年龄乘以相关温度并转换为累积度日（ADD）。蝶啶的荧光水平随ADD增加呈线性增加（雌性：R = 0.777；雄性：R = 0.802）。两性之间的差异显著（p<0.001）。头部重量和温度对蝶啶荧光均无影响。由于蝶啶荧光的变化随ADD增加而增大，为获得更精确的结果，似乎最好结合多种衰老方法。在此背景下，我们强调同一标本的不同身体部位可用于分析表皮碳氢化合物（腿部）、蝶啶荧光（头部/眼睛）和生殖营养阶段（雌性腹部）。
